Global Coastal Change

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Global Coastal Change

Ivan Valiela

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© 2006 by Ivan Valiela

BLACKWELL PUBLISHING350 Main Street, Malden, MA 02148-5020, USA9600 Garsington Road, Oxford OX4 2DQ, UK

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First published 2006 by Blackwell Publishing Ltd

1 2006

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Valiela, Ivan.Global coastal change / Ivan Valiela.

p. cm.Includes bibliographical references and index.ISBN-13: 978-1-4051-3685-3 (pbk. : alk. paper)ISBN-10: 1-4051-3685-5 (pbk. : alk. paper)1. Coast changes. I. Title.

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Contents

Preface, vi

1. Global context of coastal change, 1

2. Atmospheric-driven changes, 22

3. Sea level rise, 48

4. Alteration of freshwater discharges, 79

5. Alteration of sediment transport, 105

6. Loss of coastal habitats, 124

7. Petroleum hydrocarbons, 146

8. Chlorinated hydrocarbons, 174

9. Metals, 201

10. Introduction of exotic species, 226

11. Harvest of finfish and shellfish, 245

12. Eutrophication, 283

13. Other agents of coastal change, 324

14. Summing up, 347

Index, 357

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Preface

All environments on the earth’s surface havealways been in flux, and so they are today. Theaction of agents of change is evident everywhere,in the geological record, in the changing mosaicof land covers that carpets dry land. For a varietyof reasons, environmental change has been par-ticularly notable along the narrow coastal zonesof the world. The changes have not escaped un-noticed: there has been concern among many aboutthe alterations, especially as they have modified,thwarted, or prevented our uses of these environ-ments. There are many books with titles such as The Empty Ocean, Sea of Slaughter, and so on,most of which emphasize the alarming degree of change attributable to human exploitation,uses, and alterations of virtually all coastal environments.

Public and even scientific discussion and writ-ing about too many of the examples discussedbelow provides ample evidence of widespreadheedless unconcern with the environmental dam-age that follows so many human activities. On theother extreme, that bias is matched by the too-facile position of “viewing with alarm”, aposition with which I largely symphathize. Yes,there will be no improvement in environmentalquality unless cases are argued powerfully andrules enforced. On the other hand, it seems to methat there are issues that are more and less compelling, and we should act accordingly.There are so many causes for concern, all to somedegree and at some scale important: which agentof coastal change should be considered as thehigher and highest priorities? In each chapter, Ihave tried to provide the information I found,and thought relevant to, a thoughtful assessmentof the agents of environmental change alteringcoastal environments at global and at local spatialscales. Advocates of some of the specific topicsmay find my assessments wanting of conviction;all I can add is that the chapters hold what to meseemed assessments warranted by a careful scrut-iny of the most current data and that often, the

evidence is ambiguous and incomplete. I wouldtake it as a measure of success if the assessments I include in this book prompt skeptical or iratereaders to review the evidence included, and to explore the reference materials added in thefootnotes.

In this book I review evidence of intensity andpervasiveness of effects, and recovery from theaction of the major agents of change that are alter-ing the diverse coastal habitats and populationsof the world; a brief overview of the subjects ofthe chapters is provided at the end of Chapter 1.Throughout all chapters, I try to assess the degreeof change forced by human and non-humaninfluences.

In reading otherwise quite good books cov-ering the staggering recent changes in marineenvironments I have often felt the need to actu-ally see the evidence underlying the alarmingtrends being discussed, rather than just read text“viewing with alarm”. For this reason, I endeav-ored, perhaps to a burdensome degree, to include relevant facts, tables, figures, and referencesthroughout the chapters.

To make the material clear, I have sorted theevidence into chapters that separately focus oneach major agent of change, but, as will becomeevident, in the majority of cases there are jointeffects of more than one agent of change, andpowerful interactions. The separation of subjectmatter into the various chapters is a simple pedagogic device that should not be taken tomean that the impact of agents of change canreadily be taken in isolation. I should add thatmy focus will be on the environmental effects.Although here and there I note certain relevantpublic health and other human effects, I do sosimply to set the stage for the ecological discus-sion. A comparable treatment of the humaneffects is beyond the scope of this book.

Looking back, I see that the chapters differ inlength and detail. This disparity was more areflection of the published literature than a

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measure of the relative heft of the subjects. Sometopics—petroleum hydrocarbons, effects of met-als, impacts of overfishing, for example—seem to have led to greater and more detailed contro-versies, and attracted more logorrheic groups ofpractitioners writing more publications thanother topics. The result is more lengthy chapters.Other chapters, for example the one on eutrophi-cation, hold subject matter that extends acrossmany disciplines, and hence required more spaceto deal with the diverse materials.

I have sought to make this book accessible to a variety of stakeholders interested in environ-mental issues, including the interested lay pub-lic, the professional manager and decision-maker,and researchers and students dealing withcoastal matters. To reach such a wide audience, Iset out—ambitiously—to write three books inparallel: in each chapter I have added, as a casehistory, a vignette that showed, in an evidentand compelling way, the essential dilemma andfacts. This first “book” was intended to clearlymake the case that humans were involved in has-tening change and were in turn affected by thechanges. The vignettes were intended to bringthe material to the street level, so to speak (in thecase of sea level change in Venice, this will liter-ally be so). There is a second, more technical“book”, which provides a more general reviewof the background, principles, evidence, effects,consequences, and possible remediation. A third“book” will be found in the footnotes and in the longer boxed material, where backgroundmatters, more arcane, but perhaps interesting,details are provided, technical points and termsare defined and discussed, and references con-taining more information are given.

The subject matter covered in this book hasturned out to be dauntingly broad, but moreproblematic has been the extraordinary prolifera-tion of publications as we turn into the 21st cen-tury. As an example, a search using just a singlesoftware search “engine”, entering the relativelyspecialized term “salt marsh” yielded 991 worksduring the last 10 years. This awesome plethoraof publications has forced me to make use of apitifully small portion of the available literature,limited by time to read titles, let alone digest allthe information on sources. Every week, journals

arriving at our library carried papers that forcedrevisions of chapters already written. This hasbeen true for some time (recall Darwin’s plightabout Wallace’s paper on the idea of evolution)but the current state of scientific publication hasbrought a new dimension to the overwhelmingavalanche of new material. As a result, manyworthy papers were unfortunately left unreadand uncited. I apologize to the many authors ofthese unmentioned works; I have no solution forthis dilemma, but it is clear that the world’s sci-entific community needs to search for ways toaddress this issue. In the blizzard of recent pub-lications, there is also the danger of ignoring theolder sources that constitute the intellectual his-tory of the subject, and in many cases still meritknowing. To help readers, I endeavored to men-tion updated reviews of various fields, as theywere available.

The development of the internet has madeavailable a rich variety of sources of informationon the subjects covered in this book. Unfor-tunately, any thoughtful user will soon find thatthe information available in the internet variesenormously in quality, from the entirely com-pelling to the completely unreliable. Moreover,the half-life of material posted in the internetseems unreliably short, with entries disappear-ing with no record of their existence. Internetsources are proliferating, and often hold import-ant information inaccessible otherwise, and so Iused them, but it is with some hesitation that inthe chapters below I provide internet addressesas sources of material.

This book was in a real way made possible byhaving access to the Marine Biological Laboratory–Woods Hole Oceanographic Institution Library.I am deeply indebted to Catherine Norton, EleanorUhlinger, Colleen Hurter, and the many othermembers of the Library staff, who displayedextraordinary patience with endless queries aboutobscure materials, arcane sources, and incompletereferences. There can be few librarians moredevoted to make their library work for usersthan those in the MBL–WHOI Library, and thereare few libraries that make their impressiveholdings as easily available.

