DROWNING THENATIONAL HERITAGE:CLIMATE CHANGE ANDU.S. COASTAL BIODIVERSITY

Walter V.ReidMark C. Trexler

"j I 1 1 1 i | I

DROWNING THE NATIONAL HERITAGE:Climate Change andU.S. Coastal Biodiversity

Walter V. ReidMark C. Trexler

W O R L D R E S O U R C E S I N S T I T U T E

June 1991

Kathleen CourrierPublications Director

Brooks ClappMarketing Manager

Hyacinth BillingsProduction Manager

WRI/Walt Reid; WWF/D. BarbeyCover Photos

Each World Resources Institute Report represents a timely, scientific treatment of a subject of public concern. WRI takesresponsibility for choosing the study topics and guaranteeing its authors and researchers freedom of inquiry. It also solicits andresponds to the guidance of advisory panels and expert reviewers. Unless otherwise stated, however, all the interpretation andfindings set forth in WRI publications are those of the authors.

Copyright © 1991 World Resources Institute. All rights reserved.ISBN 0-915825-62-7Library of Congress Catalog Card No. 91-065938Printed on recycled paper

CONTENTS

ACKNOWLEDGMENTS v

FOREWORD vii

I. INTRODUCTION AND OVERVIEW 1

II. COASTAL ECOSYSTEMS: THE FRAGILE LAND/SEA MARGIN 3

Coastal Species 3Coastal Habitats 7Ecological Processes 11Economic Indicators of Coastal Biodiversity's Status 14

III. GLOBAL WARMING: AN ADDITIONAL STRESS ON COASTAL BIODIVERSITY 21

Impacts on Coastal Habitats 22Impacts on Coastal Species Diversity 28Other Impacts of Climate Change 31

IV. PUBLIC POLICY AND THE CONSERVATION OF COASTAL BIODIVERSITY 33

Public Policy Options in the Face of Uncertainty 34The Status of U.S. Policy 37Conclusions and Recommendations 38

NOTES 41

REFERENCES 45

i l l

ACKNOWLEDGMENTS

Two background papers were commissionedfor this study: Mechanisms of Wetland Loss: Im-pacts of Sea Level Rise, by Dr. Klaus J. Meyer-Arendt, and Climate Change and BiologicalResources in the Coastal Zone, by Dr. Thomas J.Smith HI. Both of these authors made significantcontributions to this report. We also thank TheNature Conservancy, the Florida Natural Areas In-ventory, the Maryland Natural Heritage Program,the Massachusetts Natural Heritage Program, andthe Oregon Natural Heritage Program for data onspecies at risk in the coastal zone, and we are par-ticularly grateful to Dr. G. David Maddox, Dr.Larry E. Morse, and Dr. Larry L. Master of The Na-ture Conservancy for their help in obtaining thesedata. Our debt also extends to Rachel Donham,

Larry Harris, and Carleton Ray for their early con-tributions to the design of this project, and to SueTerry, who tirelessly located the obscure publica-tions we requested. We thank Tundi Agardy, CurtisBohlen, Patrick Dugan, Mohamed El-Ashry, RobertFischman, David Maddox, Klaus Meyer-Arendt,Jeffrey McNeely, Kenton Miller, Larry Morse, andJames Titus for their comments and constructivecontributions to earlier drafts of the manuscript.Finally, our thanks to Kathleen Courrier for skill-fully editing the report and to Hyacinth Billings,Robbie Nichols, and Allyn Massey for their helppreparing the text and figures.

W.V.R.M.C.T.

FOREWORD

Say the words "extinction crisis," and whatmost likely comes to mind first is a tropical forestin flames—an apt image when deforestation is themain force behind a species extinction rate un-matched in 65 million years. But Americans con-cerned about saving tropical forests' vast biologicalwealth must not lose sight of losses much closer tohome, including the degradation of U.S. seashores,coral reefs, barrier islands, estuaries, and coastalwetlands.

These coastal habitats are home to teemingcommunities of plant and animal species, includingour own. Some of this diversity is far from secure:for instance, 80 species that are at risk of extinc-tion can live only on the strip of coastline that lieswithin 10 feet of sea level. Beach-front develop-ment is already fragmenting coastal habitats, andrising population, temperature, and sea levelscould compound these losses. The number ofAmericans living in coastal areas will probablyreach 127 million by 2010, a 60-percent increaseover a half-century of migration. Global warmingcould raise sea levels from two to five feet overthe next century, in many cases outpacing particu-lar ecosystems' landward march. What survivalodds do species already in trouble have if theirhabitat keeps shrinking, squeezed on one side by agrowing human presence and on the other by arising sea?

What's left of our natural heritage can't besaved unless we awaken to the choices and trade-offs required. The loss of biodiversity may be anew concept to most U.S. policymakers, but to-gether with global warming it tops the U.S. En-vironmental Protection Agency's list of high-riskthreats. Yet, as EPA points out, more visible en-vironmental problems—oil spills, toxic wastedumps, and the like—get the most attention fromcitizens and policymakers alike.

That must change, argue Walter V. Reid andMark C. Trexler in Drowning the National Heri-tage: Climate Change and U.S. Coastal Biodiversi-ty. If today's global warming forecasts are borneout over the next century, coastal zones face cer-tain losses even under the most enlightened poli-cies imaginable. Only instituting the right mix ofpolicies now can prevent widespread biological im-poverishment in the future, they contend.

Neither fleeing in droves from every coastlinenor protecting all land from inundation is political-ly and economically feasible as a long-term solu-tion, Drs. Reid and Trexler find. Instead, theycounsel a middle way that would allow for coastaldevelopment over the next few decades and forconserving wetlands and other coastal systems in ahotter future.

The authors point out that curbing the rateand magnitude of global warming would do moreto conserve coastal biodiversity than any after-the-fact measure could. But they also identify policyshifts that would help coastal ecosystems and spe-cies survive the warming that is already in store:

• Incorporating the protection of coastalecosystems as a fundamental goal in federaland state policies.

• Eliminating federal and state subsidies thatpromote coastal development and coastaldefense.

• Making wider use of such regulatory meas-ures as coastal zoning and setbacks.

• Putting property owners on notice that sealevel will rise and that large areas of what isnow dry land will eventually have to beabandoned.

• Minimizing human stresses other than sealevel rise on coastal ecosystems.

• Identifying appropriate policies for keycoastal ecosystems.

The authors also suggest that nongovernmental or-ganizations that buy land for conservation pur-poses should begin experimenting with easementand leasing options that would allow them to pro-tect wetlands and other coastal ecosystems as thesea rises.

Many of these issues have been raised in dis-cussions of land-use planning, global warmingadaptation measures, and ways to stem species ex-tinction. But Drowning the National Heritagerepresents the first attempt to weave the strands ofdata and analyses from these diverse disciplinesinto a coherent whole. This synthesis extends theanalyses and policy recommendations of suchprevious WRI studies as Keeping Options Alive:The Scientific Basis for the Conservation of Bio-diversity, Conserving the World's BiologicalDiversity, Minding the Carbon Store: Weighing

vn

U.S. Forestry Strategies to Slow Global Warming, Charitable Trust; the Netherlands Ministry for De-and A Matter of Degrees: The Potential for Limit- velopment Cooperation; the Swedish Internationaling the Greenhouse Effect. Development Authority; and the U.S. Agency for

WRI would like to thank the Mary Flagler Cary International Development. To all these institu-Charitable Trust for its generous support of this re- tions, we express our deep appreciation,search. For support of WRI's overall effort to pre-serve biological diversity, our gratitude also ex- James Gustave Spethtends to the W. Alton Jones Foundation, Inc.; the PresidentSurdna Foundation, Inc.; the H. John Heinz III World Resources Institute

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I. INTRODUCTION AND OVERVIEW

The world's ecosystems may undergo moreprofound changes over the next century than dur-ing any comparable span of human history. Globalwarming of the magnitude expected in comingdecades, accompanied by changes in sea level,rainfall, and wind and ocean currents, will signifi-cantly affect species composition, communitystructure, and the function of ecosystems. Ecosys-tems continually evolve in response to natural cli-matic changes, but the rate of climate change inthe century ahead, coupled with the existing pat-tern of human settlement and stresses on speciesand ecosystems, could overwhelm ecosystems'capacity to adapt, thus impoverishing the world'sbiological wealth. Biodiversity—the world's genes,species and ecosystems—could be an invaluable re-source in humanity's efforts to adapt to climatechange, but it may also become one of the firstvictims of that change.

To many, conserving biodiversity means pro-tecting tropical rainforests and their unmatchedspecies diversity. But biodiversity conservationought to be of concern in species-poor ecosystemstoo. In fact, the best way to think of it is usingbiological resources in ways that deliver to futuregenerations an environment rich in genes, species,habitats, ecosystems, and the knowledge needed touse them wisely. Put bluntly, no ecosystem can beused sustainably unless its basic components aremaintained. By that measure, biodiversity conser-vation is a bottom-line necessity not only in tropi-cal forests, but also in ecosystems much closer tohome.

The status of biodiversity in coastal ecosystemsstands out as a case in point. Coastal wetlands (saltmarshes and brackish marshes), coral reefs, man-groves, barrier islands, and estuaries are facing anonslaught of development related pressures.1 Al-though these ecosystems do not garner the publicattention given rainforests, they deserve compara-ble protection. The species richness of coral reefsis unparalleled in marine environments, and theprimary productivity of coastal wetlands and coralreefs ranks among the highest on earth. Adding tothis case, growing and shifting human populations,and even more rapidly growing demands onresources, have placed these ecosystems underenormous stress. Barrier islands have become

favorite sites for resorts and summer homes, coast-al wetlands have been filled to make room for in-dustry, estuaries bear the brunt of pollutionreleased along miles of rivers and coastline, andsedimentation and pollution are killing coral reefsnear cities and river mouths.

kk

Biodiversity—the world'sgenes, species and ecosys-tems—could be an invalu-able resource in humani-ty's efforts to adapt toclimate change, but it mayalso become one of the firstvictims of that change.

In the United States, the struggle to conservethe biodiversity of coastal ecosystems has centeredon wetland conservation. Prior to the 1970s, fewfederal or state programs actively encouraged theconservation of either coastal or interior wetlands.At the same time, numerous governmental incen-tives indirectly promoted the conversion of wet-lands to agriculture or other uses. Within the con-tiguous United States, 53 percent of coastal andinterior wetlands were lost between the 1780s andthe 1980s; some 10 percent were lost between1954 and 1974 alone (Dahl 1990).

Public outcry over the loss and degradation ofthe nation's wetlands, and the growing scientificunderstanding of their economic and biological im-portance, stimulated significant federal and statepolicy changes. As early as the 1970s, the CleanWater Act, the Coastal Zone Management Act, andstate coastal zone legislation began to slow the lossof coastal wetlands. By the mid-1980s, annual ratesof coastal wetlands conversion had dropped byhalf (OTA 1984), and by 1984 the Office of Tech-nology Assessment declared that "coastal wetlandsare reasonably well protected."2 Interior wetlandsstill faced significant threats, but by the late 1980sthe impressive achievements seemed to place a

goal of "no-net-loss of wetlands" within reach. In1988, the National Wetlands Policy Forum, madeup of representatives of industry, conservationgroups, farmers, ranchers, and government officials(including three state governors) recommended agoal of no-net-loss of wetlands.

kk

Coastal wetlands can with-stand modest rates ofchange in sea level unlesstheir landward movementis hindered by physicalobstructions, but foreseenrates would almost cer-tainly outpace the abilityof many coastal ecosys-tems to move or adapt.

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Has this goal become a verifiable reality? Un-fortunately, various indicators of the status ofcoastal biodiversity demonstrate that this progressin wetland protection is insufficient to meet thelong-term objectives for maintaining coastal eco-systems. Today's coastal natural resource policiesdon't ensure the maintenance of the foundationsand continued productivity of coastal ecosystemseven under current levels of stress. Add the likelyadditional stress of climate change and there iscause for considerable concern. The three- to six-fold increase in rates of sea level rise predicted bycurrent climate-change models will have profound

effects on the nation's coastal environment. Evenby conservative estimates, sea level could be 66 cmhigher by 2100, but a rise of nearly 2 meters overthat time period may be equally plausible (Warrickand Oerlemans 1990, Titus 1991). Coastal wetlandscan withstand modest rates of change in sea levelunless their landward movement is hindered byphysical obstructions, but foreseen rates would al-most certainly outpace the ability of many coastalecosystems to move or adapt.

Inundation is only one effect of climatechange. As sea levels rise, coastal erosion and theseverity of coastal flooding will increase, andcoastlines will recede unless stabilized by dikes orthrough sand nourishment. Salt-water intrusioninto groundwater, rivers, bays, and estuaries willincrease. Changes in rainfall patterns and tempera-ture will modify salinity gradients in estuaries andalter rates of river delta sedimentation, and coastalcurrents and upwelling patterns are likely to shiftgeographically and change in intensity. All of these"sea changes" will affect biodiversity in the na-tion's coastal zones.

Given these threats, what is the current statusof coastal biodiversity (species, habitats, and eco-systems)? And what potential impacts can be ex-pected from climate change? As the following re-view shows, the coastal ecosystems being affectedby climate change are not healthy and resilient. In-deed, they are already under considerable stress.

The policies needed to respond to climatechange so as to preserve coastal biodiversity differfrom those normally considered to counter sealevel rise. As spelled out below, addressing theneeds of biodiversity conservation in coastal eco-systems demands rapid and anticipatory measures,all of them justified by the value of the coastalresources under threat.

II. COASTAL ECOSYSTEMS: THE FRAGILE LAND/SEA MARGIN

It is hard to characterize the structure andfunctioning of any ecosystem, but it is particularlydifficult with the highly complex coastal marshes,coral reefs, mangroves, and estuaries located whereland meets sea. It is still more difficult to probe be-neath static descriptions of an ecosystem and as-sess its long-term "health." Habitats may persistbut lose species, species may persist but lose thegenetic diversity that enables them to adapt to fu-ture environmental change, and ecosystems may bevisually unchanged but cease to perform valuablefunctions upon which we or other species havecome to depend. The aim of biodiversity conserva-tion is to ensure that these underlying componentsof the world's living resources are maintained. Asstraightforward as this goal may appear, it is an-other matter altogether to try to measure biodiver-sity or to translate biodiversity conservation intospecific activities.

Although "biodiversity" is often equated with"number of species," there is no single measure ofbiodiversity. Rather, scientists rely on a set of indi-cators bearing upon the composition, structure,and function of habitats and ecosystems. This isnot to downplay the importance of biodiversity asan issue. Many other concepts that provide theimpetus for public policy development are equallyabstract. For instance, the concept of "economicand social development" provides the frameworkwithin which most public policy is evaluated andpromoted, but like biodiversity conservation it can-not be directly measured. We measure "develop-ment" through the use of such indicators as theGross National Product (GNP), unemployment rate,and per capita income—all concrete componentsof the broad development agenda. Just as econo-mists do not try to characterize the health of theeconomy with one indicator, so too biologists can-not evaluate biodiversity's status without examin-ing a variety of indicators.

Biodiversity conservation should be an impor-tant objective of all land- and resource-use policies.Development that leads to continuing degradationof ecosystems and the loss of species and habitatscannot be sustained over the long term. By exam-ining a variety of indicators of the long-term statusof ecosystems, planners can anticipate problems,rather than simply react to situations that are

almost beyond help. By forcing the examination ofissues well upstream of a crisis, the anticipatoryfocus of biodiversity conservation gives policy-makers the opportunity to respond while optionsto save species or ecosystem services still remain.

kk

Just as economists do nottry to characterize thehealth of the economywith one indicator, so toobiologists cannot evaluatebiodiversity's status with-out examining a variety ofindicators.

