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U.S. Department of the Interior U.S. Geological Survey

Volume 9, Fall 2019

News from the USGS Land Change Science Program

Earth Science Matters

Changes in the way we use and manage land, as well as changes in

climate, affect our natural resources, infrastructure, and communities in

complicated ways. To help managers and policy makers design

sustainable management strategies, scientists are studying the effect

these changes can have on habitats, ecosystems, and the processes that

maintain them. This research aims to improve our understanding of

environmental processes and our ability to anticipate the impacts of a

range of future changes. The USGS Land Change Science Program

sponsors research that integrates long-standing expertise in geology,

ecology, hydrology, and geography to provide a scientific basis for

sustainable management strategies being developed by the Department

of the Interior and other stakeholders.

Reconstructing extreme floods in eastern North America using sedimentary records

Photo Courtesy of Jamie Hayward, California State

University—Fullerton.

USGS and Stakeholder Engagement in the Gulf of Mexico

LCS Research Activities: Arctic Research Cruise

To manage forest response to drought, pay attention to “the little things that run the world”

Geologic records of a warmer Arctic in the past

Improved Urban Maps for the United States

Implications for mangrove range expansion with changing climate

http://www2.usgs.gov/landresources/lcs/newsletter.asp



Volume 9, Fall 2019



This issue of Earth Science Matters highlights recent collaborations with stakeholders and newly published research

products that contribute to an improved understanding of how changing land use, climate, and environment affect

communities, ecosystems, and the services they provide. Topics covered include:

• USGS collaborations with

Gulf Coast stakeholders to

support management of

coastal wetlands

• Documenting extreme flood

history in the Chesapeake Bay

watershed and the influence of

climate patterns on storms and

floods

• Geologic records of Arctic

temperature and hydrology

during past intervals of

elevated carbon dioxide in the

atmosphere

• Combined role of drought and

insects on tree mortality

• Improving urban maps by

removing rural roads from

land cover datasets

• Impacts of soil type, temperature, and local factors on mangrove distributions and health

• USGS participation in a research cruise to study glacial history of the Ryder Glacier in Greenland

Data generated by these studies provide real-world evidence needed to test and develop models that project changes

under different land use and climate scenarios.

Earth Science Matters includes a sampling of the multidisciplinary research conducted by the Land Change Science

Program to provide data and improve understanding on the rates, patterns, and consequences of changing environment,

climate, and land use. We welcome comments and feedback to shape future issues. If you would like to subscribe to

future issues, please click the “Subscribe” button on the Program Newsletter page.

Debra Willard

Coordinator, Land Change Science Program

Photo Courtesy of David Clow, USGS


mailto:[email protected]



Volume 9, Fall 2019



The U.S. coast of the Gulf of Mexico

stretches about 1,631 miles from southern

Florida through Alabama, Mississippi, and

Louisiana, ending at the U.S.-Mexico

border in Texas. Along this coastline are

numerous types of coastal wetlands that

provide many societal benefits. Coastal

wetlands comprise grassy salt marshes,

mangrove forests, freshwater forested

swamps, freshwater marshes, and tidal

flats. In addition to supporting fish and

wildlife habitat, these wetlands improve

water quality by filtering out excess

nutrients and contaminants, sequester

carbon and release oxygen, stabilize the

shoreline to control erosion, provide

recreation and tourism opportunities, and

protect coastal communities from

storms. USGS Land Change Science

Program (LCS) researchers are studying

these important ecosystems and

communicating with local natural

resource managers to better inform their

management.

Coastal wetlands have immense economic value, with estimates averaging about $194,000 per hectare per year on a

global scale (2007 US$ price level) (Mehvar et al., 2018). For example, almost all the fish and shellfish caught by the

fishing industry depend on estuaries and wetlands at some point in their life cycle, and the money brought in annually by

the fishing industry in the Gulf region reaches hundreds of millions of dollars. Loss of healthy coastal wetland habitats

can have severe impacts not only on fish populations, but on the fishing industry and regional economy as well. Coastal

wetlands also incur economic value from their recreational use (fishing, kayaking, hiking, etc.), provisioning of raw

materials (food, fiber, wood), and protective nature (prevent erosion, filter pollution, hold excess rain to help control

flooding).