I have to thank Gabrielle Tomasky and MarciCole for developing excellent graphics based

PREFACE vii

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only on my rough sketches, and Deborah Ruteckifor detailed ferreting out of inconsistencies andreferences. Graduate students in my lab—KevinKroeger, Marci Cole, Jennifer Bowen, Joanna York,Ruth Carmichael, Sophia Fox, Mirta Teichberg,Sara Grady, Jennifer Culbertson, Ylva Olsen, andNadine Lysiak—contributed many thoughts,information, and reactions during the long process of writing this book. In addition, ErinKinney, Jayne Gardiner, Dhira Dale, and ScottNickles, helped greatly by thoroughly readingand criticizing the manuscript during a courseon the subject. I am indebted to John Farrington,Judy McDowell, Bruce Tripp, Anne Giblin, MaxHolmes, Skee Houghton, and Sybil Seitzinger for

critiques of earlier drafts of various chapters, and am especially grateful to Pat Kramer, BorisWorm and Ken Tenore for extremely useful pre-publication reviews of the entire manuscript.The remaining errors are mine, but all these stu-dents and colleagues helped clarify and updateideas. Jennifer Bowen and Ruth Carmichael pro-vided data for some figures, and Joanna Yorktranslated Russian text. At Blackwell Publishing, I must thank Jane Andrew, who concertedlytrained her editorial skills and imposed a mea-sure of clarity, accuracy, and consistency on mymanuscript, and Rosie Hayden who was invalu-able in the process of bringing the manuscript topress and in ensuring its quality.

viii PREFACE

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Chapter 1Global context of coastal change

Allegorical engraving of the “opposition” of land and sea in the Venice Lagoon, taken from Bernardo Trevisan,Della Laguna di Venezia, Trattato, published in 1715. Reproduced here from Lasserre and Marzollo (2000).

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what people do can have intense, widespread,multiple effects on the coastal zones of the world.

A case history: the remarkable variety ofenvironmental changes in the Black Sea

Some 12,000 to 7,000 years ago, the body of waterwe know as the Black Sea was a fresh- to brackish-water lake, fed by several major rivers (Fig. 1.1top) whose flows had increased as glaciationdiminished. The lake was separated from theAegean Sea, a branch of the Mediterranean, bywhat is now the Sea of Marmara (Fig. 1.1 bottom,Fig. 1.2 bottom). As the climate warmed further,the sea level in the Mediterranean rose abovewhat is now the Strait of Dardanelles, and thenhigher than the Bosphorus Strait (Fig. 1.1 bottom,Fig. 1.2). Saltier sea water moved into the BlackSea in the deeper layers of water crossing theBosphorus, and somewhat fresher sea waterdrained out to the Aegean in the upper layers.During a period of years to decades,1 the BlackSea became saltier, and the entire suite of organ-isms, and biogeochemical conditions within theBlack Sea, changed across a few centuries. This isa compelling example of the ceaseless changes,driven by global-scale forcing, that have affectedcoastal and other environments throughout thehistory of the earth.

The coasts of the Black Sea have continued tobe affected by sea level rise. Differences in localgeological subsidence, reduced freshwater deliv-ery by rivers (owing to human water use, seebelow), and regional differences in heating ofwater all have conspired to create considerablevariation in the local rates of recent sea level rise(Cazenave et al. 2002). In general, however, sea

An allegorical engraving in an eighteenth cen-tury treatise on the lagoon of Venice (frontis-piece) shows the “opposition” between land andsea. The somewhat artless design leaves somedoubt about the relationship (are Sea and Landengaged in a struggle or an embrace?), but it doeseffectively convey that land and sea are linked in powerful, though perhaps ambiguous interac-tions, and that the vigorous action takes place at the land/sea boundary and unwittingly pre-sciently, under the gathering clouds of atmo-spheric change. That the scene takes place infront of an urbanized area—Venice, in this case—merely adds the coda that the presence of humans might have some influence on theinteraction between Land and Sea. There maynot be a better summary of this book.

The allegorical engraving captures the realityand extent of the coupling between land andcoastal sea that research during succeeding cen-turies was to reveal. These couplings are real andsometimes altogether extraordinary. We know,for example, that decadal-scale meteorologicaldisturbances in the Equatorial Indian and PacificOceans prompt long-distance changes in theupper atmosphere. These alter visibility enoughto change the number of visible stars in thePleiades. This number was recorded by Incaastronomers, and even today, observations ofthe number of stars visible in the Pleiades is usedas a criterion to decide on the planting date ofpotato crops in the high Andes (Orlove et al.2000). Such remarkable long-distance connectionsspeak of a far more complicated set of couplingsbetween the ladies in the Venetian engravingthan could possibly be conceived by the artist,but he captured the essence of the matter.

This book is an account of the many ways inwhich human beings have altered the multiplecouplings between land and sea in the narrowcoastal zone where the two adjoin. In this firstchapter, I begin with a case history that sub-sumes virtually all the agents of change, andnearly all the couplings, that will be dealt with inlater chapters. The recent history of the Black Seaincludes a remarkable litany of environmentalalterations, most owing to human activities. Thisextraordinary case history demonstrates that

2 CHAPTER 1

1 Some researchers (Ryan et al. 1997, 2003) have argued that theincursion was a wall of water that suddenly and violently brokethrough the higher sill of the Bosphorus, and poured rapidly intothe Black Lake, sweeping all before it. This is the “Noah’s Flood”viewpoint, harking on the biblical flood idea, because the apparentdate and the catastrophic nature of the event matched scripturaldescriptions (Kaminski et al. 2002). Myers et al. (2003) suggest thatit is more likely that the salinization of the Black Sea took placemuch more slowly, over at least decades. This view is supported bydiverse sets of evidence in many papers appearing in issues of twojournals dedicated to the matter and published in 2002 (Estuarineand Coastal Marine Science vol. 54 and Marine Geology vol. 190).

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GLOBAL CONTEXT OF COASTAL CHANGE 3

level rise has been much higher in the Black Sea (27 ± 2.5 mm yr−1) than in the Mediterranean(7 ± 1.5 mm yr−1) (Cazenave et al. 2002). The higherrate of sea level rise makes for a greater threat forlow-lying cities and wetlands on the margins ofthe Black Sea.

There is little evidence of human influence inthe Black Sea region before 4,000 years before thepresent (yr BP); earlier than this date, pollendeposits in sediments show that the watershedswere covered by forests (Mudie et al. 2002). After 4,000 yr BP, the pollen record in Black Sea sediments suggests that a few humans clearedland and engaged in limited agricultural practices.The pollen record agrees with archaeological

evidence of the earliest settlement of Troy andother settlements on the shores of the southernBlack Sea (Bottema et al. 1995).

During more recent centuries, human beingshave joined global forces as major agents alteringconditions in the Black Sea. Toward the close of the 20th century, on average, there were 67people per km2 on the watershed of the Black Sea (Leppäkoski & Mihnea 1996).2 Freshwater

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Figure 1.1 Top: outline (thick line)of the watershed of the Black Sea(from http://www.parliament.ge/SOEGEO/ english/blacksea/needs.htm). Bottom: map of theTurkish Straits area between theBlack Sea and the Mediterranean,showing the Dardanelles, Sea ofMarmara, and Bosphorus (fromMyers et al. 2003).

2 The density of people on earth during 2000 may have been 45people km−2; by the year 2050, density is projected to reach 66 peo-ple km−2 (Cohen 2003). The density of people on the watershed ofthe Black Sea is therefore at what will be the global situation in 2050.Given the situation in the Black Sea, these statistics are a soberingtocsin as to future developments on wider geographic scales.

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4 CHAPTER 1

12,000 ships might have been active across theBlack Sea colonies, with a useful lifespan of 10years. Bondyrev conjectured that more than 150million ha of forests might have been cleared bythe ancient Greeks between 800 and 400 BC.These numbers are of course mere guesswork,and do not consider regrowth of forests, but sufficeto make the point that large tracts of land werelikely altered quite early in the history of humanexpansion onto the watershed of the Black Sea.Intensive deforestation on the watershed of theBlack Sea continued into later centuries: the presence of large pine trees was one reason for the founding of the Russian Navy base in Sevastopol in the 18th century (Radchenko &Aleyev 2000).