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The threat of extinction is one important indi-cator of the status of biodiversity and the ultimateindicator of the status of species diversity. Butother indicators may be more useful from a plan-ning perspective. Various indicators of the currentstatus of coastal species, habitats, and ecologicalprocesses are examined here, along with trends insuch practical attributes of coastal biodiversity asfishery productivity and waterfowl populations.Trends in populations of economically importantspecies (such as fish and waterfowl) reveal the sta-tus of the ecosystem's underlying components interms that economic planners can more readilygrasp. Together, these indicators can be used toproject the potential impact of climate change onthe status of these ecosystems. (See Chapter HI.)Understanding the current stress that coastalecosystems face is crucial to fully appreciating howclimate change may affect coastal biodiversity.

Coastal SpeciesNearly half of the U.S. population, some 110

million people, lives in coastal counties (Culliton etal. 1990). This high density of settlement has beenat the expense of habitat: a disproportionate shareof rare and endangered species in the United States

are now found in coastal counties.3 But most ofthese species are associated with upland habitats. Ithas long been thought that few species right at thesea edge—in the zone most likely to be affected bysea level rise—are at high risk of extinction. Coast-al wetlands and barrier islands have relatively fewspecies, and the species occupying marine systemsoften have extremely large ranges.

These attributes of coastal species and ecosys-tems would seemingly insulate them from majorthreats of extinction. But a more careful examina-tion of coastal ecosystems suggests otherwise. Ourevaluation of the current threat to species utilizing,or restricted to, the zone below an elevation of 5or 10 feet of sea level shows that a number of spe-cies in this coastal fringe will be squeezed betweenincreasing development pressure from above andthe rising sea from below. (The choice of these ele-vations is dictated by the resolution of the dataavailable, but they also compare roughly with therange of estimates of sea level rise expected in thenext century (roughly 1-6 feet).)

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Florida contains the over-whelming majority of therare species restricted tothe coastal fringe.

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Some 20 species that are federally listed as en-dangered or threatened are found only within the10-foot coastal fringe of the contiguous UnitedStates, and another 33 are candidates for listing.(See Table 1.) These threatened and endangeredspecies amount to only 3.4 percent of the nearly600 listed species—scarcely surprising given thatthe land area in this zone is small. Consideringonly coastal wetlands, these ecosystems accountfor only 0.2 percent of surface area in the contigu-ous United States, but they are principal habitatsfor 15 federally listed or candidate species. Theperception that coastal species may be less threat-ened with extinction is thus unfounded: the levelof endangerment in coastal wetlands (3.5 speciesper million acres) is greater than the average forthe United States as a whole (1.9 species per mil-lion acres).

In fact, these totals underestimate the truethreat. The complexity of the federal listing pro-cess, combined with severe funding constraintsfaced by the Division of Endangered Species, hascreated a backlog of some 3,900 species waiting for

classification. More up-to-date data on threatenedand endangered species are maintained by The Na-ture Conservancy (TNC). According to TNC, 80species and subspecies that are considered rare, im-periled, or critically imperiled on a range-wide ba-sis are found only below the 10-foot contour ofthe contiguous United States.4 (See Table 1.)

Moreover, these statistics refer only to speciesthat are restricted to the area below the 10-footcontour. The picture is even more disturbing whenspecies are included that utilize the coastal fringe,often for critical portions of their life cycle, butare not restricted to this zone. For example, TNClists some 73 species in Maryland found only be-low the 10 foot contour as rare or imperiled. If allrare species utilizing this zone are included, how-ever, the total grows to 122 species. Similarly, inCalifornia, the California clapper rail and the salt-marsh harvest mouse are the only federally listedendangered animals restricted in their habitat useto below the 10-foot contour, but the peregrinefalcon, California brown pelican, light-footed clap-per rail, California black rail, California least tern,Belding's savannah sparrow, and San Francisco gar-ter snake are all rare species that live, among otherplaces, in coastal wetlands.5

Florida contains the overwhelming majority ofthe rare species restricted to the coastal fringe.Forty-five of the 80 species (56 percent) classifiedby TNC as rare, imperiled, or critically imperiledin this zone are found in the contiguous UnitedStates only in Florida. The preponderance of spe-cies in Florida reflects both the low elevation ofthe state (consequently, the 10-foot contour in-cludes more land than in many other coastal states)and the presence of tropical and subtropical habi-tat found nowhere else in the contiguous UnitedStates. Some Florida species that are rare in theUnited States and restricted to below 10 feet of sealevel are found elsewhere in the Caribbean andmay be found at higher elevations outside of theUnited States. Thus, not all of these species arethreatened with global extinction.

Threatened and endangered species are thosespecies in need of "critical care." But populationtrends of species not yet at risk of extinction areoften equally useful indicators of biodiversity's sta-tus since these statistics provide policymakers withvaluable information well in advance of any crisis.Only by monitoring trends in populations of allspecies and taking action to protect declining pop-ulations can a steadily growing list of endangeredor imperiled species be avoided.

Recent population trends of coastal species arenot encouraging. Consider the findings of the U.S. Fishand Wildlife Service, which monitors populations of

Table 1. Rare, Threatened, and Endangeredof Sea Level

Common Name

PlantsSensitive Joint-VetchSeabeach PigweedSuisun Marsh AsterSeashore SaltbushEaton Beggar-ticks

Estuary Beggar-ticks

Long's Bitter cressBig Pine Partridge PeaNodding CatopsisSmall-Flower Lily-Thorn

Key Tree-cactusGarber's SpurgePorter's Hairy-Pod

SpurgePorter's Broadleaf SpurgePorter's Broom Spurge

Geiger TreeBird's Beak

Solf Bird's BeakPt. Reyes Bird's BeakOkeechobee Gourd

Narrow-leaved CarolinaScalystem

Parker's PipewortContra Costa Wallflower

Blake's Gumplant

Johnson's Sea-Grass

Hairy Beach Sunflower

ManchineelHenry's Spider-LilyBroad-Leaved Spider-LilyInkwood

Delta Tule-pea

Seabeach Pigweed

Panhandle LilySand FlaxCarter's Small-Flowered

Flax

Carter's Large-FloweredFlax

Humbolt Owl's Clover

Name

Aeschynomene virginicaAmaranthus pumilusAster chilensis var. lentusAtriplex drymarioidesBidens eatonii

Bidens hyperborea var.hyperborea

Cardamine longiiCassia keyensisCatopsis nutansCatesbaea parviflora

Cereus robiniiChamaesyce garberiChamaesyce porteriana

var. keyensisC.p. var. porterianaC.p. var. scoparia

Cordia sebestenaCordylanthus mariti-

ntus ssp. maritimusCm. ssp. mollisCm. ssp. palustrisCucurbita okeechobeeensis

Elytraria caroliniensisvar. angustifolia

Eriocaulon parkeriErysimum capitatum

var. angustatumGrindelia stricta ssp.

blakeiHalophila johnsonii

Helianthus debilis ssp.vestitus

Hippomane mancinellaHymenocallis henryaeHymenocallis latifoliaHypelate trifoliata

Lathyrus jepsonii ssp.jepsonii

Lechea maritima var.virginica

Lilium iridollaeLinum arenicolaLinum carteri var. carteri

Linum carteri var.smallii

Orthocarpus castille-joides var. humbold-tiensis

Species in the United

TNCDesignation3

ImperiledImperiledImperiledImperiledRare

Rare

RareImperiledImperiledImperiled

Critically ImperiledCritically ImperiledCritically Imperiled

ImperiledImperiled

RareImperiled

Critically ImperiledRareCritically Imperiled

Imperiled

RareCritically Imperiled

Imperiled

Critically Imperiled

Imperiled

RareCritically ImperiledRareImperiled

Imperiled

Imperiled

Critically ImperiledCritically ImperiledCritically Imperiled

Imperiled

Imperiled

States Restricted

FederalDesignation15

Candidate (2)Candidate (2)Candidate (2)

——

—

Candidate (1)——

EndangeredThreatenedCandidate (1)

Candidate (1)Candidate (1)

—

Candidate (1)Candidate (2)Candidate (2)

Candidate (2)

—Endangered

Candidate (2)

—

Candidate (1)

————

Candidate (2)

—

Candidate (2)Candidate (2)Candidate (1)

Candidate (1)

Candidate (2)

to within 10 feet

Habitat

Marsh, Tidal marshDunesMarshMudflatsTidal Shore

Mudflats

Fresh EstuariesShallow soil over coralDry knolls near marshDunes, dry knolls

Thorn ScrubSand Pine rocklandsCoastal Scrub

Pinelands on limestonePinelands on limestone

DunesHigh Salt Marsh

Salt MarshSalt MarshSwamp Forest

Floodplain forest

Tidal FlatsStrand/Dunes

Salt Marsh

Sandy marine bottoms

Dunes, Sandy clearing

Dry knolls near marshSwampMangrove, coastal swaleDry knoll near marsh

Salt Marsh

Dunes

Bogs, swampPine rocklandPinelands

Disturbed soil, limestone

Salt Marsh

Table 1. Continued

Common Name

Semaphore cactusBig Pine Key Prickly PearFlorida Five-Petal

Boykin's Few-LeavedMilkwort

Sea-Beach KnotweedAlkali-GrassFlorida Royal PalmMiami Palmetto

Florida Water-Parsnip

MammalsDuke's Salt Marsh Vole

Key Largo Woodrat

Key Deer

Southeast Beach Mouse

Anastasia Beach Mouse

Perdido Key BeachMouse

Florida MouseKey Vaca RaccoonSalt-Marsh Harvest

MouseMangrove Fox Squirrel

Lower Keys Cotton Rat

Insular Cotton RatLower Keys Marsh

RabbitWest Indian Manatee

BirdsRoseate TernCape Sable Sparrow

Florida Prairie Warbler

Florida Clapper Rail

California Clapper Rail

Mangrove Clapper Rail

Reptiles/AmphibiansLoggerhead Sea TurtleGreen Sea TurtleAmerican CrocodileLeatherback Sea Turtle

Name

Opuntia spinosissimaOpuntia triacanthaPhyllanthus pentaphyl-

lus ssp. floridanus

Polygala boykinii var.sparssifolia

Polygonum glaucumPuccinellia laurentianaRoystonea elataSabal miamiensis

Sium floridanum

Microtus pennsylvanicusdukecampbelli

Neotoma floridanasmalli

Odocoileus virginianusclavium

Peromyscus polionotusniveiventris

P.p. phasma

P.p. trissyllepsis

Podomys floridanusProcyon lotor auspicatusReithrodontomys

raviventrisSciurus niger avicennia

Sigmodon hispidusexsputus

S.h. insulicolaSylvilagus palustris ssp.

hefneriTrichechus manatus

Sterna dougalliiAmmodraums mariti-

mus maritimusDendroica discolor

paludicolaRallus longirostris

scottiiRallus longirostris

obsoletusRallus longirostris

insularum

Caretta carettaChelonia my dasCrocodylus acutusDermochelys coriacea

TNCDesignation21

Critically ImperiledImperiledRare

Imperiled

RareRareImperiledCritically Imperiled

Critically Imperiled

Critically Imperiled

Critically Imperiled

Critically Imperiled

Critically Imperiled

Critically Imperiled

Critically Imperiled

RareImperiledImperiled

Imperiled

Imperiled

ImperiledImperiled

Imperiled

RareCritically Imperiled

Rare

Rare

Critically Imperiled

Rare

RareRareImperiledRare

FederalDesignationb

Candidate (2)Candidate (2)Candidate (2)

Candidate (2)

——

Candidate (1)—

Candidate (2)

Candidate (2)

Endangered

Endangered

Threatened

Endangered

Endangered

Candidate (2)Candidate (2)Endangered

Candidate (2)

—Endangered

Endangered

—Endangered

—

—

Endangered

Candidate (2)

ThreatenedEndangeredEndangeredEndangered

Habitat

Dry knolls near marshSand, back beachPinelands on limestone

Pinelands on rock

BeachGravel ShoreWoodlandsPinelands/scrub

Woodlands

Salt Marsh

Woodland

Woods, Mangroves

Beach/Dune

Salt Marsh

Sand Beach

Pine/ScrubStreamsSalt Marsh

Pineland

Woodland/Fresh marsh

Saltmarsh, Pine woodsSalt and fresh marsh

Warm brackish/salt water

Sand BeachFresh/Brackish marsh

Mangroves

Sandy Areas/Shoreline

Salt Marsh

Mangroves

Marsh, BeachSand BeachMangrove, baysSand Beach

Table 1. Continued

Common Name

Hawksbill Sea Turtle

Lower Key Striped MudTurtlecd

Kemp's Ridley SeaTurtle

Lower Key BrownSnakec

Lower Key RibbonSnakec

FishMangrove gambusiaFlorida Keys Sailfin

Mollyc'd

Key Blenny

InsectNortheastern Tiger

Beetle

Name

Eretmochelys imbricata

Kinosternon baurii

Lepidochelys kempii

Storeria dekayi

Thamnophis sauritus

Gambusia rhizophoraePoecilia latipinna

Starksla starcki

Cicindela dorsalisdorsalis

TNCDesignation3

Rare

Imperiled

Critically Imperiled

Critically Imperiled

Critically Imperiled

RareImperiled

Critically Imperiled

Imperiled (Var.)

FederalDesignation" Habitat

Endangered Sand Beach

— Fresh/Brackish marsh

Endangered Sand Beach

— Woodlands to salt marsh

— Forests, swamps

— Mangrove— Swamps

— Coral reef

Threatened Sand Beach

a. The Nature Conservancy classifies a species as "Rare" (G3) if it is either very rare and local throughout its range, or found lo-cally in a restricted range, or because of other factors making it vulnerable to extinction throughout its range. A species isdesignated as "Imperiled" (G2) if there are only 6 to 20 occurrences or few remaining individuals, or because of some fac-tors) making it very vulnerable to extinction throughout its range. A species is listed as "Critically Imperiled" (Gl) becauseof extreme rarity (5 or fewer occurrences or very few remaining individuals) or because of some factor(s) making it especiallyvulnerable to extinction (Morse 1987).

b. Federal candidate species designation: (1) Substantial information supporting listing has been assembled, (2) Additional infor-mation needed to clarify status,

c. Lower Florida Keys population only,d. Questionable taxonomic designation.

both game and non-game birds by censuses duringthe breeding season. Of the 21 non-passerine (non-songbird) bird species exhibiting significantly declin-ing population trends between 1980 and 1989, 4(19 percent) are associated with coastal wetlandsduring some seasons (green-backed heron, northernpintail, common moorhen, and American avocet).The populations of several coastal species havedeclined significantly over even longer periods oftime. Over the past 25 years, some 30 percent ofthe 20 non-passerine species with significantly de-clining populations are associated with coastal wet-lands or estuaries during some seasons (Americanbittern, American black duck, northern pintail,northern harrier, common tern, and black tern;S. Droege, U.S. Fish and Wildlife Service, PersonalCommunication, 10 September, 1990).

In sum, the coastal fringe already contains asignificant number of rare and endangered species,

and population trends suggest that other speciesmay be headed toward endangerment. It is againstthis background that the potential increased threatsassociated with- climate change must be examined.(See Chapter III.)

Coastal Habitats

One of the chief causes of species endanger-ment is the loss of habitats (Reid and Miller 1989),and habitat destruction also results in the loss ofimportant ecological services. A complete analysisof the status of coastal habitats would include dis-cussions of wetlands, barrier islands, coral reefs,mangroves, sea grass beds, estuaries, rocky inter-tidal, marine benthic communities, and otherhabitats. Unfortunately, sufficient data to provide aclear picture of status and trends exist only forcoastal wetlands.

The loss of coastal wetlands (including salt andtidal marshes) provides a graphic picture of howcoastal development in the United States affectsbiological diversity. Between the mid-1950s andmid-1980s, approximately 20,000 acres of coastalwetlands were lost per year in the contiguousUnited States, amounting to a conversion of 8.3percent over this period (OTA 1984).6 In themid-1970s, 4.4 million acres of coastal wetlandsremained in the United States. The losses of coastalwetlands were concentrated in the Gulf states(Louisiana, Florida, and Texas), but were also sig-nificant in New Jersey, New York, and California.During this period, New Jersey was losing 3,097acres per year, and Chesapeake Bay some 500acres per year (Tiner 1985, 1987).