However, due to their position at the land-sea interface, coastal wetlands are highly dynamic, variable, and vulnerable to

major change. Coastal wetlands face pressure directly from natural coastal hazards such as flooding and erosion but also

are indirectly threatened from human population growth and economic development. Coastal areas make up 4% of the

land area on earth but are home to about a third of the global population, and the population density along the coasts


https://www.mdpi.com/2077-1312/6/1/5



Volume 9, Fall 2019



continues to grow each year spurring increased land conversion and development (Mehvar et al., 2018). Additionally, as

the planet’s climate changes, the natural hazard events that coastal wetlands are susceptible to, including changes in

precipitation and warming temperatures, are expected to increase in probability and severity.

The Gulf Coast is home to many parks, refuges, and other public lands. Managers at those locations have responsibility

for managing their lands to preserve natural resources and the services they provide. USGS scientists are collaborating

with managers at Apalachicola National Estuarine Research Reserve (ANERR), Florida Forest Service (FFS), Florida

Fish and Wildlife Research Institute (FWRI), and Mission Aransas National Estuarine Research Reserve (Mission-

Aransas NERR) (among others) with the aim of providing unbiased, robust science to guide and support their

environmental management decisions.

These resource managers are tasked

with monitoring species, providing

public use and access to natural lands,

managing habitat and restoration

efforts, protecting and managing natural

resources to ensure their availability for

future generations, collecting and

analyzing scientific data to inform

climate change adaptation, promoting

understanding of coastal ecosystems to

diverse audiences, and promoting

public appreciation and support for

stewardship of coastal resources.

Current State of Knowledge

Wetland vulnerability assessments have been used to identify coastal areas that are most susceptible to environmental

change or stress. Previous coastal wetland vulnerability assessments have generally focused solely on sea-level rise

without considering the effects of other facets of climate change. Across the globe and in all ecosystems, macroclimatic

drivers (e.g., temperature and rainfall regimes) greatly influence ecosystem structure and function. In some coastal

wetlands, research suggests that changing macroclimatic conditions could result in the replacement of foundation plant

species (species that have a strong role in structuring an ecosystem, such as mangrove trees, salt marsh graminoids, and

succulents in coastal wetlands).

Foundation plant species are able to withstand and moderate the physically stressful tidal conditions, and they provide

primary, tolerable habitat for a wealth of other species. They supply important ecosystem goods and services, such as

water filtration, and wave energy absorption, and increase the resilience of the ecosystem under a range of environmental

stressors. USGS scientists are working to improve our understanding of the impact of macroclimate drivers and

ecosystem dynamics in coastal ecosystems by documenting how changes in temperature and rainfall regimes affect

coastal wetland systems.


https://www.fws.gov/gis/data/CadastralDB/links_cadastral.html

https://public-nps.opendata.arcgis.com/datasets/national-park-service-park-unit-boundaries

https://coast.noaa.gov/digitalcoast/data/

https://geodata.dep.state.fl.us/datasets/florida-state-parks-boundaries

https://tpwd.texas.gov/gis/

https://tpwd.texas.gov/gis/

https://www.doa.la.gov/Pages/osl/GIS-Data.aspx



Volume 9, Fall 2019



USGS Research Benefitting Gulf Coast

Stakeholders

We recently began surveying stakeholders for USGS

LCS research to evaluate their science needs and

potential synergies between them and USGS research

efforts in order to maximize the relevance of our efforts

to stakeholders in various federal, state, and local

agencies.

A common goal of the stakeholders is development of

adaptation plans for wildlife and ecosystems that

promote long-term protection and management of

valuable coastal resources given an uncertain future.

Creating these adaptation plans is an important step in

preparing and protecting local communities for any

effects of change on the natural resources that they

depend upon. USGS research on the impacts of

macroclimatic changes on coastal foundation species




Volume 9, Fall 2019



is producing maps and projections of vegetation response

to changing temperature and rainfall regimes. These

provide important evidence that support management

planning by resource managers in coastal wetlands.

Of particular interest to Gulf Coast stakeholders is USGS

monitoring and mapping of salt marsh and mangrove

extent under various past and future conditions. Maps of

potential mangrove range expansion into salt marshes

under different climate change scenarios allow

stakeholders to identify priority conservation areas and

create targeted monitoring programs. Likewise, maps of

marsh migration under different growth and

development scenarios allow stakeholders to weigh

costs and benefits of different management strategies.