Ecological alterations to the coastal landscapehave continued to this day, when about 162 million people live on the watershed of the BlackSea. As we will see in other chapters, popula-

flow through the major rivers, particularly theDanube (Fig. 1.1 top) transports land-derivedmaterials toward the Black Sea, but as humanpopulations became more numerous, their activ-ities changed the land cover on the watershedsfrom which the rivers received their water, sedi-ment, and chemical loads. For example, duringthe 8th to 4th centuries BC, more than 62 Greekcity state/colonies were founded and eventuallyringed the coast of the Black Sea. Vast amounts of timber were required to support the com-merce and defense of these Hellenic settlements.Homer reports in the Iliad that many Greekcities contributed some 1,093 ships to the TrojanWar, so it is evident that ships were plentiful.Bondyrev (2003) speculated that 2,000–4,000 treeswere required to build and outfit a ship, and thatthere might have been 100–800 oak trees perhectare, so that 25–40 ha might be felled to sup-port one ship. Very roughly, perhaps 10,000–

Figure 1.2 Top: the Bosphorus atIstanbul (from Mee 1992). Bottom:sketch of a possible version of thechanges in the postglacial sea level inthe Aegean, Marmara, and Black Sea(after Myers et al. 2003; otherversions given in Kaminski et al.2002; Major et al. 2002).

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GLOBAL CONTEXT OF COASTAL CHANGE 5

Nutrients

The yield of nitrogen and phosphorus out ofwatersheds by rivers increased as the density of human populations increased in the water-sheds of the Danube and other European rivers (Fig. 1.4). A larger number of people, the ex-pansion of urban areas, increased agriculturalexploitation, and industrial development withinthe watersheds of the Black Sea all increasednutrient loads to the sea across the second half ofthe 20th century (Garnier et al. 2002).

tion and land use changes of this magnitudecarry significant consequences for the water bod-ies that receive the exports from the altered watersheds.

Rivers such as the Danube (Fig. 1.3) flowdownslope towards receiving waters, in thiscase, the Black Sea. The rushing waters carrylarge loads of sediments and nutrients, even inpristine watersheds. Human activities on water-sheds, however, can severely alter the rates oftransport of land-derived materials to the sea,including nutrients, sediments, and water.

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Figure 1.3 Top: longitudinal profile of the altitude (vertical axis) and depth of the Danube (indicated by thewidth of the black outline) as it courses from its origin to the Black Sea. Names next to the vertical lines showlocations of cities. Bottom: extent of the cross-section of the Danube along its course. Modified from Garnier et al. 2002; redrawn from other sources.

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6 CHAPTER 1

Fluvial nutrient delivery to the Black Sea de-creased (Mee 1992) as a result of lower use of fertilizers during the more impecunious 1990s,and the capture of sediments behind dams.

Sediments

Sediments previously transported by the Danubeinto the Black Sea have accumulated on the bot-tom of reservoirs formed behind dams built tofurnish hydroelectric power and to ease naviga-tion. Iron Gate I and II dams started operation

Time courses of human activities on the water-sheds of the rivers feeding the Black Sea weremirrored in the nutrient contents of the riversand the receiving sea waters. The use of phos-phate fertilizers on the watershed of the Danube,the major source of materials to the Black Sea,increased through much of the 20th century, butdecreased in the 1990s as the Eastern Europeaneconomies suffered a downturn (Fig. 1.5 top).The concentrations of phosphate and phosphateload delivered by the Danube followed the sametime course (Fig. 1.5 middle), and there weresimilar changes in phosphate concentrations inthe water of the northwest Black Sea (Fig. 1.5 bot-tom). Similar patterns were evident with nitrate.Concentrations of nitrate in coastal waters nearthe Danube mouth increased six-fold betweenthe 1960s and the 1980s (Humborg et al. 1997),and tripled between 1970 and 1985 (Mee 1992).3

Figure 1.4 Relationship of annual nitrogen (filledcircles) and phosphorus (open circles) yields (per km2

of watershed) from European rivers to the density ofpeople in the area. Data from Garnier et al. (2002).

3 A greater delivery of nutrients increased concentrations in riverwater flowing to the Black Sea, even though considerable portionsof river-borne phosphate and nitrate were intercepted in the estuar-ies entering the Black Sea (Ragueneau et al. 2002). The retention ortransformation of available nutrients within environments hasbeen referred to as their “assimilative capacity”. In the Black Sea, asin so many coastal environments, human sources have increasednutrient loads to levels that overwhelm the assimilative capacity ofthe estuarine part of the rivers. The result is that substantial andincreasing amounts of river-borne nutrients traverse the estuary,and go on to affect the adjoining coastal waters.

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Figure 1.5 Top: phosphate fertilizer use on thewatershed of the Danube. Middle: discharge of phosphate by Danube water. Bottom:concentration of phosphate in the water of thenorthwest Black Sea. Data from Kroiss et al. (2003).

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4 The Bosphorus sill impairs circulation below 60–200 m in theBlack Sea (about 87% of the volume). Water below these depths isnot flushed, so there is time for bacterial action to consume oxygenfaster than the oxygen is supplied by physical processes, such asdiffusion, from above. Nutrient enrichment has increased the vol-ume of anoxic water in recent decades. Nutrients (ammonium inthe case of nitrogen) are recycled and released from the anoxicwaters upward. Some of the ammonium that diffuses upward fromthe anoxic deeper water is anoxically oxidized to nitrogen gas bybacteria using a newly described reaction (annamox) (Kuypers etal. 2003), but some ammonium manages to reach the oxygenatedwater above, adding to the eutrophication effect.

GLOBAL CONTEXT OF COASTAL CHANGE 7

1989), and by 27 and 52% by 1981 and 1985 (Mee1992). The lower input of fresh water has madefor a much shallower upper layer through the20th century, perhaps by as much as 30 m. Thisshoaling of the oxygenated upper layer has inturn exposed a larger area of coastal sea floor tothe anoxic lower layer, a serious developmentfor any organism living near the bottom.

Biological responses and other changes

Increased nutrient supply has altered the phyto-plankton of the Black Sea (Lancelot et al. 2002a,2002b): phytoplankton densities increased, thereare more blooms of fast growing species, and the species composition has changed (Table 1.1).For example, phytoplankton biomass increased5–10-fold between the 1960s and 1970s off theRomanian coast (Leppäkoski & Mihnea 1996).Dinoflagellates, Noctiluca in particular, and blue-green bacteria increased in abundance, outpac-ing the growth of diatoms and other groups.There were intense blooms of Mesodinium, a cili-ate, off the coast of Bulgaria in the 1980s. Some ofthe dinoflagellate and blue-green blooms weretoxic and led to shell- and finfish kills (Fig. 1.6).

The proliferation of phytoplankton biomass inthe water column in turn had at least three majorconsequences.5 First, the increased productioncreated a greater fall of organic particles sedi-menting to the sea floor, which increased bacterialdecomposition and consumed oxygen, expand-ing the extent of low oxygen water beyond thatoccurring naturally, and beyond the effect of thesmaller flow of fresh water. By the 1990s, 95% ofthe northwest Black Sea shelf, and the entire Seaof Azov were prone to episodes of low oxygen

in the Danube in 1970 and 1984 (see Fig. 1.3 top).In the reservoirs formed behind these two dams(note the two large areas about 900–1,200 kmfrom the Black Sea in Fig. 1.3 bottom), river flowslows and sediment particles settle. Behind-damcapture of particles lowered sediment discharge by the Danube by 30–40%, a decrease that has led to intense erosion of wetlands and mud-flats within the Danube delta, as well as in the sediment-starved shelf (Panin & Jipa 2002).Lower sediment supply also has led to erosion ofshorelines and beaches (Radchenko & Aleyev2000). The erosion has led to installation of un-sightly artificial groins that not only alter sandmovement, but trap tar, other pollutants, and litter. These declines in environmental quality,plus the lowered water quality, on aggregate,have deterred the tourism that has been econom-ically important in the Black Sea, the only beachregion available to millions of Eastern Europeans(Mee 1992). Crimea, historically the major touristcenter in the region, lost 85% of its tourists during the last decade of the 20th century(Radchenko & Aleyev 2000).