Between the mid-1950sand mid-1980s, approxi-mately 20,000 acres ofcoastal wetlands were lostper year in the contiguousUnited States, amountingto a conversion of 8.3percent over this period.

99

Aggregate figures of coastal wetlands loss,however severe, obscure particularly dramaticchanges in certain regions. For example, between1950 and 1967, San Francisco Bay (and the adjoin-ing Suisun Bay) lost 192,000 out of 294,000 acresof estuarine and wetland habitat (Jensen et al.1990), and by the mid-1970s only 20 percent ofthe Bay's original wetlands remained (Tiner 1984).California as a whole lost nearly 53 percent of es-tuarine and wetland acreage during this time. Simi-larly, northern New Jersey lost 75 percent of itscoastal wetlands between 1925 and 1975 (Tiner1985). In Louisiana, an area of coastal wetlandsgreater than the size of Rhode Island was lost be-tween 1900 and 1985.

In the 1970s, state wetlands protection actsand federal regulations associated with Section 404of the Clean Water Act dramatically reduced therate of loss of coastal wetlands. Before the Wet-lands Act passed in 1973, Delaware was losing al-most 450 acres of coastal wetlands each year. After1973, losses dropped to 20 acres annually (Tiner1984). In Massachusetts, where 20 percent of salt-water wetlands acreage was lost between 1951 and

1971, only five acres are thought to have been lostthrough human action in the decade beginning in1978, when stringent coastal wetland regulationsfor salt marshes were adopted (McCreary andAdams 1988).7

By most accounts, wetlands on both the eastand west coasts are now well protected by statelaws from the threats they have faced in the past.All coastal states in the lower 48, except Texas andGeorgia, have now adopted laws to protect coastalwetlands. Overall, the National Marine FisheriesService estimates, by 1981 the loss of coastal salt-water wetlands had been reduced by 70 to 85 per-cent since the 1960s. However, by this time manystates had already lost most of their coastal wet-lands and the need for preservation of the remain-ing acreage was readily apparent. In Massachusetts,for instance, less than 6.5 percent of all coastalland is undeveloped.

Massive losses of coastal wetlands continueonly in the Gulf states, where the hydrology of theMississippi river has been altered and the coastalplain is subsiding. (See Box 1.) More than 50square miles of coastal wetlands are being lost inLouisiana each year. Relative sea level rise in theMississippi delta is approximately 12 to 13 mm peryear, comparable to the predicted rate of sea levelrise under global warming scenarios. (See ChapterIII.)

The scattered information available on the sta-tus of other coastal ecosystems suggests that thesetoo are under considerable stress. Barrier islandecosystems have changed from de facto wildernessto the focus of intense development pressure in amatter of decades. Prior to World War II, only 28percent of all U.S. barrier islands were subject todevelopment pressure, but by 1980 the figure hadincreased to 70 percent (Millemann 1988). Beachecosystems, with their important nesting habitatsfor birds and sea turtles, have similarly been dis-turbed by pollution, recreational use, and the con-struction of jetties, groins, and bulkheads. Andcoral reefs have been lost to sedimentation andpollution. Coral reefs north of Miami have sufferedfrom sedimentation caused by dredging, and sew-age had similarly detrimental impacts on corals inFlorida before more stringent water quality stan-dards were put in place in the 1970s. The quantityand health of corals has also declined in responseto increased recreational fishing, coral gathering,and contamination by sewage, as well as to the de-structive impact of anchors.

Clearly, the nature of the problem affectingcoastal habitats is changing. No longer is the pri-mary threat to wetlands and other coastal ecosys-tems the massive habitat loss associated with the

Box 1. Wetlands Loss in the Mississippi Delta

The Mississippi River delta contains 41 per- A major underlying cause of wetland loss incent of the coastal wetlands of the contiguous Louisiana is subsidence, or submergence of theUnited States. The annual biological productivity land surface. But probably the single greatest rea-of the delta is extremely high—each year Loui- son for wetland loss in Louisiana is the reductionsiana ranks first nationally in tonnage of fisher- in sediment available to maintain accretion rates,ies landings, and the wetlands support the lar- As numerous studies have indicated, the sus-gest fur harvest in the United States, the largest pended sediment load of the Mississippi River hasconcentrations of overwintering waterfowl, and decreased substantially sine; the early 1960s,most of the marine recreational fishing landings. This change stems from the damming of manyMany people who live on the low natural levees Mississippi River tributaries, improved soil con-of former river distributaries have traditionally servation practices which lessened rates of ero-made their living by harvesting the abundant sion, the mining of sand deposits along river fornatural resources of the delta's wetlands. industrial use, and the dredging and on-land dis-

When sea level rise slowed about 6,000 posal of river sediments,years ago, the Mississippi River was depositing Adding insult to injury, artificial levees haveits sediments at approximately the latitude of confined the Mississippi along practically its en-Baton Rouge, which is now about 320 km (100 tire length from Cairo, Illinois southward, andmiles) upriver from the active delta. Over the various control structures have blocked or re-last 6,000 years, the Mississippi River created stricted river flow in natural distributary deltaseven major deltas by abandoning its channel channels. As a result, less sediment is availableseven times and switching to new, shorter for deltaic sedimentation and barrier islandroutes to the Gulf. Once abandoned, each old nourishment while valuable delta-building sedi-delta began to subside below sea level, and its ments are being funneled out onto the slopes ofmany wetlands reverted to open water. the outer continental shelf. Coupled with subsi-

dence and the sediment deficit, shoreline ero-kk

Between 1900 and 1985,an estimated 400,000acres of coastal wet-lands were lost in Loui-siana, an area 1.3 timesthe size of Rhode Island.

99

The long-term net gain of land that charact-erized the Mississippi River delta for 7,000 yearsreversed itself about 100 years ago. In 1980, theland loss rate was estimated to be 100 km2/yr(40 rm"2/yr) within the delta itself and 130km2/yr (50 mi2/yr) for all of coastal Louisiana.This amounts to a loss of some 100 acres perday. More recent studies have pushed the rate ofloss up to more than 150 km2/yr. Between 1900and 1985, an estimated 400,000 acres of coastalwetlands were lost in Louisiana, an area 1.3times the size of Rhode Island. This lost wetlandarea, worth at least $3,000/acre in terms ofrecreation and biological productivity, repre-sents a loss in excess of S3 billion.

sion has resulted in the loss of some 10 percentof the coastal wetlands, and such activities asdredging channels and land "reclamation" havealso damaged wetlands area directly.

Wetlands loss in Louisiana has been greatestin more inland fresh-to-brackish marshes, whichhave historically depended upon overbankflooding from the Mississippi River and its form-er distributaries to supply sediments. Marshescloser to the ocean are subject to greater sedi-mentation because of the higher tidal energy;consequently, they have not lost as much area.

Although the rates of wetlands loss are trulyalarming, and bode ill for New Orleans andother cities built on the deltaic plain, the humaninfluence on this hydrological system is alreadyso massive that few practical responses seemcapable of stemming the loss. Declining rates ofoil extraction may slow subsidence somewhat,as might regulating Mississippi River flow so asto increase sediment transport, but even withsuch changes substantial wetland area will con-tinue to be lost in the Mississippi Delta with orwithout increased rates of sea level rise.

Source: Turner 1990, Meyer-Arendt 1990,Templet and Meyer-Arendt 1988.

development of coastal infrastructure in the 1950sand 1960s. Instead, the cumulative effects of con-tinued habitat loss, pollution, overharvesting, andincreased recreational use are now to blame. Oneof the most ominous trends affecting coastalhabitats is the rapid growth of the human popula-tion taking place in coastal areas. (See Box 2.)Population trends indicate that coastal resourcemanagers will be fighting an uphill battle to main-tain biological diversity as pressures on coastalecosystems mount.

National Monuments include significant coastalhabitats (USFWS 1989). Federal and state protectedareas and wildlife refuges now protect substantialfractions of some key coastal wetlands. For exam-ple, nearly 50 percent of San Francisco Bay wet-lands are now under some form of protection,though this coverage amounts to only 10 percentof the original acreage of wetlands in the Bay. Inaddition, seven Marine Sanctuaries were establishedin the United States between 1975 and 1987 (witha total area of 2,350 square nautical miles), and a

Box 2. Trends in Coastal Human Populations

By 2010, the coastal population of theUnited States will have grown 60 percent largerthan it was in I960 to more than 127 millionpeople. (See Figure 1.) In Florida alone, coastalpopulation will have increased more than three-fold, from 5 million to 16 million, over thesame period. Seventeen of the twenty stateswith the largest statewide population increasesexpected over the thirty-year period are coastal,and only 5 percent of coastal counties are ex-pected to lose residents. In general, coastalpopulation density is increasing strikingly. InI960, the overall population density in theUnited States (excluding Alaska) was 61 peopleper square mile, compared to 248 persons persquare mile in coastal counties. By 1988,

population density in coastal counties reached341 persons per square mile, more than fourtimes the U.S. average in that year.

Not surprisingly, the growth in use of pub-lic lands in coastal areas has grown in step withthe growing coastal population. Since 1979,recreational visits to the 24 National Parks, Na-tional Seashores, and National Monuments thatinclude coastal ecosystems has increased by 63percent. (See Figure 2.) This 5-percent annualgrowth rate in visitation is more than five timeslarger than the annual growth of population incoastal counties. In the ten National Seashores,visitation increased by 78 percent over the pastdecade.Source: Culliton et al. 1990, NPS 1981 to 1989.

kk

Federal and state water-fowl managers agree thatanother roughly 386,000acres of coastal wetlandsin Louisiana need to beprotected to provide ade-quate waterfowl habitat.

ff

In recognition of the considerable threats tocoastal areas, steps have been taken to protect keyhabitats. State or federal protected areas networksnow include a significant acreage of coastal wet-lands. (See Figure 3.) Some 117 Fish and WildlifeService Refuges in coastal areas in the contiguousUnited States cover an area of 2,230 square miles,and 24 National Parks, National Seashores, and

network of 17 Estuarine Research Reserves cover-ing nearly 400,000 acres was established between1974 and 1985 (CEQ 1989).

But does this level of habitat protection meetreal needs? By all accounts, the area of wetlandhabitat currently protected will not. Even thoughacquiring additional coastal wetlands has not beena high priority of federal legislation, federal andstate waterfowl managers have determined that an-other roughly 386,000 acres of coastal wetlands inLouisiana need to be protected to provide adequatewaterfowl habitat. Doing so could mean establish-ing parks or refuges but may instead involve landmanagement practices other than land purchase,including regulatory and incentive-based interven-tions. Along the Atlantic Coast, another 50,000acres of coastal wetland habitat must be protectedto provide adequate migration and winteringgrounds for the Black Duck (Chandler 1988). InCalifornia, the State Legislature has directedCalifornia Fish and Game to increase inland andcoastal wetland acreage by 50 percent by the year

10

Figure 1. Population Growth Projections for Coastal United States Counties

140.

120.

100.

1* 80.

§§ 60J

40_

20 _

01960 1970 1980 1990 2000 2010

Source: Culliton, (1990)

2000 so that wildlife populations can be main-tained at present levels (Jensen et al. 1990).

Moreover, as important as marine and coastalprotected areas are for ensuring the conservationof biodiversity, protecting an area does not neces-sarily protect biodiversity. Management practices,the protected area's proximity to other areas ofnatural habitat, and the size of the protected areacan all influence the odds of maintaining biodiver-sity. (See Box 3) This is especially true in coastalecosystems since harvests of fish or discharges ofpollutants many kilometers away can affect a ma-rine protected area and increased sedimentation orpollution from upstream land-use practices coulddamage protected wetlands or reefs.

Ecological ProcessesAlthough seldom considered components of

biodiversity themselves, ecological processes arecertainly products of a region's biodiversity. Indi-cators of the status of ecological processes can thusshed light on the status of the underlying biodiver-sity. One of the most widespread impacts on coast-al ecological processes is pollution, and despitegains made in past decades, pollution remains aserious threat today. Some 5 million to 20 milliongallons of oil were spilled in U.S. waters each yearin the 1980s. (See Figure 4.) In 1980, about 35

percent of sewage effluents generated nationwidewere discharged into coastal and marine waters(CEQ 1989). In 1985, only 58 percent of the totalU.S. coastal zone classified as shellfish growingarea was unconditionally approved for shellfishharvest (CEQ 1989). In addition, although pollu-tion controls have cut the amounts of such tracemetals as lead and cadmium in coastal areas, cop-per contamination of oysters and mussels rosestrikingly between the late-1970s and the late-1980s (Lauenstein et al. In Press). (See Figure 5.)Similarly, one study of trends in contaminantlevels in mollusks since 1986 indicates that whileconcentrations of cadmium and chlorinated organ-ic compounds such as PCBs are decreasing, con-tamination by mercury and selenium is growing(NOAA 1989).

One impact of these pollutants on ecologicalprocesses in coastal ecosystems can be seen in theapparent increase in the number of toxic algalblooms worldwide in recent years. These bloomsare apparently caused by eutrophication resultingfrom the excess nutrients dumped into coastalwaters. At a recent conference on Ocean Marginsand Global Change, scientists noted that eutrophi-cation seems to be taking place at the mouths ofalmost all of the world's rivers (Cherfas 1990). In1988, a phytoplankton bloom was linked to massdeaths of dolphins off the Carolinas. The bloom

11

Figure 2. Recreational Visits to Twenty-Four National Parks, National Seashores, and NationalMonuments that Include Coastal Ecosystems

35.

30-

25-

20.1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989

Source: National Park Service, (1980-1989)

was caused by a species formerly restricted to theGulf Coast of the United States and its spread tothe East Coast may trace back to the increasingquantity of nutrients in these coastal waters.

For decades, coastal ecosystems, particularlywetlands, have been valued for their high produc-tivity and for their contributions to the functioningof adjacent ecosystems. Wetlands were thought toexport large quantities of nutrients to adjacentwaters, and it was believed that these nutrientswere largely responsible for the high fish and shell-fish productivity associated with estuarine andcoastal ecosystems. More recent evidence indicatesthat this "outwelling" phenomenon is a less im-portant source of carbon and nutrients than hadbeen thought (Nixon 1980). Finfish and shellfishproduction in estuaries without significant acreageof marsh can be at least as high as production inestuaries with such areas.

Yet, coastal wetlands do still contribute tonearshore productivity. For example, saltmarsh

plants like cordgrass (Spartina) are an importantsource of carbon for estuarine consumers (Haines1977, Peterson et al. 1986). Similarly, in a man-grove-dominated estuary in Malaysia, mangrovessupplied more than 55 percent of the carbon in acommercially important species of clam, 30 to 100percent of the carbon in a species of shrimp, and60 percent of the carbon in the fishes inhabitingthe inlets (Rodelli et al. 1984).

Besides the outwelling of nutrients to estuariesand coastal waters, nutrient transport also takesplace via the food chain. For example, New Jersey'shigh intertidal marshes are the primary sites for thereproduction and growth of many saltmarsh killi-fishes, which move into intertidal creeks in the falland become an important prey for larger estuarineand marine species (Talbot and Able 1984). Similar-ly, the Atlantic croaker (Micropogonias undulatus)and spot (Leiostomus xanthurus) accounted for 6 to14 percent of the material flow out of a saltmarshin the Gulf of Mexico (Currin et al. 1984).8

12

Figure 3. Status of Wetland Habitat in Key Waterfowl Wintering Areas

PacificOcean

i l l Protected

t. I Unprotected

[~1 Lost

HI Shaded Areas arePriority HabitatRanges

GREAT LAKESST. LAWRENCE

LOWLANDS

UNITED STATESPRAIRIE

Source: North American Waterfowl Management Plan, (USDI, 1986)

13

Box 3. Does the Area Protected Equal the Biodiversity Protected?