Correlation of current mangrove forest extent maps with

state forest inventory characteristics provides a way for

state forest managers to better track and predict the future of mangrove ecosystems. Developing mangrove damage

assessments after hurricanes also helps managers track the natural resources, they are responsible for and to identify

potential areas for restoration projects.

The network of collaborating scientists and land managers from the USGS and agencies throughout the Southeast and

Gulf Coast leverages their collective expertise to examine how changing land management and environmental factors

affect coastal ecosystems in a comprehensive way. Local stakeholders and resource managers noted that they are able to

spend more time focusing on the “bigger pictures” and regional trends in land management because USGS scientists are

supplying rigorous, hypothesis-driven research and science products. Further, they are using USGS research to create

targeted restoration projects and environmental resource monitoring programs in their locality.

These collaborations also are helping USGS researchers tailor their research to address pressing questions while

achieving a core mission of the agency: to provide reliable scientific information to describe and understand the Earth.

As a result, scientists and resource managers are more effectively communicating the urgency and importance of

environmental change issues in the region to the public, state and local governments, nonprofits, and universities they

serve.

We gratefully acknowledge the support of the resource managers and stakeholder institutions who helped in the creation

of this piece.

References Cited

Mehvar, S., Filatova, T., Dastgheib, A., De Ruyter van Steveninck, E., and Ranasinghe, R., 2018, Quantifying economic

value of coastal ecosystem services: a review: Journal of Marine Science and Engineering, v. 6, no. 1, doi: 10.3390/

jmse6010005. https://www.mdpi.com/2077-1312/6/1/5


https://pubs.er.usgs.gov/publication/70046181





https://www.mdpi.com/2077-1312/6/1/5



Volume 9, Fall 2019



Historically unprecedented changes in Arctic weather, sea ice, glaciers, and temperature have led to concerns about

coastal erosion, ecosystem changes, and sea-level rise. Climate changes in the Arctic are “amplified” in that the

cryosphere (glaciers, ice sheets, sea ice), experiences changes that are larger in magnitude than those in lower latitudes.

Furthermore, changes in the Arctic affect the rest of the earth. Decreasing summer sea-ice cover in the Arctic Ocean

affects weather patterns in heavily populated mid-latitude regions. Melting of Arctic glaciers and of parts of the

Greenland Ice Sheet is increasingly recognized as a major contributor to present and future global sea-level rise.

Additionally, the resulting increase in fresh water influx to the oceans from this melt has the potential to alter patterns of

ocean circulation that affect temperature regimes throughout the globe.

The USGS Land Change Science Program (along with other programs within the bureau) conducts Arctic research to

better understand the drivers and impacts of change on glaciers, sea ice, permafrost, and hydrology. One of these

research projects, Land-Sea Linkages in the Arctic, is investigating the climatic history of the Arctic Ocean and its

adjacent seas and land areas using marine sediment cores collected throughout the region. These cores capture sediments

deposited up to 500,000 years ago and allow scientists to reconstruct the distribution of sea ice over time scales ranging

from the past centuries to millennia and even longer time scales.

Recently, two members of

the project, Thomas M.

Cronin and Laura Gemery,

participated in the Ryder

2019 Expedition of the

Swedish icebreaker Oden

(Figure 1) to northern

Greenland to collect

sediment cores in a

previously unstudied part of

the Arctic. The Expedition

conducted multidisciplinary

research on glacial history of

the remote Ryder Glacier,

which extends into the ocean

from the northern portion of

the Greenland Ice Sheet.

Research focused on the

relationship between the

Greenland Ice Sheet, Ryder

Glacier, and the ocean during

climate changes of the


https://www.usgs.gov/land-resources/land-change-science-program/science-topics/arctic

https://www.usgs.gov/land-resources/land-change-science-program/science-topics/glaciers

https://www.usgs.gov/land-resources/land-change-science-program/science-topics/sea-ice

https://www.usgs.gov/land-resources/land-change-science-program/science-topics/permafrost

https://www.usgs.gov/land-resources/land-change-science-program/science-topics/water-quality-and-quantity

https://www.usgs.gov/land-resources/land-change-science-program/science/land-sea-linkages-arctic