Water

In the Black Sea there is an oxygenated upperlayer of water that is relatively fresh (22‰), andwhose relatively low salinity was historically main-tained by river flow. This upper layer is underlainthroughout the deeper areas of the Black Sea byan anoxic deep layer of salty water of Mediter-ranean origin.4 Use of fresh water for agricultural,industrial, and municipal purposes within thewatershed of the Black Sea reduced the flow ofriver water by about 15% by 1981 (Murray et al.

5 The intensified eutrophication of the coastal waters of the BlackSea (about 30% of the Black Sea area) has led to other effects, lesswell-established than the ones discussed here. For example, theincreased nutrient enrichment has altered the emission of impor-tant gases to the atmosphere (Amouroux et al. 2002). The enrichedsediments released nitrous oxide, dimethyl sulfide, and methane—gases that have substantial effects on the condition of the atmo-sphere, and are involved in global warming trends and destructionof atmospheric ozone. A considerable part of the methane pro-duced is oxidized within sediments and in the water column, butnevertheless some methane does manage to enter the atmosphere(Ivanov et al. 2002).

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8 CHAPTER 1

(Bakan & Büyükgüngör 2000). Species that livedon the sea floor were badly diminished: fisheriesfor bivalves (soft-shell clams and mussels), forinstance, have nearly disappeared, as have manyothers (Table 1.2). A single anoxic episode in the Romanian coast killed about half the fish popu-lation (Mee 1992). The shallower low oxygen layerin the water column had widespread effects onthe biodiversity of organisms living on the bot-tom of the Black Sea (Fig. 1.7). Surveys done inthe 1980s found far fewer species in the benthos,and those that survived were restricted to shal-lower depths compared to similar surveys done inthe 1960s.

Second, the increased phytoplankton densitywas large enough for the depth of light penetra-tion of the Black Sea to decrease from 50–60 m inthe 1960s to 10–35 m in the 1990s (Mee 1992).6

The decreased light, plus the lower oxygen thatresulted from the shoaling of the upper fresherlayer, severely affected the beds of algae andplants on the sea floor. By the 1990s, the area ofsea floor supporting stands of Phyllophora in thenorthwest Black Sea had been reduced to 5% ofthe area of original habitat (Zaitzev & Mamaev1997) (Fig. 1.8). Phyllophora was formerly com-mercially important as a source of agar, and provided a habitat to many coastal species. The

Table 1.1 Densities of different groups of phytoplankton species and the number of blooms (samples withdensities > 5 × 106 cells l−1) in samples taken at Constanta Station in the northwestern Black Sea, during 1960–1970 and1980–1990. Data from Humborg et al. (1997).

1960–1970 1980–1990

Cell density Number of Cell density Number of(106 cells l−1) blooms (106 cells l−1) blooms

Diatoms 7–21 8 5–300 19Dinoflagellates 17–51 4 5–810 14Euglenophytes – – 5–108 6Prymnesiophytes – – 220–1,000 3

Total blooms 12 42

Figure 1.6 Dead fish and crustaceans on a Romanianbeach during a bloom of the toxic dinoflagellate Prorocentrum cordatum. From Leppäkoski and Mihnea (1996).

6 Bakan and Büyükgüngör (2000) reported that nutrient limitation ofphytoplankton growth ceased after the 1960s; since then nutrientshave been in excess of requirements, because the density of cellsmade for poor light penetration, so that phytoplankton growth hasbeen limited by insufficient light throughout most of the Black Sea.

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GLOBAL CONTEXT OF COASTAL CHANGE 9

all the bottom of Sevastopol Bay early in the 20thcentury, but have largely disappeared (Shalo-venkov 2000). The seagrass meadows were lostas a result of dredging of the bottom to allowport and navigation activities, and also by low-ered water transparency. The fauna associatedwith seagrass meadows—including commerciallyimportant species such as oysters and mussels—disappeared by the end of the 20th century(Milchakova 1999). The changes in nutrient andfreshwater delivery from the watershed thus thoroughly altered the bottom habitats of thecoastal Black Sea.

Third, the increased density of phytoplanktonfavored proliferation of grazers in the water column, such as copepods and protozoans.7 Thebiomass of herbivorous zooplankton increasedmore than three orders of magnitude between1961 and 1983 (Bakan & Büyükgüngör 2000). Inturn, the marked increases in zooplankton in

biomass of another habitat-building alga (thebrown macroalga Cystoseira barbata) also dim-inished during the 1970s, falling from 100–8,200to 80–290 g m−2 in rocky bottoms off Romania(Leppäkoski & Mihnea 1996). Stands of the sea-grasses Zostera marina and Z. nolti covered nearly

7 Eventually populations of the herbivorous protozoan Noctilucabecame 52–88% of the zooplankton biomass. Noctiluca is not a preyreadily eaten by predators, so, as Noctiluca became relatively moredominant, much less food became available for fish and otherpredators as the decades wore on. Perhaps the preponderance ofthe unpalatable Noctiluca had an indirect effect on the reduction offisheries in the Black Sea.

0

40

80

120

160

200

0 20

1980s

1960s

40 60 80Number of species

Dep

th (

m)

Figure 1.7 Relationship of number of large benthicinvertebrate species found at different depths off thecoast of the Black Sea for the 1960s and 1980s. Datafrom Zaika (1990).

Table 1.2 Status of selected prominent organisms and communities in the Black Sea, as of 1996. The changes areapproximations derived from comparisons of recent estimates relative to some comparable data from earlier in the20th century. Adapted from Bakan and Büyükgüngör (2000).

Type of community

Macroalgal canopies

Benthos

Water column

Major kind of organisms

Red macroalgae (Phyllophora)Brown macroalgae

MollusksOystersHypanisCrabs (about 14 species)Shrimps (more than 20 species)

Fish (e.g. 20 species of gobids, all endemic to the Black Sea)

Dolphins (3 species)Monk seal

Effects relative to previous condition

Area of habitat reduced to 3%Less than 1% of previous area

30% of previous abundanceLess than 5% of previous abundance50% of previous abundance30–50% of previous abundance40% of previous abundance

20% of previous abundance

5–10% of previous abundanceFew specimens left

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10 CHAPTER 1

only five remained so by the 1990s (Zaitzev &Mamaev 1997). The magnitude and rapidity ofthe substantial human-generated changes in the biomass and biodiversity of the entire foodweb of the water column of the Black Sea areastonishing.

By 1989–1990 it became evident that the re-moval of fish (particularly of small pelagic species)left unconsumed their erstwhile prey, which thenwere available to other predators (Gücü 2002;Lancelot et al. 2002a, 2002b). An apparent resultof this available food supply was the proliferationof gelatinous predators, such as the native jellyfishAurelia aurita, through the 1980s. In 1989, thealien comb jelly Mnemiopsis sp.9 was introducedfrom the Middle Atlantic coast of North America

turn fostered increases in the numbers of fishthat fed on the zooplankton (Porumb 1989). Theresulting larger abundance of fish made it possiblefor the fishing fleet, particularly small-scaleTurkish purse seiners, to increase harvests (Gücü2002). Within two decades, the commercial fishcatch fell by an order of magnitude (Fig. 1.9).8 Asis often the case, certain species are more suscept-ible to human exploitation than others: the catchof sprat hardly changed across the time periodshown in Fig. 1.9, while the herring and sardinecatch dropped markedly. The harvest-inducedcollapse of the fish stocks was species- and size-specific: larger species of pelagic fishes weredepleted during the 1960s and again during the1980s. Catch of smaller pelagic species and bot-tom-feeding fish were lowered during the early1990s (Gücü 2002). In 1965 there were 23 speciesof fish harvested commercially in the Black Sea;

8 As usual in the case of economically important resources, otherexplanations have been forwarded for the collapse of the Black Seafisheries (Kideys et al. 2005). Some have supposed that unspecifiedpollutants have interfered with the migration of anchovies andother species. Others suggested that the fish were being eaten bythe porpoises that had been protected from harvest as endangeredspecies; Mee (1992), however, reported that “hardly a dolphin is tobe found”.

