confronting climate change in the gulf coast prospects for...

A R E P O R T O F

The Union of Concerned Scientists and The Ecological Society of America

ConfrontingClimate Change in

the Gulf CoastRegion

Prospects forSustaining Our

Ecological Heritage

SoutheasternPlain

South FloridaCoastal Plain

Florida Keys

Gulf of Mexico

Mississippi RiverAlluvial Plain

North

Central

Plain

Central Texas

Plateau

Appalach

ian Pi

edmont

Central TX/OK Plain

Southern

Texas

Plain

South

Texas

Plain

Mississippi RiverDeltaic Plain

SouthernCoastalPlain

TexasClaypan

Area

Western Gulf

Coastal Plain

ConfrontingClimate Change

in the GulfCoast RegionProspects for SustainingOur Ecological Heritage

CONFRONTING CLIMATE CHANGE IN CALIFORNIAU n i o n o f C o n c e r n e d S c i e n t i s t s • T h e E c o l o g i c a l S o c i e t y o f A m e r i c a

1

P R E P A R E D B Y

Robert R. TwilleyEric J. BarronHenry L. GholzMark A. HarwellRichard L. MillerDenise J. ReedJoan B. Rose

Evan H. SiemannRobert G. Wetzel

Roger J. Zimmerman

O c t o b e r 2 0 0 1

A R E P O R T O F

The Union of Concerned Scientists andThe Ecological Society of America

Citation: Twilley, R.R., E.J. Barron, H.L. Gholz, M.A. Harwell, R.L. Miller,D.J. Reed, J.B. Rose, E.H. Siemann, R.G. Wetzel and R.J. Zimmerman (2001).Confronting Climate Change in the Gulf Coast Region: Prospects for Sustaining OurEcological Heritage. Union of Concerned Scientists, Cambridge, Massachusetts,and Ecological Society of America, Washington, D.C.

© 2001 Union of Concerned Scientists & Ecological Society of AmericaAll rights reserved. Printed in the United States of America

Designed byDG Communications, Acton, Massachusetts(www.nonprofitdesign.com)

Printed on recycled paper.

Copies of this report are available fromUCS Publications, Two Brattle Square, Cambridge, MA 02238–9105Tel. 617–547–5552

The report is also available atwww.ucsusa.org

CONFRONTING CLIMATE CHANGE IN THE GULF COAST REGIONU n i o n o f C o n c e r n e d S c i e n t i s t s • T h e E c o l o g i c a l S o c i e t y o f A m e r i c a

i i

v Figures

vii Acknowledgements

ix Executive Summary

1 Chapter One: Climate and People as Drivers of Ecosystem Change

1 Introduction 2 The Gulf Coastal Plain 3 Climate Change and Gulf Coast Ecosystems 5 Current Regional Climate 7 Climate Variability and Change over the Past Century 7 Projections of Future Climate in the Gulf Coast Region

9 Air and Coastal Ocean Temperatures 9 Precipitation and Runoff11 El Niño/La Niña11 Fire11 Sea-Level Rise12 Hurricanes and Storms12 Coastal Currents

13 Human Drivers of Change in Gulf Coast Ecosystems

15 Chapter Two: Vulnerability of Gulf Coast Ecosystems

15 Gulf Coast Ecosystems15 Upland Ecosystems16 Freshwater Wetlands and Aquatic Ecosystems16 Coastal and Marine Ecosystems

17 Ecosystem Goods and Services18 Agriculture and Forestry19 Fisheries and Wildlife19 Energy and Transportation20 Tourism and Recreation

Table of Contents


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i v

21 Chapter Three: Consequences of Climate Change for Gulf Coast Ecosystems

21 General Cross-Cutting Impacts21 Changes in Water Availability and Flow22 Sea-Level Rise and Coastal Storms22 Changes in Biodiversity, Ecosystem Composition, and Species Invasion

23 Ecosystem-Specific Impacts23 Upland Systems25 Freshwater Systems26 Coastal and Marine Systems

50 Chapter Four: Consequences of a Changing Climate for Ecosystem Goods and Services

50 Water Resources51 Agriculture and Forestry54 Fisheries and Aquaculture55 Coastal Communities56 Public Health

56 Weather-Related Public Health Issues57 Water-Related Public Health Issues

59 Chapter Five: Meeting the Challenges of Climate Change

59 Mitigating the Climate Problem63 Minimizing Human Impacts on the Environment63 Adapting to Climate Change

64 Adaptation in Water Resource Management65 Adaptation in Agriculture and Forestry65 Adaptation in Land and Biodiversity Conservation66 Adaptation in Coastal Communities67 Adaptation to Other Climatic Hazards68 Education about Ecology and Global Warming

69 Appendix: Developing Climate Scenarios

70 References

80 Steering Committee

81 Contributing Authors

Figures

Page 27 Figure 1 The Gulf Coastal Plain

27 Figure 2 Water Control Structure

27 Figure 3 Influences on Gulf Coast Climate

28 Figure 4 Gulf Regional Average Temperature (1895–2000)

28 Figure 5 The Hydrologic Cycle

28 Figure 6 Wildfire

29 Figure 7 Relative Sea-Level Rise Scenarios for the Gulf of Mexico

29 Figure 8 Damage from Hurricane Andrew

29 Figure 9 Gulf Landfalling Hurricanes by Decade

30 Figure 10 Land-Use/Land-Cover Change, St. Petersburg-Tampa Area, Florida (1952–1982)

30 Figure 11a Ecoregions of the Gulf Coast

31 Figure 11b Case Study Areas

31 Figure 12 Pitcher Plant Bog

32 Figure 13 Hardwood Hammock

32 Figure 14 Whooping Cranes

32 Figure 15 Black Mangroves

33 Figure 16 Typical Agricultural Crops

34 Figure 17 Value of Gulf Forests Industries (1996)

34 Figure 18 Fishery Landings (1999)

34 Figure 19 Oil Rig in the Gulf of Mexico

35 Figure 20 Recreational Fishing on Kissimmee River, Florida

35 Figure 21a Open Prairie

35 Figure 21b Invasion by Chinese Tallow Trees

36 Figure 22 The Big Thicket

36 Figure 23 Perry Lake, Alabama

36 Figure 24 Swamp Forest Impacted by Saltwater


v


v i

37 Figure 25 Brown Marsh in Coastal Louisiana

37 Figure 26 Louisiana Coastal Land Loss (1956–1990)

37 Figure 27 Kemp’s Ridley Sea Turtle

38 Figure 28 Isles Dernieres

38 Figure 29a/b Healthy and Unhealthy Corals

38 Figure 30 Pitcher Plant

39 Figure 31 Declines of Regional Water Levels Due to Withdrawal from theFloridan Aquifer (predevelopment until 1980)

39 Figure 32 Aquifer Drawdown and Saltwater Intrusion

40 Figure 33 The Everglades

40 Figure 34 Shrimp Trawler

40 Figure 35 Erosion Damage from Tropical Storm Frances (1998)

41 Figure 36 July Heat Index Change by 2100

41 Figure 37 Windmill

41 Figure 38 Renewable Energy Potential in Texas

42 Figure 39 Improving Irrigation Technology

42 Figure 40 Beach Replenishment

Page 4 Current Scientific Consensus on Climate Change

8 Summary Comparison of Climate Change Scenarios for the Gulf Coast Region

24 At the Biological Crossroads: The Big Thicket and East Texas

43 Controlling a River: The Mississippi River Deltaic Plain

45 Salty Balance: The Laguna Madre and the South Texas Coastal Plain

48 Running Dry: The Panhandle Regional Ecosystem (Alabama-Florida)

52 Drying or Drowning the “River of Grass”?—The South Florida Regional Ecosystem

60 How Confident Can We Be about Climate-Change Impacts on Gulf Coast Ecosystems?

Boxes


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The authors would like to thank the Steering Committee of this project, and especiallyLouis Pitelka, for conceptual guidance and review of the report. Mary Barber (ESA) andPeter Frumhoff (UCS) provided leadership from the two sponsoring organizations.Wealso greatly appreciate the reviews and comments on earlier versions of this manuscriptfrom L.H. Allen, Steve Archer, Virginia Burkett, Don Cahoon, Doug Daigle, JohnDay, Bob Gramling, Jay Grymes, Jay Gulledge, Paul Harcombe, Jim Jones, Paul Keddy,William Landing, Robert Livingston, Irving Mendelssohn, Patrick Mulholland, JohnNielsen-Gammon, Alan Nogee, Gary Powell, Howard Ris, David Sailor, Gary Shaffer,Diana Sturm, Paul Templet, Eugene Turner, Julie Whitbeck, and the late Ron Ritschard.

Steven G. McNulty, Robert C. Abt, Daowei Zhang, and Janaki Alavalapati providedpapers in press or various statistical information. With great skill and sensitivity to scientificaccuracy, Lori Hidinger turned the technical manuscript into an accessible, readable report.Thank you also to John Barras, Art Bennett, Kinard Boone, Mark Bove, Chris Cretini,Wendy J. Danchuk, Thomas Doyle, Eddie Fisher, Scot Friedman, Pam Groce, David Guilbeau,Randall Haddock, Vikki Kourkouliotis, Greg Linscombe, Patrick Lynch, LaShaundaMalone, Antonio Martucci, Barry Meyers-Rice, Thomas C. Michot, Juan Moya, KathleenO’Malley, Shea Penland, Steve Reiter, William K. Rhinehart, Jeremy Roan, Bob Smith,Christine Taylor, Albert E. Theberge, Jr., Vivian Thomas, Bobbie Van Batavia, MelissaWeston, Rosa Wilson, Scott Wilson, Thomas Wilson, and Kim Withers for assistance withfigures. Michelle Hersh helped find and kept track of all the illustrations. Claudia Munozprovided additional assistance at various times through the writing of the report. Specialthanks to Susanne Moser for overall project coordination.

The production of this report was made possible through the generous support ofThe Henry Luce Foundation, Inc., Beldon Fund, and The Nathan Cummings Foundation.Additional foundation support was provided by The John D. and Catherine T. MacArthurFoundation, Oak Foundation, The David and Lucile Packard Foundation, The V. KannRasmussen Foundation, Wallace Global Fund, and The Mark and Catherine WinklerFoundation.

Acknowledgements


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100 years. Summer high temperatures are projectedto rise between 3 and 7°F and winter low temperaturesto warm by as much as 5°F to the east and 10°F tothe west. This would bring a dramatic increase in theJuly heat index along the Gulf Coast and a significantdecrease in winter cold spells, as well as a northernshift in the frost line.

Executive Summary

Projecting climate changes for the Gulf Coast is chal-lenging because of the complex interplay of regionaland global processes that drive the climate here andthe natural variability in air and sea-surface tempera-tures, rainfall, and hurricane activity the region expe-riences. Nevertheless, the two climate scenarios usedin this report both predict warmer temperatures andan increase in the rate of sea-level rise over the next

From Texas to Florida, the Gulf coast region is rich with ecological resources that support

the region’s economic wealth. Over time, human activities from dam construction to shore-

line development have dramatically altered natural landscapes, waterways, and ecological

processes. Pressures from human activities remain the most important agents of ecological

change in the region today. Over the century ahead, land-use changes are likely to increase as rapid

population growth continues. Global climate change, driven by rising levels of carbon dioxide and

other heat-trapping greenhouse gases in the atmosphere, will interact with, and magnify, other human

stresses on Gulf Coast ecosystems and the goods and services they provide. Confronting Climate Change

in the Gulf Coast Region explores the potential risks of climate change to Gulf Coast ecosystems in the

context of pressures from land use. Its purpose is to help the public and policymakers understand the

most likely ecological consequences of climate change in the region over the next 50 to 100 years and

prepare to safeguard the economy, culture, and natural heritage of the Gulf Coast. This summary

highlights key findings.

F

What is thelikely climate future for

the Gulf Coast region?


x

Global sea-level rise will have a disproportionateeffect along the Gulf Coast shoreline because of itsflat topography, regional land subsidence, extensiveshoreline development, and vulnerability to majorstorms. Climate models project sea-level rise alongthe Gulf Coast ranging from over 8 to almost 20 inchesin the next century. Taking regional subsidence intoaccount, the relative sea-level rise over the next 100years could range from 15 inches along most of theGulf Coast to as much as 44 inches along theLouisiana/Mississippi Delta.

Considerable uncertainty remains about whetherthe regional climate will become wetter or drier inthe future. Because future trends in rainfall, runoff,and consequent soil moisture are critical to humanand ecological well-being in the Gulf Coast, we be-lieve the most prudent approach is to assess the poten-

E X E C U T I V E S U M M A R Y

tial impacts of both scenarios. Changes in vitalclimate-related phenomena such as stream flow andwildfire frequency will depend on the balance ofrainfall received and moisture lost to evaporation ina warming climate in conjunction with human inter-vention and management. In major rivers such as theMississippi, water flows will be determined by rain-fall trends in watersheds far upstream from the GulfCoast, as well as by massive human-engineeredflood control structures.

Other vital but difficult to predict climate-drivenchanges include potential shifts in El Niño/La Niñacycles, hurricanes, storms, and coastal ocean currents.Even if storm intensities remain constant, however,disturbance from coastal flooding and erosion willincrease because rising sea levels will generate higherstorm surges even from minor storms.

The ecological impacts of climate change will haveimportant implications for the health and well-beingof human populations as well as other goods and ser-vices that ecosystems provide to society. Global warmingwill have particularly important impacts on the region’swater resources. Gulf Coast ecosystems are linked bythe flow of water from the uplands through fresh-water lakes, rivers, and wetlands to the coastal andmarine systems downstream. Vast wetland areas, espe-cially in the central and eastern parts of the region,require periods of flooding to maintain healthy habi-tats and sustain food webs. While there remains uncer-tainty about how global warming will affect rainfall,stream flow, soil moisture, and overall water availabil-ity, human consumption of water resources is almostcertain to increase as a result of the region’s populationgrowth. If climate change results in reduced runoffand lower groundwater levels for parts of the year, theconsequence could be a shortage of water to satisfyboth ecosystem needs and the growing and competinghuman demands. Besides direct water shortages, therange of impacts could include the following:

• Permanent reductions of freshwater flows in riversfrom both human activities and climate changecould substantially reduce biological productivityin Mobile Bay, Apalachicola Bay, Tampa Bay, andthe lagoons of Texas.

• More frequent or longer lasting droughts andreduced freshwater inflows could increase the in-cidence of extreme salt concentrations in coastalecosystems, resulting in a decline of valuablehabitats such as the mangroves and seagrassesin Florida Bay or South Texas lagoons.

• A drier climate along the Gulf Coast combinedwith such activities as dredging, constructingreservoirs, diverting surface water, and pumpinggroundwater could accelerate local subsidence andsinkhole formation in areas underlain by limestone.

• Changes in soil moisture could shift forest dynam-ics and composition. For instance, natural pineforests can tolerate lower soil moisture than oak-pine and oak-gum forests.

What might thesechanges mean for Gulf Coast

ecosystems and the goodsand services they provide?


x i

• The oxygen-poor (hypoxic) waters in the Gulf ofMexico off Louisiana now extend over as much as8,000 square miles, depending on the amount ofnitrate-laden fresh water discharged by the Missis-sippi River. The complex interaction of nutrientload and amount of runoff make future projectionschallenging. A 20 percent increase in discharge—as some climate models project—could increasethe risk of hypoxia and expand the oxygen-poor“dead zone.”

Sea-level rise will also affect the availability anddistribution of high-quality fresh water because manyGulf Coast aquifers are suscep-tible to saltwater intrusion. Sea-level change and coastal stormsare naturally occurring phe-nomena that help shape coastalecosystems. However, theseepisodic disturbances, coupledwith high rates of land subsi-dence and increasing humanimpacts on the coastal environ-ment, will lead to further de-gradation in coastal ecosystemsand damage to human communities. For example:

• The increasing drawdown of surface water systemsand underground reservoirs could combine withsea-level rise to increase saltwater contaminationof aquifers, particularly near the coast and inlarge urban areas such as Tampa and Houston.

• Drinking water supplies taken from the Missis-sippi River for coastal communities such as NewOrleans will be more frequently threatened bysaltwater intrusion caused by a combination ofsea-level rise, land subsidence, and periodic lowriver flows.

• Wetland loss rates over the next 20 years in coastalLouisiana, due to the combination of sea-levelrise and human alterations, will continue to con-vert land to open water, threatening the region’senormously valuable fisheries, aquaculture andcoastal agriculture, as well as navigation and otherindustries located near the coast. Future wetlandloss rates could increase as sea-level rise acceleratesin the latter part of the 21st century.

• As a result of human development, interactionsof sea-level rise with hurricanes will increasinglydisrupt the normal landward migration of barrierislands and contribute to their erosion.

• Whether or not global warming increases thenumber or intensity of hurricanes, future stormdamages are likely to rise substantially because ofthe increasing amount of development in harm’sway and the aggravating impacts of higher sealevels and degraded coastal ecosystems. Predictionsof future wave and storm surges accompanyingsevere hurricanes (categories 3–5) indicate that

Native plants and animals,

already stressed and greatly

reduced in their ranges,

could be put at further risk

by warmer temperatures

and reduced availability

of fresh water.

significant wave heights(between 3 and 6 feet) couldreach further inland if barrierislands and wetlands are lostas buffers.

• The coastal systems most vul-nerable to sea-level rise includefreshwater marshes and for-ested wetlands in subsidingdelta regions, mangroves inlimestone areas, coastal marsheswith human-altered patterns

of water flow, and areas with extensive humandevelopment.

Climate changes such as warmer temperatures,fewer freezes, and changes in rainfall or storm fre-quency will tend to shift the ranges of plant andanimals species and alter the makeup of biologicalcommunities. With increasing temperature, manyinvasive tropical species are likely to extend theirranges northward. Native plants and animals, alreadystressed and greatly reduced in their ranges, could beput at further risk by warmer temperatures and re-duced availability of fresh water. The range of poten-tial impacts on species and ecosystems include thefollowing:

• Species that are already endangered such as theCape Sable seaside sparrow and Florida panthercould become more vulnerable as their preferredhabitats change or shift with global warming.Current water-management practices and humandevelopment create additional challenges forspecies migration and adaptation.


x i i


• In the Big Thicket area of East Texas, known as“the American Ark,” diverse forest communitiescould be threatened by altered growth rates, changesin fire frequency, and intensified invasions bynonnative species such as Chinese tallow trees.

• Extensive open grassland and forest areas in SouthTexas and South Florida could become more vul-nerable to damaging invasion by Chinese tallowtrees. Those in South Florida could in additionbe threatened by melaleuca and casuarina trees.

• Coastal red mangrove communities might shiftfurther to the north on the Florida and TexasGulf Coast. Along the Louisiana coast, reducedfrost frequency would allow expansion of blackmangrove forests.

• Coral reefs off the South Florida coast alreadyendure summer sea-surface temperatures neartheir maximum tolerance and face heat stress dur-ing episodes of elevated temperature, such as thosethat accompany El Niño events. Rising oceantemperatures will exacerbate that stress.

• In freshwater streams, warmer water temperaturesand a longer growing season could reduce habitatfor cool-water species, particu-larly fish, insects, snails, andshellfish. In very shallow watersystems, higher temperaturescould lead to oxygen-deple-tion and cause potentially mas-sive die-offs of fish and inver-tebrates.

• Invasive species threatenboth freshwater and coastal aquatic ecosystems,affecting native plants, fish, and shellfish andassociated commercial and recreational fisheries.

Climate change will also indirectly affect natural andmanaged landscapes by changing the intensity andfrequency of fires and pest outbreaks. For example:

• Most southern pine plantations are not burnedregularly because of management costs and legalliabilities, despite awareness of the need to reducefuel loads. High fuel loads increase the risk ofwildfire, especially if the climate becomes morefavorable to intensified fire cycles.

• Increases in drought-related fires would havesevere impacts on managed forests and the timber-based economy of the region. Wildfires wouldalso pose substantial risks to nearby humandevelopment.

• In contrast, wildfires are critical for maintaininggrassland communities such as coastal prairies,and woody plants typically invade prairies that arenot mowed or burned. Increased fire frequencyshould help prairie conservation and the main-tenance of grazing lands.

• Warmer average temperatures and milder wintersare likely to result in a higher incidence of damageby agricultural and forestry pests such as theSouthern Pine bark beetle.

Plant growth and productivity could increasewith higher atmospheric concentrations of carbondioxide (CO

2) and modestly warmer temperatures,

as long as rainfall is not reduced. However, increasedplant growth in response to higher CO

2 varies among

species and higher CO2 could drive changes in the

mix of species and interactions within communities.Further, gains in plant productivity due to increased

CO2 could be countered by

other climate-driven changessuch as reduced moistureavailability, higher ultraviolet-Bradiation, limited nutrientavailability, increased waterstress, increases in pests andfires, and air pollution. Forexample:

Climate change will affect

natural and managed

landscapes by changing

the intensity and frequency

of fires and pest outbreaks.

• Certain agricultural crops such as corn, sorghum,and rice could become more productive due tohigher CO

2 concentrations, assuming other stresses

do not counter the fertilizer effects of CO2.

• If the climate of the Gulf Coast turns drier over-all, cotton, soybean, rice, and sorghum productiv-ity could drop without irrigation and citrus produc-tion may shrink moderately in Florida.

Global warming will also increase some healthrisks in the Gulf Coast region. The ability of the healthcare system to reduce these health risks in the face ofclimate change, however, is an important considera-


x i i i

tion in any projections of vulnerability during the21st century.

• The concentration of air pollutants such as ozoneis likely to increase in Gulf Coast cities such asHouston and Galveston. These and other metro-politan areas are already now classified in “severe”noncompliance with federal air quality standards.Ground-level ozone has been shown to aggravaterespiratory illnesses such as asthma, reduce lungfunction, and induce respiratory inflammation.

• Texas is particularly vulnerable to increasedfrequencies of heat waves, which could increasethe number of heat-related deaths and the incidenceof heat-related illnesses. However, longer periodsof extreme heat can cause problems throughoutthe region, especially among the ill or elderlyand people who cannot afford air conditioning.

industry is the biggest economic sector and wheregreenhouse-gas emissions are among the highest inthe nation, it is critical to find ways to reduce green-house-gas emissions without reducing the economicvitality of Gulf states. For example, investment in theregion’s substantial renewable energy resources (e.g.,solar, wind, and biomass) could provide incentives fornew technology development and economic diversifi-cation while reducing air pollutants and greenhousegases.

The second strategy is to reduce human distur-bances and destruction of ecosystems. Employing“best practices” in land and resource use can minimizeecologically harmful side effects while continuing toprovide significant, and often increased, economicbenefits. For example, progressive zoning initiativesthat integrate different land uses over a smaller areacan protect natural resources and open space fromsuburban sprawl. Wise land-use practices can alsohelp manage coastal areas, and best management prac-tices in agriculture and aquaculture can achieve goalssuch as water conservation and reduced farm runoff.

• Gastrointestinal diseases, respiratory diseases,and skin, ear, and eye infections can result fromeating contaminated fish and shellfish and diseasesacquired during the recreational use of coastalwaters. Since temperature, rainfall, and salinity allinfluence the risk of waterborne infectious diseases,this risk may increase with climate change.

• Hotter temperatures, extreme rainfall, and in-creased runoff can increase populations of disease-carrying insects and boost the potential for trans-mission of diseases such as malaria and denguefever. But actual incidences of these diseases willdepend primarily on the responsiveness of the pub-lic health system and on the adequate maintenanceof water-related infrastructure.

To prevent or minimize the negative impacts andprofit from the potential benefits of climate change,citizens and policymakers in the Gulf Coast regioncan and should take action now. Three basic strategies—mitigation, minimization, and adaptation—canreduce the region’s vulnerability to the impacts ofclimate change and yield significant ecological, eco-nomic, and health benefits, even in the absence of majorclimate disruption. We consider them a prudent andresponsible approach to ensuring environmentalstewardship of the region’s invaluable ecologicalresources. Because much of the region is held inprivate land ownership, strategies for dealing withboth climatic and human stresses on ecosystems mustinvolve private landowners as well as governmentalagencies and other sectors of society.

The primary goal of mitigation is to reduce themagnitude of climate stresses on society and ecosys-tems. Reducing greenhouse-gas emissions, for instance,can be seen as a type of “insurance policy” that aimsat directly reducing the risks of global warming.Clearly, in the Gulf Coast region, where the fossil-fuel

How can residents ofthe Gulf Coast region address the

challenge of a shifting climate?


x i v

Finally, Gulf Coast residents, planners, land man-agers, and policymakers can act now to minimize thepotential impacts of global climate change and betterprepare the region to deal with an uncertain future.One of the best ways to deal withuncertainty is to adopt learning-oriented, flexible approaches that in-clude monitoring, periodic review,and adjustment of previous decisionsin light of new information—a strat-egy known as adaptive management.The principal targets for adaptationinclude water resource management,agriculture and forestry, land andbiodiversity conservation, and prep-aration of coastal communities to respond to sea-levelrise and severe coastal storms such as hurricanes.

In addition, much must be done in the Gulf Coastregion to raise awareness and understanding of globalclimate change. This can begin by educating people

of all ages about the cultural and ecological heritageat stake. But it must also involve educating themabout the fundamentals of ecology and climate, andwhat drives them to change. Many Gulf residents’

livelihoods are inextricably linkedto its natural resources, andvisitors from around the worldcome to the Gulf to enjoy andlearn about its ecological heritage.Raising people’s concern andunderstanding of climate changewould help to mobilize publicsupport for climate protection.This report is intended to beginthat process by sketching the

scope of the potential impacts of global warming andstarting a dialogue about the management and policychoices that will help preserve the Gulf Coast region’secological and economic wealth.

Gulf Coast residents,

planners, land managers,

and policymakers can

act now to prepare the

region to deal with an

uncertain future.



1

C H A P T E R

O n e

Climate and People as Driversof Ecosystem Change

Introduction

The natural landscapes, waterways, andecological processes of the Gulf Coasthave been significantly altered by humanactivities ranging from upstream dam

construction to shoreline development. Such human-generated stresses will only increase with continuingrapid population growth in the region. Climate changesdriven by rising levels of carbon dioxide(CO

2) and other heat-trapping green-

house gases in the atmosphere will exac-erbate these direct human influences onGulf Coast ecosystems and the goodsand services they provide. IncreasingCO

2 levels will result in warmer temper-

atures, which in turn will contribute toan accelerated rise in sea level and tochanges in evaporation, precipitation,storms, freshwater runoff, and fireoccurrence.