https://www.usgs.gov/staff-profiles/thomas-cronin

https://www.usgs.gov/staff-profiles/thomas-cronin

https://www.usgs.gov/staff-profiles/laura-gemery

https://polarforskningsportalen.se/en/arctic/expeditions/ryder-2019

https://polarforskningsportalen.se/en/arctic/expeditions/ryder-2019



Volume 9, Fall 2019



Holocene, which covers the last 10,000 years. Understanding Holocene cryosphere-ocean history is critical as it provides

baseline information on pre-Anthropogenic natural variability and sensitivity of the ice sheet to early Holocene warming

and its contribution to sea-level changes.

Ryder 2019 took place from August 5 to September 12, 2019 and was led by co-chief scientists Dr. Martin Jakobsson of

Stockholm University and Dr. Larry Mayer, Director of the Center for Coastal and Ocean Mapping, University of New

Hampshire. The expedition explored remote regions of northwest Greenland including Ryder Glacier, which terminates

in the Sherard-Osborn Fjord, the Nares Strait, the Lincoln Sea, and the Petermann Glacier and Fjord (Figure 2). The

international team of scientists on the expedition conducted multidisciplinary studies in the fields of atmospheric

chemistry and physics, biology, climatology, ecology, genomics, glaciology, oceanography, marine geology, geophysics

and geochemistry.

One primary goal of

USGS scientists and their

Swedish collaborators

while onboard was to

investigate the dynamics

and history of the marine

cryosphere, which

includes glaciers

extending into fjords

from the Greenland Ice

Sheet and Arctic Ocean

sea ice. Greenland ice

tongues (floating ice

shelves) extend from

glaciers on the land into

the ocean (Figure 3). The

stability of these features

is influenced by both air

temperatures, which

affect melt rates on the

glacier surface, and

ocean temperatures,

which affect the bottom,

submarine portion of the

glacier. The potential instability of ice tongues, glaciers, and ice sheets under a warming climate is of concern because of

the potential contribution of melting ice to sea-level rise. Decreasing Arctic Ocean sea ice is also a major concern due to

its impacts on ecosystems, weather patterns, and ocean circulation.




Volume 9, Fall 2019



Research on Oden by Drs. Martin

Jakobsson and Larry Mayer

involved geophysical mapping of

underwater glacial landforms,

which was used by USGS

scientists to select sites for coring

of seafloor sediments deposited

during the last 10,000 years.

These long-term

paleoceanographic records from

sediment cores are needed

because instrumental records

extend back only a few decades

and glaciers, sea ice, and climate

vary over longer time scales. By

combining geologic data from the

new cores with instrumental

records, USGS researchers and

colleagues aim to improve

understanding of how the Arctic

Ocean and adjacent land masses

have been influenced by a range

of natural and anthropogenic

factors.

While on the ship, USGS

scientists began analyzing

samples from new cores they

collected (Figure 4). They

measured the physical properties

of the sediments and analyzed

calcareous microfossils [foraminifera, ostracodes] that were buried in the sediments. These on-board analyses included

using the ecology of the microfossil species in the cores to develop a preliminary reconstruction of sea-ice history to

complement previous work elsewhere in the Arctic. In addition, scientists prepared samples for radiocarbon dating and

other shell geochemical analyses to be conducted upon return to USGS. The radiocarbon chronology and

paleoceanographic reconstructions from the microfauna fossils will provide an unprecedented history of the Ryder

Glacier in Northern Greenland.


https://www2.usgs.gov/landresources/lcs/paleoclimate/



Volume 9, Fall 2019



The Ryder 2019 Expedition allowed USGS scientists to

gather much needed data for their project and to

collaborate with an array of international scientists that

aim to improve understanding of the Arctic and its role in

Earth’s climate. This research will help increase our

understanding of how Arctic glaciers and ice responded to

a warming climate in the past and thus provide insight into

how they may respond to similar warming today and into

the future.

We gratefully acknowledge the support of the Swedish

Polar Research Secretariat, the captain and crew of Oden,

Stockholm University and co-chief scientists Drs. Martin

Jakobsson and Larry Mayer.