Figure 1.8 Time course (1950s,1960s, 1970s, and 1980s) of thereduction of sea floor area coveredby a Phyllophora canopy in thenorthwest corner of the Black Sea.Adapted from Zaitzev and Mamaev(1997).

1980s

1970s

1960s1950s

9 There is some question as to the taxonomic identity of this combjelly, hence the designation as Mnemiopsis sp. (Weisse et al. 2002).Incidentally, this comb jelly was not the first alien species in theBlack Sea. In the 1940s a predatory sea snail, Rapana thomasiana,originally from Japan, invaded the Black Sea, and was particularlydamaging to the oyster shellfishery. The snail later was subject to afishery itself, and its populations declined in the 1990s (Mee 1992).Mya arenaria, the soft-shell clam, an invader from North America,appeared in the 1960s, competed with native species, and became avalued harvested stock, but now has become depleted by the lowoxygen conditions (Mee 1992).

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10 Some have concluded that the bloom of Mnemiopsis sp. was thecause of the decrease in fishery catch because the comb jellies con-sumed larval fish. Mnemiopsis sp. certainly eat fish larvae, butmodel studies suggest that the overfishing anteceded the prolifera-tion of comb jellies (Gücü 2002; Lancelot et al. 2002a, 2002b). Inaddition, fish catch data for the Mediterranean, where there wereno blooms of comb jellies, show depletion patterns quite similar tothose of the Black Sea (Lleonart & Maynou 2003), with a largedepletion of smaller pelagic species. This coincidence suggests thatfishing pressures may be involved in the time course of catch inboth seas.

11 The number of fish eggs sampled in Sevastopol Bay, in theCrimean Peninsula on the north coast of the Black Sea, ranged from2,380 to 7,990 eggs per 10 min of trawling, including 16–18 species,during the 1950s. During the 1980s, these numbers were 77–792,with 6–12 species represented. During the 1990s the numbers werelower, 60–1,027 eggs, with 3–12 species present. These reductionswere most likely the result of several factors, including lower oxy-gen, contaminants, grazing, and overfishing (Gordina et al. 2001).

GLOBAL CONTEXT OF COASTAL CHANGE 11

the abundance of smaller pelagic fish species(Shiganova et al. 2000).11 Mnemiopsis sp. havebecome less abundant in more recent years astheir plankton food supply has sharply dimin-ished, and as a new alien comb jelly, Beroe ovata, aspecialist in feeding on other comb jellies, enteredthe Black Sea in 1999, and presumably fed freelyon Mnemiopsis sp.

The booms and busts of populations in theBlack Sea food web during the second half of the 20th century demonstrate several import-ant points. Assemblages of organisms in coastalenvironments can be dramatically reshuffled bychanges in nutrient supply to producers on thebottom rung of food webs, and by changes in consumers at the top of food webs. Such bottom-up and top-down forcings interact in acomplicated fashion. Human beings are heavilyinvolved in the reshufflings, mainly by increas-ing nutrient supplies and by overfishing stocks,as well as by altering other features of theland/sea coupling.

in ship ballast water, and it quickly increased itsrange and abundance in the Black Sea.10 Therewere no native predators of the gelatinous pred-ators, and apparently sufficient food, so theirpopulations expanded freely. The largest abun-dance of larval Mnemiopsis was in the area nearthe plume produced by the flow of the Danube(Weisse et al. 2002), where the impact of enrich-ment was greatest. The data on densities of popu-lations of gelatinous species have been said to be unreliable (Weisse et al. 2002); at best, estim-ates are variable, but Mnemiopsis sp. did seem to bloom irregularly and at times profuselythrough the 1990s (Shiganova et al. 2000). Theirvoracious feeding (maybe 300 copepods per day)led to an order of magnitude lowering of zoo-plankton abundance during the late 1980s andearly 1990s (Weisse et al. 2002). Mnemiopsis alsofeed on eggs and larvae of anchovies and otherfish, and have been thought to have helped lower

Fis

h ha

rves

t (m

etric

tons

× 1

04 )

40

35

30

25

20

15

10

5

0

Merlangius merlangusSprattus sprattusClupeonella cultriventrisEngraulis encrasicolus maetricusE. e. ponticus

1984 1986 1988 1990Year

1992 1994 1996

Figure 1.9 Time course ofcommercial fish catch in the BlackSea, 1984–1997. The species includedare whiting (M. merlangus), sprat (S. sprattus), herring (C. cultriventris),and two subspecies of the Europeananchovy or sardine (Engraulis). From http://www.zin.ru/projects/invasions/gaas/mnelei_e.htm.

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12 CHAPTER 1

Concentrations of persistent organochlorineresidues in the sediments of the Danube delta are among the highest recorded (Fillmann et al.2002). High concentrations of chlorinated hydro-carbons and polychlorinated biphenyls (PCBs)were also found in the plume of the Danube(Maldonado & Bayona 2002). During the 1980s,concentrations of DDT in sediments of theDanube delta were about 1,000 times as large ascomparable Mediterranean sediments. DDT con-tents in fish caught in Turkish waters neared the limit for human consumption, and were 5–10times as large as concentrations found in theBaltic, an environment considered contaminated(Mee 1992). The recently deposited and high con-centrations of chlorinated hydrocarbons, includ-ing DDT, suggest that these compounds wereused recently within the watersheds of rivers thatcarry the compounds to the Black Sea (Fillmannet al. 2002), even though some of these organo-chlorines are banned in many countries.

If the inputs of metals and organic compoundswere not enough, the Black Sea watershed was also exposed to the largest ever accidentinvolving the release of radioactive materials.Radionuclides from the Chernobyl accident fellwidely on the watershed of the Danube, andadsorbed into soil particles. Erosion and fluvialtransport then conspired to convey the adsorbedradionuclides to the Black Sea. Radioactive materials were largely deposited in near-shoresediments under the Danube plume (Gulin et al.2002). The accumulation in sediments showed a5-year delay following peak atmospheric fallout,and the radionuclides in the surface sedimentshave decreased substantially since (Gulin et al.2002). Fortunately, radioactive contamination of organisms within the Black Sea did not reachlevels that might have biological consequences(Egorov et al. 2002).

Threats to habitats

Much as the erstwhile algal and seagrass canop-ies discussed earlier, coastal wetlands on thecoast of the Black Sea were productive habitats.These wetlands are essential for many birds andmammals, and, as we will see in later chapters,

The different conclusions reached by reason-able scholars viewing the same phenomenaabout the goings on in the Black Sea illustrateanother feature that we will have to deal withthroughout this book: data are often insufficient,and no matter their quantity or quality, differentpeople may interpret the information differently.Because data and interpretation are so manifestlycontroversial issues, here and in the followingchapters, within reasonable space limits, I makeit a point to present the actual evidence (infigures, tables, and the like) supporting the asser-tions made.

Inputs of other pollutants

In addition to nutrients, the rivers entering the Black Sea carry many other contaminants,including metals, petroleum hydrocarbons, andsynthetic organochlorines. In terms of metals,during the 1980s, the Danube alone discharged4,500 tons of lead, 1,000 tons of chromium, 900tons of copper, and up to 60 tons of mercury(Mee 1992). Significant concentrations of mercurywere found within mussels (Ryabushko et al.2002). Anthropogenic contributions have in somecases tripled the concentrations of heavy metalsfound in shallow coastal Black Sea sediments(Secrieru & Secrieru 2002). Top predators such asmarine mammals, however, do not carry highmetal loads in their tissues: mercury in porpoisesfrom the Black Sea was one order of magnitudelower than in the North Sea, for example ( Joiriset al. 2001).