Climate models predict significant temperatureincreases along the Gulf Coast over the 21st century,with summer highs projected to rise between 3 and7°F and winter low temperatures to warm by as muchas 5°F to the east and 10°F to the west. Over time,these temperature increases will have direct and in-creasing impacts on Gulf Coast ecosystems and thewell-being of the human population, and will alsoinfluence changes in other climate factors. These

include harder-to-predict changes in rainfall, evapo-transpiration, and freshwater runoff. Ecosystems andeconomic activities vary in their vulnerability to eachof these stressors, yet the critical question—and theone subject to the greatest uncertainty—is how thesechanges will interact with one another and withother ongoing human activities.

Sea-level rise, for instance, will havea disproportionate effect along the GulfCoast shoreline because of its flat topo-graphy, the regional sinking (subsidence)of the land, sprawling urban develop-ments along the shoreline, and suscepti-bility to major storms. Sea-level rise willalso affect the availability and distribu-tion of high-quality fresh water becausemany Gulf Coast aquifers (naturalgroundwater reservoirs) are susceptibleto saltwater intrusion. Fresh water is

vital for life, ecological health, and economic activity.It also links upland and coastal ecosystems in theregion. Whether rainfall increases or decreases in thefuture, demand on water resources will grow alongwith the human population, bringing the question ofwater availability for both natural and managed eco-systems front and center for land and water managersin the future. Changes in the geographic and seasonaldistribution of moisture would have significant

Climate models

predict significant

temperature

increases along

the Gulf Coast

over the 21st

century.


2

D R I V E R S O F E C O S Y S T E M C H A N G E

ecological and economic consequences. In naturalecosystems, for instance, the result could be changesin or even loss of habitats and biodiversity; in forestryand agriculture, the consequence could be an in-creased need for irrigation or a need to switch to newcrop or tree species. Any future reductions in mois-ture availability could also increase the frequency andintensity of fires, which would impact both naturalhabitats and human well-being. Other climate-drivenchanges, such as storminess or changes in the frequencyand intensity of El Niño and La Niña events, arelikely to exacerbate the problem of how to managecritical water resources.

This report synthesizes the latest scientific under-standing of potential climate-change impacts on GulfCoast ecosystems. Its purpose is to help the publicand policymakers understand the key ecological con-sequences of climate change and prepare to cope with

F I G U R E 1The Gulf Coastal Plain

See page 27for full-size color image of this figure

the expected impacts on natural ecosystems, economicactivities, and human communities in the Gulf Coastregion over the next 50 to 100 years. We first focuson the key factors (or “drivers”) that determine theregional climate and discuss possible changes in thesedrivers as the Earth warms. Next we explore theunique ecosystems of the Gulf Coast, the benefitsthey provide to humans, and their vulnerability tovarious aspects of climate change. We also considerthe effects of land use and other human pressuresthat, along with climate change, will affect regionalecosystems. We then discuss the likely consequencesof climate change for Gulf Coast ecosystems and foressential ecological goods and services. Finally, wesuggest strategies to minimize and adapt to negativeimpacts and to capitalize on potential benefits fromclimate change.

The Gulf Coastal Plain

The Gulf Coastal Plain arcs 1,550 miles fromthe tip of Florida to the tip of Texas (Figure 1).It is bordered by the foothills of the Appa-

lachian Mountains on the northeast and the southcentral plains on the northwest and extends south

to the Gulf of Mexico,including the shorelineand the coastal watersof the continental shelf.These coastal waters aregreatly impacted bywhat happens on theGulf Coastal Plain andalso by ocean currents.While the MississippiRiver watershed reach-

ing as far north as Canada is not included in the studyarea, runoff from the Mississippi River and its tribu-taries also affects the Gulf Coast region.

The Loop Current bounds the Gulf Coast regionon the ocean side. It flows from the coast of Yucatantowards Louisiana, where it splits into an east andwest flow outside the shelf regions where it reachesthe deeper ocean. The eastward flow of the currentexits the Gulf of Mexico through the Florida Straits

along the Keys and is connected to the Gulf Streamthat flows along the Atlantic coast. At times, freshwater from the Mississippi River becomes mixed withthe Loop Current and can be transported great dis-tances along the Florida shelf and out to the AtlanticGulf Stream passing by the Florida Keys. The impactof the Loop Current on the movement and chemistryof waters on the continental shelves from Mississippito Florida is not clearly understood, but this currentis an important part of the oceanography of theGulf Coast region.

Geologically, the region divides naturally into twoparts, one lying east and the other west of the Missis-sippi Alluvial Plain.1 Climatically, the region is dividedinto three distinct subregions: western, eastern, andcentral. The western subregion covers Texas; the cen-tral subregion reaches from Louisiana across to Missis-sippi and Alabama; and the eastern subregion includesall of Florida from the Panhandle to the Keys.

The region supports a diversity of terrestrial, fresh-water, and coastal ecosystems, despite little variationin terrain. This diversity results from a combinationof upland, alluvial (material deposited by flowingwaters), and shoreline physical landscapes as well asthe convergence of temperate and subtropical climates.


3

Upland ecosystems* include temperate hardwoods,pine flatwoods (or barrens), and scrub forests, as wellas coastal prairies. Freshwater wetlands and aquaticecosystems are also dominant features of the GulfCoast, including swamps, freshwatermarshes, lakes, rivers, and springs. Theshoreline hosts a variety of coastal andnearshore marine ecosystems, includ-ing barrier islands, mangroves and saltmarshes, seagrasses, estuaries and bays,and coral reefs. Few of these eco-systems remain unaltered by humanintervention and many have beenseverely transformed. For example,many of the upland forests have been converted tointensely managed plantations or lost to other uses.

The diverse mosaic of ecosystems that forms theGulf Coast landscape is linked by the flow of water.The downstream flow of streams, rivers, and aquiferslinks the uplands to the shore, and the movement of

tidal waters influences coastal ecosys-tems upstream from the Gulf. Thus,activities at the top of the watershedin the upland systems greatly impactsystems downstream. Over the past50 years, human engineering in theform of levees, dikes, dams, andwater-control structures has dras-tically changed water flow betweenecosystems, and climate change will

further stress these linkages (Figure 2).

Climate Change and Gulf Coast Ecosystems

Increasing levels of CO2 in the atmosphere are

raising temperatures around the globe and spur-ring consequent changes in rainfall, evaporation,

and runoff (see box p.4). Since the Industrial Revo-lution, atmospheric CO

2 levels have increased by

more than 30 percent, reaching concentrations high-er than any observed in the last 420,000 years.2 Theseincreasing levels of CO

2 and other greenhouse gases

have contributed to a rise in global temperatures ofabout 0.7 to 1.4°F since 1900, with the warmesttemperatures occurring in the past 20 years.3 Growingscientific evidence suggests that much of the rise intemperature over the past 50 years is caused by humanactivities. Without major reductions in human emis-sions of these greenhouse gases, scientists project theglobal temperature could increase between 2.5 and10.4°F over the next 100 years.3 Global warming willalso affect precipitation, evaporation, and runofffrom rivers, but changes in the regional and seasonaldistribution of precipitation will vary from one areato another, leaving some areas wetter and others drier.

F I G U R E 2Water Control Structure


* Major subregions and ecosystem types highlighted in bold when first mentioned.

The changes in at-mospheric compositionand global temperaturethat have already beendocumented have gen-erated international con-cern that human acti-vities—such as increasedconsumption of fossilfuels by a growing popu-lation and world econ-omy, as well as defores-tation and other land-use changes—will adversely affect the climate andnatural systems of the Earth. In the United States,government and independent scientists are contributingextensive research to the worldwide effort to betterunderstand these global changes and the implicationsfor regional climate.

The diverse mosaic

of ecosystems that

forms the Gulf Coast

landscape is linked

by the flow of water.


4


Current Scientific Consensus on Climate Change

Addressing the challenges of global climate change requires understanding the natural and

human forces that drive climate, including the many complex interactions and feedbacks

among climate, biosphere, oceans, and ice formations. It also involves projecting the poten-

tial ecological and human impacts of changing regional climates and finding environmentally sound,

technologically feasible, cost-effective, and socially acceptable ways to mitigate and adapt to these

changes.

These daunting challenges have spawned an unprecedented global research effort and also mobilized

policymakers and a wide array of interest groups to speak out on climate change. The range of

motivations, passions, and understanding involved has generated heated political debates marked

by often contradictory claims about climate change.

To provide a scientifically sound basis for global policymaking, the United Nations Environment

Programme and the World Meteorological Organization in 1988 established an international con-

sortium of scientists to review and assess the state of climate change science. This consortium, the

Intergovernmental Panel on Climate Change (IPCC), has published three comprehensive assess-

ments (in 1990, 1996, and 2001) and several more narrowly focused assessments, all based on

extensive reviews of published and peer-reviewed research on all aspects of global warming.

The multiyear assessments are conducted by thousands of climate change experts—natural and

social scientists, economists, and industry and nongovernmental experts on various aspects of global

warming—from more than 100 countries. Each assessment undergoes an extensive multistage process

of scientific peer review and finally a governmental review to generate what is widely recognized as

the most comprehensive and credible evaluation of the state of climate change science. The IPCC

reports provide short nontechnical summaries as well as detailed technical reviews of the issues,

including frank discussions of issues that remain insufficiently understood and require further inves-

tigation. A joint statement by 16 national academies of science4 and a separate statement by the

US National Academy of Sciences5 recognized the IPCC technical assessments as the most objec-

tive and comprehensive overviews of this controversial topic.

The scientific consensus emerging from the IPCC process is that global average temperature has

risen by about 1°F over the past 140 years, and the average could rise by another 2.5 to 10.4°F

by the end of the 21st century if greenhouse-gas emissions are not dramatically reduced. Other

observed changes in the global climate such as increased rainfall and more extreme rainfall events,

along with observed impacts of a changing climate—including thawing of mountain glaciers and

permafrost, earlier breakup of river and lake ice, rising sea levels, longer growing seasons, and plant

and animal range shifts—led the IPCC to conclude that these events create “a collective picture of

a warming world that is already seeing the first signs of a changing climate.”3,6 The panel also

found evidence of a human role in this change, concluding that human emissions of greenhouse

gases “have contributed substantially to the observed warming over the last 50 years.”3


5

Current Regional Climate

Understanding how the climate of the GulfCoast may change in the future and why itis difficult to project regional changes with

certainty requires understanding the factors that createthe current climate. Essentially, the Gulf Coast climateresults from the interplay of global factors, includingsuch far away processes as the El Niño/Southern Oscil-lation (ENSO), and regional factors—specifically,the latitude of the region and the influence of nearbyoceans (Figure 3).

The Gulf Coast enjoys a climate uncharacteristicof its latitude, which typically hosts warm, arid, andsemi-arid climates. The Gulf of Mexico, CaribbeanSea, and Atlantic Ocean substantially influence theregion’s climate. The region enjoys mild winters thanksto Gulf of Mexico waters, which moderate winter tem-peratures. Occasionally, however, these mild wintersare punctuated by cold air masses reaching far southfrom the northern Pacific or the Arctic, bringing lowtemperatures and freezing conditions. This situationarises when the midlatitudinal jet stream that governsthe tracks of storm systems shifts from a more east-west direction into north-south meanders, allowing

cold air and winter storms to penetrate southernregions. Summers in the region tend to be hot andhumid.

The Gulf and the Atlantic are also major sourcesof moisture, resulting in greater rainfall than typicalfor the latitude. A vari-ety of processes bringrainfall to the region,including storm frontsin the winter and spring,and thunderstorms andtropical storms in thesummer and fall. Hur-ricanes and tropicalstorms, which bringmuch-needed moistureand can also cause severeflooding, wind damage,and shoreline erosion, occur regularly in late summerand fall.

Differences in major atmospheric pressure patternsare also important for the Gulf Coast region. Theduration of the wet season in South Florida depends

F I G U R E 3Influences on Gulf Coast Climate


Policymakers and the public are most concerned, of course, with the impacts of this warming on

their parts of the world, since global average changes will not play out uniformly across all regions.

Global climate models remain limited in their ability to project regional climate changes confidently.

However, as the recent US government-sponsored effort to assess the potential consequences of

climate variability and change* suggested, uncertainty in climate projections should not prevent us

from assessing the vulnerability of our valued natural and managed ecosystems to likely scenarios of

change. That major national undertaking tried to assess, using two global climate models, potential

impacts from climate variability and change on particular US regions and sectors in the context of

other environmental and economic changes. It also examined possible adaptation options to deal

with these impacts.7 A Southeast regional assessment formed part of this national effort, focusing

primarily on the potential socioeconomic impacts of global warming.8 This report focuses more on

potential impacts on ecosystems and on the goods and services they provide to society.

* The National Assessment of the Potential Consequences of Climate Variability and Change is the result of a 1990congressional mandate (P.L. 101-606) to undertake periodic scientific assessments of the potential conse-quences of global change on the United States in the context of other pressures on the public, the environ-ment, and the nation’s resources. The synthesis report of this effort was released in November 2000, whilereports from the sectoral and regional component assessments are being released over time (1999–2001).


6

on the relative position and strength of the BermudaHigh pressure system during the summer. During thewinter, the Bermuda High is small and located southand east of Florida. In the spring, it expands and movesnorthward. If the Bermuda High fails to weaken inthe summer over South Florida, then the wet season

rains are delayed, re-sulting in drought.

Weather eventsfar from the regionalso influence the GulfCoast. For example,weather patterns overthe large continentallandmass to the northimpact the region byinfluencing runoff inthe Gulf Coast becausethe region’s rivers, prin-

cipally the Mississippi River, have watersheds that reachfar upstream where winter storms and snowmeltcontrol patterns of runoff.

More remote influences on the climate of theregion include the subtropical and tropical oceancirculation, especially the ENSO cycle. El Niño andLa Niña episodes represent opposite extremes of theENSO cycle. El Niño episodes feature the develop-ment of abnormally warm sea-surface temperaturesacross the eastern tropical Pacific, a reversal of thenormal condition in which the warmest waters are inthe western Pacific northeast of Australia. La Niñaepisodes feature abnormally cold sea-surface temper-atures across the eastern tropical Pacific. The warmertemperatures in the eastern tropical Pacific duringEl Niños are associated with significant shifts in theposition of the jet stream over North America andelsewhere, a phenomenon that brings changes intemperature and rainfall patterns worldwide.

El Niños significantly decrease temperaturesin winter (especially in Florida) and spring. DuringLa Niña, fall and winter seasons in the Gulf Coastare warmer, especially in Louisiana, followed by littlechange in spring, and higher temperatures in

summer. El Niño is also linked to substantially in-creased winter rainfall in the Gulf Coast region. LaNiña events, by contrast, are associated with regionaldrought such as occurred in the central and westernGulf Coast from 1998 to 2000.9 Moreover, ENSOstrongly influences the number of Gulf Coast hurri-canes. During La Niña events, the average numberof hurricanes coming ashore in the Gulf of Mexicois typically higher than during El Niño or non-ENSO years.10

The interaction of these regional climatic featurescreates notable climate gradients that divide the GulfCoast into three climatic subregions (Figure 1). Thewestern subregion is warm-temperate to subtropicaland changes from semi-arid to humid, moving fromwest to east. Precipitation ranges from 7 inches eachyear at the Rio Grande to 47 inches near the Missis-sippi River. The central subregion is humid and warm.Rainfall in this subregion ranges from 40 to 70 inchesper year with little seasonal pattern. The easternsubregion is humid and ranges from warm-temperateto subtropical. A distinct summer wet season andwinter dry season characterize this subregion, andprecipitation totals vary greatly from year to year,ranging from 33 to 90 inches.

Ocean currents also affect the marine and im-mediate coastal areas from the Florida Keys westacross the Gulf of Mexico. A coastal boundary currentcomes up from the Yucatan straits and is deflectedeastward off the Louisiana shelf and then southwardalong the length of the Gulf coast of Florida. Coastalcurrents connect Gulf and Atlantic waters of Floridathrough Florida Bay. The Atlantic coast of Florida isstrongly influenced by the adjacent Gulf Stream. Thesalinity and other water characteristics of the coastalboundary current in the Gulf are influenced by thedischarge patterns of regional rivers but also theMississippi River (and thus discharge from muchof the conterminous United States). Thus humanactivities such as the discharge of pollutants fromagriculture and urban areas into streams are linkedwith the water quality of coastal waters in theGulf of Mexico.

F I G U R E 4Gulf Regional Average Temperature(1895–2000)




7

Climate Variability and Change over the Past Century

The Gulf Coast, like much of the world, hasexperienced substantial climatic variabilityand change over the past 100 years, includ-

ing changes in air and sea-surface temperature, precipi-tation, and extreme events. While air temperatureshave warmed over most of the UnitedStates during the 20th century, airtemperatures cooled slightly on averagein the Southeast. After a warm periodbetween the 1920s and 1949, theregion experienced significant coolinguntil the late 1960s. Since that time,temperatures have again been increas-ing (Figure 4).10 Historical trends insea-surface temperatures from 1900 to1991 suggest a pattern of warming along the coastwith cooling in the offshore waters.11

On average, the Gulf Coast region has seenan increase in rainfall from 1900 until 1992, parti-cularly after 1950.12 Geographically, changes havevaried, with Texas, Alabama, and Mississippi experi-encing small increases in rainfall while the rest of theregion has seen little change or even decreases. As inother regions of the United States, extreme rainfallevents have also increased over the last century.13

These changes in rainfall are reflected in equallyvariable regional runoff patterns. With only a fewexceptions, no evidence has been found of any cleartrends in runoff patterns.14 The only significant trendis a small decrease in flow in the Rio Grande andNueces Rivers in southeast Texas between 1972 and1993.15

The average global sea level has risen 0.04–0.08inches per year (for a total of about 4–8 inches) over

the past century.16 Sea-level rise is more dramaticthan the global average along the Gulf Coast due tolocal subsidence (sinking). Relative sea-level rise ratesrange from 0.08 inches per year along some parts ofthe Texas coast to 0.4 inches per year in the Missis-

sippi River delta plain. Around1930, the average rate of regionalsea-level rise began to increasesignificantly.

Hurricane activity varies fromdecade to decade and historicalrecords show no discernible globaltrends in the number or location oftropical storms.17 After a very activeperiod between 1941 and 1965,

the US East Coast and the Gulf of Mexico experienceda relatively calm period until about 1990. Since then,the region seems to be reentering a period of greaterhurricane activity (unrelated to human-induced climatechange), and the number of intense (category 3, 4,and 5) hurricanes is projected to increase over thenext 25 years.18 While the ENSO cycle and hurricaneactivity show a clear correlation, ENSO is only onesource of climate variability. Further, the impact ofglobal warming on hurricanes is uncertain. Unfortu-nately, the historical record is too short to clearly linkhurricane frequency to climate variability or change.

El Niño events historically occur on average every3 to 5 years, with strong El Niños occurring onceevery 42 years. In recent decades, it appears El Niñosand La Niñas may be occurring more frequently. Therehave been two very strong El Niños in the past 18years and two major La Niñas in the past 11 years(1988 and 1999).

Projections of Future Climate in the Gulf Coast Region

Projecting climate changes for the Gulf Coastregion presents a considerable challenge be-cause of the complex interactions of regional

and global climate processes. This report relies pri-marily on two model-based climate scenarios, the sameones used in the recent US National Assessment (seeappendix).7 For the southeastern United States, the

Hadley climate model generally depicts a warmer,wetter future climate, while the Canadian climatemodel depicts a hot, dry future climate. Both sce-narios agree that the region will see higher temperaturesand an increase in sea level. Considerable uncertaintyremains, however, about the direction and extent ofchanges in rainfall in the upland areas. Because future

Sea-level rise is more

dramatic along the

Gulf Coast than the

global average due

to local subsidence.


8


Summary Comparison of Climate ChangeScenarios for the Gulf Coast Region

CLIMATE CHANGE SCENARIOS

Overall character of projection

Temperature increase• Summer maximum• Winter minimum• July heat index*

Precipitation change• Across region

• Upland regions, excepteastern Texas

• Coastal regions, exceptCentral & upper Texas coastSouth Florida

Soil moisture change• Upland regions, except

Central Texas

• Coastal regions, exceptMississippi River deltaSouth TexasCentral/upper Texas coastNorth Florida

Runoff change• Mississippi watershed• Smaller regional rivers

Average regional sea-level rise(without subsidence)

Canadian Climate CentreModel (CGCM1)

Hot – dry

Increase >7°FIncrease ~5°FIncrease 20–25°F

More intense rainfallevents; more droughts

Significant decreaseModest increase

Less rainfallMore rainfallMore rainfall

Strong decreaseIncrease

DecreaseStrong decreaseIncreaseIncreaseDecrease

IncreaseDecrease

15.6–19.2 inches

Hadley Centre Model(HadCM2)

Warm – moist

Increase >3°FIncrease <3°FIncrease 10–20°F

More intense rainfall events;longer dry periods in betweenrain events

Significant increase

Less rainfallMore rainfallNo change or less rainfall

IncreaseStrong increase

No change or decreaseStrong decreaseStrong decreaseIncreaseIncrease

DecreaseSome increase

8.4 inches

trends in rainfall are critical to human and ecologicalwell-being in the Gulf Coast, we believe the mostprudent approach is to assess the potential outcomesof both drier and wetter conditions and the ability ofnatural and managed systems to cope with change ineither direction. Other difficult to predict climate-

driven shifts in ENSO events, storms, fire (drivenby moisture changes), and coastal ocean currents willalso impact the future climate of the Gulf Coast. Thetable above summarizes the major projections forboth models, while subsequent sections provideadditional detail.

* The July heat index is a measure of human comfort based on combining temperature and humidity.


9

Air and Coastal Ocean TemperaturesAlthough climatologists are quite confident aboutpredictions of an increase in global average tempera-tures, model projections for regions the scale of theGulf Coast are less certain. Both climate models usedin this report, however, project significant increases insurface air temperature in the Gulf Coast by 2100.The Canadian model—which is at the upper end ofcommonly used GCM models in terms of its sensi-tivity to increases in greenhouse gases—projects in-creases in summer maximum temperatures of morethan 7°F and increases in winter minimum tempera-tures approaching 5°F to the east and near 10°F tothe west. The Hadley model, which is less responsiveto increasing greenhouse gases, projects an increase insummer maximum temperatures of more than 3°Ffor much of the region and an increase in winterminimum temperatures of less than 3°F.

These temperature changes will change the fre-quency and magnitude of heat stress and the frequencyand severity of Arctic cold fronts reaching the GulfCoast. The July heat index (a measure of human com-fort based on combining temperature and humidity)for the Gulf Coast increases dramatically in bothclimate models, approaching 20 to 25°F warmer formuch of the region in the Canadian model and 10to 20°F warmer in the Hadley model (see Figure 36).Although the increases in winter minimum tempera-tures appear to be smaller than the increases in sum-mer maximum temperatures in both models, thechanges are likely to be associated with significantdecreases in winter cold spells because of the warm-ing predicted for the central United States. A northernshift in the frost line should occur in the Gulf Coastalong with the increases in winter temperatures.

Precipitation and RunoffGlobally, higher temperatures should lead to higherrainfall because a warmer climate increases the rateof evaporation and speeds up the hydrologic cycle.Regionally, the outcome is considerably more complexto predict, especially in the Gulf region given themany influences on its climate. A number of factors,as discussed above, influence rainfall. These factorsrespond differently to a warming climate and manyof their interactions remain unclear. Global climatemodels also do not simulate smaller scale events such

as hurricanes or thunderstorms, so projections of futurerainfall do not include changes in Gulf precipitationfrom these types of storms, however important.

Despite these challenges, both climate modelsproject a tendency toward lower rainfall for muchof the immediate coastal areas. The exception is asegment of the Texas coast, which both models pro-ject should become more humid. Over South Florida,the two models disagree about the direction ofchange. The similarities in model projections alongmuch of the coastline suggest that the Gulf of Mexicoand the different responses of land and sea surfacesto warming may strongly influence changes incoastal precipitation.

The two models give different projections for up-land regions in the Gulf Coast. The Canadian modelprojects large decreases in precipitation and the Hadleymodel projects large increases; either outcome wouldhave major impacts on upland ecosystems. Othermodels show increases in rainfall during the growingseason and decreases in the dormant season.19 Inter-estingly, while precipitation projections from globalclimate models vary by model and region, manyclimate models—including the Hadley and Canadian—project more frequent brief, strong summer rainfallevents (defined as 2 inches or more over a 24 hourperiod) with longer dry periods between them, inde-pendent of whether average rainfall goes up or down.

The most important factor for terrestrial andaquatic ecosystems is not just rainfall, but the amountof available moisture. Moisture availability depends on

• changes in evaporation

• the type of rainfall event(e.g., slow and steady versus short and intense)

• changes in river runoff

Each is discussed below.As temperatures rise, evaporation should also

increase. On land, this could lead to drier soils unlesssufficient rainfall compensates for the loss of moisture.This drying process creates a feedback where less evap-oration promotes even warmer temperatures, driersoils, less evaporation, and less rainfall. Conversely,where a sufficiently large increase in rainfall accom-panies temperature increase, higher rates of evapora-tion do not lead to drier soils and the cooling effect


1 0

F I G U R E 5The Hydrologic Cycle


of water evaporating from the surface helps moderatethe temperature (Figure 5). This is the prediction ofthe Hadley model, which indicates increases in rain-fall, little or no major soil moisture deficits in the Gulfregion, and less warming than in the Canadian model.

The Canadian modelshows greater warming,allowing the atmosphereto evaporate more mois-ture from the soils thanis available from rain-fall. Thus, the Canadianmodel predicts driersoils and much warmertemperatures in all areasof the Gulf Coastexcept Texas, while theHadley model predictssmaller decreases in soil

moisture in much of the coastal region, and increasesin much of Florida and Texas.