Volume 9, Fall 2019



The threats posed by extreme flooding to many U.S. cities, and nearby infrastructure,

built along rivers are not well constrained due to limited data. For most rivers in the

eastern United States, reliable streamgage measurements extend less than 100 years

and often capture only a handful of the major floods recorded by historic sources (e.g.

newspapers and other written accounts). In order to fill this critical gap, scientists can

study geologic signatures of past flood events buried in coastal sediments. Geologic

reconstructions of past floods can be used to: (1) assess the magnitude of these historic

events, (2) extend records of flooding deeper into the past and (3) identify what drives

changes in extreme precipitation on long timescales. At present, however, few such

reconstructions exist for the eastern United States.

In a recent study, USGS scientists, along with university collaborators from the

College of William and Mary, Woods Hole Oceanographic Institution, University of

Rhode Island and Texas A&M, began to fill this knowledge gap by reconstructing

extreme floods on the Susquehanna River over the past two thousand years. The

Susquehanna has the largest watershed on the U.S. Eastern Seaboard. Sediment core

MD99-2209, collected from the main stem of Chesapeake Bay (water depth = 26

meters) near Annapolis, Maryland by the research vessel Marion Dufresne in 1999,

was analyzed for coarse-grained sediment layers thought to have been deposited

during large floods.

Several such layers were identified downcore. The ages of these ‘paleo-events’ were

determined using lead (210) during the past ~100 years and radiocarbon deeper in the

core. Additionally, the abundance of ragweed pollen increased directly after Colonial

land clearance, providing an additional age marker. The most recent ‘flood’ deposits

found in this core can be attributed to hurricane Agnes (1972) and the Great Flood of

1936. However, many other coarse-grained layers in the sediment core predate

robust historic records and are indicative of prehistoric floods on the Susquehanna

between 1800–1500, 1300–1100, and 400–0 CE. A possible explanation for

increased flood frequency during these intervals is that cooler conditions near

Chesapeake Bay—relative to the tropical North Atlantic—produced favorable

conditions for tropical cyclone development and landfall in the Susquehanna

watershed. Ongoing work, elsewhere in Chesapeake Bay, aims to develop a

complementary record of coastal inundation during intense hurricane strikes in order

to further test this hypothesis.

The paper, “The Mighty Susquehanna—Extreme Floods in Eastern North America

During the Past Two Millennia” was published in Geophysical Research Letters. It

is available at: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018GL080890


https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018GL080890



Volume 9, Fall 2019



The geologic record includes examples of past climates that were much different from today, and the Eocene epoch

(from 56 to 33.9 million years ago) included the warmest climates of the last 66 million years. During the Eocene, a

series of abrupt warming events, known as “hyperthermals”, coincided with pulses of carbon injection into the

atmosphere, and they are recorded in the geologic record by changes in carbon isotope values. These events had

significant impacts on the distribution of plant and animal communities, and analysis of the events provides insights into

the feedbacks between changes in the global carbon cycle and climate extremes.

The largest hyperthermal event was the Paleocene-Eocene Thermal Maximum (PETM at ~55.5 million years ago), when

a massive amount of carbon was injected into the atmosphere. Carbon injection has been hypothesized to affect the

global hydrologic cycle and seasonal contrasts in temperature, and paleoclimate proxies from sediments deposited during

hyperthermals provide evidence to evaluate those hypotheses.

USGS researchers and colleagues from

Brandon University, Lamont-Doherty Earth

Observatory, and Utrecht University recently

analyzed the impact of hyperthermal events in

the Arctic using sediment cores collected by

the Integrated Ocean Discovery Program

(IODP) Expedition. Analyses of pollen,

biomarkers from soil bacteria, and other

organic-walled microfossils from the sediment

cores allowed the scientists to reconstruct

vegetation, atmospheric temperature, and

hydrology before, during, and after the PETM.

During the Paleocene and early Eocene, the

continents were arranged differently than today

(Figure 1), and the Arctic Basin was more or

less land-locked, with limited exchange

between the Arctic Ocean and the Pacific and

Proto-Atlantic Oceans. The coring site used in

this study, IODP Site 302-4A, is located on

Lomonosov Ridge, a continental fragment that

broke away from the Eurasian continent ~57

million years ago. During late Paleocene-early

Eocene time, the site is thought to have been in

relatively shallow water, and pollen from

nearby landmasses was preserved in the ocean

sediments.