Rivers also transport petroleum hydrocar-bons into the Black Sea. About 50,000 tons ofpetroleum compounds were discharged annu-ally during the 1980s by the Danube into theBlack Sea (Mee 1992), but only about 2,600 tonsduring the 1990s (Bakan & Büyükgüngör 2000).Small-scale discharges across many differentsites, derived from discharges of municipal,domestic, and industrial sources, were morethan an order of magnitude larger than amountsreleased from accidents and ballast water dis-charge from tankers, but high concentrations of oil have been recorded along shipping lanes(Mee 1992).

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GLOBAL CONTEXT OF COASTAL CHANGE 13

Black Sea as we turn towards the 21st century isan unfortunate harbinger of the complex suite of alterations that can be expected in coastalenvironments as people make more intensiveuse of land on watersheds, and on the wateritself. The accelerating and bewilderingly diversechanges that seem the fate of environmentsalong the coasts of the world, do, however, havesome common root causes.

Underlying causes of global coastal change

The central facts about change in the coastalzones of the world are that: i) there are increas-ingly more people in the world and their activitieshave historically been focused at the land/seaboundary, for biological, cultural, economic, andgeographic reasons; and ii) these people consumeresources. These two central features, as we willsee throughout the chapters of this book, bringabout changes in coastal environments. Thechanges generated by humans, moreover, have,during the 20th century, become large enough toexceed the changes pressed upon coastal environ-ments by “natural” or non-anthropogenic forces.

Increases in human populations

Global population numbers and growth

The best estimates of total numbers of humansavailable suggest that the human population onearth has increased, particularly during the 20thcentury (Fig. 1.10). We can take a closer look atestimates of recent human population growth by examining the probable course of eventsbetween 1950 and 2050 (Fig. 1.11 top). Humanpopulations across the last half of the 20th cen-tury increased dramatically, although there is aglimmer of future relief from the pace of growth.Predicted rates, based on censuses and well-established population models, predict a lowerrate of people added per year (Fig. 1.11 middle),and a decrease in annual growth as we move intothe 21st century (Fig. 1.11 bottom). In fact, thereis an 80% chance that by the year 2100—two tothree generations from now—the size of the

play important ecological functions at the inter-face between the land and sea. In the Black Sea,coastal wetlands have been subject to alterationand destruction by wastewater discharge andtoxic pollutants, “reclamation” of wetlands foragriculture, filling for construction, and thedumping of dredge spoils and solid waste (Bakan& Büyükgüngör 2000). The losses of these valu-able habitats have not been measured, nor theconsequent effects assessed, but they are surelynot minor.

Signs of some recovery

Within recent years, there are some signs ofrecovery in the coastal Black Sea. The nitrogenand phosphorus loads to the Black Sea havedecreased by 25 and 50%, respectively (Lancelotet al. 2002a, 2002b). Nutrient concentrations inthe Danube outflow decreased, perhaps by halfor so, between the 1980s and 1990s (Lancelot etal. 2002a, 2002b). The biomass of Mnemiopsis sp.during 1995 was an order of magnitude lowerthan during 1990 (Weisse et al. 2002). It would bereassuring to report that the lowering of nutrientloads might be the result of improved manage-ment practices, but it seems more likely that theeconomic decline suffered by central Europeancountries within the Black Sea watershed mightbe a more reasonable explanation (Garnier et al.2002). This speculation again demonstrates thepowerful ties between environmental changesand human activities, and the influence of factorscompletely external to ecology on environmentalconditions.

In the Black Sea we have a remarkable case history where eutrophication has become a prim-ary environmental challenge, exacerbated byoverfishing, loss of habitats, reduction of freshwater and sediment supplies, introduction ofalien species, and a host of other agents of envir-onmental change (Bakan & Büyükgüngör 2000).Perhaps the examples to be reviewed in thechapters that follow lack the remarkable com-pounded variety and intensity of perturbationsvisited upon the Black Sea shores, but we will seethat similar changes are occurring in manylocales, and at global scales. The situation in the

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14 CHAPTER 1

estimates by Lutz et al. (2001) are that there is a 95% probability that the human populationvalue will lie between 6.6 and 11.4 billion people.In addition, there are some discrepancies amongdifferent methods of arriving at the estimates:Bongaarts and Bulatao (2000), for example, givethat same range as 7.9–10.9 billion. Even just considering the Lutz et al. (2001) values, there isan uncertainty of about 27% in the best estimates.Regardless of the uncertainty, however, we can expect substantial increases in the number ofhuman inhabitants of the earth before popula-tion growth tapers off.

We need to note, however, two salient facts.First, we will still have to deal with in the course of our next two generations—regardlessof the uncertainty of the estimates—substantialincreases in human numbers. By the end of thepresent century there will be about 11 billionpeople on earth, a substantial increase from thecurrent population of about 6 billion (Fig. 1.10).Second, during the 21st century the number ofpeople living in urban environments will increasefaster than the rural population (Fig. 1.11 top). In 1800 about 2% of humans lived in cities; thispercentage increased to 12% by 1900, and to 47%

human population will have stopped growing orcould decrease (Lutz et al. 2001).12

Global population numbers are shown as awell-defined curve in Fig. 1.11, but there is a substantial uncertainty in the estimates (Keilman2001). The curve represents best estimates, and there is a range of probable values lower and higher at each year. For the year 2050, forinstance, when the world’s population is onaverage expected to reach about 9 billion people,

12 The causes of the decreases are beyond the scope of this book.Suffice it to say that powerful economic and social mechanismshave altered human population dynamics. Economic stringencies,increased availability of birth control measures, emergence of theissue of women’s rights, delayed first reproduction, demand formore education, improved infant mortality, social security, andhealth plans, are among the underlying factors. In certain regions,diseases such HIV/AIDS will certainly have some effect, althoughit is the case that except for the Black Plague in the Middle Ages(Fig. 1.10), diseases (and wars) have not prevented human popula-tion growth. The decreased growth rates will bring other difficultissues to the fore, including the impending social and economic crisis inherent in the increasing preponderance of older age groupsin many countries (Cohen 2003). We might note, in passing, that theposited mechanisms for decreased human population growth arenot ecological: we have successfully forced ourselves outside theambit of the ecological forces that govern population numbers in allother species.

12

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5,0007,000

Num

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eopl

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illio

ns)

OldStoneAge New Stone Age

BronzeAge

IronAge

ModernAge

MiddleAges

2100

Years BC Years AD

2000

1975

1950

19001800Plague

3,000 1,000 1 1,000 3,000 5,000

Figure 1.10 Estimated populationacross human history. Adapted fromPopulation Reference Bureau andUnited Nations, http://www.prb.org, http://www.un.org/popin/wdtrends.html.

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Figure 1.12 Top: frequency distributions of gainsand losses of area covered by agricultural, forest, orurbanized land covers, 1982–1992 in 16 watersheds of the eastern USA. USDA data, from Van Breemen etal. (2002, fig. 5). Bottom: number of watersheds withdifferent percentages of urbanized land cover within51 eastern US watersheds. Each bar is broken up intothose watersheds where the human populationwithin the urbanized areas were increasing,decreasing, or showed no change across the previousdecade. Data from Dow and DeWalle (2000).

GLOBAL CONTEXT OF COASTAL CHANGE 15

sheds with the greater proportion of urban landcovers (Fig. 1.12 bottom). At present rates of urban-ization in Europe, urban areas will double in lessthan a century (El Pais, Nov. 3, 2005). Urban sprawlis therefore becoming pervasive worldwide, andits spread is accelerating.