The warming at the surface and the changes inmoisture with height create the energy for intenserainfall events such as severe thunderstorms. Thus,both models create the conditions for more frequentand intense summer rains with longerdry periods in between, especiallyalong the coast where sufficient mois-ture is available. Intense rainfall eventshave already increased over the pastcentury.13 Such rainfall events aresignificant for runoff because highrainfall cannot be absorbed quicklyenough by soils. Moreover, the largeareas of impervious surfaces createdby humans (e.g., roadways, parking,etc.) promote rapid runoff duringthese intense storms.

Finally, the differences in theHadley and Canadian models with regard toprecipitation and evaporation carry through to theirrespective projections for runoff. Again, the balancebetween water lost to evaporation and gained asrainfall will be crucial.19 If significantly increasedevaporation (water lost from soil and water surfaces)and evapotranspiration (water lost through plantsthemselves) do occur without increased rainfall,

freshwater runoff from regional rivers shoulddecrease,20 whereas if rainfall exceeds those losses,runoff should increase. The Canadian model projectsdecreased stream runoff, while the Hadley modelindicates there could be some increases in regionalrunoff in the next century.

Importantly, these predictions of runoff alsodepend on the climate to the north of the Gulf Coastregion. Runoff into the Gulf of Mexico comes fromstreams whose watersheds are relatively small, com-bined with rivers whose watersheds extend far beyondthe Gulf Coast—such as that of the Mississippi River,one of the largest watersheds in the world. Thusprojections for runoff must incorporate the moisturebudget of the entire basin. Several studies suggest thatprecipitation and runoff from the greater MississippiRiver watershed is likely to increase—including a 20-percent increase in precipitation in the Ohio Riverbasin, which controls more than two-thirds of theMississippi River discharge.21 The Canadian modelpredicts much drier soils and a greater tendency to-ward drought in the Mississippi watershed, while theHadley model predicts that much of the region southof North Dakota will experience increased rainfall.The timing of peak runoff may also change if snow

cover decreases and snowmelt occursearlier in the spring. Human fac-tors are also important in runoffprojections, such as the massiveflood-control systems that havebeen engineered along the Missis-sippi River, which can significant-ly alter the relationship betweenrainfall upstream and runoff fardownstream in the Gulf Coast.Altogether, the Gulf region maysee increased discharge from theMississippi River but decreasedrunoff from smaller rivers whose

watersheds are primarily influenced by regionalclimatic changes.

Although specific projections are impossible tomake, changes in precipitation, evapotranspiration,and runoff are likely to be extremely important forthe many ecosystems in this region that rely heavilyon reliable freshwater availability. The discrepanciesin model results suggest that we must consider the


The discrepancies in

model results suggest

that we must consider

the effects of either an

increase or a decrease

in regional rainfall in

the assessment of

ecological impacts.


1 1

effects of either an increase or a decrease in regionalrainfall in the assessment of ecosystem impacts.

El Niño/La NiñaAs described earlier, the ENSO cycle involves large-scale fluctuations of ocean temperatures, rainfall, at-mospheric circulation, and vertical motion of air andair pressure changes across the tropical Pacific.22

These

fluctuations result in climate variations over muchof the globe.

A small increase in overall ocean temperatures inrecent decades may have tipped the system towardmore frequent and intense ENSO events with thepotential for more severe regional droughts and floodsin different parts of the world. Unfortunately, currentclimate models are unable to assess with confidencehow ENSO may change in the future. Some modelssuggest that El Niño and La Niña conditions willbecome more frequent and intense under global warm-ing conditions, while others indicate little change.3,23

Given the impacts of the ENSO cycle on regionalprecipitation patterns and hurricane activity, futurechanges in ENSO should be of great importanceto the Gulf Coast region.

FireThe El Niño/La Niña cycle of 1997–2000 demon-strates how extremes in rainfall create enormous con-sequences for wildfire frequency and intensity. Increasedtime between rain events leads to the drying of plantmaterials that serve as fuel, and this buildup in fuelsgreatly increases the risk of more intense wildfires(Figure 6). Several regional changes that are notclimate related exacerbate this risk:

• increased numbers of dense young pine plantationswith relative thick canopies close to the understory

• many more sources and a greater frequency ofignition, since most fires are human-causedthrough arson or carelessness

• increased litter accumulations where fires havebeen suppressed

Fire is an important factor shaping the communitycomposition of both upland terrestrial and wetlandecosystems. Depending on changes in the balance ofrainfall and evaporative moisture loss from ecosystems,

the risk of wildfire may increase or decrease in thefuture. These climatic changes will interact withspecific management practices to determine the im-portance of fire to Gulf Coast ecosystems in the future.

Sea-Level RiseAs described above, sea-level changes along astretch of coastline resultfrom both global andlocal processes. Globalchanges in sea level haveseveral sources:

• expansion or con-traction of seawaterin response totemperature changes

• the melting orgrowth of snow-packs and glaciers

• changes in the sizeof major ice capson Greenland andAntarctica.

Local rising or sinking ofland along the shorelinealso affect sea level. Sce-narios of sea-level rise alongthe Gulf Coast must ac-count for local effectssuch as faulting, subsidence (sinking), and shoreerosion of the coastline, both natural and human-induced, together with projected changes in globalrates of sea-level rise. Projections of future sea-levelrise typically take the historic local trend in sea leveland add to it the acceleration in historic global sea-level rise projected by climate models. The global proj-ections for sea-level rise range from about 5 to 35inches over the next 100 years.3 For the Gulf Coast,the Hadley model predicts an average sea-level rise of8.4 inches, while the Canadian model predicts 15.6to 19.2 inches over the next 100 years. Projections inthis report are based on a rise of 13 inches over 100years above the current rate, which represents amidrange estimate rather than the most conservativeor worst-case scenario. Taking regional subsidence

F I G U R E 6Wildfire



F I G U R E 7Relative Sea-Level Rise Scenariosfor the Gulf of Mexico


1 2

F I G U R E 8Damage from Hurricane Andrew


F I G U R E 9Gulf Landfalling Hurricanesby Decade


rates into account,24 therelative rise of sea levelin the Mississippi Riverdeltaic plain will rangefrom 21 to 44 inches,whereas the rest of theregion could see a risefrom 15 to 17 inchesover the next 100 years(Figure 7).

Hurricanes andStormsThe Gulf region expe-riences severe tropicaland extratropical storms.Climate change mayaffect both, but themechanisms and inter-actions of many influ-ential factors are stillincompletely under-stood. For example,predictions of futurechanges in hurricanefrequency and intensityassociated with global

warming remain uncertain. The frequency of futurehurricanes depends in part on whether global warm-ing intensifies El Niño and La Niña conditions. Asmentioned before, hurricane activity is linked withENSO conditions, with El Niño events decreasingthe probability that hurricanes will make landfall inthe southeastern United States and La Niña eventsincreasing it.10,25

Also important to Gulf Coast systems is thepossibility that warmer tropical and extratropical sea-surface temperatures will increase the potential formore intense hurricanes with greater wind speed andprecipitation.26 The IPCC concluded in its latest assess-ment that the intensity of peak wind speeds and thetotal and peak precipitation associated with tropical

cyclones are likely to increase. Any changes in hurri-cane frequency or track, however, remain unknown.3

Even if storm intensities remain constant,however, the disturbance from coastal flooding anderosion will increase as sea level rises (Figures 8 and 9).In other words, even coastal storms that are consid-ered relatively minor today will exert the floodingimpact of major storms in the future simply becausehigher sea levels will bring higher storm surges.

Passing storm fronts also strongly influence coast-al sea levels; they can raise water levels more than3 feet in the Mississippi River delta (compared witha tidal amplitude of 1 foot). However, changes in thefrequency or tracks of frontal systems are also stilluncertain. For example, ENSO—with its influenceon the position of the jet stream and thus the abilityof storm systems to penetrate far south—willinfluence local storm and flooding patterns.

Coastal CurrentsReductions in freshwater delivery to the coast fromriver runoff would cause changes in the coastal oceancirculation and a reduction in the westward-flowingcoastal current along the Louisiana-Texas coast. Equal-ly important would be changes in the eastward-flow-ing arm of the coastal currents that flow from theMississippi River delta toward the MississippiSound.

Where runoff increases locally, we can expectincreased stratification of fresh and salt water alongthe coast, with lighter fresh water on top and theheavier salt water below. This stratification, especiallyover warm, shallow coastal waters, increases the like-lihood of hypoxia (oxygen-poor waters) and mayaffect the Loop Current.27 Where runoff decreases,diminished stratification of fresh and salt water willalso make wind mixing more effective and reduce thesea-surface temperature of the coastal ocean, thusmaking hypoxia less likely there. Areas where hypoxiaoccurs are sometimes called “dead zones,” as livingorganisms dependent on oxygen either die or moveelsewhere to oxygen-richer waters.



1 3

Human Drivers of Change in Gulf Coast Ecosystems

In addition to the climate drivers discussed above,other growing human pressures are causing sig-nificant changes to Gulf Coast ecosystems. While

discussed in less detail below, these human impactson the environment are currently the most importantdrivers of ecosystem change. They include populationgrowth, engineering of natural water flows, and in-terference with coastal processes, habitat fragmenta-tion, and water and air pollution (Figure 10). Humanactivities have already impacted the ecosystems of theGulf Coast so heavily that few remain unaltered.

The population of the five Gulf Coast statesincreased over the past decade to more than 48.5million in 2000. This 19.2 percent increase is higherthan the average population increase for the UnitedStates as a whole during the past decade and primarilyreflects significant increases in Florida and Texas. Pop-ulation growth in coastal areas of the nation has beenmore rapid than elsewhere, with more than half theUS population now living within 80 miles of coastalland.28 Currently, Gulf Coast states host 18.3 percentof the total US population that lives near the coast.Over the next 25 years, the total population in GulfCoast states living near the coast will increase by44 percent compared with an average of 23 percentfor the total United States.29 Nearly 80 percent of theregion’s coastal residents live in Florida, where thepopulation boomed from less than 3 million in 1950to almost 16 million in 2000.29 Population growthsignificantly affects the distribution of surface andgroundwater, both of which are critical for GulfCoast ecosystems.

To meet the demands of a growing populationfor flood protection, freshwater supply, wastewaterprocessing, irrigation, water for industrial purposes,and other needs, major physical features of the GulfCoast have been engineered over the past century(Figure 2).

Human alterations to water flows through up-stream dams and impoundments, channelization,dredge and spoil operations, and diking affect boththe quantity and quality of discharge as well as thesediment feeding into coastal waters. These alterationsaffect ecological services such as estuarine produc-tivity, which depend on freshwater discharge from

rivers, wetlands in the alluvial basins, and sandsupplies from barrier islands.30

The sandy beaches of Gulf Coast barrierislands—the long, narrow islands with sandy beachesthat parallel shorelines—make them highly valuableas resort and tourist destinations. Yet constructionof buildings, roads, bulk-heads, seawalls, and anyother type of shore har-dening disrupts thenatural movement ofsediment. In response,the beach face and near-shore erode, threateningbuildings and narrowingthe beach, while the“ribbon of sand” doesnot grow landward. Even-tually, this process threat-ens not only human habi-tation but also the exis-tence of the barrier islandsand the habitats and pro-tection to shorelinesthey provide.

Increased urbanization, industrialization, andagricultural land use also have significantly alteredthe natural landscapes of the central Gulf Coast. Theyhave tended to reduce both water quantity and qual-ity in the watersheds. The pressures on freshwaterresources are particularly evident during water defi-cits, such as the summer drought of 2000, when bothcities and farming areas suffered from salinizationand reduced availability of critical water resources.Airborne contaminants and excess nutrients gener-ated by human activities also impact the quality offreshwater resources when they are deposited onbodies of water.

Irrigation for agriculture is becoming increasinglyimportant throughout the Gulf Coast to buffer theeconomic losses associated with extreme droughts.Four of the five states in this region are ranked amongthe top 20 US states in terms of acreage of land underirrigation.31 Fresh water is also diverted in this regionfor thermoelectric power production, industrial uses

F I G U R E 10Land-Use/Land-Cover Change,St. Petersburg-Tampa Area,Florida (1952–1982)



1 4

such as the petrochemical industry, and householduses. Removing fresh water for human uses withoutregard for the needs of river and coastal habitats typi-cally results in degradation of these aquatic ecosystems.

Human settlements and activities in the regionhave also greatly reduced orfragmented natural habitats.For example, increased develop-ment along the coastline hasreduced wetland and mangrovehabitat. In the upland areas,agriculture and timber planta-tions have replaced naturalprairies and forests.

Humans are also both direct-ly and indirectly responsible forthe movement and establish-ment of nonnative invasivespecies that further degradenatural habitats and threatennative plant and animal speciesas well as human enterprises.Increasing human population and consumptionof resources, which have led to increasing trade in theregion and beyond, along with increases in humanmobility, have resulted in unprecedented levels ofintroduction of nonnative species. When these intro-

duced species become permanent residents and dra-matically increase, they can produce severe, sometimesirreversible, impacts on agriculture, recreation, andnatural resources as well as threatening biodiversity,habitat quality, and ecosystem functioning.32

In summary, while humanalterations of the landscapehave enabled the populationof the Gulf Coast region togrow and thrive, they havealso caused widespread degra-dation of natural ecosystems,species losses and invasions,structural changes in eco-systems, and changes in theinteractions within plantand animal communities.Cumulatively, these humanpressures on Gulf Coast waterresources, ecosystems, bio-diversity, and habitats are themost important drivers of

ecosystem change in the region today. As a result,many ecosystems are vulnerable to any additionalstressors, such as those that will arise from a rapidlychanging climate.


While human alterations of

the landscape have enabled

the population of the Gulf

Coast region to grow and

thrive, they have also caused

widespread degradation of

natural ecosystems. As a result,

many ecosystems are vulnerable

to additional stressors such as

a rapidly changing climate.


1 5

C H A P T E R

T w o

Gulf Coast Ecosystems

The flat Gulf Coast landscape formed as aresult of changes in sea level over the past125 million years. Rising and falling sealevels, along with sediment-carrying

water flowing in rivers, repeatedly eroded and builtup land. The resulting combination of uplands, allu-vial plains built from waterborne sediments, shorelinelandforms, and the most extensive wetland areas inthe United States hosts a diversity of ecosystems thatremain vitally linked by the flow of water (Figures 11a& 11b). Distributed across this landscape is a varietyof natural as well as managed ecosystems, includingforestry, agriculture, and aquaculture operations.Below we describe the ecosystems of the Gulf Coast,proceeding from the upland toward the ocean, thendiscuss the many valuable goods and services that theregion’s human communities obtain from them.

Upland EcosystemsNearly 70 million acres of coastal plain forests oncestretched from Virginia to Florida to eastern Texas.Seven pine species are indigenous to this region, butlongleaf pine dominated most of the historic forests.Unfortunately, only a few natural longleaf pine forestsstill exist due to logging, development, and humansuppression of the natural fire cycle upon which theydepend. The lower coastal plain was once a continu-ous moist pine barren known as Gulf Coast pitcher

F I G U R E 1 1 a & 1 1 bEcoregions of the Gulf Coast

See pages 30 & 31for full-size color image of these figures

plant bogs,33 but only 3 percent of this habitat remainstoday34 (Figure 12). Managed forests of shortleaf andloblolly pines now dominate the more upland andnorthern parts of the coastal plain, while plantationsof slash pine dominate the lowland and moresouthern areas.

The drier western end of the Gulf Coast regiononce harbored extensive grasslands known as coastalplain prairies. Many of the same prairie speciesfound in the tallgrassprairie of the centralUnited States character-ize coastal plain prairies,such as Little Bluestem,Indian grass, tall drop-seed, Texas cupgrass,goldenrod and blazingstars.35 Less than 1 per-cent of the originalprairie remains.36 Therest has been convertedto cropland, ranches,and urban areas. Coastalprairie is the sole habitatof the federally endan-gered Attwater’s prairiechicken and serves asimportant habitat for

Vulnerability ofGulf Coast Ecosystems

Case Study Areas


1 6

several other critically imperiled birds, such as thewhooping crane (Figure 14).37

Freshwater Wetlands and Aquatic EcosystemsFreshwater systems of the Gulf Coast include rivers,streams, lakes, swamps, marshes, and aquifers. Severalriver systems flow across the region with watershedsthat vary in size from a few square miles around smallstreams and springs in Florida to the vast watershed

of the MississippiRiver, which drainsabout 40 percent ofthe continental UnitedStates and two prov-inces of Canada. Lakesin the region wereformed either by majorriver systems or bydissolved limestone rockin Florida. A uniquefeature of Florida lakesis that many of theirwatersheds extend under-ground in the lime-stone terrain, connect-ing lake water “seeps”with deep aquifers.38

Seven aquifer (ground-water) systems withinthe Gulf Coast regionsupply much of thefresh water for agricul-ture, domestic needs,and industrial use.

The distributionof water in the rivers,lakes, and shallowaquifers of the GulfCoast once supportedthe largest wetlandregion in the UnitedStates, including for-ested wetlands andfreshwater marshes.

Today, these wetlands have been reduced to less thanhalf of their historic extent, yet they remain a notice-able and ecologically important part of the landscape.

Forested wetlands, swamps, and other wetlands covera vast area and are unique in the biosphere, as theyare adapted to tolerate the harsh conditions of satu-rated soils for long periods of time.39 Freshwater marshes,such as the Everglades in South Florida and themarshes of the Louisiana deltas, are another impor-tant component of the wetland landscape of the GulfCoast (Figure 13). Marshes are wetlands dominatedby herbaceous plants rooted in saturated soils withfew trees and shrubs.40 Changes either in drainagepatterns or in the sources, quantity, and quality offresh water can restrict the development or survivalof wetlands. Several rare and endangered bird specieslive or nest in freshwater marshes, including the woodstork, Everglades snail kite, Cape Sable seasidesparrow, and Mississippi sandhill crane.

Coastal and Marine EcosystemsThe 1,550 miles of shoreline that extend fromFlorida Bay to Laguna Madre in Texas include 37estuarine ecosystems that vary in geology, climate,and water salinity (saltiness). These represent themost diverse estuarine habitats in North America.

Gulf Coast estuaries, lagoons, and bays are waterbodies where seawater from the Gulf of Mexico mixeswith freshwater runoff from the land. An importantaspect of estuarine health is how long fresh waterremains in these systems. Seasonal variations in fresh-water runoff into coastal waters can cause rapid changesin salinity, nutrient availability, and sediment supply.These physical and chemical characteristics of estu-aries control the susceptibility of these systems toeutrophication (nutrient overenrichment). A varietyof flora and fauna, such as seagrasses and shellfish,inhabit the submerged regions of the estuaries.

The Gulf Coast also includes extensive commu-nities of coastal marsh vegetation in intertidal zones(areas influenced by the changing floods and ebbsof tide). Coastal marshes are the exclusive winteringground of the federally endangered whooping crane,and coastal Louisiana provides wintering habitat for70 percent of the migratory waterfowl using thecentral and Mississippi flyways.41

Mangrove communities are unique forestedwetlands that dominate the intertidal zone of tropicaland subtropical coastal landscapes. Four mangrovespecies are commonly found in the region: red

E C O S Y S T E M V U L N E R A B I L I T Y


F I G U R E 1 2Pitcher Plant Bog


F I G U R E 1 3Hardwood Hammock


1 7

mangrove, black mangrove, white mangrove, and but-ton bush.42 Mangroves provide habitat for a diverseset of plants and animals, including oysters, juvenilefish and shrimp, and sponges in reef environments(Figure 15). They also provide important rookeriesfor bird colonies, particularly along the shores of theEverglades National Park.

Long, narrow islands with sandy beaches thatparallel shorelines all along the Gulf of Mexico fromTexas to southwest Florida are known as barrier islands.In the central region of the Gulf Coast, they typicallyformed when deltas eroded and sand deposits werereworked to form sandy islands and beaches.*43 Bar-rier islands can migrate landward as sea level rises andthus are one of the most dynamic ecosystems of theregion. Beach vegetation along the Gulf Coast is richwith a broad array of plants, such as sea oats, bitterpanicum, beach morning glory, as well as small blackmangroves in some of the back barrier marshes.44

Shrubs and trees on stable barrier islands provide cri-tical stopover habitat for migrating birds.45 Sea turtlesdepend on beaches for nesting sites. These beaches

The ecosystems of the Gulf Coast contributesignificantly to the region’s economy andculture, producing resources, benefits, and

amenities for human use and enjoyment. These eco-logical goods and life-support services are diverse andoften taken for granted, but to the extent we canmeasure them, they add significantly to our regionaland national wealth. Their esti-mated direct value, as detailedbelow, exceeds $160 billion per year.Forestry and timber processing,agriculture, commercial fishing,recreation, energy production andpetrochemical industries, as well aslight manufacturing, characterizethe regional economies along theGulf Coast. Many of these enter-prises depend heavily on the region’secological resources.

F I G U R E 1 4Whooping Crane


F I G U R E 1 5Black Mangroves


are also important nest-ing grounds for severalspecies of birds, includ-ing the federally listed,but slowly returning,brown pelican, and serveas wintering grounds forseveral waterfowl.

Coral reefs are di-verse communities ofmarine plants and ani-mals that colonize shal-low subtropical waters.46

The coral reefs of SouthFlorida historically couldcope with changes in sealevel, and those livingreefs that exist todayoccur in areas wherestressors such as sedi-ment turbidity and eutro-phication are low.

Ecosystem Goods and ServicesEstuaries and coastal

marshes serve as nur-series to several com-mercially important fishand shellfish species such as penaeid shrimp, crabs,and various finfish during critical stages of their lifecycles. Coastal marshes also provide water purifica-

tion, sediment stabilization, andstorm protection services. Man-groves, for example, have uniqueroot systems that trap sediment andprotect coastal shorelines from ero-sion and storm damage. Coral reefsprovide numerous benefits to fish-eries, recreation, tourism, and coast-al protection wherever they exist.Similarly, barrier islands and beachesbuffer coastal wetlands and uplandecosystems from the damaging

* In other areas, barrier islands are formed by the emergence of underwater shoals, or by the drowning and isolation of mainlanddune lines during a rising sea level.

The region’s ecological

goods and services

are diverse and often

taken for granted, but

they add significantly

to our regional and

national wealth.


1 8

effects of tropical storms. With their extensive beaches,they are the foundation for much of the Gulf Coastregion’s coastal tourism industry.47 Upland forestsensure freshwater flow and purify water as it movesthrough them.

Agriculture and ForestryThe flat terrain and mostly mild and humid climatemake this region well suited for agriculture and for-estry.48 The five Gulf Coast states produced 14 percentof the total value of agriculture in the United Statesin 1997, at a value of $28 billion.49 About 44 percent

of the agricultural valuein the region derivesfrom the region’s majorcrops, including cotton,hay, soybeans, citrus,and rice, while livestockand poultry producethe remainder (Figure16). Cattle and calfproduction is signi-ficant in Florida, andTexas cattle productionis valued at $7.3 billion.Texas and Mississippiare ranked first andfourth nationally incotton production, witha total value of $2 bil-lion. Alabama and Mis-sissippi are the fourthand fifth largest pro-ducers of poultry, ata value of $3.2 billion.Citrus crops in Floridaare a $1.5 billion indus-try and represented

60 percent of the total US value produced fromcitrus in 1997.50

Agriculture throughout the coastal region dependson the availability of fresh water, not only to supportproduction, but also to prevent the encroachment ofsaltwater into shallow groundwater wells in coastalcounties. Much agriculture in the Gulf Coast region

is rainfed, nonirrigated agriculture. However, in EastTexas and Louisiana, rice depends on irrigation, as dosoybeans and cotton there and elsewhere in the centralGulf, as well as citrus and sugarcane in Florida, if toa lesser extent.51 The extensive irrigation system inSouth Florida and in the more arid western coastalplain of Texas allows intensive production of citrusfruits, vegetables, sugarcane, grain sorghums, cotton,and beef. In regions where little irrigation is possible,rainfall determines yields from crops of cotton andgrain sorghums, making them vulnerable to the riskof crop failure in years of insufficient rainfall.

Southern forestry is becoming increasingly im-portant in the context of national timber production.Over the past decade, decreases in timber harvestingon public lands in the West have led to increasingharvests from the privately owned forests in the south-eastern United States.52 These plantations are grownfor both timber and pulp fiber on cutting and re-planting cycles of 20 to 40 years. In 1996, southeast-ern timber production was valued at $98.8 billion,or 37 percent of the entire US timber productionvalue. The five Gulf states contributed almost half($46.4 billion or 47 percent) of this southeasternproduction.*53 Alabama and Texas are the most im-portant states for forest products, together producingabout 10 percent of the national inventory and morethan half of Gulf Coast production. Alabama’sforestry is valued at about $12.9 billion, Texas’s at$12.3 billion, Louisiana’s and Mississippi’s at $7.1billion each, and Florida’s at $7.0 billion (Figure 17).Because the timber and wood products industry issuch a large part of the regional economy, under-standing how climate change may impact the health,composition, and productivity of forests in theregion is vitally important.

Most of the forest area in the region is privatelyowned, with about 40 percent owned and managedby forest industries. The many nonindustrial privateforests rarely have formal management plans. Theseprivate forests are increasingly being divided amongmore and more owners, and differences in manage-ment from one parcel to the next are disrupting thelarge-scale ecosystem processes found in large,unfragmented forest tracts.


F I G U R E 1 6Typical Agricultural Crops


F I G U R E 1 7Value of Gulf Forest Industries(1996) (in $billion)

* The southeast region includes 13 states.



1 9

Fisheries and WildlifeThe rich waters of the Gulf Coast states yielded 1.95billion pounds of fish and shellfish in 1999, worthmore than $758 million dockside*54 (Figure 17). The1999 harvest represents 21 percent by weight and 22percent by value of the national commercial fisheryharvest. The Gulf Coast has the largest and mostvaluable shrimp fishery in the United States, and in1999 the region produced 78 percent of the nationaltotal shrimp landings.54

The large acreage of coastal

marshes along the Gulf Coast is thought to be thereason for this bountiful harvest of shrimp.55 Thisregion also contributed 58 percent of the nationaloyster production.54,56 Recent figures on commerciallandings indicate that Louisiana is second only toAlaska in domestic fisheries in the United States.Approximately 95 percent of Louisiana’s harvestedfish and shellfish depend on fragile coastal wetlandsas nurseries and essential habitat. Reductions inharvest of natural fisheries in other US regions haveplaced increased demand on fisheries in the GulfCoast region.