Habitat conservation is an important compo-nent of biodiversity conservation, but it is mis-leading to consider the total "area" of habitatconserved a sufficient measure of the status ofbiodiversity. At least three other important con-siderations related to the habitat area conservedhave direct implications for species diversity, animportant component of biodiversity.

First, management can profoundly affectthe species present in an ecosystem and itsfunctioning. For example, many coastal wildliferefuges are managed primarily as winteringwaterfowl habitat, but this management goal of-ten conflicts with the management of the habitatfor non-game species. Such conflicts are not re-stricted to game versus non-game species.Managing wetlands to save the endangered saltmarsh harvest mouse in the San Francisco Baymakes it difficult to save the endangered clapperrail under scenarios of sea level rise since themouse may need well-maintained dry dikedareas while the rail may do better under morenatural wetland conditions (Shellhammer 1989).

Second, in any habitat, the number of spe-cies at risk of extinction increases exponentially withthe loss in area (Reid and Miller 1989). With, say,

pollutant assimilation or fish production, the eco-system function decreases in direct proportion tothe amount of wetland area lost. But this guide-line doesn't hold in the case of wetlands' role inproviding viable habitats for plant and animal spe-cies. A rule of thumb is that losing 90 percent ofa habitat will doom 50 percent of its species toextinction. But if the area of habitat lost is in-creased by another 5 percent, the percent of spe-cies at risk would increase by 15 percent.

Third, from the standpoint of maintainingviable species populations, the extensive frag-mentation of wetlands may be as damaging asthe loss of habitat area itself. Even though iso-lated pockets of wetland habitat along disturbedand developed coastlines have become criticalreservoirs for biodiversity, the species they con-tain face significantly increased threats. Wherepreviously a local population of a species thatwas wiped out by a serious storm would quicklybe re-established by immigrants from adjoiningwetlands, populations in isolated fragments maybe permanently exterminated. Fragmentationalso presents serious difficulties for migrantbirds, which need suitable habitat to rebuildenergy reserves during seasonal migrations.

Although the continuing degradation of coastalecosystems will have somewhat less impact on ad-jacent ecosystems than scientists believed ten yearsago, there remain important energy and nutrientlinkages among coastal ecosystems that are influ-enced by habitat loss or degradation.

Economic Indicators of CoastalBiodiversity's Status

It is difficult to assign dollar values to themany benefits of coastal biodiversity. Biologicalresources traded in economic markets representonly the tip of the iceberg—many aspects of bio-diversity are essential for the continued serviceswe obtain from coastal ecosystems but they arenot bought and sold. Nonetheless, where economicassessments can be made, they are valuable indica-tors of the status and trends of coastal biodiversity,particularly since relatively long-term data are of-ten available for these indicators. Moreover, theseecological services directly benefit people—oneprincipal reason for local concern and governmentaction to maintain biodiversity.

Commercial fishing and waterfowl hunting aretwo important industries that rely heavily onhealthy coastal ecosystems. Commercial fishing is amajor U.S. industry, with landings valued at $3-2billion in 1989- Nine of the 20 most importantU.S. fisheries involve species that depend on coast-al ecosystems for at least some part of their lifecycle. (See Table 2.) These species account for 51percent of the value of harvest from these 20 fish-eries and 44 percent of the tonnage.

Trends in coastal fish harvests present a dis-turbing picture of the status of coastal ecosystems.Serious population declines of many commerciallyimportant coastal species are significantly reducingtheir contribution to human economies. Between1970 and 1989, the harvest of oysters dropped by44 percent and landings of spiny lobster declinedby 34 percent. (See Figure 6.) Similarly, commer-cial landings of striped bass have declined continu-ously since 1973, with a fall of 92 percent since1982.9 Landings are not equivalent to populationtrends, since they reflect both population size andfishing effort. But in both the oyster and lobsterfisheries, the price offered per pound to fishermen

14

Figure 4. Gallons of Oil Spilled in United States Waters

§9

20.

15.

10 _

5_

1982 1983 1984 1985 1986 1987 1988 1989

Source: United States Coast Guard, D.A. Lentsch, personal communication, (August 29,1990)

Figure 5. Trace Metal Contamination in Coastal Ecosystems

35 _

30 _

25.

20.

1 ».Z io

5-

I I DecreaseE l No ChangeI I Increase

Copper Lead Cadmium Silver Nickel Zinc

Each bar represents the number of paired coastal sampling sites in which a comparison of tissue metal concentrations insamples of mussels or oysters between samples taken in the late-1970s and the late-1980s exhibited a significant decrease orincrease or no significant change. A total of 36 paired sites was used for the study.

Source: Lauenstein, et al., (in press)

15

Table 2. 1990 Commercial Fish and Shellfish Harvest—Top Twenty Species by Value.

Species

Salmon (5 species)Shrimp (spp. all coasts)Pollock (Atlantic and Alaska)Lobster (American and Spiny)Snow (tanner) crabSea ScallopsFlounder (spp. all coasts)King CrabTuna (all species)Cod (Atlantic and Pacific)HalibutMenhaden (Atlantic and Gulf)OysterBlue CrabSablefishDungeness CrabHard ClamsRockfishSwordfishSea Herring (Atlantic and Pacific)

Total Coastal DependentTotal Oceanic

Notes:a. Species utilize near-shore coastal areas,

CoastalDependent

yesyesnoyesa

nonoyesb

nonononoyesyesyesnoyesyesnonono

Quantity(1000 lb)

785,868351,514

2,385,23761,051

164,64333,757

202,48926,39189,413

450,56075,168

1,988,72629,926

206,72097,59040,9849,278

133,62311,768

209,003

2,890,6883,677,153

but not wetlands or estuaries.b. Species vary considerably in their use of coastal and estuarine habitats.

Value($1000)

591,234467,571196,843175,562160,082132,594119,831106,204103,543103,14785,14584,46283,58580,98973,27245,53444,92542,33838,32129,432

$1,102,459$1,070,921

has increased over the last decade (adjusted for in-flation) and so fishing intensity is unlikely to havedecreased.

Declines of fish and otherpopulations have manycauses and in no case ishabitat loss or degra-dation the only one.

Other fisheries dependent on coastal ecosys-tems show similar declines. Between 1983 and1989, landings of bay scallops fell by 88 percent.For all three species of scallops (bay, sea, calico),landings declined by 50 percent between 1975 and

1985, with catch per unit effort in 1985 alsoreaching historically low levels (CEQ 1989).

Declines of fish and other populations havemany causes and in no case is habitat loss or de-gradation the only one. Oyster harvest is thoughtto have declined due to a combination of drought,disease, hurricane, water pollution, loss of coastalhabitat, and overharvesting. Factors implicated instriped bass population declines include overhar-vesting, chemical contamination, habitat loss, andhybridization with other species. Further evidencethat habitat loss and degradation is not solely toblame for these trends can be seen in the fact thatseveral other coastal-dependent fisheries are appar-ently holding their own or even increasing in pop-ulation. Landings of the American lobster have in-creased by 56 percent over the past two decades,and both blue crab and dungeness crab yields haveincreased or at least remained constant. (See Figure7.) Such differences in population trends may exist

16

Figure 6. Trends in Landings in Fisheries Dependent on Coastal Ecosystems (Oyster, Spiny Lobster,Striped Bass, Bay Scallop)

.14

-12

-10

16

•3

•jn g

Vt itut I_ 2

01970 1972 1974 1976 1978 1980 1982 1984 1988 1990

Source: National Marine Fisheries Service, (1980-1989)

Figure 7. Trends in Landing in Fisheries Dependent on Coastal Ecosystems (Blue Crab, AmericanLobster, Dungeness Crab)

•I 200-

Blue Crab

i I i i i i r i

1970 1972 1974 1976 1978 1980 1982 1984 1986

_60 _

-50

70

at (A

_30 O

.20 o |

1988 1990

Source: National Marine Fisheries Service, (1980-1989)

17

in part because not all marine species dependequally on coastal ecosystems. Nevertheless, clearevidence indicates that many coastal-dependentfisheries are under stress.

The coastal species whose declining popula-tions have received most attention are ducks, manyof which winter in coastal wetlands or estuaries.Among ten species accounting for over 97 percentof the North American breeding duck population,populations declined by 34 percent between 1970and 1989 (Reynolds 1990). (See Figure 8.) Speciesin the Atlantic flyway have declined particularlydramatically, with populations dropping by nearly50 percent since the mid-1960s (Flather and Hoek-stra 1989). Although all ten species use coastalwetlands and estuaries in the winter, the canvas-back, redhead, and scaup are particularly depen-dent on coastal ecosystems. The canvasback popu-lation declined significantly from 1980 to 1985—apparently because of habitat degradation and adecline in its preferred winter food (wild celeryand other submerged aquatic vegetation) through

much of its range—but has recovered somewhatsince. (See Figure 9) Redhead populations in-creased somewhat from the early-1960s to theearly-1980s, but since 1986 populations have fallenby over 30 percent. Scaup populations too havedeclined over the past decade, falling by 38 per-cent from their recent peak in 1979-

Not all waterfowl have shown such strikingpopulation declines. Goose populations, for exam-ple, have actually increased by nearly 75 percentbetween 1966 and 1982, apparently because condi-tions on their more northerly breeding groundshave improved. In addition, geese have benefittedfrom the expansion of cropland acreage: they for-age in fields during winter and now breed in previ-ously unused nesting habitat (Flather and Hoekstra1989). But as with fisheries populations, the sig-nificant population declines among many speciesthat utilize coastal ecosystems demonstrate thatcomponents of the biodiversity of coastal eco-systems are under serious stress.

Figure 8. Waterfowl Population Trends 1955 to 1990. Total Populations of Ten Most Abundant Ducks,Populations of Mallards and Pintails

50

.12

'' ~"\ Mallard

14

1955 1960 1965 1970 1975 1980 1985 1990

Source: Reynolds, et al, (1990)

18

Figure 9. Waterfowl Population Trends 1955 to 1990. Population Trends for Three Species HighlyDependent on Coastal Ecosystems During Winter

2_

1955 1960 1965 1970 1975 1980 1985

1200

. 200

1990

Source: Reynolds, et al, (1990)

19

III. GLOBAL WARMING: AN ADDITIONAL STRESSON COASTAL BIODIVERSITY

Undisturbed ecosystems can often "absorb"surprisingly large impacts without changing dra-matically, but for ecosystems that are alreadythreatened—among them, U.S. coastal ecosys-tems—added pressure may prove disastrous. Thepotential impacts of climate change represent suchan "added pressure." A solid scientific consensusexists that the human-caused increase in concentra-tions of "greenhouse gases" in the atmosphere willcommit the planet to an increase in global temper-atures of some 1 ° to 3 °C during the next century(Schneider 1989, IPCC 1990a). (See Box 4.) Giventhe already considerable pressures on coastal bio-diversity, what will the added impact of climatechange be?

Even after decades of research that shouldhelp clarify the ecological impacts of changes insea level, precipitation, or coastal currents, an-swers to this question remain speculative. Nonethe-less, the basic indicators used in the previous chap-ter can be employed again to assess the impacts oncoastal biodiversity of global warming—especiallysea-level rise and changes in ocean temperature.

World sea level has changed continuallythrough geological history. Some 120,000 yearsago, global temperatures were 1 ° to 2 °C warmerthan they are today and the sea was about 6meters higher. At the last glacial maximum, whenglaciers reached as far south as Illinois (15,000years ago), the Earth was 5 °C colder and sea levelwas some 100 meters below its level today (Titus1990). As the glaciers retreated, sea level began torise rapidly until about 6,000 years ago, when therate of change slowed significantly. Measurementsin the Caribbean indicate that sea level rose at anaverage rate of only 0.4 millimeters per year forthe past 3,200 years, allowing shorelines to stabi-lize or expand and allowing many shallow marineenvironments to build (UNEP 1988).

In the last century, global sea level has risen ata rate of 1.0 to 2.0 mm per year (Warrick andOerlemans 1990), with one estimate suggesting thatthe rate of rise may have increased between 1920and 1970 to 2.4 + 0.9 mm per year (Peltier andTushingham 1989). The rate of sea level rise in thepast century appears to be somewhat greater thanaverage rates over the prior two hundred years,but as yet no firm evidence links the apparent

acceleration in sea level to human-caused globalwarming (Warrick and Oerlemans 1990).

Future rates and magnitudes of sea level riseunder scenarios of global warming, though easierto predict than many aspects of climate change,are still surrounded by considerable uncertainty.Estimates of the sea level rise expected by the year2100 range from 10 cm to nearly 3.4 meters (Hoff-man et al. 1983, PRB 1985). The Intergovernmen-tal Panel on Climate Change (IPCC) predicts thatby 2030 global-mean sea level will be 8 to 29 cmhigher than it is today, with a best estimate of 18cm; by 2100, sea level is expected to be 31 to 110cm higher, with a best-estimate of 66 cm (Warrickand Oerlemans 1990, Oerlemans 1989). Manyresearchers nevertheless consider the IPCC predic-tions of sea level rise conservative (Pugh 1990,Titus 1991). The IPCC assumes that some glaciers,particularly in the Antarctic, will actually increasein size as temperatures rise and thus partly offsetany sea level rise, but many glaciologists believethat the glaciers will instead shrink and that a netcontribution to sea level rise is not only possible,but likely. These experts believe that a sea levelrise of as much as 200 cm by 2100 is entirely pos-sible. Over the next few centuries, this means, thesea could rise by some six meters (Titus 1991).

ftPolicies for responding tosea level rise must takeinto consideration notonly the magnitude of theexpected sea level rise butalso the uncertainty asso-ciated with the estimates.

Jf

Policies for responding to sea level rise musttake into consideration not only the magnitude ofthe expected sea level rise but also the uncertaintyassociated with the estimates. The costs of under-estimating sea level rise are likely to be high; ac-cordingly, Edgerton (1991) argues that policymakers

21

Box 4. A Primer on Global Warming

Life on earth is dependent on the so-called"greenhouse effect," which keeps the planetabout 59 °F warmer than it would otherwise be.It was the French mathematician and physicistJean Fourier who first described in 1827 howEarth's thin atmospheric blanket warms theearth. The atmosphere, Fourier suggested, pos-sesses special greenhouse-like properties thatpermit solar energy to enter and strike the earthas visible light, but which then impede the ener-gy's return into space as infrared heat. These"properties" are in fact the so-called greenhousegases, which permit solar energy as visible lightto pass through the atmosphere, but which ab-sorb and re-radiate a portion of the same energyas it leaves Earth's surface as infrared heat. Thenet effect is a warming of the atmosphere. Therelative warmth of a cloudy versus a cloud-freenight sky is an accentuated example of this ef-fect, since the water vapor making up clouds isitself a greenhouse gas.

Global warming becomes a threat onlywhen the normal—and necessary—greenhouseeffect is amplified by human activities. By in-creasing atmospheric concentrations of the natu-rally occurring greenhouse gases, primarilywater vapor (H2O), carbon dioxide (CO2), meth-ane (CH4), nitrous oxide (N2O), and troposphericozone (O3), and by adding new synthetic green-house gases, such as the chlorofluorocarbonsand halons (CFCs), human activities are causingthe atmosphere to trap an increasing proportionof the infrared heat that would otherwise escapeback into space. All other things being equal,the additional heat-trapping capacity of the at-mosphere will tend to raise global temperaturesbeyond those that would otherwise prevail.

As early as 1896, the great Swedish chemistSvente Arrhenius suggested that burning enoughfossil fuels to double atmospheric CO2 concentra-

tions might raise average global temperatures by10 degrees F. This is not far from the 3-to-8-degrees F increase that current climate modelsproject for a doubling of atmospheric CO2. Ifthese models are correct—and they are the bestthat scientists can do for now—the unprece-dented rise in atmospheric greenhouse gas con-centrations during the last 40 years may have al-ready committed the planet to an additionalaverage temperature rise of 2 to 4 degrees F be-yond the 1 degree F rise already observed overthe past century. (This 1-degree warming cannotbe conclusively attributed to human activities,but it is consistent with modelled predictions.)