The remarkable image shown in Fig. 1.13 conveys the startling degree to which the earth isalready urbanized. The development of large met-ropolises and innumerable smaller urban areasthroughout the sample area (Europe) is evident.

by 2000 (Cohen 2003). The years 2005–2010 are amomentous transition in human history; by thishalf decade, half of us will be living in urban set-tings. The increased urbanization of the earth’ssurface manifests itself directly by the changingland uses on watersheds (Fig. 1.12). The percentageof urban land covers on watersheds of the east-ern USA has increased in recent decades, at theexpense of forest and agricultural land covers(Fig. 1.12 top). In addition, the largest increasesin urbanization are taking place in those water-

10

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01950 1970 1990 2010 2030 2050

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)an

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ater

shed

s

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0−5 −4 −3 −2 −1 0

Area in watershed with changing land use (%)1 2 3 4 5 6

100

Figure 1.11 Top: estimated and projected totalworld population, and breakdown into rural andurban populations, 1950–2050 (data from FAO,http://www.fao.org). Middle: number of peopleadded annually; and bottom: annual percentageincrease, 1980–2020 (data from Population ReferenceBureau and United Nations, http://www.prb.org,http://www.un.org/popin/wdtrends.html).

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16 CHAPTER 1

Local population density and growth

The facts about global population growth areevident. Population density, however, varies atlocal spatial scales, particularly near coasts. Inaddition to the proliferation of urban centers andaccompanying sprawl, Fig. 1.13 highlights a sec-ond spatial feature: people accumulate near thecoast.

People have preferred to settle along coast-lines through human history. Whether it wasbecause waterways were the major means oftransport, or because resources were more read-ily available along shores, humans seemed to settle along coasts, and still do so today. As of1990, about 23% of the human population livewithin the narrow strip within 100 km fromcoasts (Nicholls & Small 2002). The density ofpeople in near-coast zones is 112 people km−2;this is 2.5 times the mean global population density of 44 people km−2 (Nicholls & Small2002). We can see this pattern in the shorelinesthat are so clearly outlined by the night lightingin the image of Fig. 1.13. Near-shore settlement(and activities) is evident throughout the world(Fig. 1.14): there are a surprisingly large numberof us that live within 5 km of the shoreline.

The pattern of emphasized human use of near-coast areas occurs not only at a global spatialscale, but at smaller scales as well. The urbaniza-tion of landscapes and the tendency for fasterdevelopment nearer to coasts are evident at a

The environmental consequences of the spreadof urban sprawl cannot be overemphasized, aswill become evident in the chapters that follow.The concentration of people in urban centers neces-sarily leads to greater demands in the consump-tion of energy, water, food, and other resources,as well as complicating the disposal of liquid and solid wastes, and concentrating contamina-tion of air, water, and soils. This uncoupling ofday-to-day human experience from the source oftheir sustenance may make it more difficult todevelop social and political support for measuresto maintain sustainable environmental uses.

Figure 1.13 Mosaic of enhanced night images of theEuropean region. From http://www.gsfc.nasa.gov/topstory/2003/0815citylights.html.

500

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( )

Pop

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indi

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km−2

) (–

)

Distance from coast (km)

0 20 40 60 80 100

Figure 1.14 Worldwide estimates of the number of people (left verticalaxis) and people per unit area (rightvertical axis) living in 5 km bandsaway from the coast. From Nichollsand Small (2002).

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GLOBAL CONTEXT OF COASTAL CHANGE 17

people km−2. About 40% of coastal people live insmall towns or settlements at densities of morethan 1,000 people km−2. The remaining half of the coastal population lives in rural or isolated areas. The quite uneven along-shore distributionmeans that there are going to be quite disparateeffects on the coastal environments receivinginputs in different parts of the world’s coasts.Such marked spatial heterogeneities of humanpressures on coastal environments are going to appear more than once in the chapters that follow.

Use of resources

Human beings of course consume resources, andmore people means more pressure on the envir-onments that produce the required resources.For the sake of brevity, here we will deal withonly one aspect of one important human activity,agricultural production of food. This may seeman odd choice in a book about coastal envir-onments. There are at least two reasons for discussing food production here. First, peoplegrow food on land, and what happens to coastalenvironments is in large measure—but of coursenot completely—caused by what people happento do on land, a point to be made repeatedlythroughout the chapters below. Second, as in theallegorical Venetian engraving, land and sea arecoupled: increasing food yields on land oftenleads to increased transport of materials to re-ceiving coastal environments. Such exports, aswe will see in subsequent chapters, force substan-tial coastal environmental alterations.

As human populations increased through the 19th and 20th centuries (see Fig. 1.10), foodproduction had to increase just to feed people, letalone to allow an improved standard of livingand nutrition. The first approach was to find moreand more arable land to bring under cultivation,a strategy that was effective up to about 1940.After the mid 20th century, the rate of populationincrease was faster than the feasible expansion ofarea of cultivable land, and the ratio of croplandto people slowly decreased (Fig. 1.16).

The pressure to increase yield on a per parcelbasis forced the development of improved

global scale (Fig. 1.14), as well as at smaller localspatial scales (Fig. 1.15). People built dwellingsclose to the coast of Waquoit Bay, a small waterbody on the coast of Cape Cod, Massachusetts,and, as the decades passed, those who found thenearer-shore plots occupied filled in as close towater as was then possible (Fig. 1.15).

The pattern of impressive near-shore develop-ment we have been documenting is widespread.Culliton et al. (1990) compiled information onthe rate of population increases in each countythroughout the United States, and found thefastest rates of human population growth incoastal counties. This was true for every stretchof coast throughout the United States, and, wemight suspect, for other areas of the world. Wemay conclude that rates of increase in humanpopulations are greater near shores, and thatthese will increase in parallel but faster thanworld totals.

The human populations accumulated againstthe shorelines of the world are not, however, uni-formly distributed. There are pronounced localdifferences in human density along the coastalstrips of the world (Nicholls & Small 2002).About 10% of coastal people live concentrated in urban areas at densities greater than 10,000

600

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Distance from shore (m)

Num

ber

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ouse

s 1984197419551938

Figure 1.15 Number of houses located in 100 mbands away from shore along the coast of WaquoitBay, Cape Cod, Massachusetts, 1938–1984. Thenumber of houses built by each of four dates are also indicated. From Valiela et al. (1992).

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18 CHAPTER 1

decrease in use of fertilizers might suggest that,since the world population has continued toincrease, as the centuries turn, we might enter aperiod where per capita nutrition for the world’shuman population diminishes, and pressureswill build to increase yields again.15

The worldwide use of nitrogen fertilizer hasno doubt been a life-saver for many people inmany places, as well as improving the quality ofnutrition worldwide. It turned out, however,that a substantial portion of the nitrogen used as fertilizer eventually reaches the sea, and theexported nitrogen has manifold effects on aqua-tic systems (cf. Chapter 12). The Haber–Boschprocess yields ammonium, which is reduced to nitrate, either in the production of fertilizer or by bacteria in the environment. This nitrate is a highly mobile form of nitrogen and travelsreadily in moving water. About 11% of the nit-rogen fertilizer used for crops travels down-stream in rivers (Seitzinger & Kroeze 1998) andmost of that reaches estuarine and near-shore

agricultural practices. Chief among the newmethods was the fertilization of crops, usingmanures as a nitrogen supply and phosphatesmined from far-off guano islands (Anderson1993), or later on in the century, industrially produced nitrate.13 The application of nitrateincreased markedly through the last half of the20th century (Fig. 1.16). The collapse of the USSRand its huge agricultural sector created the evident dip during the early 1990s, and the slow-ing of the world economy in general diminishedfertilizer use toward the end of the 20th century.With the aid of fertilizers, the production of grainsand meat—the core agricultural staples—have,in recent decades, more than kept pace with thedemands of a growing population.14 The recent

13 Fritz Haber, a German chemist, applied a suggestion by CarlBosch to develop the first successful commercial reaction that led tomass production of nitrogen fertilizers and military explosives.Hydrogen and nitrogen, when appropriately heated and com-pressed, produce ammonium (NH4), a compound that can then beused for many purposes. During World War I, Haber directedGerman chemical warfare activities. Haber won the Nobel Prize in1918 for his discovery. After the Nazi rise to power, Haber defectedto the UK. The Haber–Bosch process is one of those crucible inven-tions that have changed the world as we know it, for good or bad.14 There are unfortunate regions of the world where famine is still common. These regrettable conditions are more the result of political and social issues affecting distribution than a matter ofmagnitude of food supply. These aspects once again illustrate thatwhat might be said at a global scale may not apply at local scales.