Aquaculture is also an important industry in theGulf Coast, a fact made possible by the mild tempera-tures and availability of water. Mississippi has the mostvaluable aquaculture industry in the United States, at$290 million annually, followed by Florida (third),Alabama (fifth), Louisiana (seventh) and Texas (eleventh),for a total annual revenue of about $500 million.57

This region produced 51 percent of the national valuein aquaculture products in 1998, including food fish,baitfish, ornamental fish, shrimp, crawfish, and oysters.

Alluvial and shoreline ecosystems of the GulfCoast are important regions for supporting wetlandwildlife. For example, the region provides habitatfor 5 million wintering waterfowl.About $50 million is spent annuallyon hunting waterfowl along theMississippi River fly-way. Louisi-ana wetlands support direct in-come from wildlife resources,including the largest fur harvest inthe United States (41 percent oftotal). More than 25,000 wildalligators are harvested yearly from

wetlands, with hides and meat from both wild andfarm harvests exceeding $11.5 million in 1992.58

Energy and TransportationThe economy of the Gulf Coast is perhaps bestknown for its rich energy resources. Approximately95 percent of the oil and 98 percent of the naturalgas produced on the fed-eral outer continentalshelf comes from the cen-tral and western regions ofthe Gulf of Mexico. Thecoastal zone and outercontinental shelf of theGulf of Mexico producenatural gas valued at $7.4billion annually, and pe-troleum refining generatesannual revenues of $30billion for the domesticmarket nationwide. The Gulf Coast states provided49 percent of the total US crude oil in 1998 by pro-ducing 1.1 billion barrels in that year (Figure 19).59

The waterways of the Gulf Coast, especially theintracoastal waterway and the region’s major rivers,form one of the most important transportation sys-tems in the United States and include several inter-national seaports. Eleven of the top twenty US portsby cargo volume in 1999 are found in the Gulf Coastregion, including New Orleans, Houston, Mobile,and Tampa. Port facilities located between the mouthof the Mississippi River and Baton Rouge handle over230 million tons of cargo annually, valued at morethan $30 billion. The cargoes managed by these portfacilities make up approximately 25 percent of the

nation’s total exported commo-dities.60 This commercial-industrial infrastructure along thecoast is significant to national andinternational commerce and re-quires intact landscape elementsand ecosystems such as barrierislands and wetlands for protec-tion from coastal storms.


F I G U R E 1 8Fishery Landings (1999)

The waterways and

infrastructure along the

Gulf Coast are significant

to national and inter-

national commerce and

are protected by barrier

islands and wetlands.

* Wholesale value off the vessels.


2 0


F I G U R E 1 9Oil Rig in the Gulf of Mexico


F I G U R E 2 0Recreational Fishing on KissimmeeRiver, Florida

Tourism and RecreationThe Gulf Coast region also supports a largerecreation and tourism industry (Figure 20). Forexample, the 6,777 total fishable acres of fresh waterin the five-state region (22 percent of the total in theUnited States) support an attractive and lucrativefreshwater sport and recreational fishery. The tourismvalue of this fishery approaches that of the commer-cial catch. Coastal ecosystems support more thanone-third of the national marine recreational fishing,hosting 4.8 million anglers in 1995 who caught anestimated 42 million fish.62

Tourism in the Gulf Coast states contributes anestimated $20 billion to the economy each year, muchof which is beach and outdoor-oriented. Evidence ofincreased investment in a growing ecotourism indus-try across the region includes new state parks andwildlife sanctuaries, businesses, and conservationgroups.63

This diverse environment, with the wealth ofgoods and services it provides to Gulf residents, isvulnerable in many ways both to changes in climateand to the growing pressures from human develop-ment and activities. The interaction of all thesedrivers of change will determine the future ofGulf Coast ecosystems.



2 1

Natural ecosystems must constantlyadjust to natural variations in climate.Generally they are more sensitive toclimate extremes than to changes in

average conditions. In addition to natural and human-induced changes in climate, other human disturbancesincreasingly buffet natural systems. Because both hu-man and climate-related disturbances can have impor-tant impacts on the goods and services that

C H A P T E R

T h r e e

Consequences of Climate Changefor Gulf Coast Ecosystems

ecosystems provide, it is important to evaluate thesignificance of ecosystem changes driven by humanactivities relative to those driven by climate change.Not every driver of change is equally certain orequally significant for ecosystems. Here we high-light those potential consequences of climate changethat will require special consideration in the man-agement of both ecological and economic systemsin the future.

Changes in Water Availability and FlowGulf Coast ecosystems are linked by the flow of waterfrom the uplands through freshwater lakes, rivers,and wetlands to the coastal and marine systems down-stream. Especially in the central and eastern parts ofthe region, vast wetland areasrequire some duration of floodingto maintain healthy habitats andsustain food webs.64 The prospectof changes in rainfall, stream flow,and overall water availability makesthe Gulf Coast particularly vulner-able to climate change. In addi-tion, engineering projects and grow-ing water demand will exacerbate

climate-driven changes in water flow. Besides thedirect impact on water flow, changes in moisture avail-ability will influence the intensity and frequency offires, which will affect forest, mangrove, and prairie

ecosystems.64

In general, Gulf Coastestuaries should benefit fromany degree of increased rainfall,but even a slight decrease infresh water could cause severechanges in habitat and waterquality. These impacts are likelyto be greatest in areas that havemassive engineered water-

General Cross-Cutting Impacts

The prospect of changes

in rainfall, stream flow, and

overall water availability

makes the Gulf Coast

particularly vulnerable

to climate change.


2 2

C L I M A T E C H A N G E C O N S E Q U E N C E S

management systems,* or in coastal areas that arealready water-scarce. Permanent reductions of fresh-water flows due to combined effects of human activi-ties and climate changes could lead to major reduc-tions of biological productivity in bay systems such as

the lagoons of Texas, orin Mobile Bay, Apala-chicola Bay, and TampaBay (see Figure 5).

Sea-Level Rise andCoastal StormsSea-level change andcoastal storms are nat-urally occurring phe-nomena that help shapecoastal ecosystems.However, increased fre-quency of storms com-bined with higher sealevels can increase thesalinity (salt concentra-tions) in coastal ecosys-tems and freshwateraquifers and cause othernegative impacts. Thesystems most vulnerableto sea-level rise includefreshwater marshes andforested wetlands insubsiding delta regions,mangroves in limestone

areas, coastal marshes with human-altered water flowpatterns, and areas with extensive coastal develop-ment. Because of high rates of land subsidence in thecentral subregion, for instance, ecosystems in thatarea face greater than average stress from rapid sea-level rise and coastal storms. The greatest economicimpacts can be expected in the most highlydeveloped and populated areas.

Even if storms remain at current intensities, dam-age to ecosystems could increase because a growinghuman population inhibits natural recovery. If storms

and hurricanes occur more frequently, there could beincreased local damage to mangrove forests, tempo-rary increases in sediments and organic material dis-charged to coastal waters, increased physical damageto coral reefs, and increased physical disturbance toupland pine forests. Although the native forests ofthe region are adapted to hurricanes, replacementof natural forests with plantation monocultures, andother habitat alterations by humans have put manyecosystem types at greater risk.

Changes in Biodiversity, EcosystemComposition, and Species InvasionClimate changes such as warmer temperatures, fewerfreezes, and changes in rainfall will tend to shift theranges of plant and animal species and thus alter themakeup of biological communities in the future.

Increased air temperatures may cause a migrationof species from subtropical ecosystems typical of theeastern and western subregions towards what is nowthe warm temperate central subregion. Warmer watertemperatures could result in the expansion of tropicalwetlands and tropical and subtropical species north-wards, although any such shifts of species’ rangesmay be impeded by human developments.

Changes in the frequency of freezing weather willalter ecosystems in the eastern and western sections ofthe Gulf region. Vegetation along the shoreline of theGulf Coast is strongly influenced by the frequencyof frost. With global warming likely to reduce frostfrequency, tropical communities such as mangrovesmay shift further north over time, and the specificspecies currently found at any given site are likely tochange. For example, coastal red mangrove commu-nities might shift further to the north on the Floridaand Texas Gulf Coast. Along the Louisiana coast,reduced frost frequency would allow greater expan-sion of black mangrove forests (see Figure 15).

With increasing air and water temperatures,many exotic (non-native) tropical species are likelyto extend their ranges northward. This would allowsome nonnative invasive species to gain a greaterfoothold. Extensive open areas such as those in

F I G U R E 2 1 aOpen Prairie


F I G U R E 2 1 bInvasion by Chinese Tallow Trees


* While freshwater delivery to estuaries can be controlled through canal systems, they do not allow water storage in floodplainwetlands and freshwater release during dry periods. Thus, brown marsh and freshwater/saltwater stratification are likelyproblems during droughts in estuaries with upstream freshwater management systems.


2 3

South Texas or South Florida are especially vulner-able. Invasion by exotic plant species is also one ofthe most serious threats to forests and grasslands inthe region. For example, Chinese tallow tree is alreadya major component of forest understories, and climatechange is likely to enhance its establishment anddominance (Figure 21).65 Melaleuca and casuarina(Australian pine)—two other invasive exotic specieswidely regarded as pests in southernFlorida—have high potential to movenorthward if temperatures permit.Increased frequency of hurricanes orwildfires could accelerate the invasionof these species, which might gainground as ecosystems recover from suchdisturbances.

Although exotic species from tropicalareas have already invaded the region, especiallySouth Florida, climate change might, directly orindirectly (such as through altered fire frequency),favor these highly opportunistic species to thedisadvantage of native plants and animals.66 While amajority of the 119 native fish species of Florida aretemperate species existing near the southern limit oftheir distribution, almost all of the 28 exotic speciesestablished in recent years are subtropical or tropical.67

Warmer winter minimum temperatures along withfewer frosts will most likely produce a northwardshift in the range of subtropical exotics. The highconnectivity of lakes, streams, and wetlands in Florida,through both natural waterways and human-madechannels and other connections, further enhancesthe potential for the rapid spread of invasive subtrop-ical aquatic species northwards as the climate warms.One current example is the ongoing northward

spread of the exotic walking catfish, which is replac-ing less competitive native species.68

Populations of native plants and animals—alreadystressed and greatly reduced in their ranges—couldexperience further stress from warmer temperatures,putting those species at increased risk for loss of localpopulations or even complete extinction.69 Examplesinclude the endangered Cape Sable seaside sparrow

and Florida panther. Moreover, somespecies may not be able to migrate inresponse to changing climate, if theyexist in habitat fragments or reserveshemmed in by farms, cities, roads,and engineering works.70

In addition to direct stress,warmer air or water temperaturescan also impact native species in-directly. For example, evidence

suggests that the gender of sea turtles is determinedby the surrounding temperature at critical stages indevelopment, with warmer temperatures producingmore females.71 Warmer temperatures could thuscreate reproductive problems for an already declin-ing species.

The potential effects of a changing climate onisolated parks and reserves and on small tracts offorest tucked between human settlements and farmscould be substantial because of the limited oppor-tunities for natural species to migrate and the greaterpotential for the spread of exotics in disturbed areas.Furthermore, if climate change increases the inci-dence of droughts, fire danger will also increase,threatening these areas. Tracts of land near humanpopulations are more likely to burn because mostwildfires are caused by carelessness or arson.72

Ecosystem-Specific ImpactsUpland SystemsThe Gulf Coast region’s upland ecosystems are par-ticularly sensitive to potential changes in the watercycle and fire frequency. Variations in soil moistureare important factors in forest dynamics and compo-sition: many natural pine forests can tolerate low soilmoisture, while oak-pine and oak-gum forests requiremedium to high soil moisture.73 Over time, increas-ing temperature and decreasing soil moisture would

almost certainly change the distribution of trees andother plant species in these systems.

If droughts become more frequent or intense, therisk of wildfire could increase. In ecosystems that arenot adapted to fire, recovery from catastrophic firescan take decades or longer. Increases in drought-related fires would have severe impacts on managedforests and the timber-based economy of the region.

If droughts

become more

frequent or intense,

the risk of wildfire

could increase.


2 4

AT THE BIOLOGICAL CROSSROADS:THE BIG THICKET AND EAST TEXAS

The exceptional diversity of the Big Thicket area of East Texas has

led conservationists to call this region the “Biological Crossroads

of North America” and the “American Ark.” There, within a

limited geographical area, can be found several of the major forest types

of the eastern United States.74 Upland areas of the Big Thicket, formerly dominated by longleaf

pine, are now mostly loblolly and slash pine plantation forests. Wetter parts of the Big Thicket host

loblolly-shortleaf pine forests. The most rapidly expanding forest type is oak-hickory-pine forest.

In the low-lying flood plains, bottomland hardwood forests predominate, harboring species

such as sweetgum and water oak (Figure 22).

The forested areas of the Big Thicket also support a high diversity of vertebrate animals, with

400 species occurring in a 10-square-mile area. These forests are the primary habitat for the red-

cockaded woodpecker.75 Coastal prairies in the Big Thicket provide habitat for several endangered

bird species. The Big Thicket is also a popular area for

fishing, hunting, birding, hiking, camping, and canoeing.

Climate change has the potential to impact these diverse

plant communities by altering the growth rates of species,

changing the intensity and frequency of disturbance, and

potentially facilitating invasion by exotic plant species.

Historically, fire played a critical role in determining the

dominant vegetation of the Big Thicket by preventing

encroachment of hardwood saplings into pine forests

and allowing successful recruitment of young pines.74 Fire

frequency is likely to increase if climate change leads to

drier conditions in the area.76 With greater demand for

water in the Neches River and higher moisture deficits, invasion by Chinese tallow trees is likely to

intensify. Climate change will also influence the spread of pests, especially the Southern pine beetle,

in an area where losses to the forest industry are already running about $236 million per year.77

Moreover, any barriers to dispersal or migration by plants and animals would hinder their ability

to respond to changes in climate.78


F I G U R E 2 2The Big Thicket

Wildfires already cause extensive loss of standingtimber and release large amounts of carbon to theatmosphere.

In contrast, wildfires are critical for grasslandcommunities such as coastal prairies and bogs, whichare well adapted to natural cycles of burning.79 Be-cause woody plants typically invade prairies that are

not mowed or burned, increased fire frequencyshould help prairie conservation and help maintaingrazing lands in good condition.36,37

Any increase in storm and hurricane frequencycould hasten forest turnover, possibly resulting in theaccelerated replacement of canopy trees with differ-ent, more competitive species, even under current



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climate conditions. The changing climate and theavailability of species best suited for a site may limitthe type of species that dominate forests after futuredisturbances and the rate at which they take over.78

Carbon dioxide (CO2) serves as a natural fertilizerof plant growth, so higher concentrations of CO2 inthe air could increase forest productivity (tree growth).These CO2-driven gains could offset or possiblyreverse predicted declines in growth of pine forestscaused by higher temperatures and the higher plantrespiratory demands that warmer temperatures cause.80

While market forces exert a dominant influenceon agricultural crop production and farm income, itis useful to look at climatic and other environmentalinfluences on crop yields. Model studies suggest thatcertain agricultural crops such as corn, sorghum, andrice could also become more productive due to high-er CO2 concentrations, assuming warmer tempera-tures do not create additional water stress. Crops suchas wheat, rice, barley, and most vegetable crops areexpected to increase yields by 15 to 20 percent witha doubling of CO2. Corn, sorghum, sugar cane, andmany tropical grasses are expected to show increasesof only 5 percent.81 However, limited water availa-bility could reduce or cancel out these productivitygains, especially in areas where irrigation is not pos-sible. Other factors that could potentially counterany benefits of higher CO2 include

• higher ultraviolet-B (UV-B) radiation• limited nutrient availability• increased water stress• increases in pests and fires• air pollution from nitrogen, sulfur, and toxic

compounds

Freshwater SystemsThe freshwater ecosystems of theGulf Coast depend on the avail-ability and flow of water throughthe region. Several climate-relatedfactors, such as rainfall, runoff,and groundwater (aquifer) re-charge, have dramatic impacts onGulf Coast water cycles and leavefreshwater ecosystems vulnerableto climate change.

Bays and estuaries along the Florida and Texascoasts have historically received a significant influxof fresh water from groundwater. However, upstreamwater-management systems have largely reducedthese outflows of groundwater (Figure 23). Alongwith this reduction in outflow has come increasedwater use by agricultural, industrial, and urban in-terests, as well as the draining of wetlands for floodcontrol. This combination of increased demand forfresh water and diminishing or uncertain ground-water recharge rates (the time it takes to replenishgroundwater reserves) suggests potentially seriousconsequences in a warming climate, since more sur-face water will be lost toevaporation and not beavailable to rechargegroundwater resources.In one recent study forAustin, Texas, scientistsprojected that climatewarming could increasethe average annual lossfrom lakes and reser-voirs via evaporation bymore than a foot.82

Sea-level rise alsothreatens the ground-water reserves in coastal plain aquifers. The risk ofsaltwater intrusion into these aquifers increases as thelevel of the seawater rises, especially if undergroundfreshwater levels are declining because of greaterhuman consumption and potentially lower rechargerates. The risk is greatest if climate turns drier in thefuture, but it will remain significant even if the climate

grows wetter, because humanwater use and sea-level rise areboth certain to increase.

Changing surface runoffpatterns driven by changes inrainfall could also alter river,lake, and coastal ecosystems. Forexample, if rainfall and runofffrom urban and agriculturalareas increase, they most likelywill carry more fertilizer andother contaminants into lakesand coastal waters, increasing


F I G U R E 2 3Perry Lake, Alabama

This combination of

increased demand for fresh

water and diminishing or

uncertain groundwater

recharge rates suggests

potentially serious con-

sequences in a warming

climate.


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the risk of eutrophication (excessive nutrient enrich-ment). Such effects would exacerbate human-drivenstresses that are already driving changes in theregion’s rivers and lakes.83

Changes in flooding patterns could alsosignificantly affect river ecosystems. Flowing rivers

remodel landscapes,carrying sediment andnutrients downstreamto form new land andsupport plant growth.They also erode landand carve new channels.Periodic rejuvenation offloodplains by erosionand deposition is essen-tial to the health ofriver ecosystems. Froman ecological perspec-tive, flood pulses arenot disturbances, butrather essential pro-cesses that define thebiology and water qual-ity of river ecosystems.If climate change resultsin more intense rainfallevents, humans arelikely to try to reduceflooding by increasingchannelization of riversand building dams,

levees and reservoirs, all of which are functionally lesseffective in flood control than maintaining floodplainhabitats that can receive and slow the overbank flows.

Higher water temperatures and a longer growingseason would reduce habitat for cool-water species,particularly fish, insects, snails, and shellfish. Warmerwater holds less dissolved oxygen, which is critical forall living organisms. In shallow water systems, highsurface temperatures can lead to anoxia or hypoxia(oxygen-free or oxygen-poor waters) and cause poten-tially massive die-offs of fish and invertebrate species.Low-oxygen conditions would become more exten-sive in a warmer climate with longer periods of lowflow, and the consequences for stream ecosystemscould be severe.

Plant growth (productivity) in freshwater wetlandecosystems would increase with higher concentrationsof CO2 and modestly warmer temperatures, as longas precipitation is not reduced. For freshwater marshes,this may mean increased accumulation of organicmatter, enhanced rates of soil formation, and—forsystems close to the coast—an increased ability tocope with sea-level rise. However, increased plantgrowth in response to higher CO2 levels varies amongspecies, and higher CO2 could change the mix ofspecies and interactions within aquatic communities.As with forests and agricultural systems, gains inaquatic plant productivity due to increased CO2could be countered by other climate-driven changes.For example, a significant reduction in rainfall wouldlower wetland productivity far more than elevatedCO2 could increase it.

Coastal and Marine SystemsSea-level rise will alter coastal wetlands along theentire Gulf Coast, causing increased flooding, greatersaltwater penetration, and higher rates of coastalerosion. Wetlands naturally respond to sea-level riseby building additional substrate or moving inlandonto adjacent uplands (Figure 24). Thus, the accel-erated sea-level rise projected for the next 50 to 100years would normally be unlikely to have a catastrophicimpact on most Gulf Coast wetlands. However,where sea-level rise coincides with human land-usechanges in the drainage basin, the consequencescould be severe, leading to losses of wetlands in areaswhere coastal development hinders natural inlandmigration.84

Increased droughts in upland and coastal areaswould also have negative impacts on coastal and marineecosystems by reducing the flow of fresh water intoestuaries, bays, and lagoons. If droughts occur morefrequently or last longer, the incidence of hypersalinity(extreme salt concentrations) in coastal ecosystemswill increase, resulting in a decline of valuable habitatssuch as the mangroves and seagrasses in Florida Bayor South Texas lagoons and coral reefs in the FloridaKeys where their salt tolerance is exceeded. The25-month drought in coastal Louisiana that extendedthrough summer 2000, for example, along withreduced river flow contributed to severe dieback ofsome 100,000 acres of marsh (Figure 25).85


F I G U R E 2 4Swamp Forest Impacted by Saltwater


F I G U R E 2 5Brown Marsh in Coastal Louisiana



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F I G U R E 2

Water Control Structuref r om page 3

The natural landscapes, waterways, and ecologicalprocesses of the Gulf Coast have been significantly alteredby human activities, including water control structures suchas this pump station in South Florida. The station is part ofone of the world’s largest water management systems, builtby the US Army Corps of Engineers, to protect the urbanareas of South Florida from flooding and to support agri-culture while simultaneously draining nearly 65 percentof the original Everglades and fundamentally changingits character.

Photo Credit: South Florida Water Management District

F I G U R E 1

The Gulf Coastal Plainf r om page 2

The Gulf Coastal Plain arcs1,550 miles from the tip ofFlorida to the tip of Texas. Theregion is divided into threesubregions that differ in climate:western (Texas), central (Louisiana toAlabama) and eastern (Florida). Despitelittle variation in terrain, the Gulf Coastsupports a diversity of freshwater,coastal, and upland terrestrial ecosystems.

Credit: Amanda Wait/DG Communications

F I G U R E 3

Influences on Gulf Coast Climatef r om page 5

The Gulf Coast region is substantially wetter than theclimate of other locations at this latitude because moistair flows in from the Gulf of Mexico, Caribbean Sea, andAtlantic Ocean. The region enjoys mild winters occasion-ally punctuated by cold air masses from the north thatbring low temperatures and freezing conditions. Summerstend to be hot and humid, with rainfall brought by thunder-storms and tropical storms. Another influential climate featureis the Bermuda High pressure system, which controls theduration of the wet season in South Florida. During thewinter, the Bermuda High is small and located southand east of Florida; in the spring, it expands and movesnorthward. If the Bermuda High does not move northin the summer, then the wet season rains are delayed, resulting in drought.More remote influences on the climate of the region include the El Niño-SouthernOscillation cycle (not depicted) and continental weather patterns to the north.



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F I G U R E 6

Wilfiref r om page 11

Wildfires have shaped many of theregion’s ecosystems. Grasslands andprairies are maintained by wildfiresand some natural forests also dependon them for regeneration. Yet timberproduction and homes located at thecommunity/forest boundary face greatrisks from wildfires. If rainfall decreasesand/or evaporative moisture loss in-creases with global warming, thelikelihood of wildfires occurring willincrease.

Photo Credit: South Florida WaterManagement District

F I G U R E 4

Gulf Regional Average Temperature(1895–2000)f r om page 6

While air temperatures warmed over most of the UnitedStates during the 20th century, they cooled slightly onaverage in the Gulf region. Such regional differences arenot inconsistent with the global warming trend. In addi-tion, climate varies from year to year and decade to decadeas shown in these temperature curves. The five Gulf Coaststates experienced a warm period between the 1920s and1949 and then substantial cooling until the late 1960s,when temperatures again began to rise. This warming hasbeen less than the previous cooling, hence the slight down-ward trend of the regional average for the 20th century.

C O L O R F I G U R E S

The Hydrologic Cycle

Subsurface Runoff

Watershed Boundary

Ocean

WetlandsGroundwater

Saltwater Intrusion

Evaporation

Evaporation Transpiration

Condensation

Precipitation

Surface Runoff

Delta

Forest Rice and Crawfish Ponds

Barrier Islands

Infiltration

F I G U R E 5

The Hydrologic Cyclef r om page 10

Gulf Coast ecosystems are connected by the flow of water, from theuplands to the coast. Any change in the hydrologic cycle underlyingthis connection will affect both natural and managed eco-systems and the goods and services they provide. This hydro-logic cycle depiction illustrates how water availability andflow is a function of both a changing climate andhuman activity. A changing climate will affectrainfall, evaporation, transpiration, surface andsubsurface runoff, and groundwater recharge.Human activities—such as creating impervioussurfaces, using surface and groundwater forhuman demands, and altering river channelsand deltas—also greatly impact the water cycle.

Credit: Melissa Drula, Annie Bissett/DG Communications


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F I G U R E 7

Relative Sea-Level Rise Scenariosfor the Gulf of Mexicof r om page 11

Climate models project that sea-level rise (SLR)—alreadyoccurring along the Gulf Coast—will continue at a faster rateover this century and beyond, increasing coastal erosion andflooding during normal high tide as well as during severe storms.Sea-level rise projections are shown here for different parts ofthe Gulf of Mexico, with two different scenarios for Louisianadue to its wide range of land subsidence rates. By the late1990s, this road—the only land access to the rural communityof Isle de Jean Charles in Terrebonne Parish, Louisiana—wasregularly flooded by wind-driven tides, forcing the local gov-ernment to raise the road several feet at a cost of $2 million.

Photo Credit: Denise Reed

F I G U R E 9

Gulf Landfalling Hurricanes by Decadef r om page 12

Hurricane activity varies from decade to decade and iscorrelated with the El Niño-Southern Oscillation cycle. The1990s ushered in a period of greater hurricane activity thatis unrelated to human-induced climate change, and thenumber of intense hurricanes (categories 3–5) is projectedto increase over the next 25 years. During El Niño events,the probability that hurricanes will make landfall in thesoutheastern United States goes down, while the probabilityincreases during La Niña events. With global warming,hurricane intensity (maximum wind speeds, rainfall totals)may increase slightly, although changes in future hurricanefrequency are uncertain.