Volume 9, Fall 2019



Pollen evidence (Figure 2) from the core indicates that late Paleocene

Arctic climates were warmer than today, with mixed conifer-hardwood

forests (with pine, spruce, and walnut) occupying landmasses near the

coring site. Today, these areas are underlain by permafrost, and plant

communities consist of dwarf shrubs, grasses, mosses, and lichens.

Bioclimatic analyses, based on climatic requirements of plant groups

identified in the pollen record, indicate a generally warm late Paleocene

climate (mean annual temperature averaging ~13˚C/55˚F). Independent

analysis of lipid biomarkers also indicates a warm late Paleocene

(14.6˚C/58˚F). In contrast, present day mean average temperatures in

Greenland are currently ~4˚C/39˚F.

During the PETM hyperthermal event, broad-leaved swamp forests (with

members of the cypress family, palms, and other warm temperate to

subtropical plants) dominated the nearby landscape. Both bioclimatic

analyses and biomarkers indicate that PETM mean annual temperatures

increased by as much as 3.5˚C/5.4˚F, driven primarily by warmer winters.

Analysis of other organic microfossils indicates that runoff of water and

nutrients from the continents to the oceans also increased during the PETM, resulting in lower salinity, decreased oxygen

content of water, and changes in algal communities in the Arctic Ocean.

After the peak of the PETM, forested wetland and lowland vegetation dominated the landscapes, and subtropical plants

were absent. Mean annual temperatures decreased but remained warmer than the late Paleocene baseline, and normal

marine conditions returned.

The study shows that the PETM injection of carbon to the atmosphere was accompanied by a significant warming of air

temperatures, particularly during the winters. The resulting restructuring of plant and animal communities includes the

northernmost known occurrence of palms and other taxa that are now native to tropical and subtropical latitudes.

Increased runoff of water and nutrients from the land to the ocean resulted in lower salinity and availability of oxygen in

ocean waters, which affected the composition of algal communities that are the base of the marine food chain.

This research is part of a broader international effort to document the interactions between natural changes in greenhouse

gas concentrations, climate, and plant and animal communities on land and in the ocean across the globe. Through

studies of past abrupt events, earth scientists are developing large datasets that can be used to test results of global

climate models that simulate past, present, and future climate. The results also provide a unique window on how the

Earth system has responded to extreme events of the past - yielding insights on impacts of potential changes in the

future.

The paper “Arctic vegetation, temperature, and hydrology during Early Eocene transient global warming events” was

published in Global and Planetary Change and is available here: https://www.sciencedirect.com/science/article/pii/

S0921818119300979?via%3Dihub


https://www.sciencedirect.com/science/article/pii/S0921818119300979?via%3Dihub

https://www.sciencedirect.com/science/article/pii/S0921818119300979?via%3Dihub



Volume 9, Fall 2019



It seems remarkable that, in the 21st Century, we still don’t fully understand why trees die during drought. Developing

this understanding is key if we are to maintain healthy forests, along with their invaluable goods and services. This is

especially true as droughts are expected to become more frequent and severe. Recent research in this area has mostly

focused on two proposed mechanisms of drought-induced tree death: hydraulic failure (dehydration) and carbon

starvation (metabolic collapse). Both mechanisms can kill trees directly or contribute to tree death indirectly by making

trees more vulnerable to natural enemies like insects. Regardless, it is widely accepted that the most physiologically

stressed trees will be the ones that die during drought. That said, recent research indicates a weak relationship between

metrics related to physiological stress and tree death during drought. Something else must also be going on…but what?

Part of the answer to this question is being unraveled in the forests of California’s Sierra Nevada where USGS research

scientists have tracked the fates of tens of thousands of trees annually for 37 years. Every year, newly-dead trees get

“autopsied” to delineate cause of death. One such example is bark removal that reveals characteristic galleries (tunnels)

left by tree-killing bark beetles (Figure 1).

During California’s historically unprecedented 2012-2016 drought, some 2,000

monitored trees died and received autopsies, providing a unique window into

mechanisms of drought-related tree death. The majority of the dead trees were killed

by native bark beetles however, the size and stress level of trees that were killed

depended heavily on the particular tree

preferences of different bark beetle species

as demonstrated in Figure 2. Thus, even

during such an extreme drought, substantial

proportions of stressed trees survived

because their size was one that mostly

avoided fatal beetle attack. Conversely,

substantial proportions of comparatively

unstressed trees died because they were of a

size selectively killed by outbreaking

beetles. That is, idiosyncratic tree selection

by bark beetles meant that tree stress was

only weakly related to tree death.