15 It seems inevitable that crops that are more effective at uptakeand retention of nitrogen will be created using genetic engineeringmethods. There are sectors of society that are suspicious of thesenew developments, but given what we will find out in Chapter 12about the consequences of increased application of fertilizers(across poorer and poorer soils), it may be concluded that develop-ing genetically engineered crops is an attractive option that mightbe a necessary recourse to meet increased demand for food.

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Figure 1.16 Time course of percapita cropland area, production of grain and meat (data simplifiedfrom Galloway 1998), and worldnitrogen fertilizer production (from http://www.fao.org).

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GLOBAL CONTEXT OF COASTAL CHANGE 19

Human activities can interact with or accel-erate rates of natural changes. In the vari-ous chapters we will investigate just how far anthropogenic actions have enhanced changesdriven by “natural” agents. We will concentrateon evidence about ecological or biogeochemicalchanges, largely caused by human activities ofone sort or another. As will become evident, inthe current global condition, we cannot divorcehumans from ecology. We will consider not justecological alterations, but how these environ-mental changes interact with people’s use ofcoastal environments.

A first group of two chapters deals with ecological changes driven by changing globalatmospheric and climate alterations. These chap-ters include features of, and effects on, climaticwarming, increased ultraviolet radiation, andthe accelerated rise in sea level. A second groupof two chapters addresses coastal change createdby human use of water on land, with chapters onthe consequences of the interception of freshwater before it arrives at the shore (Chapter 4)and of the interception and increased erosion of terrestrial sediments (Chapter 5). Chapter 6 covers human destruction of the various habitatsthat occupy the near-shore zones. These includethe losses of salt marshes, mangroves, and coralreefs, as well as other less threatened habitats.Three chapters deal with toxic substances—petroleum hydrocarbons (Chapter 7), chlorinatedcompounds (Chapter 8), and metals (Chapter9)—that humans add to coastal environments.Three chapters deal with changes that humansforce on coastal food webs, including nutrientadditions (Chapter 12 on eutrophication), whichalter ecosystems by effects that permeate up foodwebs and create pervasive effects, and human-driven alterations in the species composition ofcoastal environments (Chapter 10 on biologicalinvasions, and Chapter 11 on overharvest ofcoastal stocks). Chapter 13 contains informationon a miscellany of other agents of environmentalchange (litter, thermal, sound, and radioactivepollution, and human pathogens). The finalchapter addresses ways in which the agents ofchange and their effects interact, and how wemight compare the various agents of change in

environments. Once in the coastal environments,the land-derived nitrate enters and stimulatesmany reactions and transformations, and promptswholesale alterations that will be considered inChapter 12. Suffice it to say that human demandsfor food have increased transport of a highlyreactive compound that thoroughly alters thereceiving coastal environments. As it turns out,much of the nitrogen discharged to coastal envir-onments (Nixon et al. 1996; Seitzinger & Giblin1996) is converted to N2 gas (a relatively unavail-able form of nitrogen) by bacteria in coastal envir-onments or is buried in coastal sediments. Coastalecosystems thus to a degree intercept land-derived nitrogen, but in the process the coastalenvironments are thoroughly altered.

Much like population growth in the coastalzones of the world, the use and impact of fertil-izer nitrogen has a highly heterogeneous distri-bution. Fossil fuel combustion is widespread inmany countries, and adds oxidized nitrogen com-pounds to the atmosphere. Depending on winddirection, atmospherically transported nitrogencompounds can be deposited in different coastalenvironments. In addition, humans produce pro-digious amounts of waste water that contain nitro-gen, and its inevitable local disposal adds to the spatial heterogeneity of nitrogen impacts oncoastal waters. This example makes evident howhuman demand for resources forces changes oncoastal systems. It also makes the point that thecoastal systems themselves are not independentof what takes place on land.

Contents of this book

If there is one reality about coastal environments,it is that they have always changed. There isplentiful evidence that there have been enorm-ous changes along the coastlines of the world in geological and shorter time scales. The notionthat there is something that could be called the“balance of nature” will certainly be far less com-pelling after we parse the available evidence. Inthis book we examine those changes that areaffecting and altering the world’s coastal envir-onments within time scales of days to centuries.

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20 CHAPTER 1

Garnier, J., and 5 others. 2002. Modelling transfer and reten-tion of nutrients in drainage network of the DanubeRiver. Estuar. Coast. Shelf Sci. 54:285–308.

Gordina, A. D., and 5 others. 2001. Long-term changes inSevastopol Bay (the Black Sea) with particular referenceto the ichthyoplankton and zooplankton. Estuar. Coast.Shelf Sci. 52:1–13.

Gücü, A. C. 2002. Can overfishing be responsible for thesuccessful establishment of Mnemiopsis leidyi in the BlackSea? Estuar. Coast. Shelf Sci. 54:439–451.

Gulin, S. B., and 5 others. 2002. Radioactive contaminationof the north-western Black Sea sediments. Estuar. Coast.Shelf Sci. 54:541–549.

Humborg, C., V. Ittekkot, A. Cociasu, and B. V. Bodungen.1997. Effect of Danube River dam on Black Sea biogeo-chemistry and ecosystem structure. Nature 386:385–388.

Ivanov, M. V., N. V. Pimenov, I. I. Rusanov, and A. Lein.2002. Microbial processes of the methane cycle at thenorth-western shelf of the Black Sea. Estuar. Coast. ShelfSci. 54:589–599.

Joiris, C. R., and 7 others. 2001. Total and organic mercury in the Black Sea porpoise Phocoena phocoena relicta. Mar.Pollut. Bull. 42:905–911.

Kaminski, M. A., and 5 others. 2002. Late glacial to Holocenebenthic foraminifera in the Marmara Sea: Implications forthe Black Sea-Mediterranean connections following thelast deglaciation. Mar. Geol. 190:165–202.

Kedeys, A. E., A. Roohi, S. Bagheri, G. Finenko, and L. Kamburska. 2005. Impact of invasive ctenophores onthe fisheries of the Black Sea. Oceanography 18:76–85.

Keilman, N. 2001. Uncertain population forecasts. Nature412:490–491.

Kroiss, H., M. Zessner, and C. Lampert. 2003. Nutrient management in the Danube basin and its impact on theBlack Sea. J. Coast. Res. 19:898–906.

Kuypers, M. M. M., and 8 others. 2003. Anaerobic ammonium oxidation by annamox bacteria in the BlackSea. Nature 422:608–611.

Lancelot, C., J.-M. Martin, N. Panin, and Y. Zaitzev. 2002a.The North-western Black Sea: A pilot site to understandthe complex interaction between human activities andthe coastal environment. Estuar. Coast. Shelf Sci. 54:279–283.

Lancelot, C., J. Staneva, D. Van Eeckhout, J.-M. Beckers, andE. Stanev. 2002b. Modelling the Danube-influencedNorth-western continental shelf of the Black Sea. II: Eco-system response to changes in nutrient delivery by theDanube River after its damming in 1972. Estuar. Coast.Shelf Sci. 54:473–499.

Lasserre, P., and A. Marzollo. 2000. The Venice LagoonEcosystem Project: Genesis, goals, and overview. Pp. 1–22 in Lasserre, P., and A. Marzollo (eds). TheVenice Lagoon Ecosystem: Inputs and InterconnectionsBetween Land and Sea. UNESCO and ParthenonPublishing Group, Paris.

terms of the intensity of the changes, the exten-siveness of the effects, the possibility of recoveryfrom the perturbations, and how to assess therelative priorities we might place on addressingthe issues raised by the chapters in this book.This last chapter also evaluates how we might setpriorities for management or restoration of theimpending or already present changes.

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Chapter 2Atmospheric-driven changes

Appearance of coral reefs off Easter Island, before (March 1999) and after (March 2000) a major bleaching event.From Wellington et al. (2001), courtesy of the authors.

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