F I G U R E 8

Damage from HurricaneAndrewf r om page 12

In 1992, Hurricane Andrew broughtwidespread destruction to Florida and theAtlantic seaboard with damages estimatedat about $27 billion. Damages from futurestorms are likely to be aggravated by sea-level rise, and the costs can be expectedto be substantially higher because morecoastal development already lies in harm’sway. Should global warming increase theintensity of hurricanes, the impacts onpeople and property in coastalcommunities are likely to increase.



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Land-Use/Land-CoverChange, St. Petersburg-Tampa Area, Florida(1952–1982)f r om page 13

To accommodate the rapid populationgrowth in the Gulf states, especially inFlorida and Texas, and coastal areasmore generally, urban centers expandinto surrounding natural habitats andagricultural areas, as shown in this pairof maps of the St. Petersburg-Tampaarea. As more land is developed forhuman uses, plants and animals losetheir habitats, and potential migrationcorridors—needed to adapt to climatechange—are obstructed.

Credit: US Geological Survey, Gulf of MexicoIntegrated Science Program

SoutheasternPlain

South FloridaCoastal Plain

Florida KeysGulf of Mexico

Mississippi RiverAlluvial Plain

North

Central

Plain

Central Texas

Plateau

Appalach

ian Pi

edmont

Central TX/OK Plain

Southern

Texas

Plain

South

Texas

Plain

Mississippi RiverDeltaic Plain

SouthernCoastalPlain

TexasClaypan

Area

Source: Based on ecoregions mapof the United States and descriptionsby James M. Omernik (1986, 1987)

EasternSubregion

CentralSubregion

WesternSubregion

Western Gulf

Coastal Plain


F I G U R E 1 1 a

Ecoregions of the Gulf Coastf r om page 15

Despite little variation in terrain, the Gulf Coast region hosts a diversity of ecosystems that evolved on upland, alluvial(material deposited by flowing waters), and coastal landscapes under the influence of temperate and subtropical climates.Upland ecosystems include temperate hardwoods, pine flatwoods (or barrens), scrub forests, and prairies. Freshwaterwetlands and aquatic ecosystems encompass swamps, freshwater marshes, lakes, rivers, and springs. The near-shore areasinclude barrier islands, mangroves and salt marshes, seagrasses, estuaries and bays, and coral reefs. The five case studies—shown in Figure 11b and highlighted in this report—represent some of the diversity of ecosystems and the species richnessof the region.



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F I G U R E 1 2

Pitcher Plant Bogf r om page 16

The lower coastal plains—whichextend about 60 miles inland fromthe coast and run from the westernedge of North Florida to the easternborder of Mississippi—were oncea continuous moist pine barrencommonly known as Gulf Coastpitcher plant bogs. Only threepercent of these habitats remaintoday, serving as home to uniquecarnivorous plants (well over halfof the approximately 45 NorthAmerican species occur in the GulfCoast), as well as the endangeredpine barrens tree frog, the oddflightless grasshopper, and aunique spittlebug.

Photo Credit: Robert Twilley

F I G U R E 1 1 b

Case Study Areasf r om page 15



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Whooping Cranesf r om page 17

The Whooping Crane—the rarest of the world’s 15 cranespecies—historically wintered along the Texas Gulf coast,and nonmigratory populations occurred in Louisiana andpossibly other areas in the southeastern United States. TheAransas-Wood Buffalo population in Texas is one of onlythree wild populations remaining. Habitat loss, pollution intheir wintering grounds, and vulnerability to natural andhuman-caused disturbances continue to threaten thismagnificent bird.

Photo Credit: Gwenn Hansen

F I G U R E 1 5

Black Mangrovesf r om page 17

As global warming increasesaverage temperatures, thefreeze line will also move north-ward. Black mangroves, quitesensitive to freezing tempera-tures, are moving northwardand establishing themselvesmore firmly on the Louisianacoast—one biological indicatorthat warming is alreadyunderway.


F I G U R E 1 3

Hardwood Hammockf r om page 16

Hardwood hammocks are typical habitats in SouthFlorida. Made up of dense stands of trees, thesehammocks are slightly elevated “islands” created bythe flow of water in the middle of sloughs (the deeperand faster-flowing center of broad marshy rivers).Many tropical tree species such as mahogany andcocoplum grow alongside temperate species suchas live oak, red maple, and hackberry. Due to theirelevation, hammocks rarely flood, and they areprotected from fire by natural moats formed whenacids from decaying plants dissolve the limestonearound them.

Photo Credit: Susanne Moser



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Typical Agricultural Cropsf r om page 18

The Gulf region is well suited for agriculture,with the five states combined producing $28billion—or 14 percent—of total agricultural valuein the United States in 1997. Citrus, sugarcane,peanuts, rice, and cotton are among the leadingcrops. Only with sufficient water during thegrowing season, from rainfall or irrigation, willyields be maintained in the future.

Photo Credits: US Department of Agriculture (citrus,peanuts, rice), South Florida Water Management District(sugar), Susanne Moser (cotton).


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Oil Rig in the Gulf of Mexicof r om page 20

The economy of the Gulf Coast is perhapsbest known for its rich energy resources.Approximately 95 percent of the oil and 98percent of the natural gas produced on theouter continental shelf comes from thecentral and western regions of the Gulfof Mexico. While reducing emissions fromthe production and refining of these fossilenergy resources would directly reduce therisks of global warming, it is critical to findways to cut emissions without undermin-ing the economic vitality of the region.


F I G U R E 1 7

Value of Gulf Forest Industries (1996)(in $billion)f r om page 18

In 1996, the five Gulf states accounted for $46.4 billionof the national timber production. Alabama and Texastogether produced about 10 percent of the national inven-tory and more than half of Gulf Coast production. Majorchanges in forestry can be expected in the future, althoughprojections are difficult to make because the direct impactsfrom climate change will interact with shifts in global timbermarkets. If the drier climate scenario plays out, savannasand grasslands would expand at the expense of forests,particularly in the uplands of the Gulf Coast, and fireswould become more frequent. Wetter climate conditions, on the other hand, would increase the productivity of hardwoods at theexpense of softwoods and would leave the region’s forests more vulnerable to pests such as the Southern pine bark beetle.

Photo Credit: Robert Twilley. Chart: Amanda Wait/DG Communications

F I G U R E 1 8

Fishery Landings (1999)f r om page 19

The rich waters of the Gulf ofMexico yielded 1.95 billion poundsof fish and shellfish in 1999, worthmore than $758 million dockside.The Gulf Coast has the largest andmost valuable shrimp fishery inthe United States, and in 1999 theregion produced 78 percent of thetotal national shrimp landings. Manyof the harvested fish and shellfishdepend on fragile coastal wetlandsas nurseries and essential habitat.Continuing wetland loss—projectedto increase with global warmingover the 21st century—will under-mine this valuable sector of theGulf economy.




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Recreational Fishing onKissimmee River, Floridaf r om page 20

Alluvial and shoreline ecosystems—such as swamps and marshes—supportwetland wildlife, including waterfowl,alligators, and fur-bearing animals. Agrowing ecotourism industry dependson these ecosystems for recreationalactivities such as hunting, fishing,hiking, canoeing, and birdwatching.


F I G U R E 2 1 a

Open Prarief r om page 22

The remaining areas of the once-vastcoastal prairies that extended from theCarolinas to South Texas are threatenedby both urban sprawl and invasive species,particularly the Chinese tallow tree. Onceestablished, the tree transforms a diversecoastal prairie (top) into a biologicallyimpoverished forest within 30 years(bottom). It is not yet known what roleclimate change will play in prairie invasions,but the combination of climatic and humanstresses on ecosystems frequently rendershabitats more vulnerable to invasion.Already, the Chinese tallow tree has be-come an abundant invader in the under-story of many Gulf Coast forests, andclimate-related disturbances such as hurri-canes tend to accelerate its invasion andestablishment. In addition, drier conditionswith fewer flooding episodes as projectedby some climate models appear to favorChinese tallow at the expense of nativespecies.

Photo Credits: Evan Siemann

F I G U R E 2 1 b

Invasion byChinese Tallow Treesf r om page 22


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Perry Lake, Alabamaf r om page 25

Freshwater ecosystems such as Perry Lake or nearbyCahaba River in Alabama are particularly vulnerable toclimate-related changes in the water cycle, includingchanges in rainfall, runoff, and groundwater (aquifer)recharge. Potentially diminishing rainfall and ground-water recharge rates due to global warming wouldhave serious consequences for freshwater ecosystems,especially when combined with human activities suchas drainage of more wetlands for flood control, reduc-tions in groundwater outflow caused by upstreamwater-management systems, and increased waterusage by agricultural, industrial, and urban interests.

Photo Credit: Randall Haddock, Cahaba River Society,Birmingham, Ala.

F I G U R E 2 4

Swamp Forest Impacted by Saltwaterf r om page 26

The combination of sea-level rise and less freshwater runofffrom land lead to saltwater intrusion into once vibrant coastalestuaries. This example from Falgout Canal in Louisianaillustrates the problem, which could become more seriouswith climate change. This navigation canal dredged in the1960s allowed salt water into a freshwater swamp, resultingin dead cypress trees surrounded by brackish marshvegetation.


F I G U R E 2 2

The Big Thicketf r om page 24

The Big Thicket National Preserve, whichincorporates more than 97,000 acres ofpublic lands and waters, is internationallyrecognized for its splendid biologicaldiversity, encompassing bald cypressswamps, as well as upland pine savannahsand sandhills. The preserve is home to avariety of endangered species such as thered-cockaded woodpecker and brown-headed nuthatch.

Photo Credit: US National Park Service



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Louisiana Coastal Land Loss(1956–1990)f r om page 43

More than 12,000 square miles of coastal wetlandswere once part of the Mississippi River delta, repre-senting nearly 40 percent of the total coastal saltmarsh in the continental United States. These wetlandsare disappearing at an average rate of 25 square milesper year or about 50 acres per day. The normal eco-logical processes that built and nourished these vastwetlands have been profoundly disrupted by humanintervention—construction of dams, levees andchannels in the river, and the conversion of morethan 80 percent of forested wetlands to farms andcities. The combined effects of sea-level rise andhuman alterations to sediment supply will continuethe current wetland loss rates for the next 20 years.Later in the 21st century—as temperatures increasemore—loss rates are likely to increase.

Credit: US Geological Survey, National WetlandsResearch Center (1998), MAP 98-4-525

F I G U R E 2 5

Brown Marsh in CoastalLouisianaf r om page 26

Should climate change lead to more droughtsin upland and coastal areas, reduced flow offreshwater into these coastal ecosystemswould harm estuaries, bays, and lagoons.The 25-month drought in coastal Louisianathat extended through summer 2000, alongwith reduced river flow into the marsh area,contributed to severe dieback of some100,000 acres of marsh.

Photo Credit: Greg Linscombe, Louisiana Departmentof Wildlife and Fisheries

F I G U R E 2 7

Kemp’s Ridley Sea Turtlef r om page 46

The endangered Kemp’s Ridley sea turtle—shown hereemerging from egg-laying in the beach sands of PadreIsland National Seashore, Texas—is one of six sea turtlesfound in the Gulf Coast region. Sea turtles are threatenedprimarily by human activities such as disturbance or destruc-tion of nesting sites, artificial lighting along developedbeachfronts, entrapment in fishing nets, water pollution,and being hunted for their eggs and leather. Further lossof nesting habitats due to beach erosion from acceleratingsea-level rise will substantially reduce their prospects forsurvival.

Photo Credit: US Geological Survey


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Isles Dernieresf r om page 47

Louisiana’s Isles Dernieres is a low-lying island chain thatserves as home to brown pelicans, other shorebirds, and ahost of fishery species. These islands also serve as “hurricaneprotection” for coastal communities, oil and gas facilities,and seaport infrastructure on the mainland. Yet these invalu-able islands are severely threatened by human interferencewith natural coastal processes such as sea-level rise, localland subsidence, sediment transport and hurricane- andstorm-driven waves and overwash. Since the late 1990s,over $30 million has been spent to restore the heightand width of these protective islands.


F I G U R E 2 9 a / b

Healthy and Unhealthy Coralsf r om page 47

Healthy coral reefs (top) are among the most beautiful andbiologically diverse ecosystems on the planet. In the pastfew decades, however, unprecedented declines in thecondition of coral reefs in the Gulf of Mexico have beendetected including extensive coral bleaching due to highertemperatures (bottom), growth of algae on reefs, loss of thedominant algae-grazer (a sea urchin), and pervasive over-fishing of reef species. The shallow waters surrounding theSouth Florida reefs make them especially vulnerable to thehigher ocean water temperatures that are expected toaccompany climate change in the Gulf.

Photo Credits: Mike White, Florida Keys National Marine Sanctuary (top/healthy); S. Miller, NOAA, Office of Oceanic and Atmospheric Research,National Undersea Research Program (bottom/bleaching)

F I G U R E 3 0

Pitcher Plantf r om page 48

The endangered green pitcher plant is a perennialherb that lives on decaying insects and leaves that fall onto its leaves. Although 31 of the known remaining34 populations occur in Alabama, protecting the habitat of this endangered species is hampered by a lackof state protection laws. Pitcher plants live in mixed oak or pine flatwoods, seepage bogs, and along streambanks, and fire appears to help maintain their habitat, whereas reduction of streamflow and moisture affecttheir habitat negatively. Increased residential, agricultural, and forestry development, fire suppression, andclimate-driven alteration of its little remaining habitat further threaten this unique plant. Photo Credit: Henry Gholz



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F I G U R E 3 1

Declines of Regional WaterLevels Due to Withdrawalfrom the Floridan Aquifer(predevelopment to 1980)f r om page 51

Drawdown of underground water reservoirsto meet human demands combines with sea-levelrise to increase saltwater contamination of aquifers,particularly near the coast. Large groundwaterwithdrawals in the coastal zones of Florida (e.g.,Pensacola and Tampa) or Alabama (e.g., GulfShores) have already increased salinity in wells.These problems are common in coastal aquifersacross the Gulf region and are likely to increasewith growing population and acceleratingsea-level rise.

F I G U R E 3 2

Aquifer Drawdownand Saltwater Intrusionf r om page 51

As sea level rises, salt water penetratescoastal aquifers more deeply. Fresh waterdrawn from wells near the coast canthus be contaminated by saltwater—a risk increasing with growing humanwater demand, increasing drawdown,potentially reduced groundwaterrecharge, and sea-level rise.



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The Evergladesf r om page 52

Decades of managing water primarily for urbanand agricultural uses has put the Greater Ever-glades critically at risk. Climate changes andaccelerating sea-level rise will cause shifts in plantand animal communities and increased successof invasive species. Other significant impacts couldresult from more intense hurricanes or from morefrequent or intensive droughts, which wouldincrease the risk of major wildfires. Restorationefforts that do not account for climate-relatedchanges are likely to leave the Everglades lessable to adapt to a warmer world.


F I G U R E 3 4

Shrimp Trawlerf r om page 54

Family-owned shrimp trawlers alongside largecommercial fishing operations are as much a partof the coastal landscape as crawfish ponds andaquaculture tanks. The fishing and fish farmindustries are particularly vulnerable to changesin freshwater availability, increases in salinity dueto saltwater intrusion into coastal ground- andsurface water, and water quality declines in coastalareas, as well as to losses of marsh, mangroveand seagrass habitat.

Photo Credit: Thomas Minello, National Marine Fisheries Service

F I G U R E 3 5

Erosion Damage from TropicalStorm Frances (1998)f r om page 55

Tropical Storm Frances hit the Texas coastline in1998, causing severe erosion damage to housesalong the shorefront, such as those shown hereon the west end of Galveston Island. With accel-erating rates of sea-level rise, even minor stormsin the future could wreak major havoc, damaginghouses, infrastructure, and industrial facilities.Over time—short of significant and sustainedincreases in investment in shorefront protection—second and third-row homes will becomeoceanfront property.




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July Heat Index Change by 2100f r om page 56

The July heat index is projected to increase with global warming more in theSouth than in any other region of the United States. Urban areas such as Dallas,Houston, Baton Rouge, Birmingham, and Tampa are especially vulnerable to morefrequent heat waves and a resulting increase in heat-related illnesses and deaths. Ineach of these cities, deaths attributed to extreme heat conditions average about 28per year, and this rate could more than double to 60 to 75 deaths per year with a3°F warming of average summer temperatures. Vulnerability to heat-related stressdepends largely on people’s ability to protect themselves from temperature extremes—for example, on whether they can afford air conditioning—and on their pre-existing health condition.

F I G U R E 3 8

Renewable Energy Potential in Texasf r om page 62

Texas has a variety of clean energy resources—wind, solar, biomass, and geothermal. The state hasbegun to develop some of this supply, and it has the market power to help spread the use of renewableenergy. Other Gulf states can also increase and further diversify their energy production with renewablessuch as solar, hydro, and biomass, and thereby reduce their production of greenhouse gases.

Credit: Texas State Energy Conservation Office

F I G U R E 3 7

Windmillf r om page 62

Many environmental, economic, and publichealth benefits can result from reducing thecombustion of fossil fuels and the emissionsof heat-trapping gases that accompany fossilfuel burning. One way to reduce fuel con-sumption is to increase use of alternativeenergy sources such as wind power. ThisZond Z-40 550 kW wind turbine is locatedon a wind farm in West Texas (Fort Davis),one of a growing number of wind farmsthroughout the state.

Photo Credit: Brian Smith, courtesy of the USDepartment of Energy/National RenewablesEnergy Laboratory


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Improving IrrigationTechnologyf r om page 63

Pivot irrigation, as shown here on a cottonfield in Mississippi, is widely used, but otherwater-conserving technologies are available.Exploring these options is essential if we areto help natural and managed ecosystemsbetter adapt to a changing climate. In theface of a changing climate, for example,the cost-benefit analysis applied to humanactivities such as agricultural irrigation shouldbe reassessed. The potential benefits of sus-tained or increased agricultural yields orprevention of saltwater intrusion into surfacewaters must be weighed against potentialnegative side-effects such as further draw-down of groundwater resources, increased

F I G U R E 4 0

Beach Replenishmentf r om page 66

Typical responses to the landscape changesassociated with rising sea level have includedbuilding seawalls and other hard structuresto hold back the sea, raising the land andreplenishing beaches—as shown here inCorpus Christi, Texas—or allowing the seato advance landward and pulling humandevelopment back from the shoreline in anad hoc manner. Each of these options canbe costly, both monetarily and in terms oflost landscape features, habitats, buildings,and infrastructure. Beach replenishment,while avoiding some of the negative side-effects of shoreline hardening, will be requiredmore frequently as faster sea-level rise in-creases coastal erosion. The most affordableoption is likely to require long-term plan-ning for an inevitably rising ocean.

Photo Credit: Texas General Land Office,Coastal Projects Division

salinization of soils, or withdrawal of essential fresh water from natural ecosystems. Technicallyfeasible solutions are available to adapt to and mitigate climate change, and the cost of thesesolutions is frequently lower than the cost of doing nothing.

Photo Credit: US Department of Agriculture



4 3

CONTROLLING A RIVER:THE MISSISSIPPI RIVER DELTAICPLAIN

Over the past century, the nearly 1.3 million square mile

watershed of the Mississippi River has experienced major

environmental changes, including conversion of more than 80 percent of forested

wetlands to agriculture and urban areas, channelization, dam construction, and leveeing of the river.

The lower Mississippi deltaic plain has also been engineered by construction of flood-control levees

and massive structures that keep the river from switching channels and also restrict sediment and

freshwater supply to river flood plains (Figure 26).

This has been especially damaging to the region’s wetlands. The more than 12,000 square miles of

coastal wetlands associated with the Mississippi River delta represent nearly 40 percent of the total

coastal salt marsh in the conterminous United States. These wetlands are disappearing at an average

rate of about 25 square miles per year or about 50 acres

per day, and more than 1,000 square miles of freshwater

wetlands in Louisiana have already been lost or converted

to other habitats.86 Only about 20 percent of the original

37,500 square miles of bottomland hardwood forests and

swamps in the lower Mississippi River valley remain today.

Some of these wetland losses are due to delta subsidence

(sinking), which results in relative rates of sea-level rise of

up to 0.39 inches per year.24 Although subsidence is a natu-

ral process, human interference with river and sediment

flow and withdrawal of groundwater have exacerbated it.

Adequate inflow of fresh water and sediment is critical for sustaining existing wetlands and expand-

ing delta landscapes along the coast.

One of the most critical climate-change issues for the delta is how future rates in sea-level rise

will affect the already highly altered and rapidly degrading coastal wetlands of Louisiana. Landscape

models project that the combined effects of increased sea-level rise and human alterations to sedi-

ment supply will continue the current wetland loss rates in the Terrebonne and Barataria Basins

until 2018. These simulations demonstrate that from 1988 to 2018 the region will lose nearly 900

square miles of coastal wetlands to open water, threatening navigation and the industrial, agricultural,

and fisheries sectors of the regional economy.87 Future wetland loss rates could increase as sea-level

rise accelerates in the latter part of the 21st century. Although hurricanes can play a positive role in

wetland development by remobilizing sediments and assisting in building marsh substrate, chan-

nelized coastal landscapes such as Louisiana’s allow storm surges to move farther inland, increasing

saltwater penetration into interior freshwater marshes. Sea-level rise will exacerbate this disturbance

whether or not hurricanes and storms become more frequent or intense in the future.


F I G U R E 2 6Louisiana Coastal Land Loss(1956–1990)


4 4

If increased drought reduces freshwater flows,the result will also be reduced nutrient inputs, slowerflushing of nutrients and contaminants, and altera-tions in estuarine food webs. While nutrients such asnitrogen are critical for plant growth and ecosystemfunctioning, too much canincrease algal growth and otherproblems such as hypoxia andanoxia. Again, the interaction ofclimate-related changes withother human pressures is criti-cal: in relatively pristine water-sheds with fewer sources ofnutrients and contaminants,impacts on estuaries may be less severe than in de-veloped areas, such as the heavily industrialized andurbanized Tampa and Galveston Bays, which havenumerous point and nonpoint sources of nutrientsand contaminants. In addition, many of these estu-aries receive deposits of nutrients and contaminantsfrom the atmosphere. These factors can combine todegrade water quality in estuaries and to threatenfisheries and human health through such changes asincreased harmful algal blooms and accumulation oftoxic metals. As in freshwater wetlands, plant growthin coastal wetlands could increase with higher con-centrations of CO2. Studies of mangroves have shownenhanced produc-tivity with elevated CO2 concentra-tions. But again, productivity gains due to increased

CO2 concentrations may be countered by other climate-driven changes.

Changes in surface runoff patterns—either de-creases due to drought or increases caused by fresh-water influxes during floods—will also impact coastal

ecosystems by changing the salinityand perhaps shifting the mix ofplant and animal species in thecommunity. However, the com-plex interactions of climate andhuman activities that influence thequantity and quality of freshwaterrunoff illustrate that the outcomedepends at least as much on how

water is managed as on climate-induced changesin rainfall.

An extensive levee system has reduced floodingfrom the Mississippi River into adjacent wetlands bychanneling freshwater flows directly to the shallowcontinental shelf off the Louisiana and Mississippicoasts. During periods of high river discharge, a largemass of oxygen-poor bottom water can form in thenorthern Gulf of Mexico as the fresh water forms astratified layer above the denser salt water and deli-vers more nutrients into the Gulf.89 These river dis-charges are affected by climate far upstream in thewatershed, in the western and midwestern UnitedStates. Climate-change projections for the Ohio Riverbasin, for instance, suggest there will be higher

Major changes in the upper and lower watersheds of the Mississippi-Atchafalaya river system have also

increased the likelihood of low-oxygen conditions in Gulf waters. Wetland destruction has removed

the watershed’s nutrient-buffering capacity; river channelization for flood control and navigation has

shunted fresh water to the continental shelf; and major increases in nitrogen fertilizer washed into the

Mississippi River Basin have quadrupled nitrate concentrations in the river system. On the Louisiana

continental shelf, hypoxia can extend over as much as 8,000 square miles, depending on the amount

of freshwater discharge, which controls the addition of nutrients and the stratification of shelf waters.

Climate model studies predict a 20 percent increase in discharge from the Mississippi River watershed,

which could lead to an expanded hypoxic or “dead zone.”88 This delta region—with big population

centers such as New Orleans—represents one of the most vulnerable regions of the Gulf Coast, an area

where the combined effects of engineered and altered landscapes, natural subsidence, and climate

change will have tremendous consequences for human well-being, natural resources, and biodiversity.


Changes in surface runoff

would impact coastal

ecosystems and fisheries

by changing water quality

and the mix of species.


4 5

SALTY BALANCE: THE LAGUNAMADRE AND THE SOUTH TEXASCOASTAL PLAIN

The Laguna Madre, the only hypersaline lagoon in the United

States, is part of the South Texas Coastal Plain, which extends

inland from the western Gulf of Mexico as a gently sloping prairie of short grasses, mesquite

trees, thorny brush and prickly pear cactus. Much of the plain is used as rangeland, with some crop-

land and improved pasture. Two major river systems encircle this semi-arid region of South Texas:

the Nueces River to the north and the Rio Grande River to the south. These rivers provide the only

continuous sources of surface fresh water for the cities and estuarine systems of South Texas.

The Laguna Madre formed between the mainland and Padre Island, which at 130 miles is the longest

barrier island in the United States. At its widest, Padre Island measures 3 miles across and has dunes

that rise 25 to 40 feet behind wide sandy beaches on the Gulf side. The upper Laguna Madre ex-

changes water with Baffin Bay, the “saltiest” bay in the United States. Tidal currents in the lagoon

are weak, circulation is sluggish, and residence times of water masses are long. During exceptionally

dry periods, high salinity may cause fish and other animals to leave or die. The lagoon also suffers

periodic large fish kills due to severe freezes. The shallowness of the lagoon and the long distances

to deep water worsen the conditions that can lead to fish mortality.

The South Texas Coastal Plain supports unique ecosystems and wildlife, including barrier island dunes

and beaches, Tamaulipan brushlands, Laguna Madre seagrasses, intertidal wind flats, Baffin Bay, and

the Rio Grande delta. Some areas are biologically diverse, such as Padre Island, which hosts more than

600 species of plants, and the Tamaulipan brushland with more than 600 vertebrate animal species

and 1,100 plant species, including an endemic oily oak tree species. Padre Island beaches serve as

nesting grounds for endangered Kemp’s ridley sea turtles and threatened green sea turtles (Figure 27).