Based on their relative abundance in the at-mosphere, their radiative properties, and theiratmospheric lifetimes, the relative contributionsof the various greenhouse gases to future globalwarming can be estimated. Projected increasesin atmospheric carbon dioxide concentrationsare expected to account for roughly half of theglobal warming that occurs over the next severaldecades.

The actual pace and eventual magnitude ofglobal warming will depend on variables as dis-parate as human population growth, the energysupply mix, the efficiency with which energy isproduced and consumed, oceans' response totemperature change, deforestation rates, theemission rates of CFCs and other syntheticgreenhouse gases, and both positive and nega-tive climatic feedbacks. All projections are un-dermined by the significant uncertainties stillsurrounding most of these variables, and the na-ture and magnitude of climatic feedbacks remainparticularly poorly understood and controver-sial. The increased cloudiness likely to be asso-ciated with global warming could accentuate ormoderate the warming, depending on the typeof clouds that become more common.

should plan for sea level rises that have only a 10or 15 percent chance of being exceeded. Overall,Edgerton concludes, nations should plan for a70-cm rise in sea level by 2050.

As noted earlier, one of the most importantaspects of sea level rise from the standpoint of bio-diversity is the rate rather than the magnitude ofrise. The IPCC predictions suggest rates of sea levelrise some three to six times higher than that expe-rienced over the last century. By the year 2100,

the rate of sea level rise could easily exceed 10mm/year.

Impacts on Coastal Habitats

Can Wetlands Keep Pace With Rising Sea Levels?

The geologic record bears out the hypothesisthat rates of sea level rise expected under condi-tions of global warming might well be at the very

22

limit of wetlands' capacity to keep pace. The rateof sea level rise following the end of the Pleisto-cene (15,000 years ago until 6,000 years ago) isestimated to have been 10 to 20 mm/yr (Titus andBarth 1984, Grigg and Epp 1989). Little wetlanddevelopment took place during this period andmost present coastal marshes in the United Statescame after this period of rapid sea level rise(Stevenson et al. 1986). In general, little wetlandformation is likely to take place at rates of sealevel rise above 10 mm/yr. (See Box 5.)

How would the predicted three- to six-fold in-crease in rates of sea level rise affect coastal wet-lands? Clearly, the loss of wetlands in Louisiana, al-ready occurring at alarming rates, will increase. Inaddition, 11 of 14 wetland sites in the United Statesthat are currently growing faster than the rise in sealevel would probably begin to shrink if local rela-tive sea level rise increased by 4.5 mm/yr to theaverage rate of 6.0 mm/yr (as predicted by IPCC)for the next century. (See Box 5 and Table 3.) (Infact, annual sea level rise would be less than thisamount during the first half of the century and

greater during the second.) If higher estimates ofsea level rise prove true, all wetlands could on bal-ance lose area. In some cases, marsh accretion ratesmay match the increase in sea level, but even suchwetlands will be placed at the limit of their capaci-ty to keep pace.

Although wetlands are clearly threatened bythese rates of sea level rise, quantifying the actualareal loss of wetlands that would result is difficult.The change in areal extent depends not only onrates of relative sea level rise and accretion, butalso on the composition and steepness of the shore,the presence of any such protecting structures asdikes or levees, and the presence of barrier islands.One study now under way at Butler University inIndiana has modelled impacts on coastal wetlandsat 93 sites based on: elevation data from topograph-ic maps, Landsat images of plant communities pres-ent at the sites, and measured or inferred rates ofrelative sea level rise and marsh accretion (Park etal. 1989).

Richard Park and his colleagues (1989) at Butlerexamined the potential impact of sea level rise

Box 5. The Growth and Evolution of Coastal Wetlands

How well coastal wetlands survive climatechange and resultant sea level rise depends uponthe rates of relative sea level rise and marshaccretion. Relative sea level rise is a function ofboth land submergence and real water level rise.Since both processes lower land surface relativeto water levels, it is often difficult to separatethe relative magnitudes of each. Global estimatesof sea level rise conceal a significant variation inrelative sea level change found in variousregions of the United States, ranging from over10 mm per year decline in the sea surface alongthe coast of southeastern Alaska to a 10 mm peryear rise along the northeastern Maine and Loui-siana coasts (Stevenson et al. 1986).

In Louisiana, a major underlying cause ofwetland loss is subsidence, or submergence ofthe land surface. Subsidence stems partly fromthe added weight of the sediments that havebeen deposited, as well as from natural patternsof sedimentation. But the withdrawal of gas, oil,and water from subsurface deposits, as well ascompaction by such man-made structures aslevees, roads, and buildings, have also signifi-cantly increased rates of subsidence.

In marsh accretion, the marsh surface buildsupward through sedimentation. In organic

sedimentation, the decay of organic matterbuilds up the marsh surface; in inorganic sedi-mentation, the second principal mechanism ofmarsh accretion, mineral sediments carried byrivers or tidal action are added to the marsh.

In the face of rising relative sea level, coast-al marshes may keep pace if vertical marshaccretion increases sufficiently. At the currentrate of sea level rise, most coastal wetlands ofthe East and Gulf Coasts of the United Stateshave kept pace with sea level rise (Stevenson etal. 1986). (See Table 3) Out of 18 U.S. wetlandsfor which sufficient data on accretion rates andrelative sea level rise are available, only foursites (encompassing the Mississippi River Deltaand Blackwater Marsh in the Chesapeake Bay)have not accrued sediment fast enough to keeppace with relative sea level rise.

How well coastal wetlands keep pace withsea level rise depends on how high the tidalrange is. In general, wetlands in regions withrelatively small tidal ranges have lower rates ofvertical accretion because less sediment istransported by tidal action (Stevenson et al.1986). By the same token, coastal areas withhigher tidal ranges are less vulnerable to sealevel rise.

23

Table 3. Comparison of Coastal Wetland Accretion Rates with Current and Predicted Rates of RelativeSea Level Rise in the United States. (Modified from Day and Templet 1989, Stevenson et al.1986)

Location

LouisianaDeltaic Plain

Chenier Plain

GeorgiaSapelo Is.Savannah R.

South Carolina

North Carolina

MarylandBlackwaterNanitoke

DelawareLewesLewes

New YorkFresh P.Flax P.

Connecticut

Rhode Island

Massachusetts

WetlandType

BrackishStreamsideBackmarsh

SalineStreamsideBackmarsh

Brackish

Saline

Saline

BrackishBrackish

SalineSaline

SalineSaline

Saline

Saline

MeanAccretion

Rate (mm/yr)

14.65.9

13.77.5

7.0

4.011.0

2.5

3.0

2.66.1

4.7>10.0

4.35.5

5.0

4.3

5.5

Relative SeaLevel Rise

(RSL, mm/yr)

11.011.0

13.013.0

12.0

2.52.5

2.2

1.9

3.93.2

2.22.2

2.22.2

1 9

1.9

0.9

NetGain/Loss(mm/yr)

+ 3.0-4.1

+ 0.7-5.5

-5 .0

+ 1.5+ 8.5

+ 0.3

+ 1.1

-1 .3+ 2.9

+ 2.5+ 7.8

+ 2.1+ 3.3

+ 3.1

+ 2.4

+ 4.6

Net Gain/Losswith 4.5 mm/yrIncrease in RSL

- 1.5- 8.6

- 3.8-10.0

- 9.5

- 3.0+ 4.0

- 4.2

- 3.4

- 5-8- 1.6

- 2.0+ 4.3

- 2.4- 1.2

- 1.4

- 2.1

+ 0.1

under three likely scenarios for the next century:50, 100, and 200 cm rise by the year 2100. Theyalso examined three scenarios for protecting coast-al lands from inundation. Under the first, all dryland is assumed to be protected from sea level riseby the establishment of dikes or levees. Under thesecond, only areas with residential and commercialdevelopment are sheltered. Under the third, only

areas already served by dikes or levees are pro-tected. These three scenarios for coastal protectionparallel the types of responses that policymakerscan use to address the likely impacts of sea levelrise on coastal biodiversity.

If the primary goal is to minimize impacts oncoastal biodiversity, coastal ecosystems should beallowed to migrate landward with rising sea levels

24

unhindered by new physical obstructions (scenariothree). In contrast, attempts to minimize impactson existing coastal infrastructure by building dikesand levees (scenario two) or even to protect all dryland from inundation (scenario one) would reducethe area available for coastal ecosystems displacedby the rising sea.

The results of Park's study show that under aconservative scenario of a sea level rise of 50 cmby 2100, over 26 percent of coastal wetlands inthe East and Gulf states would be lost if all dryareas are protected from inundation, 17 percentwould be lost if all residential and commercialareas are protected, and 14 percent would be lostif only currently diked areas are protected from in-undation. (See Figure 10 and Table 4.) In compari-son, their model predicts 11 percent of coastalwetlands will be lost over the same time at thecurrent rate of sea level rise (primarily losses oc-curring in the Mississippi River delta).10

At the higher rates of sea level rise predictedby some climate models, Park's study indicates thatthe impacts on coastal wetlands would increasedramatically. With a 1-meter rise by 2100, 46 to52 percent of coastal wetlands would be lost.

While the impacts on Louisiana would be particu-larly devastating—where a loss of 84 percent ofwetlands would be expected—most other regionswould also lose roughly one-third of their coastalwetlands. With a 2-meter rise over this period,some 61 to 70 percent of wetlands would be lost.These estimates of wetlands loss compare roughlyto estimates made by the U.S. Environmental Pro-tection Agency (26 to 82 percent loss under the100 cm scenario, 29 to 90 percent loss under the200 cm scenario) (Titus 1991).

kk

Some regions will be hurtmore than others if sealevel rises.

99

Some regions will be hurt more than others ifsea level rises. For example, if sea level rises by 50cm by 2100, wetlands in southern and westernFlorida are likely to keep pace with sea level rise

Figure 10. Predicted Wetland Loss by 2100 Based on Three Scenarios of Sea Level Rise

80

70_

60_

50-

40.

30_

20_

10 _

0

Level of Protection

LJ No Added Protection1 1 Development ProtectionLJ All Dry Land Protection

50 100

Sea Level Rise by 2010 (in Millimeters)

200

Source: Park, et al., (1989)

25

and may actually increase in area if not blockedfrom migrating landward. (See Table 4.) If no fur-ther barriers to landward migration are erected,wetland area could hold its own in the mid-Atlantic and Northeast states at this lower end ofpredicted sea level rise; but wetlands would be lostelsewhere, and in the northern Gulf states the arealost would increase 20-fold.

Regional differences are also apparent in theextent to which the construction of barriers willincrease the loss of wetlands. In regions like

Louisiana, where extensive wetlands project from arelatively short fixed coastline, the construction ofbarriers does not significantly increase the amountof wetlands that would be lost by 2100. In con-trast, in the northeast the area of wetlands lostwould increase nearly 5-fold under the 100-cm sce-nario if barriers were established around existingdevelopment. (See Table 4.) In general, Atlanticwetlands would be especially vulnerable to theprotection of dryland by dikes while wetlandsalong the gulf coast would be affected less.

Table 4. Regional Estimates of LosseScenarios of Sea Level Rise

AreaRegion Protected

NortheastAll Dry Land ProtectedDevelopment ProtectedNo Added Protection

Mid-AtlanticAll Dry Land ProtectedDevelopment ProtectedNo Added Protection

South AtlanticAll Dry Land ProtectedDevelopment ProtectedNo Added Protection

S & W FloridaAll Dry Land ProtectedDevelopment ProtectedNo Added Protection

LouisianaAll Dry Land ProtectedDevelopment ProtectedNo Added Protection

Other N. GulfAll Dry Land ProtectedDevelopment ProtectedNo Added Protection

CurrentArea

453

786

3,673

2,257

4,564

1,984

TOTAL: East and Gulf Coastsof United States

All Dry Land ProtectedDevelopment Protected 13,717No Added Protection

s of Coastal Wetlands Expected by the Year 2100(Modified from Park et al. 1989). Areas in square

Change in Wetland Area by 2100 with Sea Level

CurrentArea (Percent)

-27 (-6.0)

+ 177 ( + 22)

+ 40 (+ 1)

+ 92 (+ 4)

-1,804 (-39)

-13 (- 1)

-1,535 (-11)

50 cmArea (Percent)

-42 (- 9)-33 (- 7)+ 7(+ 1)

-263 (-33)- 1 7 ( - 2)-54 (+ 7)

-486 (-13)-121 (- 3)-25 (- 1)

-258 (-11)+ 147(+ 6)+ 216 (+10)

-2,209 (-48)-2,036 (-45)-2,006 (-44)

-421 (-21)-297 (-15)-265 (-13)

-3,679 (-26)-2,453 (-18)-2,019 (-14)

100 cmArea (Percent)

-77 (-17)-74 (-16)-15 (- 3)

-434 (-55)-252 (-32)-196 (-25)

-1,377 (-37)-1,103 (-30)

-998 (-27)

-959 (-42)-549 (-24)-537 (-24)

-3,585 (-78)-3,856 (-84)-3,857 (-84)

-754 (-38)-805 (-41)-787 (-40)

-7,186 (-52)-6,639 (-48)-6,390 (-46)

under Variousmiles.

Rise Indicated

200 cmArea (Percent)

123 (-27)128 (-28)157 (-35)

611 (-78)492 (-63)452 (-57)

2,157 (-59)1,898 (-52).1,777 (-48)

1,257 (-56)788 (-35)730 (-32)

4,350 (-95)4,343 (-95)4,345 (-95)

1,090 (-55)1,055 (-53)1,043 (-53)

9,588 (-70)8,704 (-63)8,416 (-61)

26

Significant changes in community compositionof wetlands may be in store under various sce-narios of sea level rise (Park et al. 1989). Along theMid-Atlantic Coast, vegetated wetlands are ex-pected to decrease in area while tidal flats in-crease. In the southeastern states, from NorthCarolina to Texas, the relative (and absolute) areaof mangroves is likely to increase, while saltmarshand tidal freshwater marshes would decrease.

An important influence on wetlands loss in theUnited States, particularly on the East Coast, areever shifting barrier islands. In theory, barrier is-lands migrate landward while maintaining theirtopographic profiles as sea level increases. Wavesmaintain the barrier island profile by redistributingsediments onto the back of the barrier as the sea-ward side erodes. However, on barrier islands ex-periencing development pressure, physical struc-tures prevent the landward transport of sand andthe sand that is transported landward tends to bebulldozed back to maintain the beachfront profile.Overall, efforts to stabilize barrier islands have notbeen highly successful, and such artificial structuresas seawalls and groins have usually accelerated theremoval of beach sediments by wave action (El-Ashry 1971, Meyer-Arendt and Davis 1988).

As barrier islands disintegrate and adjoiningtidal inlets widen, marine wave action penetratesfurther into the formerly protected tidal marshes.While the increased wave action does increase tid-al sedimentation rates, the erosion of wetlandscaused by increased wave action is more than off-setting (Meyer-Arendt 1990). Moreover, positivefeedback tends to speed barrier island erosion: aswetlands are converted to open water, the volumeof water in the bay increases. Because more wateris then moved in and out of the bay with thetides, the ends of the barrier islands are erodedand the tidal inlets are widened.

Can wetlands keep pace with sea level rise?Even conservative projections of the sea level riseexpected during the next century imply strains onU.S. coastal wetlands' ability to maintain their area.Under the IPCC's conservative "best estimate" sce-nario, nearly twice as much coastal wetland areawill be lost over the next century as would other-wise be the case. Over the range of plausible esti-mates for sea level rise by the year 2100 (0.5 to 2meters), some 15 to 70 percent of the remainingcoastal wetlands on the East and Gulf Coasts of theUnited States could be eliminated.