These findings shine a spotlight on what scientist and author E.O. Wilson calls

“the little things that run the world”, in that the small size of insects and other

invertebrates belies their overwhelming importance in shaping our world Figure

3). The findings further suggest that, even during extreme droughts formerly

thought to kill trees directly (by hydraulic failure or carbon starvation), tree

survival in selected areas might be substantially enhanced by controlling bark

beetle populations. Targeted control methods have already been developed for a




Volume 9, Fall 2019



few particularly damaging bark beetle species, providing “proof of

concept” which may help future efforts to maintain healthy forests.

Furthermore, this research highlights the need to find targeted control

methods for each species in a highly diverse array of bark beetles.

The paper, “Which trees die during drought? The key role of insect host

-tree selection” was published in Journal of Ecology and is available

here: https://besjournals.onlinelibrary.wiley.com/doi/abs/10.1111/1365-

2745.13176


https://besjournals.onlinelibrary.wiley.com/doi/abs/10.1111/1365-2745.13176

https://besjournals.onlinelibrary.wiley.com/doi/abs/10.1111/1365-2745.13176



Volume 9, Fall 2019



Monitoring and understanding land-use change in America is critical given our continued growth, urbanization, and

dependence on natural resources. To achieve more accurate assessments of urban land changes, USGS scientists from

the Patterns in the Landscape – Analyses of Cause and Effect (PLACE) team employed two decades of satellite data to

interpret and study landscape change across the conterminous United States from 1992-2011.

Beginning in 2015, a small group of geographers came together to improve United States urban land maps by making

adjustments to multidecadal, national-scale land-use maps produced by the National Land Cover Database (NLCD).

NLCD has been the seminal source for wall-to-wall land-use/land-cover maps of the country, and part of the NLCD

effort centers on mapping developed lands. Existing change estimates generated by NLCD and others covering the 1990s

and early 2000s represent the best available data for land managers and other researchers, but uncertainties remained.

Early in their exploratory effort, the PLACE team determined that rural roads included in the developed classes of

NLCD maps were problematic due to inconsistencies in road location, density, and continuity. In addition, some

classification techniques associated with rural areas and impervious surfaces contributed to artificial increases in areas

classified as developed. To mitigate these challenges, scientists hypothesized that a series of post-processing techniques

could effectively improve the NLCD maps spanning the years 1992-2011. The team edited and removed rural roads in

the NLCD developed class by intersecting a suite of geospatial land use data and manually removing misclassified areas.

Their efforts resulted in higher accuracy maps of urban land and improved urban change estimates spanning a 19-year

period.

The removal of roughly 230,000 square kilometers of rural roads from the NLCD developed class resulted in maps that

better characterize the urban footprint, with a national accuracy approaching 99 percent in 2001 and 2006. These urban

maps provide improved inputs for modeling applications and policy decisions that rely on quantitative and spatially

explicit information regarding urban lands.

Examples of before and after maps for urban areas of Atlanta, GA and Houston, TX are shown in Figure 1. Since their

publication, the revised maps have been used in peer-reviewed land-use forecasting efforts and by the NLCD team to

help develop its 2016 land-use/land-cover map. Additionally, USGS researchers are actively using these data to develop

annualized urban maps for California to further refine our communal understanding of contemporary land use changes in

the West.

By creating novel protocols to improve existing land cover data, the resulting maps contribute to an improved national

urban map repository. These efforts advance our understanding of the rates and causes of land change in the United

States while helping managers and stakeholders make more informed decisions to better prepare for the future.