The Laguna Madre accounts for 75 percent of Texas’s seagrass habitat, which supports many rare

and endangered species and provides vital nursery grounds that sustain a bountiful commercial

harvest of shrimp, blue crabs, red drum, spotted sea trout, and southern flounder. The threatened

green sea turtle, once abundant enough to support commercial harvest in South Texas, feeds on

submerged turtle grass rooted in the lagoon bottom. At the Laguna Atascosa National Wildlife Refuge,

the endangered aplomado falcon has recently been reintroduced. The banks of the Arroyo Colorado

and nearby thorny chaparral uplands shelter ocelot, jaguarundi, indigo snakes, horned lizards,

chachalaca, green jays, kiskadee flycatchers, and other unusual animals.

The most important human impacts on this region over the past 30 years have been water diversion

and flood-control projects, brushland clearing, pollution, continued dredging of the intracoastal

waterway, and the pressures of population growth. The lower Laguna Madre, for instance, has lost

about 60 square miles of seagrass cover due to reduced water clarity since the 1960s. Extensive

agriculture has fragmented and reduced the areas of native terrestrial ecosystems. And both the


4 6

northern and southern ends of Padre Island have been

developing rapidly as resort and residential real estate.

In addition, the large number of people now living in

“colonias” without sewage treatment contributes to the

contamination of ground and surface waters and poses a

human health problem. This is exacerbated by untreated

wastewater from Mexican municipalities released into

the Rio Grande.

In addition to human impacts, parts of the Rio Grande

watershed have experienced severe drought since 1993,

and low flow has exacerbated water quantity and quality

problems. Also, a lengthy, unprecedented brown tide

(Aureoumbra lagunensis, a type of toxic algal bloom) has

persisted in the Laguna Madre since 1990. The bloom

began in association with high salinities and a nutrient pulse from a fish kill caused by a 1989 freeze.91

Global warming will compound these human pressures on Laguna Madre, in some case improving,

in others worsening the situation. For example, if future climate change brings a prolonged and

more intense wet season in this region, the reliability of rainfall and soil moisture could improve.

The gentle slope of South Texas prairies helps the land retain rainfall and runoff. In wet periods,

freshwater ponds form in swales over clay soils, water is stored in sandy soils, wildlife and native

plants increase their productivity, and salinity is moderated in the Laguna Madre and Baffin Bay. If

rainfall decreases in the future, however, it would not take much of a reduction in moisture to spur

increased desertification. Moreover, models project that all types of coastal wetlands in Texas would

decline with less freshwater delivery to the estuaries, thus exacerbating wetland losses already occur-

ring. Over the long term, such coastal wetland losses would diminish estuarine-dependent fisheries.92

Warmer winters are especially important from an ecological point of view. A northward shift of the

freeze line would bring dramatic effects to the Coastal Bend and upper Laguna Madre, allowing

southerly biotic communities to expand northward and, due to fewer disturbances from frost, mature

and develop more complex ecosystems over time. Already, without a fish kill in the Laguna Madre

since 1989, mean fish size increased and predation patterns appear to have changed, altering

community interactions.93


F I G U R E 2 7Kemp’s Ridley Sea Turtle

discharge from the Mississippi River in the future,particularly during El Niño events.90 Increases inprecipitation and water flows would exacerbate thealready serious problems of eutrophication and strati-fication that create the hypoxic “dead zone” in theGulf, while a drier upstream climate would reducethe size of the near-shore hypoxic zone.

Interactions of sea-level rise with hurricanes andother severe storms have been dominant factors shap-ing the coastal terrain for the last several thousandyears.16,94 Barrier islands typically move toward themainland as sea level rises through a process of beacherosion on their seaward flank, overwash of sedimentacross the island during storms, and deposition of the



4 7

eroded sediment in the quieter waters of the bay. Therate of this natural migration (roll-over) depends onthe rate of sea-level rise and the frequency and sever-ity of storms and hurricanes. Human developmentdisrupts overwash and sediment movement, but stormsand sea-level rise continue. The result is erosion ofthe beach face and nearshore areas. The vulnerabilityof barrier islands and island communities to increasederosion is already evident along the Gulf Coast inareas like Dauphin Island, Alabama, or Isles Dernieres,Louisiana (Figure 28).

Even if coastal ecosystems can keep up with pre-sent and future rates of sea-level rise, the combinedimpacts of sea-level rise, episodic hurricanes, andhuman interference with natural barrier processesthreaten the survival of coastal ecosystems in the longrun. For example, mangrove forests that are stressedby hurricane wind damage are limited in their abilityto produce peat, and this keeps the forests from accu-mulating substrate and growing vertically to keeppace with sea-level rise. Extended seawater floodingthen kills the trees and either slows restoration orcauses a total loss of habitat.

In the Gulf, rising ocean temperatures will altercoral reef ecosystems. Coral growth is generally re-stricted to average water temperatures between 72°Fand 86°F, and winter temperatures below 64°F affectcorals adversely.95 Currently, summer sea-surface tem-peratures in South Florida occur near the maximumtemperature tolerance of many corals.95,96 Thesespecies face heat stress during episodes of elevatedtemperature, such as those that accompany El Niñoevents.97 The past few years have seen unprecedenteddeclines in the condition of coral reefs in the region,including often extensive coral bleaching, growth ofalgae on reefs, loss of the dominant herbivore (a seaurchin), and pervasive over-fishing of reef species(Figure 29).95,98 The shallow waters of the SouthFlorida reefs will make them especially vulnerableto future episodes of higher sea-surface temperaturesthat are expected to accompany climate change inthe Gulf Coast. In the tropics and subtropics, higher

temperatures and changesin rainfall often coincide,meaning that nearshoremarine organisms mayhave to cope with fluc-tuations in salinity whilethey are stressed to theirlimits of heat tolerance.99

Coral reefs may alsobe at risk from increasesin atmospheric CO2 con-centrations, which willeventually reduce the al-kalinity of surface waters.This in turn would de-crease the calcificationrates of reef-buildingcorals, resulting in reefswith weaker skeletons,reduced growth rates,and increased vulner-ability to erosion duringsevere tropical storms.

Cl imate- inducedchanges in ocean tem-peratures might also altercirculation patterns inthe Gulf of Mexico andCaribbean Sea.100 If so,South Florida could seechanges in coastal andmarine ecosystems, sinceit lies at a critical inter-section of the Loop Cur-rent and the Gulf Stream. The interaction betweenthese major circulation systems controls the distribu-tion, recruitment, and survivability of coastal marinefish and invertebrate communities of the FloridaKeys and other areas of South Florida.101 These cur-rents also influence the residence time of water innearshore environments and the transport of sedi-ments and nutrients along the coast to Florida Bay.


F I G U R E 2 8Isles Dernieres

See page 38for full-size color images of this figure

F I G U R E 2 9 a & 2 9 bHealthy and Unhealthy Corals


4 8

RUNNING DRY:THE PANHANDLE REGIONALECOSYSTEM (ALABAMA-FLORIDA)

Florida’s largest river, the Apalachicola, together with the

Chattahoochee and Flint Rivers in Georgia and Alabama, are

known collectively as the ACF river system. Together they drain

more than 19,000 square miles of watershed that starts in the lower piedmont plateau and flows

through the flat coastal plain to form a delta at the shoreline of the Florida panhandle.101 The

Apalachicola Bay at the mouth of the river system is characterized by zones of extreme salinity

fluctuation controlled by the combined effects of river flow, seasonal winds, tides, and the shape

of the river basin.

Ecosystems in the Apalachicola drainage basin include upland forests, swamps, marshes, and flood-

plain wetlands. The sections of the watersheds from the Florida panhandle to Mobile Bay support

some of the richest biodiversity in all of North America. The flora of the drainage basin includes

117 plant species, including 28 threatened and 30 rare species. Nine plant species are found only

in the panhandle region, while 27 are found only in the general Apalachicola area.102 The floodplain

forests of this region are habitat to more than 250 species of vertebrates, excluding fish, and repre-

sent one of the most important animal habitats in the Southeast.102 Moreover, the highest density

of amphibian and reptile species in the United States occurs in the upper watersheds. Two species

of birds, the ivory-billed woodpecker and Bachman’s warbler, are considered extinct (Figure 30). The

barrier islands in this region provide important habitat for Gulf

migratory birds. The AFC river system is also known for its

diversity of fish, with 85 species.103 Some species are restricted

to the river basins in this central Gulf Coast region, including

the striped bass, which occurs only in the Apalachicola River.104

Increased demands for water by large upstream cities such

as Atlanta have promoted engineering and water-manage-

ment projects that now divert freshwater resources from the

AFC river system. In addition, agriculture extracts well over

300 million gallons per day for irrigation, largely from the

Flint River. Massive water consumption by the households and

industries of the metropolitan Atlanta region results in minimal upstream storage and marked reduc-

tions of water downstream of the city. In addition, the water released back into the system from

Atlanta is reduced in quality. Small flows from reservoirs are released to dilute urban wastes, mostly

from the Atlanta area, in order to achieve minimally acceptable water quality. Further reductions in

reservoir water levels would threaten a multimillion-dollar recreational industry in this watershed.

F I G U R E 3 0Pitcher Plant

See page 38for full-size full color image of this figure



4 9

The current regulation of river flows by reservoirs and by intensive water withdrawals has eliminated

much of the floodplain and the dynamic habitats it provided for plants and animals. While human

consumption of fresh water is expected to continue to increase, thus likely leading to further reduc-

tions of freshwater flow in the Apalachicola Bay system, future rainfall and streamflow are uncertain.

Increased moisture may help to alleviate the risk of drying out the area, while additional climate

change-related reductions in rainfall and streamflow would markedly reduce the plant and animal

productivity and threaten the unique biodiversity of this ecoregion.105

CONFRONTING CLIMATE CHANGE IN THE GULF COAST REGIONU n i o n o f C o n c e r n e d S c i e n t i s t s • Th e Ec o l o g i c a l S o c i e t y o f Am e r i c a

5 0

The ecological impacts of climate changewill have important implications for thegoods and services that ecosystems pro-vide to society. As the previous chapter

indicates, climate-driven changes must be viewed in

C H A P T E R

F o u r

Consequences of a Changing Climatefor Ecosystem Goods and Services

the context of human pressures and land-use changesthat are already stressing ecosystems. Below we focuson the consequences of climate change for water, air,land, and coastal resources, as well as for the healthand well-being of human populations.

Water Resources

Current and growing demands on freshwaterresources by cities, farms, and industriesleave the Gulf Coast vulnerable to even

slight changes in the seasonal or geographic distribu-tion of fresh water. Changes in the supply and dis-tribution of rainfall could have significant impactson the productivity of agriculture, aquaculture, andforestry, as well as on industrial, recreational, andtransportation activities.

Despite the uncertainty about how global warm-ing will affect future Gulf Coast water supplies, thetrend in human population growth in the regionmakes it highly likely that human consumption ofwater resources will increase. If climate change resultsin reduced runoff and lower groundwater levels inthe spring and summer, the consequence could be aneventual shortage of water to satisfy the growing andcompeting human demands. In the Floridan aquifersystem, increases in water withdrawals for public sup-ply and agriculture have already resulted in declinesin groundwater levels (Figures 31 & 32).

The increasing drawdown of surface and under-ground water reservoirs could combine with sea-levelrise to increase saltwater contamination of aquifers,particularly near the coast and in most of SouthFlorida. For example, large groundwater withdrawalsin the coastal zones of Baldwin and Mobile countiesin Alabama, which include the Mobile Bay and GulfShores regions, have increased salinity in wells (Figure32). Drinking water supplies taken from the Missis-sippi River for coastal communities such as NewOrleans are frequently threatened by saltwater intru-sion caused by a combination of sea-level rise, landsubsidence, and periodic low river flows. Groundwaterrationing is already being implemented periodicallyduring dry conditions in urban regions of Texas,Alabama, and Florida.

An increase in local subsidence and sinkholeformation has also been associated with growinggroundwater and natural gas withdrawals. Sinkholesare natural features of limestone geology. However,activities such as dredging, constructing reservoirs,

CONFRONTING CLIMATE CHANGE IN THE GULF COAST REGIONU n i o n o f C o n c e r n e d S c i e n t i s t s • The Ec o l o g i c a l S o c i e t y o f Am e r i c a

5 1

diverting surface water, and pumping groundwatercan accelerate the rate of sinkhole expansion, result-ing in the abrupt formation of collapse-type sink-holes. Drought can exacerbate the frequency of col-lapse of these sinkholes, so under the scenario of adrier future climate in the Gulf Coast, this riskwould increase.

One of the largest users of surface water inAlabama is thermoelectric power generation. Higherwater temperatures could reduce the efficiency ofpower plant and other industrial cooling systems andmake it increasingly difficult to meet regulatory

standards for acceptabledownstream water tem-peratures, particularly dur-ing extremely warm peri-ods . These problemswould be compounded ifa warmer climate also be-comes drier, resulting indecreased runoff, parti-cularly in areas that are alsoaffected by rising sea levels.

Agriculture and Forestry

Agriculture and forestry in the Gulf Coast relyheavily on adequate freshwater resources, andthe greatest impacts of climate change would

be felt through the combination of decreased soilmoisture (due to warmer temperatures and possiblyreduced rainfall) and reduced water availability forirrigation.

Based on both climate scenarios considered here,drier conditions are possible for the cropland areas inthe immediate coastal zone, particularly in southwestTexas, the lower Mississippi Delta, southern Alabama,and the Florida Panhandle.106 In the drier climatescenario, cotton, soybean, and sorghum productivitywould drop without irrigation, while there would beonly modest decreases in the production of hay.Citrus production may shrink moderately in Florida.According to model studies, rice yields in Louisianacould decrease by the year 2030 and then possiblyincrease by 2090, assuming that water is availablefor increased irrigation.107

Fertilization of crop growth byhigher atmospheric carbon dioxide(CO2) is unlikely to compensatecompletely for projected increasesin water demand associated withwarmer temperatures. In model-based studies, potential yields athigher CO2-concentrations arerealized only with increased irri-gation.106 Thus, increased demandfor water by other sectors is likely

to amplify negative im-pacts of warming on agri-culture.106

Vegetation models usingthe drier climate scenarioproject an expansion ofsavannas and grasslands atthe expense of forests, par-ticularly in the uplands ofthe Gulf Coast.108 Thesechanges in plant commu-nities would be influencednot only by reduced soilmoisture but also by in-creased fire frequency. Ifsuch shifts from forests todryland vegetation are real-ized, the results could bedramatic by the end of the21st century.

Although the amount of wateravailable will greatly influencelong-term changes in forest com-position across the region, forestmanagement can change the com-position and productivity of foreststands locally over relatively shortperiods. For example, soil nutrientavailability largely controls theproductivity of the even-aged plan-tation stands that now dominate


F I G U R E 3 2Aquifer Drawdownand Saltwater Intrusion

F I G U R E 3 1Declines in Aquifer Levels


The greatest impacts of

climate change on agricul-

ture and forestry would

be felt from a combination

of decreased soil moisture

and reduced water avail-

ability for irrigation.


5 2

E C O S Y S T E M S E R V I C E S

DRYING OR DROWNING THE“RIVER OF GRASS”?—THE SOUTHFLORIDA REGIONAL ECOSYSTEM

The predrainage landscape of South Florida was a mosaic of

habitats connected by fresh water. The water flowed in rivers,

streams, and shallow sheet flows across the gently sloping

landscape below Lake Okeechobee, through sawgrass interspersed with tree islands and tangled

mangrove forests, to shallow estuaries, and out to the coral reefs off shore.109 Wading birds, alligators,

sawgrass plains, mangroves, and tropical hardwood hammocks are still among the most recognizable

features of this landscape.110 The Everglades wetlands once extended over 3 million acres111 within a

total South Florida wetland system of 8.9 million acres, which included the Big Cypress Swamp, the

coastal mangrove communities, and Florida Bay.112

The natural evolution of this landscape mosaic has been driven by the slow relative rise in sea level

over the past 3,200 years, as well as extreme episodic events—in particular, fires, freezes, tropical

storms, hurricanes, floods, and droughts.17 The large variability in rainfall from year to year can bring

excessive flooding in some years and drought in others. However, this natural year-to-year variability,

along with the normal seasonal variability in rainfall, is a major contributor to the high productivity

and biodiversity of these wetlands (Figure 33).112

The same episodic events that control the natural landscape also affect human populations. To

protect the growing population from severe storms and to support agriculture (especially the sugar

industry), South Florida developed one of the world’s most extensive water-management engineering

systems.113 These engineering efforts have caused a change in

the timing and supply of clean water flows, reducing the Ever-

glades to a degraded remnant that continues to decline.114 The

natural variability of surface water flows has been altered dra-

matically, so that now in very wet years, massive amounts of

fresh water are discharged through canals and via enormous

pumps into a few coastal estuaries. The historical sheet flows

of water that used to occur along other parts of the coast have

been reduced substantially, commonly resulting in saltwater

intrusion and occasionally in hypersaline conditions in systems

such as Florida Bay.

As a result of the water-management system, the Greater

Everglades is an endangered ecosystem whose sustainability

is critically at risk.115 While a great deal of uncertainty remains

about the specific impacts to be expected from climate change,

global warming is likely to exacerbate the effects of human

stressors on the Greater Everglades ecosystem. Among the

F I G U R E 3 3The Everglades



5 3

the forestlands of the Southeast, and most of thesestands are now routinely fertilized. By selecting differ-ent species (or even genotypes) and controlling standdensity (through planting and thinning, fertilization,changes in rotation length, and use or prevention offire), human management will continue to exert thedominant control over the makeup and productivityof forests in the region. This also implies that manage-ment practices can be used to adaptto an altered physical environment.However, extreme, long-lastingdroughts could still have a negativeimpact on these managed systems,given their generally shallower fineroots (which leave them moresensitive to soil water deficits) andhigh canopy leaf areas (which in-crease evapotranspiration), relative tomore open, natural stands of trees.

Forest managers, as well as anincreasing number of other land-owners, are well aware of the naturalrole of fire in southern pine forestsand would prefer increasing use of prescribed firesto reduce fuel loads and wildfire risks.116 However,the structure of younger managed forest stands, withcontinuous tree canopies near the ground and highaccumulation of fuels, prohibits the use of prescribedfire during the first decade or so of the typical planta-tion cycle. The costs and legal liabilities of attemptingto manage fire, even in older stands, apparently stilloutweigh the risks of losses through wildfire, sincemost forest plantations are still not burned. This

situation will lead to increased risk of wildfire if theclimate becomes more favorable to fire in the future.During the summer of 1998, drought resulted inmore than 2,500 fires that burned roughly 500,000acres in Florida, destroying valuable timber anddamaging roughly 350 homes and businesses(see Figure 6).

Economic forces have historically been majordrivers of changes in the relativedistribution of agriculture andforestry. Since most of the forests,along with croplands, are on pri-vately owned land, market forcesstrongly affect land use.117 Pro-jected impacts of climate changeon the productivity of forests andagricultural areas could lead toreallocation of land uses as land-owners adjust to changing eco-nomic conditions. For instance,the wetter climate-change scenarioprojects increased hardwood pro-ductivity at the expense of soft-

woods, resulting in decreased revenues in the latterduring the next couple of decades.118 This shift wouldcause a slight decline in the amount of forestland,particularly in the Gulf Coast region. Given the cur-rent trend of increasing pine plantations in uplandregions of Mississippi, Louisiana, and Alabama, anincrease in regional rainfall could mean that futureconversions of cropland to forestland would eithercontinue at current trends or at slightly lower ratesthan without climate change. However, under the

impacts that can be expected are ecosystem shifts due to sea-level rise and increased success of invasive

exotic species. Other major effects could result from more frequent or more intense hurricanes or from

more frequent or intensive droughts, which would increase the risk of major wildfires.

The greatest risks the Everglades face from climate change, however, may well be accelerated sea-level

rise and the damaging impacts of elevated storm surges. Since the flow of water is the most critical factor

in the survival of the region’s unique mosaic of habitats, any changes in water balance will certainly affect

this unique and valuable landscape. An enormous restoration process recently approved by Congress, the

Comprehensive Everglades Restoration Project (CERP), however, does not take into account either sea-

level rise or potential shifts in water flow driven by climate change.

While economic forces

are typically the domi-

nant factors controlling

the productivity of agri-

culture and forestry,

yields may increase due

to higher CO2 levels

if water resources are

not limited.


5 4


drier climate-change scenario, conversion of forestsinto some other land use, such as rangelands, seemssignificantly more likely.

Warmer average temperatures and milder winterswill also result in a higher incidence of damage byagricultural and forestry pests such as the Southernpine bark beetle, which caused over $900 million indamage to southern US pine forests between 1960and 1990.119 Milder winters without frost will allowthe larvae of several types of pest to produce moregenerations per year. While moderate water stress can

F I G U R E 3 4Shrimp Trawler


actually increase plants’ resistance to plant-feedingpests, severe stress can increase the susceptibility offorests and crops to infestation by pests. Already,agriculture in the Gulf and other Southeastern statesconsumes 43 percent of the insecticides and 22 per-cent of the herbicides used by US farmers, even thoughthe region has only 14 percent of the nation’s crop-land.106,120 This heavy use of restricted chemicalsacross the Gulf Coast landscape reinforces concernsabout water use and water quality and how climatechange may affect both in the future.

Fisheries and Aquaculture

As mentioned earlier, shrimp, blue crab, andmenhaden fisheries in the Gulf of Mexico areconsistently among the highest valued com-

mercial fisheries in the United States.54 Assessing theconsequences of climate change for these fisheries is

complex because of poten-tially competing effects oftemperature, water availa-bility and flow, and impactson wetlands. Increases insea-surface temperatures,for example, could en-hance the annual yieldof shrimp in the Gulf ofMexico. Warmer waterand higher growth rateswould increase produc-tivity of some commerci-ally valuable, estuarine-

dependent marine species, and productivity could befurther enhanced over time if wetlands were able tomigrate inland in response to sea-level rise (a ratheruncertain prospect).121 However,any enhanced fisheries productivityis likely to be temporary becauseof other long-term effects onfishery habitat. The annual yield ofshrimp in the Gulf of Mexico, forexample, declines when the annualdischarge of the Mississippi Rivergoes up, expanding the size of thedead zone on the Louisiana shelf.122

Impacts on coastal marshes in Texas

and Louisiana, which serve as nurseries, also affectfisheries production.123 Rapid sea-level rise andwarmer winter temperatures are likely to negativelyimpact these habitats. If long-term reductions infreshwater flow into estuaries and rapid sea-level riseresult in a net loss of coastal marsh area, thesefisheries will most likely decline.124

In the semi-arid Laguna Madre of Texas (see box,p.45), the lack of fresh water and highly saline shore-lines both limit the development of marshes. If globalwarming extends this low-rainfall climate patternnorthward, the existing intertidal marshes will dimin-ish in area because of shoreline retreat and enlargedsalt barrens landward. Such loss of marsh habitat isunlikely to be compensated for by mangroves orseagrasses and would cause fishery yields to declinebelow historic levels. Significant declines have alreadybeen observed in shrimp and blue crab commercialyields in South Texas bays and the Laguna Madreduring the drought and warm winter conditions ofthe 1990s.125 Also, densities of small fishes, shrimps,and crabs have recently been observed to be lower

in Laguna Madre seagrass beds,compared with coastal areas else-where in the Gulf of Mexico.34

The large aquaculture industryin Louisiana and Mississippi placeshigh demands on freshwater re-serves, particularly groundwater(Figure 34). In most of the GulfCoast states, about 50 percent ofaquaculture ponds use ground-water. In Louisiana, 75 percent use

Increased groundwater

salinity resulting from

more droughts and salt-

water intrusion could

negatively impact the

region’s aquaculture

industry.


5 5

groundwater. Increased groundwater salinity resultingfrom more frequent droughts and saltwater intrusioncould negatively impact the region’s aquaculture in-dustry. During the two-year drought from 1999 to2000, salt contamination of surface and shallowgroundwater limited crawfish farming in southwestLouisiana, leading to economic devastation of manycrawfish-farmers.

Climate change is also likely to affect the recre-

Coastal Communities

Much concern about climate change hasfocused on the potential of more frequentextreme weather events having the great-

est direct economic and human health impacts inthe United States. The Gulf Coastis particularly vulnerable in thisregard.128 Of the top 15 most no-table* weather disasters in theUnited States, 9 occurred in GulfCoast states.129 The top three statesin the nation in terms of averageannual losses from hurricane, flood,and tornado damage are Florida($1.7 billion), Louisiana ($966.9 million) and Texas($909.4 million), with Mississippi following in seventhplace ($463.5 million) and Alabama in eighteenth($185.0 million).130

The most significant impacts will result fromhurricanes and floods, especially as sea level increases,with additional impacts from droughts and thunder-storm-related hazards (hail, tornadoes, and lightning).The number of such events and amount of lossessteadily increased from 1949 to 1994, based on statis-tics from both the insurance industry and the FederalEmergency Management Agency.131 While nationaleconomic losses show an increasing trend, from a fewhundred million dollars annually in the late 1970s to$2.5–$21.9 billion annually from 1989 to 1997, trendsin the frequency and intensity of tropical storms andhurricanes do not show a consistent parallel increase.132

However, intense rainfall events (more than 2 inchesin a 24 hour period) have increased in frequency.3

This suggests that the increasing losses are primarily

ational and sport fishing industry. Increased tempera-tures are unlikely to directly harm most target speciessince they exist in already warm environments.However, runoff affects freshwater habitats and anyreduction in runoff would limit the capacity of theseaquatic ecosystems to support fishing activity. Thus,both coastal and freshwater fisheries of the GulfCoast are vulnerable to potential changes in theflow and availability of water in the 21st century.127

due to societal changes, including a growingpopulation in high-risk coastal areas, and lifestyleand demographic changes that leave more peopleand property at greater risk.133

Against the backdrop of increas-ing societal vulnerability to hazards,how might trends in weather-relatedhazards change in the future? Arecent review of studies has con-firmed that extreme events such asfloods and droughts are indeed in-creasing, but not uniformly acrossthe globe or the United States.134

The observed evidence is consistent with the gen-eral predictions of climate models, which suggestmore extreme weather events as a result of globalwarming.