Coral Reefs

Both sea level rise and changing water temper-atures will influence U.S. coral reefs located in

southern Florida, on small isolated banks in theGulf of Mexico off Louisiana and Texas, and offPuerto Rico and Hawaii. At current rates, sea levelrise (1 to 2 mm/yr) does not inhibit coral reefs' up-ward growth, estimated to be roughly 10 mm peryear (Grigg and Epp 1989). But sea level rise underscenarios of global warming is likely to equal orexceed these limits.

High rates of sea level rise during the Pleisto-cene deglaciation (estimated at 10 to 20 mm peryear) prevented most corals from keeping pacewith sea level, and many coral islands drowned(Grigg and Epp 1989).n Corals tend to be mostsensitive at the northern end of their ranges,where cooler water temperatures and lower lightintensity slow growth. Maximum rates of net reefgrowth decrease from 10 mm/yr near the equatorto 1 mm/yr at higher latitudes (Grigg and Epp1989). Because many corals in the United Statesare at the northern limit of their range, they tendto grow relatively slowly.

Accordingly, sea level rise of the magnitudenow predicted, if maintained for several centuries,could cause a significant loss in the areal extent ofcorals in the United States. However, some scien-tists have argued that in the short term (50 to 100year's), sea level rise and sea temperature warmingcould actually benefit corals (Buddemeier andSmith 1988). They suggest that sea level rise willrejuvenate depauperate reef flats near the oceansurface and that higher coastal water temperaturescould increase the range of U.S. and other highlatitude corals.

Recent evidence of coral ' 'bleaching'' thoughtto be caused largely by unusually high water tem-peratures provides reason to doubt these putativeshort-term benefits of climate change and amplereason to believe that rapid climate change couldseriously harm the world's corals. Coral bleach-ing—the loss of the mutualistic algae living withthe coral—is believed to stem from such stresses assedimentation, pollution, or unusually cold orwarm water temperatures. During bleachingevents, corals lack the primary energy needed togrow, and if bleaching is frequent or protracted,the coral ultimately dies (Goreau 1990a).

Coral bleaching has been observed sporadicallyaround the world for decades, but all such casesinvolved such locally confined stresses as muddyriver water plumes or high temperatures caused bypoor water circulation. In the past decade, how-ever, coral bleaching has taken place on an un-precedented scale. Major bleaching episodes at sitesaround the world have taken place in 1980, 1983,1987-88, and 1990 (Goreau 1990a, Williams andWilliams 1990, Williams 1990). In many cases, the

27

corals died as a result (Goreau, Personal Communi-cation, October 10, 1990). In the Caribbean, all ofthe major bleaching episodes in the 1980s havebeen associated with above-normal water tempera-tures (Goreau 1990b).

At any latitude, a water temperature rise of 2 °to 3°C above normal can cause bleaching. If watertemperatures increase slowly over a number ofyears, corals will probably adapt physiologically tothe new environmental conditions. But a rapid ele-vation in sea temperature—a rise like that pre-dicted to accompany global warming—may cause acoral die-off. Unfortunately, the pattern of the1980s suggests that such a situation may already beupon us.

Impacts on Coastal Species Diversity

Rare and Endangered Species

As discussed in Chapter II, a significant num-ber of rare, threatened, and endangered species de-pend on or use the coastal fringe. The Nature Con-servancy (TNC) lists 80 species and subspeciesrestricted to below the 10 foot contour as rare, im-periled, or critically imperiled. (See Table 1.) Manyof the animals and other species in this zonewould have no physical problem dispersing tohigher elevations at the pace of sea level rise, butplants and any species already threatened or en-dangered would. Many of these species are consid-ered endangered precisely because their habitat hasbeen lost, so further losses could prove disastrous.Moreover, coastal development adjacent to criticalhabitats for endangered species could block thedispersal of species if sea level rises. Thus, the im-pacts of sea level rise, particularly the loss of wet-lands, will significantly increase extinction threatsand will create new candidates for species to belisted as rare and endangered.

A more precise assessment of the potential im-pacts of sea level rise on coastal species diversitycan be obtained by examining impacts state bystate. (See Table 5.) Although the global extinctionof a species represents an ultimate and irreplace-able loss, the loss of species from a portion oftheir range—known as extirpation—can underminethe region's local species diversity and the geneticdiversity of the species more generally. Then too,local extirpation is a step toward global extinction.For this reason, examining trends in the loss ofspecies from portions of their ranges can putthreats to species diversity into perspective.

A substantial number of species are at risk ofextirpation from individual states as a result of globalwarming. In Oregon, Massachusetts, Maryland,

North Carolina, and Florida, some 41 species thatutilize the coastal fringe are federally listed asglobally endangered or threatened and another128 are candidates for listing.12 (See Table 5.) Butthe picture is more disturbing at the state level. Inthese five states alone, TNC has designated some461 coastal species found beneath the 10-foot con-tour to be at risk of local extirpation (rare, im-periled, or critically imperiled) and has found thatbetween 3 and 70 species considered rare at thestate level are restricted in their habitat use towithin 5 feet of sea level.13 (See Table 5.) Withinthese states, Florida's vast area of low-lying wet-lands holds the most species at risk, while Ore-gon's steep coast is home to the least.

As populations utilizing the narrow coastalband are subjected to the continuing threats of de-velopment from above while their habitat shrinksfrom sea level rise below, threats to species diver-sity grow. Sea level rise is certain to contribute tothe extirpation of species in individual states andmay well contribute to the extinction of somecoastal species in the United States.

Coastal Plant Communities

While the status of individual species in coast-al regions provides a good measure of threats tospecies diversity, judging threats at the level ofplant and animal communities is far more diffi-cult.14 To begin with, the designation of a commu-nity or ecosystem is much more subjective thanthe designation of a species. Each species is a sepa-rate and unique entity, while communities are incontinual flux as new species immigrate in or dieout locally. Moreover, community processes andspecies interactions change continually as speciesevolve or co-evolve in each other's presence. Inthe absence of comprehensive data, the likely im-pacts on coastal communities nationwide cannotbe evaluated confidently, but the following casesdo indicate the range of impacts.

One end of the spectrum is represented by theplant community found on three bird rookeries offthe coast of Maine. Machias Seal Island, MatinicusRock, and Gull Rock are each small (less than 12acres) islands, located 8 to 19 miles from shore.The plant community for the three islands amountsto only 110 species none of which are currentlyfederally listed or candidate species. Only five areconsidered rare at the state level by TNC, and onlythree of these are restricted to within 10 feet ofsea level. Accordingly, the impact of sea level riseon this community is likely to be fairly small.

At the other end of the spectrum are the bar-rier island communities common along the southern

28

Table 5. Federal Threatened and Endangered, and State Rare Species in Coastal Regions.State totals refer to the number of species determined by TNC to be "Critically Imperiled,""Imperiled," or "Rare or Uncommon" in that state. A species may be common in otherstates and still be listed if rare in the particular state. Superscript indicates the number ofsubspecies (or varieties) included in the total.

Region Birds MammalsReptiles

Amphibians Fish Plants Total

I. Federally Listed (Endangered, Threatened) Species Found Within 10 Feet of Sea Level(Candidate Species in Parentheses)

OregonMassachusettsMarylandNorth CarolinaFlorida

4(2)021

82 (52)

00l i

087 (97)

0001

9(93)

0000

l(2i)

(2)0

1(12)(7)

12i(83u)

4(4)0

4(12)2(7)

38(108)

II. Rare Species Restricted to Within Five Feet of Sea Level

OregonMassachusettsMarylandNorth CarolinaFlorida

011110

193

0000

0001

II4

00002 i

32

913810274

320491170

III. Rare Species Found Within 10 Feet of Sea Level

OregonMassachusettsMarylandNorth CarolinaFlorida

711716

1358

01l i0

1915

1121

011091

8221

1O22

19I67 i 8

1642

12221

258

Atlantic seaboard of the United States. AssateagueIsland is a 37-mile long, 17,652-acre, barrier islandoff the coast of Maryland and Virginia with a maxi-mum elevation of 25 feet. The island is not threat-ened with submergence from sea level rise in thecoming century, but the rising sea level is likely tocause it to shift landward, which could reduce itssize. Assateague and adjacent Wallops Island con-tain 589 plant species, of which 27 percent arenon-native species introduced in recent decades.Among the plants on the islands, two species arecandidates for federal listing and four species areconsidered by TNC to be very rare or imperilednationally.

Using the greater resolution provided by anexamination of the rarity of species at the level ofthe state, Assateague Island can be seen to be quiteunique in its species composition. Some 23 percent(97) of the native species on Assateague and Wallops

islands are considered rare, imperiled or criticallyimperiled in the state of Maryland or Virginia byTNC.15 And many of these species live close to thesea, where they stand to be further threatened bysea level rise. Twelve of the rare and imperiledspecies are restricted to elevations of less than 10feet throughout their range. Moreover, another 16species that are currently not at risk in the twostates are also restricted to these low elevationsand could become rare if coastal habitats changedsignificantly.

If sea level rises at the high rates suggested bysome scenarios of climate change, the species com-position of Assateague's plant community is likelyto change dramatically. Even if none of the specieswere to become globally extinct, the extirpation ofa number of species from Assateague itself wouldmean that the community that now exists will beno more.

29

Fisb and Wildlife Population Trends

Coastal fish and wildlife populations are in-fluenced by a variety of factors, including bothbreeding and non-breeding habitat loss and degra-dation, pollution, harvesting, and reduction infood availability. Predicting the impact of climatechange generally on these populations, or even the

kk

Predicting the impact ofclimate change on coastalfish and wildlife popula-tions or even the specificimpacts of a loss of coast-al wetlands on thesepopulations is fraughtwith difficulty.

99

specific impacts of a loss of coastal wetlands onthe populations, is thus fraught with difficulty.

For instance, the dramatic decline in wadingbird populations in south Florida, from well over 1million birds 100 years ago to the current popula-tion of 16,000 breeding birds, is due in part tohabitat loss and degradation, but plume huntingalso took its toll at the turn of the century andwater management practices have been linked tothe decline more recently (Harris 1988, Walters etal. In Press). Similarly, shrimp abundance tends tobe greater in areas with more wetland vegetation(See Figure 11; Turner 1977, Turner and Boesch1988), but this general trend doesn't help inpredicting the impact of wetlands loss on shrimpabundance because the impact depends on the pat-tern of wetland loss. Despite the massive losses ofcoastal wetlands in Louisiana during the past 30years, landings of such commercially importantspecies as shrimp have increased. No doubt in-creased fishing effort is partly responsible, but an-other factor is the increased length of marsh shore-line that has resulted from canal construction,

Figure 11. Relationship of Wetland Area to Shrimp Yield in 23 Sites Worldwide

60-

50-

40-

% 30.O

20_

10-

100 200 300

Wetland Area (1000 Hectares)

400 500

To remove the influence of latitude (temperature and sunlight) on productivity, yield was mathematically adjusted to acommon latitude of 15° using the equation determined by Turner (1977) for the relationship of yield/acre with latitude.

Source: Adapted from Turner, (1977)

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along with growing open areas in the back-marshthat has allowed shrimp access to a larger portionof the marsh (Browder and Rosenthal 1989).

Data relating wetland loss to productivity forother fisheries is largely anecdotal, though thought-provoking. For example, fish harvest declined in aFlorida estuary following wetland loss to dredging,and the whiting fishery in Western Port, Australiadeclined by about 80 percent in size coincidentallywith the loss of sea grass beds in the bay (Turnerand Boesch 1988).

Despite the difficulties associated with calcu-lating the impact of wetland loss on fisheries, theNational Marine Fisheries Services has estimatedthat the loss of estuarine marshes between 1954and 1978 (a loss of roughly 8 percent of marsharea) cost the United States fishing industry some$208 million per year (Tiner 1984). Using this as abenchmark, it can be seen that a reduction ofcoastal wetland area by a further 20 to 70 percentduring the next century could amount to annuallosses in excess of $ 1 billion.

Other Impacts of Climate Change

Besides sea level rise and ocean temperaturechanges, other changes associated with globalwarming are likely to have significant impacts oncoastal biodiversity. However, since global climatemodels still do not agree on regional details ofchanges in precipitation, temperature, wind speed,and storm frequency, it is even more difficult toaccurately predict the impacts of these factors thanthose of sea level rise.

Precipitation and Freshwater Runoff. Changesin precipitation patterns caused by global warmingwill alter salinity gradients in coastal estuaries.Freshwater inflow provides a direct source ofnutrients to estuarine ecosystems, as well as asource of sedimentation. In six estuaries in Texas,for example, the major source of carbon, nitrogen,and phosphorous was freshwater inflow (Arm-strong 1982). Moreover, the pattern of use of estu-aries by finfish and shellfish is often a function ofthe seasonal pattern of freshwater inflow. Interan-nual variation in the harvest of a large number ofestuarine-dependent fisheries has been correlated withvariations in freshwater inflow (Cushing 1982).

Anticipating the effects of climate change onfreshwater inflow is clearly problematic, not onlybecause of the uncertainty inherent in climatemodels, but also because flow patterns into nearlyevery U.S. estuary are affected by upstream humanuses, dams, and diversions. In general, though, in-creased freshwater runoff would increase produc-tivity in coastal areas (especially if the normal

timing of flows does not change) and decreasedrunoff would decrease productivity.

Temperature. Increased air temperature andassociated water temperature will alter the range ofa number of coastal species. For example, thenorthern limits to the distribution of mangroves inthe southeastern United States are controlled bywinter temperature (Markley et al. 1982, McMillanand Sherrod 1986). Similarly, the endangered WestIndian (Florida) manatee (Trichechus manatus)needs water that is 22 °C or warmer during winter.The ranges of other tropical plant and animal spe-cies will likely extend northward as a result ofwater temperature increases, while the ranges ofnorthern estuarine species will contract.

Atmospheric Carbon Dioxide (CO^ Atmos-pheric CO2 concentrations are likely to doublefrom pre-industrial levels by 2075. Because CO2 isthe base from which all plants build carbohydrates,increased concentrations may "fertilize" someplants, increasing their growth rate. Moreover,since not all plants follow the same chemical path-way in photosynthesis, elevated CO2 is likely to fa-vor growth in certain species more than others,perhaps altering community compositions. For ex-ample, the experimental CO2 enrichment of a natu-ral coastal wetland increased growth rates of bothbulrush (Scirpus olneyi) and cordgrass (Spartinapatens), but the effect was greater on bulrush, thespecies utilizing what is known as a "C3" photo-synthetic pathway, than on cordgrass, which usesa "C4" pathway. Presumably, the bulrush couldoutcompete cordgrass if more CO2 becomes avail-able. More generally, this experiment suggests thatchanging CO2 concentrations will further alter thespecies composition of coastal communities.

Ocean Currents. Ocean currents such as theGulf Stream are likely to be affected by changes intemperature and wind patterns predicted to accom-pany global warming (Bakun 1990, Mikolajewicz etal. 1990). Because forecasting the magnitude ordirection of such changes in ocean currents isfraught with uncertainty, even potential effects oncoastal ecosystems are hard to gauge. One studyhas suggested, however, that by intensifying thealongshore windstress on the ocean surface, green-house warming could accelerate coastal upwelling(Bakun 1990). Such increase in windstress has beendocumented off California for the period 1946 to1988. Increased intensity of an upwelling system islikely to increase productivity in those waters; itcould also change the composition of nearshoremarine communities.

Disturbance Patterns. Coastal wetlands aresubject to a variety of episodic disturbances, in-cluding hurricanes, lightning, floods, and fire.

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Other climatic influences on wetlands such as rain-storms, wave action, cold spells, or sustainedstrong on-shore or off-shore winds may also beconsidered "disturbances" when their intensity ex-ceeds the standard ranges encountered over dec-ades. A 100-year flood or a 100-year cold-spell, forexample, would be considered a "disturbance" toan ecosystem.