The paper, “Removing Rural Roads from the National Land Cover Database to Create Improved Urban Maps for the

United States, 1992 to 2011”, was published in Photogrammetric Engineering & Remote Sensing and was recognized as

the third-place recipient of the 2019 ESRI Award for Best Scientific Paper in Geographic Information Systems. It is

available at: https://pubs.er.usgs.gov/publication/70195240. Geospatial data are also available at: https://doi.org/10.5066/

F79G5K05.


https://www.usgs.gov/centers/wgsc/science/patterns-landscape-analyses-cause-and-effect

http://www.mrlc.gov/


https://doi.org/10.5066/F79G5K05

https://doi.org/10.5066/F79G5K05



Volume 9, Fall 2019






Volume 9, Fall 2019



The northern range limit of most

tropical plants and animals is

determined by extreme freeze

events. In coastal wetlands along

the Gulf of Mexico and Atlantic

coasts of the United States,

freeze events govern the northern

extent of mangrove forests.

Many climate model simulations

indicate that winter temperatures

may warm in the coming

decades; if that were to occur, it

is likely that tropical, freeze-

sensitive mangrove forests would

expand northward at the expense

of temperate, freeze-tolerant salt

marshes. To better anticipate and

prepare for potential mangrove

range expansion, there is a need

to advance understanding of the

influence of microclimate.

Macroclimate refers to climatic

conditions that occur across very

large spatial scales (i.e., typically

up to 100 km horizontally and 10 km vertically). In contrast, microclimate refers to climatic conditions that vary across

much smaller spatial scales (i.e., typically less than 100 m horizontally and less than 10 m vertically). While

macroclimate is governed primarily by continental-scale atmospheric circulation systems, microclimate is also regulated

by local factors near the earth’s surface including proximity to vegetation, soil, and water.

A recent study by USGS scientists and Florida International University synthesized hypotheses regarding the effects of

microclimatic variation on temperature gradients and corresponding mangrove freeze damage. Temperature data from

the literature and from temperature loggers placed in the field were used to quantify temperature gradients produced by

microclimatic factors. Then, literature-derived mangrove freeze damage data were used to quantify the ecological effects

of these temperature gradients. Microclimatic gradients due to local factors (e.g., proximity to water, soil, or vegetation)

can determine whether temperatures are below or above a threshold at which mangrove damage and/or mortality will

occur. For example, temperatures during a freeze event may be warmer near the ocean, close to the soil surface, and

beneath the canopy of larger mangroves; thus, these are areas where mangrove freeze damage and mortality may be

reduced by microclimatic conditions.




Volume 9, Fall 2019



The paper identifies the following six

microclimatic factors, which produce

air temperature gradients that

influence mangrove responses to

winter temperature extremes: (1)

distance from the ocean; (2) distance

from wind buffers; (3) mangrove

canopy cover; (4) height above the

soil surface; (5) local slope concavity;

and (6) tidal inundation. Variation in

these factors produces local

temperature differences that range

from 2 to 14°C, with associated

effects on horizontal and vertical

patterns of biological damage from

freezing. These results clarify the

influence of microclimate on spatial

patterns of biological damage and

mortality due to winter temperature

extremes.

The largest temperature gradient

observed was related to distance from the soil surface. During chilling and freezing events, temperatures were ~9-14°C

warmer near the soil surface compared to temperatures at just one meter above the soil surface. These observations

indicate that there is a protective buffer zone near the soil surface, in which mangrove propagules, roots, and above-

ground material are more protected from freeze effects compared to taller plant sections that are exposed to colder air.

As mangroves expand into new areas in response to warming winter temperatures, the protective buffer zone near the

soil surface will likely play a critical role to promote ecological resilience. If the newly-arrived individuals can grow and

reach the reproductive stage, there is a good chance that their propagules and low-lying plant strata will be thermally

protected and able to rapidly regenerate following winter temperature extremes. As mangrove ranges expand in response

to climate change, microclimatic variation is expected to produce both adverse environments where mangrove expansion

is prohibited and expansion hot spots where mangroves are protected. Subsequent expansion into newly-available habitat

will occur from protection zones, and microclimatic gradients may even produce positive feedback cycles that ultimately

accelerate the rate of range expansion in response to warming. Collectively, these findings regarding the role of

microclimate can improve predictions of mangrove range expansion in response to changing macroclimate.

The paper “Microclimate influences mangrove freeze damage: implications for range expansion in response to changing

macroclimate” was published in Estuaries and Coasts and is available here: https://link.springer.com/article/10.1007%

2Fs12237-019-00533-1


https://link.springer.com/article/10.1007%2Fs12237-019-00533-1

https://link.springer.com/article/10.1007%2Fs12237-019-00533-1

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