The number of intense hurricanes makinglandfall has decreased over the period 1944 to 1996,even while economic damages have soared.135 Rapidpopulation growth anddevelopment in vulner-able coastal areas areprimary reasons behindthis increase in dam-ages.136 For example,damages associated withHurricane Andrew in1992 were estimated atabout $27 billion, nearlythree times the costs ofany other weather-relatedevent in the Southeast in

F I G U R E 3 5Erosion Damage from TropicalStorm Frances (1998)


* “Notable” was a function of economic losses, death toll, event magnitude, and meteorological uniqueness.

A growing population

in coastal areas leaves

more people and

property at greater risk

from climate change.


5 6

the past decade. Should global warming increase thenumber or intensity of hurricanes, the impacts onpeople and property in coastal communities are likelyto be severe, especially when aggravated by sea-levelrise. But even without an increased frequency or inten-

sity of storms, future stormdamages are likely to rise sub-stantially just because of theincreased amount of develop-ment in harm’s way (Figure35). Predictions of futurewave and storm surges accom-panying severe hurricanes

(categories 3–5) indicate that significant wave heights(between 3 and 6 feet) will occur as far inland as NewOrleans, if barrier islands and wetlands are lost asbuffers.137 The ravages of Hurricane Andrew in 1992on Florida and Hurricane Georges in 1998 on coastalAlabama, Mississippi, and Louisiana, or even TropicalStorm Frances on Texas in 1998 should serve as atelling wake-up call to Gulf Coast inhabitants.138

F I G U R E 3 6July Heat Index Change by 2100


So far, no trend has been detected in the frequency,duration, or magnitude of droughts in the UnitedStates.139 The most severe droughts in the MississippiRiver Basin occurred in the 1930s and mid-1950s,with other major water deficits occurring in the early1990s139 and again in 2000. However, projectingfuture water deficits requires analyzing more thanrainfall and other indicators of available moisture. Itrequires consideration of increased demand on surfaceand groundwater resources and also the consequencesof engineered water systems. As discussed earlier,water demand is increasing in the Gulf Coast region,and higher temperatures will increase evapotrans-piration. Whether or not these trends will amountto increasing water deficits depends both on yet-uncertain rainfall changes and on water management.The potential damage that prolonged moisture deficitscan bring, given current water consumption in theGulf Coast, became evident during 2000 with lossesestimated at $4 billion to agriculture and relatedindustries.140

Public HealthWeather-Related Public Health IssuesThe July heat index is projected to increase the mostin southern states (Figure 36), and Texas is particu-larly vulnerable to increased frequencies of heat waves,which could increase the number of heat-relateddeaths and the incidence of heat-related illnesses.Urban areas such as Dallas and Houston areespecially vulnerable to theseextreme events, as is Tampa. Ineach of these cities, deaths attrib-uted to extreme heat conditionsaverage about 28 per year, andthis rate could more than dou-ble to 60 to 75 deaths per yearwith a 3°F warming of summertemperatures. Vulnerability toheat-related stress depends largely on people’s ability toprotect themselves from temperature extremes, thatis, on whether or not they can afford air condition-ing. Also, the elderly, the very young, and those whosehealth is already compromised are most prone toillness during heat waves.141

Air quality issues associated with a changingclimate include changes in near-surface ozone (smog),particulate pollution, visibility, and pollen counts.Climate change is likely to produce conditions thatenhance ground-level ozone formation. Increasedconcentrations of air pollutants will be particularly

evident, for instance, in theHouston-Galveston area, whichis one of several Gulf Coast citiescurrently classified as an area of“severe” non-compliance withfederal air quality standards.Ground-level ozone has beenshown to aggravate respiratoryillnesses such as asthma, reduce

lung function, and induce respiratory inflammation.142

Even modest exposure to ozone can cause healthyindividuals to experience chest pains, nausea, andpulmonary congestion.142 In much of the nation, awarming of 4°F could increase ozone concentrationsby about 5 percent.143


Heat-related deaths per year

in Dallas and Houston could

more than double with a

3°F warming in summer

temperatures.


5 7

Upper and lower respiratory allergies are in-fluenced by humidity. Even as little as a 2°F warming,along with wetter conditions, could increase respira-tory allergies due to increased pollen counts inMississippi and Louisiana.142,144

Water-Related Public Health IssuesChanges in water availability and flow will influencethe prevalence of diseases and waterborne pathogens,especially in densely populated areas. Such changesare typically associated with extreme events andhotter temperatures, which can lead to expandedhabitat for and infectivity ofdisease-carrying insects andan increase in the potentialfor transmission of diseasessuch as malaria and denguefever.145 Gulf Coast states arecited as particularly vulner-able to these changes; indeedboth malaria and denguefever vectors have alreadyincreased markedly, even during the droughts ofrecent years.146 Vulnerability to climate-change andwater-related health risks is particularly severe in areaswhere water supply and quality, waste-disposalsystems, and in some cases even electricity for heatingand cooling, are already substandard (as for examplein the “colonias” of South Texas).147

Although mosquitoes are abundant in many areasof the Gulf Coast, factors other than climate stronglyaffect the risk of mosquito-borne disease outbreaks.Infrastructure, sanitary, and public health improve-ments have led to a reduction in cases of dengue feverin Texas from 500,000 in 1922 to only 43 between1980 and 1996.148 The ability of the health care sys-tem to reduce our health risks in the face of climatechange is thus an important consideration in any pro-jections of vulnerability during the 21st century.

Besides the water- and temperature-dependentimpacts on disease-carrying insects, a variety of hu-man health risks stems from disease organisms thatreside in coastal waters. Those risks can be exacer-bated by warmer temperatures and increased rainfall.They include human infections that are acquired byeating contaminated fish and shellfish and diseasesacquired during the recreational use of water.149

Gastrointestinal diseases, respiratory diseases, andskin, ear, and eye infections can all result, and someof these can be fatal, particularly to children, theelderly, and immune-compromised people. Micro-organisms associated with diseases in coastal wateroccur naturally (e.g., Vibrio vulnificus, as well as toxicalgae and red-tide dinoflagellates) and can enter water-ways through the disposal of human and animalwastes.

Changes in temperature, rainfall, and ENSOcycles, together with human factors such as water andsewage management, will determine the distribution

of human health risks along theGulf Coast, both in geographyand timing. In Florida, 30percent of the population usesseptic tanks, which contributeabout 210 million gallons ofwaste every day. Those wastescontain microbes that can reachgroundwater and nearby sur-face water bodies. Over the

past decade, surveys of indicator bacteria and humanintestinal viruses in fresh water and nearshore coastalwaters demonstrate that water quality in many ofFlorida’s canals and tributaries has been impacted bywastewater from nearby residential areas. In addition,the contamination is related directly to rainfall,stream flow, and water temperature. Increased rainfallevents associated with El Niño in southwest Floridaare statistically related to a decrease in water quality.A high incidence of intestinal viruses in nearshorewaters and canals has been detected during strongrain events such as those that occurred during the1998 El Niño. Rainfall has also been linked to adecrease in coastal water quality (measured usingbacteria levels) over the past 25 years in the TampaBay region. Overall, between 70 percent and 95percent of the sites surveyed along the west coast ofFlorida to the Florida Keys tested positive for humanintestinal viruses, including coxsackie, Hepatitis A,and the Norwalk viruses, which are associated withdiarrhea, aseptic meningitis, and myocarditis,respectively.150

Along Louisiana’s coast, viral and bacterial con-tamination of shellfish has repeatedly caused illness(neurotoxic poisoning etc.) and closed important

Changes in water availability

and flow—typically associated

with extreme events and hotter

temperatures—will influence

the prevalence of diseases

and waterborne pathogens.


5 8

fisheries. The protozoan Perkinsus marinus is the mostimportant pathogen threatening the Gulf ’s sig-nificant oyster industry.151 Prevalence of P. marinushas been related to salinity and temperature, with lowtemperatures and salinities usually limiting infectionand higher temperatures and salinities typically in-creasing it. Long-term climatic changes could produceshifts in salinity and temperature that favor P. marinusprevalence and disease. Centers of infection have beenfound along the central to northern Texas coast inGalveston Bay, the Barataria Bay area of Louisiana,and Tampa Bay.151


Warmer coastal waters and nutrient pollutioncan also increase the intensity, duration, and extent ofharmful algal and cyanobacterial (formerly, blue-greenalgae) blooms, particularly in Florida and Texas. Theseblooms damage habitat and shellfish nurseries andcan be toxic to both marine species and humans.About two-thirds of the Texas coastline was closed toshellfish harvesting in 1996 because of contaminationby an unusually large bloom of marine algae, or redtide. In summer 2000, a red tide bloom along thebeach at Galveston caused the closing of recreationaland commercial operations.


5 9

Climate change is likely to have a numberof disruptive impacts on Gulf Coastecosystems, as discussed above, especiallyin light of ongoing human pressures on

the environment. They vary in the degree of scientificcertainty (see box, p.60), however, we believe that inorder to prevent or minimize the negative impactsand to profit from the potential benefits of climatechange, people and policymakers in the region canand should take action now.

We outline here three basic strategies for protec-ting ecosystems and maintaining ecological goods andservices in the face of a changing climate:

• mitigation, which involves reducing the paceand magnitude of global warming and thusminimizing climate-driven ecosystem change

• minimization, which involves reducing the humandrivers of habitat destruction and species loss

C H A P T E R

F i v e

Meeting theChallenges of Climate Change

• adaptation, which involves changing the way wedo business in order to minimize the severity ofclimate-change impacts and enhance the abilityof ecosystems and Gulf Coast communities tocope with climate change

Together, these approaches can reduce the region’svulnerability to the impacts of climate change andyield significant ecological, economic, and healthbenefits, even in the absence of major climate disrup-tion.* We consider them a prudent and responsibleapproach to ensuring stewardship of the Gulf Coast’sinvaluable ecological resources. Because much ofthe land in the region is privately owned, strategiesfor dealing with climatic and human drivers of eco-system change must involve private landowners as wellas governmental agencies and other sectors of society.

Mitigating the Climate Problem

The primary goal of mitigation is to reducethe magnitude of climate stressors that induceecosystem change. Reducing greenhouse-gas

emissions can be seen as a type of “insurance policy”that aims at directly reducing the risks of global

warming. Clearly, in the Gulf Coast, where the fossil-fuel industry is the biggest economic sector and wheregreenhouse-gas emissions are among the highest inthe nation, it is critical to find ways to reduce green-house-gas emissions without reducing the economic

* The vulnerability of a system to climate change is a function of its sensitivity to changes in climate and its ability to adapt.See note 3.


6 0

Potential Impactson Gulf CoastEcosystems

Across All Systems

Upland Ecosystems

High Confidence

Increased competitionfor fresh water amongnatural, urban, andagricultural ecosystemuses

Enhanced spread ofinvasive species anddecrease in nativebiodiversity

Increase in humanhealth effects fromheat extremes

Increased pests suchas pine bark beetlesimpacting forests,agriculture, andresidential areas,especially under moistclimate conditions

Medium Confidence

Subtropical vegeta-tion moving intocentral warmtemperate regionunless hindered orotherwise destabi-lized by humanalterations of thelandscape

Increased forestdisturbance fromfires, storms, andother physicalstressors, andchanges in commu-nity composition

Increased agriculturalproductivity due toCO2 fertilizationwhere water is not alimiting factor;reduced where wateris a limiting factorand pests increase

Lower Confidence

Major ecosystemchanges in wetland,agricultural, andforest ecosystemsunder drier climateconditions

Under drier condi-tions, reduced forestproductivity; expan-sion of grasslandvegetation from westto east; shift in moistto dry forests, andfrom dry forests tosavannah vegetation

Under drier condi-tions, fire frequencyand intensity mayincrease, benefitingprairie systems, butnegatively affectingproduction forestsand wildlife

HOW CONFIDENT CAN WE BE ABOUT CLIMATE-CHANGE IMPACTS ON GULF COAST ECOSYSTEMS?

The climate change assumptions that underlie the assignment of confidence levels include• an increase of 3–10°F in air temperature over the next 100 years• a concurrent increase in coastal and inland water temperatures• a 13-inch average sea-level rise• an unchanged frequency of severe storms, including hurricanes (except for continued decadal

changes in storm frequency such as the projected return to higher storm activity in the GulfCoast region in the next decade), but possible slight increase in hurricane intensity

• still uncertain changes in the direction and magnitude of water availability

The assigned confidence levels reflect both the level of certainty in climate-change projections andthe expected ecosystem response to those changes. In addition, the climate-change impacts areviewed against the backdrop of expected continued increases in population and land-use changes.

Confidence Levels

M E E T I N G T H E C H A L L E N G E S


6 1

Medium Confidence

With reduced streamflow in small regionalrivers, decrease inproductivity ofdown-streamecosystems

Higher urban runoffimpacting waterquality and fisheriesof lakes and estuaries

Lower Confidence

Increased flooding ofnatural systems andfloodplains in urbanareas

High Confidence

Increased salinizationof groundwaterresources

Decrease dissolvedoxygen in lakes andstreams due to higherwater temperature

Potential Impacts onGulf Coast Ecosystems

Freshwater Wetlands& Aquatic Ecosystems

* “Confidence” refers to the level of “scientific certainty” and is based on expert understanding andjudgment of the extant scientific literature supporting likely ecosystem impacts of certain climate-related changes. The focus here is on impacts on ecosystems and their goods and services, assum-ing plausible climate scenarios for the region. Note that the level of confidence is NOT synonymouswith the degree of ecosystem vulnerability to climate change, nor to the relative economic orsocial importance of any particular change.

Coastal and MarineEcosystems

Habitat losses inwetlands not able tomigrate inland, accu-mulate substrate assea level rises, oradapt to increasedsalinity and waterlevels

Increased floodingassociated with stormsurges due to sea-level rise

Erosion and eventualloss of barrier islandsunable to migratelandward

Saltwater intrusioninto coastal aquifers

Reduced growth andstability of coral reefsdue to increased seatemperatures andother stressors

Declining estuarinewater quality due tocombined changes inrunoff and contami-nation from agricul-tural and urbansources

Increased salinity ofestuaries dominatedby local runoff anddroughts

Increased incidenceof marine andwaterborne patho-gens under bothclimate scenarios

Change in frequencyand duration ofstratification andhypoxia on thecontinental shelf offthe Mississippi Riverdelta as a result ofchanges in nutrient-laden runoff

Increased stress in tidalmarshes in regionsbecoming drier

With reducedstreamflow from localrivers and increasedsalinity of estuaries,reduced wetlandhabitat, changes inestuarine food web,and long-term declinesin marsh-dependentfisheries

With reduced stream-flow from local rivers,reduced aquacultureproductivity; with in-creases, increased aqua-culture productivity

Confidence Levels


6 2

vitality of the region (seeFigure 19). Fortunately,according to a growing num-ber of studies by governmen-tal agencies as well as indepen-dent research institutions,climate protection and otherenvironmental benefits canbe achieved simultaneouslywith economic gain.152

Texas, with the highestannual emissions of green-house gases of any state in theUnited States, is responsiblefor a significant share of theglobal burden of CO2.153

While emissions from otherGulf Coast states are smaller,crude oil and natural gasproduction, the petrochemicalindustry, and reliable suppliesof energy are critically impor-tant to the whole region.Against this backdrop, it isremarkable how many oppor-tunities for environmental,economic, and public healthcobenefits can arise from re-ducing the consumption offossil fuel and the emissionsof heat-trapping gases. InTexas and Florida, for instance,where a number of cities cur-

rently fail to meet air pollution limits, reducing emis-sions from fossil-fuel burning could help meet federalclean-air standards.153,154 Gulf Coast states have animmediate opportunity here to devel-op implementation plans to meetthose standards while also reducingglobal warming pollutants.

Moreover, both Florida and Texashave ample opportunities to contributeto and benefit from the developmentof clean energy technologies andalternative energy markets (Figure37). Florida produces only smallamounts of fossil fuel but depends

heavily on petroleum and electricity, and thus onenergy imports. Fossil-fuel consumption is greatestfor transportation and for electricity production. Inlight of its rapidly growing population, support oftougher federal vehicle fuel-efficiency standards, effortsto reduce vehicle miles traveled, and the developmentof renewable energies such as solar would be mosteffective.155 Through the international Cities forClimate Protection Campaign, a number of commu-nities—such as Alachua, Broward, Delta, Hillsborough,Miami-Dade, and Orange Counties in Florida; MiamiBeach, Riviera Beach, and Tampa, Florida; NewOrleans, Louisiana; and Austin, Texas—are alreadytackling emission reductions. They are, for example,improving energy efficiency, supporting small-scaleuse of renewable energy, reducing vehicle milestraveled, cutting waste, and taking other landscapingand planning measures.156 These can serve as modelsto other Gulf Coast communities, as does the guber-natorial initiative on energy conservation in Alabama.

Texas has a variety of clean energy resources—wind, solar, biomass, and geothermal. The state hasbegun to develop some of these and has the marketpower to help spread their use (Figure 38).157 Theindustrial, transportation, and building sectors havesignificant potential for reducing emissions by switch-ing from coal and oil to natural gas and by usingalready available technologies to achieve energy effi-ciencies.153 With its strong technology and knowledge-based economy, Texas could also make a significantcontribution by further developing such technologiesfor marketing regionally, nationally, and globally.

Texas recently passed an electricity-restructuringbill that tries to assure a bigger role for clean energysources in meeting the state’s energy needs. The state’sNatural Resource Conservation Commission decided

in fall 2000 to develop an inventoryof greenhouse-gas emissions and aplan to address the emissionsproblem.

Louisiana is already switchingmost of its energy production fromoil to natural gas and has begun todevelop solutions to climate change.The state has recognized four criticalopportunities to reduce global warm-ing pollutants: increasing energy

F I G U R E 3 7Windmill

F I G U R E 3 8Renewable Energy Potentialin Texas




Reducing greenhouse-

gas emissions can be

seen as a type of

“insurance policy”

that aims at directly

reducing the risk of

global warming.


6 3

efficiency wherever possible, promoting its naturalgas resources, promoting and developing renewableenergy resources, and improving the state’stransportation systems.158

In addition, forest conservation, afforestation,and reforestation provide largely unexplored oppor-tunities to reduce atmospheric CO2, as do agricul-tural land-use practices that help sequester carbon insoils.159 While some current agricultural and forestry

F I G U R E 3 9Improving Irrigation Technology


operations already help to sequester carbon, it isnatural forest protection and reforestation that canmake a noticeable contribution to the region’smitigation strategies. Such activities can also yieldimportant ecological benefits if biodiversity and otherenvironmental considerations are taken into account.In summary, these examples highlight the modest butimportant beginnings and opportunities emergingthroughout the Gulf Coast states.

The second important strategy, immediatelyavailable to Gulf Coast states, is to reducethe impact of human drivers of habitat dis-

turbance and destruction. Already stressed ecosystemstypically are more vulnerable to additional stressors,such as those associated with climate change.

The litany of pressures from an increasing popu-lation include suburban sprawl and habitat fragmen-tation (see Figure 10), increased use of surface andgroundwater resources, diminished water quality,engineering of river flows and runoff, land-use prac-tices such as pest control and fire suppression, anddevelopment of barrier islands, wetlands and otherecosystems for human use. In addition, there aremarket-driven pressures on agriculture to increaseyields with high chemical inputs, on fisheries to over-harvest, and on forestry to re-place diverse natural forests withplantations of a fast-growingspecies for increased yields.

While these types of landand resource uses currently yieldenormous economic benefits to

the Gulf Coast, implementing“best practices” can minimizetheir ecologically harmful sideeffects. For example, progres-sive zoning initiatives thatintegrate different land usesover a smaller area can protectnatural resources and openspace from suburban sprawl.160

Best practices can also improvethe management of agricul-tural and aquatic ecosystemsto achieve goals such as water conservation and reducedfarm runoff (Figure 39). Furthermore, critical evalu-ation should be given to the role of federal and statesubsidies that promote the development and recla-

mation of certain ecosystemsthat are also particularlyvulnerable to climate change,such as coastal marshes,flood plains, and wetlands.

Minimizing Human Impacts on the Environment

Adapting to Climate Change

Finally, Gulf Coast residents, planners, landmanagers, and policymakers can take actionsnow that will minimize the potential impacts

of global climate change and leave the region betterprepared to deal with an uncertain future. Clearly,climate change magnifies the problem environmentalmanagers face all the time: how to balance the un-certainty of environmental changes against the

certain costs involved in making managementchanges. Moreover, the time horizon and geographicscale of human management of ecosystems or naturalresources does not necessarily match the naturalcycles and processes in these systems. Ecosystems mayreact with time lags to climatic and human pressures.Thus, we always face the risk of over- or underadapt-ing to climate change. One of the best ways to deal

Implementing “best practices”

can minimize the ecologically

harmful side effects of land and

water resource use.


6 4

with this irreducible uncertainty in environmentalmanagement is to adopt learning-oriented, flexibleapproaches that include monitoring, periodic review,assessment and adjustment of previous decisions inlight of new information—a strategy known asadaptive management.

In the immediate future, the principal targets foradaptation in the Gulf Coast should include

• those natural and managed ecosystems facing thegreatest risk of losing their environmental assetsor natural resources to climate change

• those decisions that affect land and water man-agement in the long-term

• those climatic changes that are most likely tooccur

That does not mean discounting plausible but cur-rently less certain climate changes that could be enor-mously important in the future. Instead, adaptationmeasures should be examined for their feasibilityunder either drier or wetter climate conditions inthe future.

Given these targets, the following areas seem mostimportant for consideration in current policy-making,planning, and management decisions.

Adaptation in WaterResource ManagementAdaptation options in water re-source management are amongthe most important, since so manyGulf Coast ecosystems and eco-nomic activities are potentially atrisk if climate change reduceswater resources. However, be-cause future water scenarios areuncertain, the greatest emphasisnow must be placed on increasingwater management flexibilityrather than on planning for onlya wetter or only a drier future. For example, theprospect of extended periods of drought punctuatedby more extreme rainfall and flooding events—ascenario much of the region has already experiencedin recent years—would most likely produce signifi-cant public pressure for short-sighted but long-lasting

measures such as channelization, reservoir construc-tion, levees, etc. Past experience in the Gulf Coastand elsewhere has shown that such “solutions” moreoften exacerbate rather than alleviate the problemover the long term.

The key to increasing water management flex-ibility is to be able to address year-to-year and seasonalwater variability and weather extremes as they occur.Hence, water districts could begin now—withoutcommitting to any particular future climate scenario—to review their policies, rules, and decision-makingprocedures and identify and improve those thatrestrict their flexibility and adaptive capacity. Forexample, current rules for freshwater use for specificpurposes would limit water management optionsunder different climate scenarios. In addition, GulfCoast communities and districts could review andproduce water plans to address their water needsduring drought-of-record conditions, and identifywater-management strategies for periods when stream-flows, reservoir storage, and groundwater levels are50 and 75 percent below normal. Water plans shouldalso identify increasing water demands that are drivensolely by population growth and increasing waterdemands from relevant water users such as agriculture,urban areas, and industries. Texas mandated such an

assessment in a 1997 amend-ment to the Texas Water Code.This legislation changed waterplanning in Texas from astatewide to a regional activitywhere water supply, storage,and use of streams, river basins,reservoirs, lakes, and ground-water aquifers must now bedocumented for improvedmanagement decisions.161

Another useful measure hasbeen enacted in Florida. Thestate established a regulatoryand taxation authority based

on watershed boundaries, which allows districts tomanage at the appropriate scale to address water-cycle changes.

Regular opportunities arise in the normal lifecycle of water-management infrastructure to replace,repair, and if necessary relocate systems to address

Water districts could begin

now—without commiting to

any particular future climate

scenario—to review their

policies, rules, and decision-

making procedures and

identify and improve those

that restrict their flexibility

and adaptive capacity.



6 5

saltwater intrusion problems, and to reduce publichealth risks from septic systems by investing inmodern sewage and wastewater treatment systems(see Figure 32). However, such opportunities to adaptto changing environmental conditions are frequentlymissed without a greater awareness of climate changeand growing human demands on water systems.

Finally, most of the water-management systemsof the Gulf Coast region have been developed to re-move excess water and prevent flooding rather thanto store water for use duringperiods of reduced precipitation.One central goal of the Compre-hensive Everglades RestorationProject is to limit the presentdischarge of fresh water to the seaby increasing storage in wetlandsfor future needs. This approachshould be examined throughoutthe region to increase adaptabilityto either a wetter or drier future.

Adaptation in Agriculture and ForestryFarmers are already accustomed to making season-to-season adjustments in their farming operations, andthus they may be able to respond to changes in long-term environmental conditions by choosing morefavorable crops, cultivars, and cropping and irrigationsystems. For example, changes in planting and har-vesting dates for one crop or shifts to different cropvarieties might maintain or increase yield under dif-ferent climatic conditions. Given the diversity ofcrop-management options and the uncertainty aboutsoil moisture and the availability of irrigation waterin the future, farmers in the Gulf Coast region couldbenefit from improved information on weather andclimate forecasting, such as access to improved ENSOforecasts.162 In addition, farmers need to becomeaware of how their land-use practices contribute tolarger regional issues of water quantity and quality,since they are important participants in meeting thechallenge of climate change in the region.

Potential strategies for foresters include changes ingenetic stock and silvicultural systems that can increasewater use efficiency or water availability. Improvedtechniques in sustainable land management shouldinclude better information on the likelihood of fire,

pests, drought, storms (hurricanes), and other naturaldisturbances.106 Forest management offers opportu-nities to adjust species, genotypes, soil fertility, spac-ing, rotation lengths, and fire management to accom-modate some of the expected consequences of climatechange. Strong consideration of the implications ofclimate change for sustainable forestry is important,given increasing demand for forest products incoming decades.