Global warming may alter climatic variability,thus subjecting coastal ecosystems to higher (orlower) frequencies of disturbance. Although the ex-pected rise in sea surface temperatures associatedwith global warming has stimulated considerablespeculation that hurricanes may grow more fierceor numerous in coming decades, this conclusionhas not been supported by climate modelling andscientists don't agree on how climate variabilitywill change under global warming scenarios (EPA1989).

Despite the lack of a consensus on whatchanges in disturbance patterns are in store, it isknown that in almost all ecosystems, disturbance isa major determinant of species composition andecological processes. Thus, even in the absence ofa significant increase in temperature, coastal eco-systems could be profoundly affected by changesin the variability of climatic patterns.

For example, hurricanes, some with long-lasting impacts, are a part of coastal life in thesoutheast United States. The saline tide generatedby Hurricane Audrey, which struck Louisiana in1957 killing 160,000 ha of sawgrass (Cladium

jamaicense), converted almost all of this habitat toopen water by the following year (Valentine 1977).Much of this area was revegetated by 1972, butbulltongue (Sagittaria falcata) and water lily(Nymphaea odorata) became the dominant species,not sawgrass. In turn, these vegetation changes af-fected the animal community composition. Ducksthat once fed on the sawgrass seeds used themarsh minimally for several years following the

hurricane. Once annuals became established, ducksbecame more abundant than before, but as theperennial community took hold waterfowl usedropped.

Hurricanes also influence the deposition ofsediments on coastal wetlands. A single small hur-ricane can deposit 22 mm of sediment some 7 kminland from the ocean shore (Rejmanek et al.1988). Because the grasses and sedges that domi-nate coastal marshes in the United States can easilygrow through the sediment deposits, communitycomposition remains more or less the same after ahurricane. But in mangrove forests, sedimentmovement by hurricanes is a major cause of treemortality. Hurricane Donna killed over 40,000 haof mangroves in south Florida in I960 (Craigheadand Gilbert 1962).

The intense rainfall of hurricanes also affectsecosystems by washing tremendous amounts of or-ganic matter into estuarine waters from freshwaterand coastal marshes. Large-scale fish die-offs fol-lowing the passage of hurricanes have been at-tributed to oxygen depletion caused by decompos-ing organic matter that was washed into theestuary. The frequency of extreme temperaturesmay also influence the species composition ofcoastal ecosystems, as for example, infrequentsevere winter freezes in Florida Bay limit the de-velopment of coral reefs along the Florida Keys(Jaap 1984).

Major disturbances are already relatively fre-quent in coastal wetlands. Wind tides 1.5 metersabove normal (generally associated with tropicalstorms or hurricanes) occur approximately everyeight years in Louisiana delta marshes and accountfor major episodes of sedimentation (Gosselink1984). In south Florida, coastal habitats experiencehurricanes at regular intervals of about three tofive years (Meeder and Meeder 1989). Any changein this disturbance regime may alter coastal com-munity composition.

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IV. PUBLIC POLICY AND THE CONSERVATIONOF COASTAL BIODIVERSITY

Coastal ecosystems are vitally important to theUnited States. They provide the foundation of itsfishing and sport-hunting industries, habitat forlarge numbers of species, pollution-filtration sys-tems, flood control mechanisms, recreational desti-nations, and storm buffers. Apart from our ethicalresponsibility to ensure that species in coastal eco-systems are not driven to extinction, preservingthese ecosystems makes sense from a practicalstandpoint as well: if their biodiversity is degradedthey can't provide valued services. For this reason,concern over the conservation of biodiversity mustgo hand in hand with the design of sustainable pat-terns of use of these ecosystems.

From one standpoint, the history of protectionof coastal ecosystems in the United States is aremarkable success story. Following two hundredyears of destruction and alteration that culminatedin the loss of nearly 10 percent of U.S. coastalwetlands in the twenty years prior to 1974 alone,losses of coastal wetlands have been sharply cur-tailed. Less pollution is discharged into coastal eco-systems now too, and the establishment of coastalprotected areas has further reduced environmentalthreats.

Unfortunately, this sharp reduction in the rateof wetlands loss took place only after most coastalwetlands in some U.S. regions had already beenlost. Moreover, trends in wetland acreage may un-derstate the true impact on coastal ecosystems, in-cluding the degradation of wetland functions orthe more pronounced loss of the ecologically im-portant shoreline expanse of wetlands. And suchecosystems as barrier islands, mangrove swamps,beaches, and coral reefs, have not been closelymonitored over this period and by all appearanceshave been significantly degraded. In future years, itwill also be increasingly difficult for coastal ecosys-tems to hold their own: conventional pressures oncoastal ecosystems will mount dramatically as bothhuman populations and recreational use of coastalecosystems grow.

If global warming exacerbates these threats, aspredicted, wetland ecosystems and their associatedspecies may not be able to keep up. Depending onhow fast sea level rises and how much dry land isprotected, 14 to 70 percent of the remaining coast-al wetland acreage in the United States will be

eliminated. And the impacts of climate change willnot be restricted to sea level rise, but will also in-clude changes in air and water temperatures,precipitation patterns and amounts, coastal cur-rents, and the frequency of storms or fires. Somewetlands could benefit from some combination ofthese events, but the overall impact on U.S. coastalecosystems will be negative. Climate change is like-ly to substantially elevate threats of extinction orextirpation of coastal species, and decrease popula-tions of wetland-dependent species. It could alsoharm coral reefs. Even today, coral bleaching, ten-tatively linked to global warming, seems to threat-en the nation's few coral reefs.

kkComplacency in the faceof prospects for coastalbiodiversity in the UnitedStates is a mistake.

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Complacency in the face of prospects forcoastal biodiversity in the United States is a mis-take. Climate change will exacerbate already sig-nificant pressures on coastal ecosystems. A varietyof indicators, including the numbers of threatenedand endangered species reliant on coastal habitats,trends in productivity of coastal fisheries, trends inwaterfowl populations, and trends in other wildlifedependent on coastal habitats, all suggest thatwhile wetland acreage (outside of Louisiana) maybe stabilizing, the biological diversity of coastalecosystems already faces serious threats.

For nearly a decade, scientists and policymak-ers have studied the possible impacts of future sealevel rise on coastal development and coastal eco-systems and debated how best to respond. Thusfar, little of this work has been translated intochanges in federal or state policy. Several states arebeginning to consider policy changes in anticipa-tion of a rising sea, and Maine has even enactedlegislation. But, overall, the framework of policiesguiding U.S. coastal development is changingrapidly enough to meet the challenge of coastal

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development, but too slowly to save coastalecosystems.

Public Policy Options in the Face ofUncertainty

A range of options is available to decision-makers for responding to the impacts of climatechange, particularly sea level rise, on coastal devel-opment and coastal ecosystems.16 At one end ofthe spectrum is retreat—deciding to construct nomore dikes, levees, or any other barriers to thesea. This is by no means a "do-nothing" policyoption since no such retreat will be possible unlesssteps are taken today to prevent the developmentof land likely to be submerged in the future. At theother end of the spectrum is a policy of complete-ly protecting coastal development against sea-levelrise. Between these extremes are many other poli-cy strategies. With a "do-nothing" approach, sealevel rise and related climatic events lead tohaphazard coastal abandonment and protection,with unknown economic and biological costs. Al-ternatively, prescribed coastal development couldbe accommodated to sea level rise over time. Forexample, buildings can be raised on pilings andmoved back as the sea advances.

The various responses would have differentimpacts on coastal biodiversity, and each optionalso poses quite different legal, economic, and po-litical problems. The pure retreat option would, intheory, best protect coastal ecosystems becausethose ecosystems would be free to migrate land-ward without human impediment. The economicand political costs of abandoning current and fu-ture coastal developments, however, make thepure retreat approach untenable. For all options,the substantial uncertainty surrounding the physi-cal and biological impacts of climate change posefurther obstacles to practical policy.

it

Of the three general typesof policy responses avail-able, only one—actingnow to make adaptationlater possible—can ensurethe protection of coastalecosystems.

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Balancing such obstacles against a need to pre-serve coastal ecosystems, what are the most effective

and politically realistic policy options? As the fol-lowing review shows, of the three general types ofpolicy responses available, only one—acting nowto make adaptation later possible—can ensure theprotection of coastal ecosystems.

Pay-as-You-Go Biodiversity Conservation

In 1987, a National Research Council study(NRC 1987) of the impacts of climate change oncoastal engineering policy concluded that "Con-struction of almost any conceivable protectionagainst sea level rise can be carried out in a rela-tively short period of time" and that, therefore,"if a substantial increase [in sea level] should oc-cur, there will be time to implement protectivemeasures." For several reasons, this "pay as yougo" policy option is commonly suggested as an at-tractive way to respond to the many uncertaintiesinvolved in predicting how climate change will af-fect coastal development (NRC 1987).

The "pay as you go" option does have severaladvantages:

• Since economic impacts of sea level rise willbe felt decades into the future, the costs ofbuilding dikes, levees, or other containmentstructures seem small when economically dis-counted back to the present.17 These discount-ed costs often appear comparable to the per-ceived high costs of acting now to preventdevelopment on coastal land, so economic dis-counting favors a do-no thing-no w approach.18

• Preventing the expansion of coastal infrastruc-ture now is politically difficult, while doingnothing now is par for the course in a policy-making system almost incapable of lookingmore than a few years into the future.

• Engineering "solutions" to the problems of sealevel rise are relatively well understood, theyare easy to plan, and their costs can be easilyquantified.19 Such alternatives as zoning res-trictions, in contrast, are difficult and timeconsuming to carry out. Similarly, because it'seasier to quantify the first-order costs of en-gineering solutions than their societal and eco-nomic costs (including the loss of biodiversi-ty), a bias toward engineering solutions results.For some coastal ecosystems, the pay-as-you-

go approach might be implemented as a policy of"no net loss." For example, since wetland man-agers have had increasing success restoring or evencreating wetland ecosystems, future wetland lossdue to sea level rise could be offset by creatingnew wetland habitat. To work, however, actionsto mitigate wetlands loss would have to extendwell beyond existing project-related mechanisms,

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such as the issuance of a Section 404 permit underthe Clean Water Act. Establishing a federal andstate commitment to counter wetlands loss specifi-cally resulting from sea level rise and global warm-ing would require legislation.

More generally, though, the "pay as you go"approach to global climate change is not likely tohelp conserve coastal biodiversity. Few coastalecosystems can be readily re-created, and artificial-ly created wetlands or other coastal ecosystemsmay not be able to provide all of the services thatnatural ecosystems do. Adopting such a strategywould most likely result in a patchwork of "habi-tats" that meet some areal and composition re-quirements but lack rare species, continuity withadjacent ecosystems, and certain natural ecosystemfunctions.

An additional problem with the "pay as yougo" approach is that the belief that engineering so-lutions will be available to address rising sea levelseventually becomes a self-fulfilling prophecy. With-out anticipatory policies, development will pro-ceed apace in coastal areas. By mid-century, whenrising sea levels will become a significant threat tocoastal development, the expensive coastal infra-structure added over six decades will increase thejustification for physically protecting the shores.Already, along the Atlantic Seaboard, steps taken toprotect developed coastal areas from sea level risewould significantly increase the expected loss ofwetlands if climate changes as predicted. (SeeTable 4.) If coastal development is not restricted,wetlands loss will be even more severe. If it isdecided to protect all dry land, for example,projected wetlands loss will double by 2100. (SeeTable 4.)

The impacts of engineering solutions on coast-al biodiversity go beyond simply impeding themigration of coastal wetlands. Dams and saltwaterintrusion barriers that might be constructed to re-duce impacts on water supplies and coastal devel-opment would exacerbate the harm to coastalecosystems. Since such barriers would retain river-borne sediments, they would slow the growth(accretion) of deltaic wetlands. Similarly, channel-ing rivers for flood control in the face of rising sealevels would block the flow of sediments towetlands.

Clearly, the "pay as you go" policy responseto sea level rise, while highly desirable from thestandpoint of deferring costs until events categori-cally prove them necessary, does not meet needsfor biodiversity conservation. Biodiversity cannotbe conserved by means of the relatively quicktechnological fixes that may protect cities andother coastal developments. Needed instead are

policies that meet current threats to coastal ecosys-tems and enable wetlands and other coastal eco-systems to adapt to expected shifts in the nation'scoastline.

Fleeing the Rising Sea

The option of pure retreat clearly offers coast-al biodiversity the most opportunity to adapt tochanging environmental circumstances. Withouthuman interference, ecosystems could move land-ward and enjoy the greatest likelihood of remain-ing intact. Even retreat, however, would not leavecoastal ecosystems unscathed: if sea level rises rela-tively rapidly, some 14 to 60 percent of wetlandarea on the East and Gulf coasts—an area largerthan Rhode Island and potentially as large asMassachusetts—would still be inundated. (See Table4.) Nevertheless, only policies designed to slow therate of climate change itself would do more tominimize the impact on coastal ecosystems.

Yet, however great their conservation poten-tial, the zoning, landuse, and land ownershipchanges needed to make large-scale retreat possibleare both economically and politically infeasible.Three problems stand out in particular:

• Governmental and non-governmental organiza-tions lack the financial resources needed tocondemn or purchase the tens of thousands ofsquare kilometers of land that might be neededfor future wetlands or other coastalecosystems.

• Preventing the development of private lands,or denying owners the right to protect theirproperty through seawalls or other measures,might well be seen as an unconstitutional tak-ing of property, even if it were politicallypalatable (Fischman 1990). Similarly, regulatinglandowners' freedom to develop their proper-ty, thus lowering its future purchase price forthe government, could also constitute an un-constitutional taking (Sax 1989).

• Preventing development on many coastal landsdecades in advance of possible ocean en-croachment is perceived as an economicallyinefficient use of a scarce resource (shoreline)with high opportunity costs and few economicbenefits (Titus 1991). In principle, these landscould be used prior to inundation and stillprovide suitable habitat when the time camefor them to be abandoned.Even if pure retreat appears infeasible on a

large scale and economically inefficient over thelong term, it would probably go farther than anyother option toward maintaining certain criticalcoastal habitats since it avoids the problem of later

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having to abandon coastal property developednow. It thus makes sense for policymakers andconservancy organizations to block the further de-velopment of areas landward of important coastalwetlands, including the habitats of endangered orrare species.

kk

Even if pure retreat ap-pears infeasible on a largescale and economically in-efficient over the longterm, it would probablygo farther than any otheroption toward maintain-ing certain critical coastalhabitats since it avoids theproblem of later having toabandon coastal propertydeveloped now.

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Acting Now to Make Adaptation LaterPossible

The most politically and economically efficientway to conserve biodiversity while meeting otherpolicy objectives is neither protection nor retreat.Far preferable to either are innovative policy op-tions that meld the goal of short- to mid-termcoastal development with the long-term goal ofconserving wetlands and other coastal ecosystems.All such options currently attempt to institutional-ize the assurance that current and future develop-ment will make way as necessary for migratingecosystems (Titus 1991). Proponents of these so-called "presumed mobility approaches" argue thatthey allow continuing economic use of coastaldrylands, while simultaneously keeping them avail-able for coastal ecosystems when the time comes.The various approaches being discussed include:

• Not interfering with the development ofcoastal property, but simply prohibitingthe construction of bulkheads or othermeasures to impede ocean advance (Titus1986, Titus 1991, Fischman 1990). Currentlandowners might not object to such restric-tions considering that property loss would oc-cur far into the future, if ever.20 Of course, fu-ture landowners could argue many years fromnow that such a regulation constituted a

regulatory taking and should be overturned—adefinite problem with this approach.21

• Combining discretionary permittingprocesses with bans of bulkheads andother landuse restrictions. To the extentthat building a beach house or other structureis a privilege rather than right,22 governmentswould certainly be able to impose conditionson building, remodelling, or repair permits. A"presumed mobility" clause could, for in-stance, legally prevent the landowner fromtaking steps that might impede ocean en-croachment. Under these circumstances, de-velopers would have incentives to designhouses that could be easily moved, thus lower-ing the future costs of adaptation.