Forestry and agricultural land-use planningwould also benefit from bettercommunication and coordination,such as on decisions about theconversion of marginal lands.Land-use decisions affect carbonand nutrient sequestration, whichcan influence not only the atmo-sphere but also water resources. Thisis particularly important to considerin rehabilitation programs for cer-

tain types of forests, such as those that previouslyinhabited large alluvial plains of the Gulf Coast.163

Land-use changes have important feedback effectson climate by modifying the amount of carbon thatis stored in terrestrial ecosystems and by modifyingthe local and regional climate.3 Both natural andmanaged ecosystems in the Gulf Coast, but especiallyforests, currently store substantial amounts of carbon.The amount of carbon stored in ecosystems at anytime in the future will depend on a variety of factors.The largest impact will occur as a result of changes inland use and underlying market forces. For example,the establishment of new forests on former agricul-tural land will increase ecosystem carbon content inproportion to the amount of woody biomass accu-mulated in trees, along with lesser amounts accumu-lating in the litter layer and soil. However, increasedharvesting of forest plantations, or conversion offorests of any type to urban or other generallynonforested land uses, will lead to proportionatedecreases in ecosystem carbon content.

Adaptation in Land and BiodiversityConservationAnother critical area for climate-conscious planningand management is land and species conservation inthe region. Species currently protected within park

Forest managers can

prepare for a changing

climate by adjusting

species, soil fertility,

spacing, rotation length

and fire management.


6 6

or conservation land boundaries may migrate out ofthese areas as the climate changes and lose the protec-tion that ensured their survival. Constructing bufferzones through conservation easements and migrationcorridors may help these species and habitats toadapt.

Conversely, in the process of ecosystem restora-tion, it would be short-sighted and imprudent not toconsider climate change and sea-level rise.164 Louisiana,for example, through its Coast 2050 wetland-restora-tion plan has an opportunity to include these consid-erations.165 The most prominent regional example isthe unprecedented effort under way now for theecological restoration of South Florida’s Everglades(see box, p.52).166 In 2000, Congress approved afederal funding bill of $7.8 billion for restructuringthe water-management system and acquiring largetracts of land for water storage and nutrient re-

moval.167 The human-domi-nated nature of these hydro-logical and ecological systemswill fundamentally affect theirability to adapt to climatechange over the next century.The South Florida restora-tion scenarios were analyzedand the final proposed planselected in the absence of anyassessment of the implica-tions of climate change.

Adaptation in Coastal CommunitiesSea-level rise is already occurring and virtually certainto accelerate in a warmer world. An assessment ofpotential land loss along the Atlantic and Gulf coastsdue to sea-level rise has identified Louisiana, Florida,and Texas as having the most vulnerable lowlands. Assea level rises, the statistics used to identify the prob-ability of coastal flooding will have to be reevaluated.A 50-year or even more frequent flood may becomeas severe as a 100-year flood. Currently, coastalinsurance rates are not adjusted for the growing riskfrom sea-level rise and associated coastal erosion. Inorder to sustain actuarial soundness and adequatelyreflect the increasing risk, flood insurance rates (set atthe federal level through the National Flood InsuranceProgram) would need to be adjusted regularly.168 The

Federal Emergency Management Agency estimatedin 1991 that the number of households in the coastalflood plain would increase from 2.7 million to 6.6million by 2100 under a sea-level rise scenario of15.6 inches over 100 years.169 While the total eco-nomic impact of such a sea-level rise is still uncertain,it is clear that much coastal development is atincreased risk in this century.168

Typical responses to the landscape changes asso-ciated with a rising sea level in the past have includedbuilding seawalls and other hard structures to holdback the sea, raising the land and replenishingbeaches (Figure 40), or allowing the sea to advancelandward and retreating from the shoreline in an adhoc manner. Each of these options can be costly, bothmonetarily and in terms of lost landscape features,habitats, buildings, and infrastructure.

Wise long-term planning can reduce some ofthese future costs. The direct impacts on coastalcommunities will become evident in two ways: eitherthrough gradual erosion and permanent flooding ofcoastal areas with resulting damage to buildings,infrastructure, and natural ecosystems, or throughincreasing damages during extreme events, such ascoastal storms as the storm surge increases and thebeach or wetland buffer is gradually lost.168 Thus,adapting to sea-level rise involves reviewing the localand regional long-term plans (for example, in shore-front zoning and land-use plans, growth objectives,etc.) and the local and state policies and regulationsin place for dealing with the immediate impacts ofcoastal floods, tropical storms, and erosion.

Florida’s Southwest Regional Planning Council,for example, recently decided to include the threatfrom sea-level rise in its planning. Other environmen-tal-protection measures already in place in Floridahave the associated benefit of reducing some of theimpacts of climate change. For example, the state hasenacted stringent controls on construction seawardof a “coastal control line,” reducing further degrada-tion of the shoreline and barrier habitats.

Barrier islands serve a protective function for in-dustrial installations, roads, and human settlements.Recent studies show that restoring degraded barrierislands in some parts of coastal Louisiana couldreduce storm surge elevations by up to four feet innearby coastal communities.170 Communities from

F I G U R E 4 0Beach Replenishment




6 7

Texas to Florida will have to adopt restoration strat-egies to maintain the important function that barrierislands provide.

Given the negative ecological and economic con-sequences of seawalls and other “shoreline hardening”structures in the long run, states have every incentiveto prohibit such construction and to enforce setbacksand retreat when the encroaching sea comes too closeto assure reasonable public safety. Meanwhile, theycan sustain economic use of coastal areas for years tocome by allowing carefully enforced hazard-consciousdevelopment of shorefront property. States and com-munities can also commit resources to buying landand preserving open space after shorefront property hasbeen damaged beyond repair. Inthe past, this option has beeninhibited by high coastal propertyvalues and limited local resources,but state funds have been estab-lished elsewhere to support suchefforts. It is equally important toconsider the continuing econ-omic and environmental benefitsthat come from healthy beachesand habitat preservation for ecotourism and fisheries.

Since many coastal communities rely on wetland-dependent fisheries for their economies and on wet-lands directly as storm buffers, it is important to pro-vide opportunities for the natural landward migra-tion of coastal wetlands as sea level rises. This can beachieved through conservation or flowage easementsfinanced and managed by governments, privatelandowners, or conservation groups.

Both shorefront and upland adaptation strategiesare supported by the public trust doctrine, whichallows local and state governments to enforce thepublic’s right of access to submerged lands, and towetland and beach preservation, even on privateproperty. The Gulf Coast region derives enormouseconomic benefits from healthy coastal ecosystems.These benefits should be included in cost-benefitanalyses of various coastal management options.

Adaptation to Other Climatic HazardsIn the past, Gulf Coast communities have respondedto storms, floods, wildfires, and other disasters pri-marily through efforts to protect themselves while

remaining in hazardous locations. These responseshave led to major human alterations of landscapes,vegetation, and water flow, frequently resulting infurther environmental degradation that vastly exceed-ed the consequences of the episodic event that pro-voked them. For example, partly in response to thedevastating hurricanes and floods in the region in theearly part of the 20th century, people constructedengineered water systems, levees, and seawalls. Inmany ways, the Gulf Coast is more prepared fordealing with too much water than with too little.Regional disaster-management efforts are well honedfor floods and storms, but less so for droughts. Withopposing climate scenarios for the region and con-

tinuing uncertainties aboutthe future frequency of hur-ricanes and tropical storms,Gulf Coast states are welladvised to review and en-hance their preparedness fordisasters related to heat waves,extended drought, andwildfires. This could includepreparing emergency water-

management plans for urban areas to ensure cost-effective reliability during low-supply times and forcoastal areas where saltwater intrusion into coastalaquifers would be aggravated by low freshwaterrunoff. It could also include organizing small land-owners into blocks large enough to develop pre-scribed fire plans to reduce wildfire hazards in theever-expanding interface between the human-dominated urban and rural portions of the landscape.

Climate change–conscious hazard managementshould also include a review of insurance coverage invarious segments of the population (such as flood-plain residents) and sectors of the economy (such asfarmers, small businesses, forest landowners). Forexample, after Hurricane Andrew, a number of insur-ance companies wanted to withdraw their coverage inthe most immediate coastal areas in Florida, but wereprevented from doing so by state law.171 While insur-ance withdrawal from hazardous areas would reducethe liability of insurance companies and help sustaintheir economic viability overall, coastal residents wouldbe left without insurance coverage and thus increasinglyvulnerable to severe storms.

Communities from Texas

to Florida will have to adopt

restoration strategies to main-

tain the protective function

that wetlands and barrier

islands provide.


6 8

Education about Ecologyand Global WarmingFinally, we need to raise awareness and understandingof global climate change in the Gulf Coast region.This can begin by educating people of all ages aboutthe cultural and ecological heri-tage at stake. But it must alsoinvolve educating them aboutthe fundamentals of ecologyand climate, and what drivesthem to change. Many Gulf resi-dents’ livelihoods are inextri-cably linked to its natural re-sources, and visitors from around the world cometo the Gulf to enjoy and learn about its ecological heri-tage. Raising people’s awareness and understandingof climate change will help to mobilize public supportfor minimizing and adapting to climate change.


Raising people‘s awareness and

understanding will help mobilize

public support for minimizing

and adapting to climate change.

With the help of the region’s science capacity,decision-makers can also improve their understand-ing and ability to identify those water, air, and landresources that are critical to maintain economic ac-tivity and environmental quality in the region. This

may include developinginventories that track theincremental demands on,and use of, these resourcesas population increases andas market forces and landuses change. Such inven-tories would be an impor-

tant component of adaptive management schemesfor Gulf Coast natural resources, so that adjustmentscould be made when yet-uncertain climate changesmanifest unequivocally in the future.


6 9

Scientists use two basic tools for projectingfuture climate change, an activity betterthought of as developing plausible futurescenarios rather than forecasting the future.

These tools include

• historical observations and trends that canbe projected into the future

• mathematical models that capture the mostimportant processes determining climate

Building on these two methods to generate plausibleclimate conditions and extremes, scientists use “whatif ” scenarios to examine the vulnerability of naturaland human systems and the likely impacts of climatechange.

Historical observations, such as those describedin Chapter 1, help scientists identify trends in importantclimate variables such as temperature and rainfall andchanges in important weather patterns and events suchas the El Niño–Southern Oscillation (ENSO) cycleor hurricanes. Computer-based climate models usemathematical representations of the processes thatgovern atmospheric and oceanic circulation to projectfuture climate variables such as rainfall, temperature,and seasonal changes in climate. General circulationmodels (GCMs) are the most sophisticated type ofclimate model. In this report, we use the outputs fromtwo GCMs used for the US National Assessment: theHadley Centre climate model172 and the CanadianCentre climate model.173 The scenarios that these twomodels generate are quite different and we view themas spanning a large fraction of the current climate-changeprojections.

Two of the most significant differences betweenclimate models involve how they treat complex cloudprocesses and the interaction between the land surfaceand the atmosphere. Both are simplified compared

Appendix: Developing Climate Scenarioswith the real world, in part because current climatemodels overtax even the world’s fastest computers.The differences in the way the models treat thesecomplex processes are sufficient to cause differentprojections of surface warming, evaporation, and ratesof rainfall. The differences also influence projectedpatterns of atmospheric circulation (e.g., the strengthof the Bermuda High). However, neither model canbe easily dismissed or said to be more or less likelythan the other because each has different strengthsand weaknesses and captures many features of globalclimate reasonably well. For the southeastern UnitedStates, the Hadley climate model generally depicts awarmer, wetter future climate, while the Canadianclimate model depicts a hot, dry future climate.

Despite these significant differences, the projectionsagree on a number of points: Both models agree thattemperatures will increase (more in the Canadianmodel than in the Hadley model), and both projectan accelerating rate of regional sea-level rise. The modelsdiffer in their projections of changes in rainfall andrunoff and consequently in soil moisture—all criticalfactors that affect water availability to ecosystems andpeople in the region. Because adequate water resourcesare critical to the well-being of both humans andecosystems, we believe the most prudent approachis to assess the potential outcomes of both drier andwetter conditions and the ability of natural andmanaged systems to cope with change in eitherdirection.

GCMs cannot project changes in small-scale climatefeatures, such as hurricanes and thunderstorms, orsecondary changes, such as fires. To include thesefeatures, we have supplemented the model resultswith a number of other published studies to analyzethese other important climate-related drivers ofecosystem change.


7 0

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165. Bourne, J. (2000). Louisiana’s vanishing wetlands:Going, going, … Science 289(15 September):1860–1863.

166. Governor’s Commission for a Sustainable SouthFlorida (1995). Final report to Florida GovernorLawton Chiles, October 1995. Coral Gables, Fla.

167. For an overview, see Harwell, M.A., et al. (1999).A science-based strategy for ecological restorationin South Florida. Urban Ecosystems 3(3/4):201–222.

See also Harwell (1998) in note 113.


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168. The Heinz Center (2000). Evaluation of erosionhazards. Washington, D.C.: The H. John Heinz IIICenter for Science, Economics and the Environment.

169. Federal Emergency Management Agency (1991).Projected impact of relative sea level rise on the Na-tional Flood Insurance Program. Report of Congress.Washington, D.C.: FEMA.

170. Louisiana Coastal Wetlands and Restoration TaskForce and the Wetlands Conservation and RestorationAuthority (1998). Coast 2050: Toward a SustainableCoastal Louisiana. Baton Rouge: Louisiana Depart-ment of Natural Resources. Available on the LDNRwebsite at www.coast2050.gov.

McBride, R.A., et al. (1992). Analysis of barriershoreline change in Louisiana from 1853 to 1989.In Louisiana Barrier Island Erosion Study, Atlas ofShoreline Changes in Louisiana from 1853 to 1989,S.J. Williams, S. Penland, and A.H. Sallenger, eds.US Geological Survey Miscellaneous Investigations,Series I-2150-A, pp. 36–97.

T. Baker Smith & Sons, Inc. (1999). Barrier islandplan. Phase 1, Step J, Assessment of managementalternatives. Deliverable to Louisiana Departmentof Environmental Resources under contract 2509-98-02.

171. Leggett, J. (1994). The emerging response of theinsurance industry to the threat of climate change.Industry & Environment 17:41–45.

172. Mitchell, J.F.B., and T.C. Johns (1997). Onmodification of global warming by sulfate aerosols.Journal of Climate 10:245–267.

Mitchell, J.F.B., et al. (1995). Climate response toincreasing levels of greenhouse gases and sulphateaerosols. Nature 376:501–504.

173. Boer, G.J., G.M. Flato, and D. Ramsden (1999).A transient climate change simulation with historicaland projected greenhouse gas and aerosol forcing:Experimental design and comparison with the instru-mental record for the 20th century. Climate Dynamics16:405–426.

Boer, G.J., G.M. Flato, and D. Ramsden (1999).A transient climate change simulation with historicaland projected greenhouse gas and aerosol forcing:Projected climate change for the 21st century. ClimateDynamics 16:427–450.

Boer, G.J., et al. (1984). The Canadian Climate Centrespectral atmospheric general circulation model.Atmosphere-Ocean 22(4):397–429.

Flato, G.M., et al. (1999). The Canadian Centre forClimate Modelling and Analysis global coupled modeland its climate. Climate Dynamics 16:451–468.

McFarlane, N.A., et al. (1992). The Canadian ClimateCentre second-generation general circulation modeland its equilibrium climate. Journal of Climate5:1013–1044.

A national steering committee provided guidance and oversight to ensure thescientific review and integrity of the report. The Steering Committee members were

Dr. Louis F. Pitelka (Chair), Appalachian Laboratory,University of Maryland Center for Environmental Science, Frostburg, Md.

Dr. Mary Barber, Ecological Society of America, Washington, D.C.

Dr. Christopher Field, Carnegie Institution of Washington, Department of Plant Biology, Stanford, Calif.

Dr. Peter C. Frumhoff, Union of Concerned Scientists, Cambridge, Mass.

Dr. Geoff Heal, Columbia University, Graduate School of Business, New York, N.Y.

Dr. Jerry Melillo, Marine Biological Laboratories, Woods Hole, Mass.

Dr. Judy Meyer, University of Georgia, Institute of Ecology, Athens, Ga.

Dr. William Schlesinger, Duke University, Nicholas School of the Environment, Durham, N.C.

Dr. Steven Schneider, Stanford University, Department of Biological Sciences and theInstitute for International Studies, Stanford, Calif.

Steering Committee


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Robert Twilley, the lead author of this report, is professorof biology and director of the Center for Ecology and Envi-ronmental Technology at the University of Louisiana atLafayette. Most of Dr. Twilley’s research has focused onunderstanding the ecosystem ecology and managementpractices of mangrove wetlands both in the Gulf of Mexico(from Florida to the Yucatan Peninsula) and throughout LatinAmerica. Specifically, he works on the nutrient biogeochem-istry of wetland and coastal ecosystems, and on coupledecological and socioeconomic models of ecosystem manage-ment in places such as the coastal Everglades, ChesapeakeBay, Albemarle Sound (North Carolina), and coastalLouisiana including the Mississippi River estuary. Dr. Twilleyreceived his Ph.D. in 1982 in plant and systems ecologyfrom the University of Florida, studying mangrove ecosystemsat Rookery Bay as part of his dissertation research. Heco-edited The Biogeochemistry of Gulf of Mexico Estuaries.In 1993, Dr. Twilley directed the scientific advisory panelof the Coastal Restoration of Louisiana Initiative.

Eric Barron is distinguished professor of geosciences andthe director of the Earth and Mineral Sciences EnvironmentInstitute at Pennsylvania State University. His areas ofspecialization include global change, numerical modelsof the climate system, and study of climate change through-out Earth’s history. He received his Ph.D. in the study ofoceanography and climate at the Rosenstiel School of Marineand Atmospheric Sciences at the University of Miami in1980. For five years he worked on global climate modelingat the National Center for Atmospheric Research. He hasbeen an active member of the advisory boards for earthsciences at NASA and NSF, including five years as chairof the science executive committee of NASA’s Earth Observ-ing System. He is past chair of the climate research committeeof the National Research Council and currently chairs theNRC’s board on atmospheric sciences and climate. He wasa member of the synthesis team for the US National Assess-ment of Climate Change Impacts. He is a fellow of theAmerican Geophysical Union and the American Meteoro-logical Society, and provided the overview of climate modelsand climatic processes to this report.

Henry L. Gholz is professor of forest ecology in the Schoolof Forest Resources and Conservation at the Universityof Florida. His primary scientific focus is on the carbon,water, and nutrient dynamics of forests in the southeasternUnited States. He is currently involved in a collaborativeprogram to quantify the long-term regional carbon balance

of northern Florida. He has been interim chair for the schooland developed its agroforestry and tropical forestry programs.Currently on leave from the university, Dr. Gholz is directingthe NSF’s Long-Term Ecological Research Program. Dr.Gholz received his Ph.D. in forest science at Oregon StateUniversity in 1979. He served as an advisor to the US Agencyfor International Development while a AAAS fellow in1994–95. He is a member of the NRC’s standing committeeon agricultural biotechnology, health and the environment.He contributed to the report sections on upland ecosystems,in particular forests, agriculture, and potential impacts onbiodiversity in the Gulf region.

Mark Harwell is professor of marine ecology at theRosenstiel School of Marine and Atmospheric Sciencesand, since 1991, the director of the Center for Marineand Environmental Analyses at the University of Miami.His primary interest is in ecological risk assessment andecosystem management. Before going to Miami, he wasthe associate director of the Cornell University EcosystemsResearch Center. Dr. Harwell (with Jack Gentile) was aleader in developing the US EPA ecological risk assessmentframework, including the concepts of ecological indicatorsand endpoints. He has led several large risk assessments,including on fuel spills in Tampa Bay, on the global changeeffects on Biscayne Bay, and on the Everglades restorationprocess. He chaired the US Man and the Biosphere Human-Dominated Systems Directorate and led its core project onecological sustainability and ecosystem management. Forten years, he served on the EPA’s science advisory board,including two terms as chair of the ecological processesand effects committee, working repeatedly on risk-relatedtopics. Dr. Harwell led a five-year international study toassess the global environmental consequences of nuclearwar, with emphasis on ecological responses to climate change.He is a member of the US Global Change ResearchProgram’s National Assessment coastal sectoral assessmentteam. Dr. Harwell has served as a member of the NASboard on environmental studies and toxicology and wasrecently elected a fellow of AAAS. In this report, he providedinput on Florida’s coastal ecosystems, biodiversity, and on riskand resource management issues.

Richard L. Miller is NASA’s chief scientist at the JohnC. Stennis Space Center in Mississippi. His research interestsinclude the role that river-dominated coastal margins playin the transport and fate of organic carbon, the applicationof remote sensing technologies to the transport of particles

Contributing Authors


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and the measurement of water column productivity, andthe development of new technology for coastal ocean mea-surements. His work contributes to a better understandingof the global carbon cycle and the role of organic carbon inglobal climate change. Dr. Miller received his Ph.D. in1984 from North Carolina State University. In this report,he contributed to the sections on climate change, oceanand coastal currents, and their connection to freshwaterand sediment input from rivers and estuaries.

Denise J. Reed is a professor in the Department of Geologyand Geophysics at the University of New Orleans. Herresearch interests include coastal marsh response to sea-levelrise, the contributions sediments and organic material maketo marsh soil development, and how these are affected byhuman alterations to marsh hydrology. She has worked incoastal marshes in northwest Europe, southern Chile andthe Atlantic, Pacific, and Gulf coasts of the United States.She has been involved in restoration planning both in Louis-iana and in California, and in scientifically evaluating theresults of marsh restoration projects. Dr. Reed was a memberof the coastal and marine resources sector team for the USNational Assessment of Climate Variability and Change.She received her Ph.D. from the University of Cambridge,U.K., and has worked in coastal Louisiana since 1986.In this report, she contributed to sections on coastal ecosystemresponse and potential mitigation and adaptation strategies.

Joan B. Rose, an international expert in water pollutionmicrobiology, is currently a professor in the College of MarineSciences at the University of South Florida. Her researchfocuses on waterborne disease-causing agents, specificallyviruses and protozoa, and technologies for detecting andcontrolling them. During the last five years, Dr. Rose hasbeen developing microbial risk assessment approaches tomodel the adverse health effects associated with low-levelcontamination of drinking water. She currently serves onthe water science and technology board of the NationalAcademy of Sciences and on the board of life sciences.She has served on the EPA science advisory board on waterfiltration and coli bacteria testing and she has recently beeninvited to join the National Drinking Water Advisory Coun-cil. In 2000, Water Technology named Dr. Rose one of themost influential people in water in the 21st century. Recently,she was awarded the 2001 Clarke Water Prize. Dr. Rosereceived her Ph.D. from the University of Arizona in 1985.In this report, she contributed especially to the section onthe water-related health concerns.

Evan Siemann is assistant professor in the Departmentof Ecology and Evolutionary Biology at Rice University.He researches how local environmental factors interactwith post-invasion adaptation to determine the likelihoodand severity of Chinese Tallow Tree (Sapium sebiferum)

invasions into East Texas coastal prairie, mesic forests, andfloodplain forests. He is also exploring the ecosystem-levelimpacts of exotic tree invasions into coastal prairies andis engaged in projects to control exotic plant and animalinvasions into Texas ecosystems. Other research interestsinclude fruit crop biochemistry, weed management in fieldcrop systems, and the relationship between biodiversityand ecosystem services. Dr. Siemann received his Ph.D. in1997 in ecology from the University of Minnesota. In thisreport, he contributed to sections on agriculture, forestry,terrestrial ecosystems, and biodiversity and species invasions.

Robert G. Wetzel is a professor in the Department ofEnvironmental Sciences and Engineering in the School ofPublic Health at the University of North Carolina at ChapelHill. The dominant theme that threads throughout his 15books and over 400 scientific publications is the manyconnections between biota of upland and land-water interfaceregions and lakes and rivers. In particular, he works on thechemical and competitive biotic regulation of plants, animals,and microorganisms living in wetlands and open water.Dr. Wetzel has been a faculty member at Michigan StateUniversity, the University of Michigan, and until recentlythe University of Alabama. He has received numerousawards of excellence (e.g., Hutchinson Medal, Naumann-Thienemann Medal, elected member of AAAS and the RoyalDanish Academy of Sciences). He is on the editorial boardof 12 scientific journals and has served on over 200 boardsand panels concerning the functioning and restoration offreshwater ecosystems. Dr. Wetzel received his Ph.D. fromthe University of California, Davis. In this report, he con-tributed to sections on the impacts of freshwater ecosystemsand resources.

Roger J. Zimmerman is director of NOAA’s NationalMarine Service Fisheries Laboratory (NMFS) in Galveston,Texas. Prominent NMFS issues in the Gulf concern manage-ment of shrimp and reef fish fisheries, protection andconservation of sea turtles and marine mammals, and therestoration of coastal wetlands. Dr. Zimmerman’s expertiseis in marine crustacean biology and estuarine ecology. AtNOAA, he has served as scientist and advisor on such fisheriesissues as impacts of sea-level rise, loss and restoration ofcoastal wetlands, delineation of essential fish habitat, effectsof low oxygen in offshore waters, the ecology of commerciallyimportant shrimp and crab species, and management ofestuarine systems. Since 1981, Dr. Zimmerman has alsotaught and advised students through Texas A&M Universityon estuarine ecology of the Gulf of Mexico. Dr. Zimmermanreceived his Ph.D. in biological marine sciences from theUniversity of Puerto Rico in Mayaguez. In this report, hecontributed to sections on coastal ecosystems, especiallyin Texas, and on fisheries.

Founded in 1915, the Ecological Society ofAmerica (ESA) is a scientific, nonprofit orga-nization with more than 7,000 professionalmembers. Through its reports, journals,membership research, and expert testimonyto Congress, ESA seeks to promote the res-ponsible application of ecological data andprinciples to the solution of environmentalproblems.

The Union of Concerned Scientists is a nonprofitpartnership of scientists and citizens combiningrigorous scientific analysis, innovative policy dev-elopment and effective citizen advocacy toachieve practical environmental solutions.Established in 1969, we seek to ensure that allpeople have clean air, energy and transporta-tion, as well as food that is produced in a safeand sustainable manner. We strive for a futurethat is free from the threats of global warmingand nuclear war, and a planet that supports arich diversity of life. Sound science guides ourefforts to secure changes in government policy,corporate practices and consumer choices thatwill protect and improve the health of ourenvironment globally, nationally and in com-munities throughout the United States. UCS seeksa great change in humanity’s stewardship ofthe earth.

The Union of Concerned ScientistsTwo Brattle Square, Cambridge, MA 02238-9105Phone: 617-547-5552 • Fax: 617-864-9405

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