• Fundamentally changing the nature ofland ownership along coastal zones.Ownership could be taken through govern-mental eminent domain and then leased backto the original landowners for a specified peri-od on condition that no steps would be takento counter sea level rise. Landowners wouldbe in a much weaker position to object to theend of the lease than if they still owned theland (Titus 1991), though the governmental ac-quisition of the land in the first place posesdaunting problems of legal authority and en-tails high compensation costs (Fischman 1991).Since leasing has never been attempted at thisscale, it would also pose major informational,legal, and organizational problems of its ownin coming years.

• Large-scale purchasing of upland wet-land conservation or "flowage ease-ments" by governments or by conserva-tion groups. Considering the landowner'sdiscounted cost of losing land in the distantfuture, the purchase of such a right ought tobe inexpensive, probably less than 1 percentof the current market value of the land (Titus1991). Taking ownership of the easement outof governmental hands could make the processsignificantly less susceptible to political and le-gal reversal at later dates. Courts rarely inter-fere with legally drafted deed provisions, soforced abandonment when the time comesought to be largely immune to courtchallenges.

• Use the public trust doctrine to enforcethe public's right to wetland conservationon private property. The public trust doc-trine holds that the public retains certain rightswith respect to tidal and other periodically orsometimes submerged lands, including coastalshorelines. It is not clear, however, whether

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government has a responsibility to act to safe-guard public trust wetland rights, or whetherprivate responsibilities under the public trustdoctrine extend to ensuring that wetlands donot disappear under rising seas (Fischman1991).

The success of most of these options dependson two key assumptions. One is that landownersand courts will discount the future value of coastalproperty. If so, measures can be put into place toprotect coastal ecosystems (prevention of bulk-heads, purchase of easements) at a relatively lowcost today (both politically and economically) sincethe net present value of the action is low. The sec-ond assumption is that future landowners facedwith losing the land will not succeed in reversingthe policies established today. Both of these as-sumptions are somewhat tenuous given the politi-cal pressure that can be brought to bear on land-use planning in a crisis.

To some extent, the nature of climate changeitself is likely to influence future political decision-making significantly. If sea level rise is incremen-tal, claiming a house here and a house there overtime, political constituencies might have difficultyforming around the issue of reversing policiesagainst protecting the land being lost. But if cli-mate change is experienced as, say, intense stormsand tidal surges, political pressure could easily bebrought to bear to protect property interests. InChatham, Massachusetts, a small group of deter-mined landowners got policies against coastaldefenses overturned when it became clear theywere about to lose their houses through coastalerosion (Fischman and St. Amand 1990). In the af-termath of Hurricane Hugo, political pressure thathad already been building to reform South Caroli-na's strict Beachfront Management Act of 1988quickly succeeded in making the law considerablymore flexible from the standpoint of landowners(Fischman 1990).2'

One innovative idea for overcoming future po-litical opposition has been put forward by JosephSax (Sax 1989). His proposal involves the "pur-chase" of an "insurance policy" against the daythat sea level rise requires abandonment of privateproperty. Property owners today would sell theconservation or flowage easement to their land tothe government, but instead of being paid in cashthey would receive the insurance policy. This in-surance policy would stay with the property overtime, helping maintain its value and reducing land-owner incentives to take protective measures. Themoney itself would be invested so that a pre-setsum could be paid to the landowner when the

property has to be abandoned. By providing afinancial benefit at the time of actual impact, thepolicy would presumably be far less likely to comeunder attack by landowners. Although it clearlypresents challenging implementation problems, notthe least of which is the size of the fund needed tocompensate the entire class of coastal propertyowners, this approach does appear to reduce theuncertainties surrounding the effectiveness of manyof the other measures.

If sea level rise is incre-mental, claiming a househere and a house thereover time, political consti-tuencies might have diffi-culty forming around theissue of reversing policiesagainst protecting theland being lost.

Underlying all of these policy options is thepresumption that policymakers and the publicknow how important these coastal ecosystems andtheir biodiversity are. As always, the basic politicalfacts of life in the United States make public educa-tion an important component of any effective re-sponse. As Fischman and St. Amand note: "[t]hemost effective strategy today for encouraging thisevolution in the doctrine [of presumed mobility] isto put private landowners on notice of the impor-tance that the public places on coastal wetlandsand of the role that fastlands will play in the fu-ture viability of marsh ecosystems." (Fischman andSt. Amand 1990).

The Status of U.S. PolicyVarious state and federal policies for protect-

ing wetlands and other coastal ecosystems have ex-isted in the United States for some time. In particu-lar, Sec. 404 of the 1972 Clean Water Act and theCoastal Zone Management Act contain legalmechanisms for slowing or mitigating the loss ofcoastal wetlands and for addressing other impactson coastal ecosystems, including pollution. Moststates also now have coastal zone managementlaws regulating coastal development and dischargesinto coastal ecosystems. In general, federal andmost state policies on coastal ecosystems provide a

37

"reactive" policy framework. Such policies reflectthe assumption that the coastline would be un-changing in the absence of identifiable develop-ment projects, and they provide a mechanism formitigating or denying development proposals.

This reactive policy framework provides nomechanism for dealing with the anticipated im-pacts on coastal ecosystems of sea level rise in-duced by climate change. Yet, for several reasons,some progressive measures are being put intoplace. Governments are coming to grips with theproblems created by seawall and bulkhead con-struction in response to even current rates of sealevel rise and coastal erosion. Awareness of the im-portance of coastal wetlands is also growing.

Existing measures that will help provide a bio-logical buffer in the face of future sea level riseinclude:

• Most coastal states restrict seawalls and bulk-heads to protect recreational beaches and insome cases to help mitigate negative impactson wetlands (Edgerton 1991).

• Maine has adopted "presumed mobility" as aguideline for areas developed after 1987. Per-mits for construction are issued only if theproposed development will not unreasonablyaffect wildlife habitat, interfere with naturalwater flow, or interfere with the natural sup-ply or movement of sand within the coastalsystem. Buildings are allowed only if the de-veloper demonstrates the site will remain sta-ble after a three-foot sea-level rise. These ruleshave survived legal challenges, though theyhave not yet faced public pressures for rebuild-ing after, say, a major storm. The rules havenot stopped coastal development, but theyhave influenced the location and type of de-velopment (Fischman and St. Amand 1990).

• In North Carolina, the Coastal Area Manage-ment Act of 1974 frames the need for regula-tory intervention in terms of the danger that"uncontrolled or incompatible developmentcould unreasonably endanger life or proper-ty." The law requires particular setbacks fornew construction and prohibits erosion-controlstructures. Applicants for development permitshave to sign acknowledgments that they un-derstand the hazards of building permanentstructures in essentially unsuitable areas. Theapparent success of the Act, some regulatorssay, stems from its emphasis on protectingproperty and life, rather than preserving thebeach or environment per se. This wording,they contend, gives them a stronger tool inseeking compliance with the Act and raisesfewer "takings" issues (Fischman and St.

Amand 1990). Other observers note, in addi-tion, the particularly effective working rela-tionship state and local landuse agencies haveestablished to implement the Act.

• In South Carolina, a construction setback zoneextends landward from the first primary dunefor forty times the length of annual erosion(Edgerton 1991) (See Note 23).These state policies are a start in the right

direction. Still, experience with honoring legal pro-visions when they really start to hurt casts theirlong-term ability to maintain coastal ecosystemsinto doubt. More innovate strategies need to betested and applied to achieve this aim.

Conclusions and RecommendationsSurveying the policies available to respond to

sea level rise and thereby minimize impacts oncoastal biodiversity, it is easy to forget that climatechange will seriously harm coastal biodiversity inthe United States even with the most enlightenedpolicy response. Virtually nothing can be done tomitigate some of the impacts of climate change onsome coastal ecosystems. Even under the option offull retreat, rapid sea level rise will substantially re-duce coastal wetland area, exacerbate threats tocoastal species, and, along with increased watertemperatures, threaten coral reefs. Accordingly, thehighest priority now should be slowing the rateand ultimate magnitude of global warming. Evenfor coastal systems that may be able to adapt to achanging environment, the most obvious prescrip-tion for "pro-active" policy is still to slow futureglobal warming. Regardless of which policy is re-lied upon to respond to rising sea levels, its im-plementation will be made much easier and cheap-er if the rate of climate change is slowed.

Several types of policies will no doubt playimportant roles as the nation responds to sea levelrise. Engineering solutions will be deployed indensely populated and developed coastal regionsto protect the financial investment already madethere. Where coastal uplands appear particularlyimportant to the migration or formation of wet-lands in the face of sea level rise, and where thosecoastal uplands can be purchased at modest cost,retreat makes sense. But the single most importantinfluence on the fate of coastal biodiversity incoming decades will be success in implementingadaptive solutions.

Some of these adaptive (or ' 'presumed mobili-ty") solutions seem more promising than others.For example, if the funds can be amassed, the pur-chase of flowage easements by non-governmentalorganizations (instead of governments) should

38

work well. In contrast, zoning restrictions on bulk-head construction may be overturned when thereality of sea level rise becomes apparent. Never-theless, the ultimate success of policies based onthe concept of presumed mobility will dependheavily on how and how fast climate changemanifests itself and on how much effort is spentpreparing landowners and others for sea level riseand its impact on current land uses.

In sum, five fundamental conclusions arisefrom this analysis:

1. Most policies proposed for mitigating theimpacts of climate change neglect theneed to conserve biodiversity.

2. Some detrimental impacts on biodiversitycan't be prevented by any policy responseto climate change. In these cases, the needis to slow the rate and reduce the ultimatemagnitude of global warming and its eventualimpacts on coastal ecosystems. Reliance ontechnological fixes in these cases is illfounded.

3. Biodiversity conservation requires coast-al development policies that promote ac-commodation to sea level rise, ratherthan defend against it.

4. Success in conserving biodiversity as sealevel rises depends on how fast responsepolicies are implemented. It could takedecades before the need to take action to pro-tect coastal development would make itselfevident, and by then it could be technicallytoo difficult or too costly to make manychanges that are feasible now.

5. Long-term environmental education isneeded to make the adaptive responsesintended to promote long-term biodiver-sity conservation politically acceptable.

In light of these conclusions, the followingeight policy options would help conserve coastalbiodiversity in the face of climate change:

1. Slow the Rate and Magnitude of GlobalWarming.Although often overlooked in technical discus-

sions of response to sea level rise, slowing globalwarming in the first place would do more than anyafter-the-fact measures could do to conservebiodiversity.

2. Incorporate the Protection of CoastalEcosystems as a Fundamental Goal inFederal and State Policies.Legal findings that coastal wetlands migration

is in the interest of human health, safety, and

welfare can help defend against future charges ofregulatory taking (Fischman 1990). Federal andstate commitment to biodiversity conservationcould be promoted through policy declarations. Amodel might be "It is a [State][Federal] policy topromote the conservation of biological diversity onpublic and private lands."

At the federal level, Executive Order 11990should be reissued to establish a no-net-loss goalfor coastal wetlands. A broad doctrine of no-net-loss should be adopted for coastal wetlands basedon the length of the wetland/water interface andthe functions of the wetlands, as well as on totalwetland area. To the extent possible, the samecriterion should be applied to other coastal eco-systems. The no-net-loss criterion should specifical-ly include climate-change-induced sea level rise asan action to be mitigated by the government giventhe role of human activities in contributing toglobal warming.

3. Eliminate Federal and State Subsidiesthat Promote Coastal Development andCoastal Defense.The pooling of risk through federal flood in-

surance, for example, can encourage coastal de-velopment.24 So can federal or state beach nourish-ment or seawall construction projects.

4. Make Wider Use of Such Regulatory Mea-sures as Coastal Zoning and Setbacks.

Public policymakers and analysts must come toaccept that the coastline is not, nor will it ever be,a stable entity. An important policy goal, therefore,is maintaining greater flexibility in the face of anever-changing coastline.

5. Put Property Owners on Notice that SeaLevel Rise Will Occur and that PublicPolicy Goals Will Dictate the Abandon-ment of Large Areas of Dry Land.The sooner property owners are put on no-

tice, the more likely that eventual abandonment ofthe land will be seen as a foregone conclusion,rather than as a public infringement of privateproperty rights.

6. Minimize Anthropogenic Stresses on Coast-al Ecosystems Other Than Sea Level Rise.Beach maintenance, groundwater pumping,

flood prevention, sedimentation, and pollution dis-charge are just several of the activities whose im-plications for coastal ecosystems need more carefulconsideration during planning processes.

7. Based on the Distribution of Key CoastalEcosystems, Identify Where DifferentPolicy Options Should be Pursued.

39

Where does land purchase or condemnationmake sense? Where is defense against the oceanacceptable from a biodiversity standpoint? Whereshould "flowage easements" or other approachesbe used? This identification process will requireconsiderable site-specific research over the nextseveral years.

8. Non-governmental Organizations Interestedin Land Acquisition for Conservation Pur-

poses Should Begin to Experiment with theVarious Easement and Leasing OptionsDescribed Above, Focusing on Lands ofParticular Conservation Importance.Given their experience with procuring and pro-

tecting lands already of conservation concern,through easements and other means, such organiza-tions are in an excellent position to undertake ex-perimental programs looking at lands likely to be ofconservation importance in the future.

Walter V. Reid is an Associate with the WRI Program in Forests and Biodiversity. Before joining WRI, Dr.Reid was a Gilbert White Fellow with Resources for the Future. He has also taught at the University ofWashington and worked as a wildlife biologist with the California and Alaska departments of Fish and Gameand with the U.S. Forest Service in Alaska. Mark C. Trexler is an Associate with the WRI Program in Cli-mate, Energy and Pollution, and directs the program's work on domestic and international forestry as a re-sponse to global warming. Before joining WRI, Dr. Trexler worked with such organizations as the Interna-tional Union for the Conservation of Nature and Natural Resources and the California Energy Commission onenvironmental and energy policy issues.

40

NOTES

1. Coastal wetlands refer to coastal salt and brack-ish marshes. This more commonly accepted defi-nition differs from the Convention on Wetlandsof International Importance especially as Water-fowl Habitat (known as the Ramsar Convention)which defines any flooded area as a "wetland."

2. Inland wetland loss has continued to be a seri-ous problem, but even here the "swampbuster"provisions in the 1985 farm bill (the Food Secu-rity Act of 1985, P.L. 99-198), as well as the re-peal or alteration of several tax code provisionsproviding incentives for wetland conversionthrough the 1986 Tax Reform Act (P.L. 99-514)have made significant inroads into the rates ofloss in the 1980s.

3. Although the average county in the contiguousUnited States contains only 3-4 federally listedthreatened and endangered species, coastalcounties tend to contain many more listed spe-cies with nearly half containing as many as 10-20 listed species (Flather and Hoekstra, 1989).

4. The Nature Conservancy classifies a species as"Rare" (G3) if it is either very rare and localthroughout its range, or found locally in a re-stricted range, or because of other factors mak-ing it vulnerable to extinction throughout itsrange. A species is designated as "Imperiled"(G2) if there are only 6 to 20 occurrences orfew remaining individuals, or because of somefactor(s) making it very vulnerable to extinctionthroughout its range. A species is listed as "Crit-ically Imperiled" (Gl) because of extreme rarity(5 or fewer occurrences or very few remainingindividuals) or because of some factor(s) makingit especially vulnerable to extinction (Morse1987). The Nature Conservancy, in cooperationwith the various state Natural Heritage Invento-ry Programs, has the most complete data onthreatened, and endangered species, but data onthe species elevational ranges are accurate onlyto within 10 feet (5 feet for species threatenedwithin the state), and thus greater resolution incoastal areas is not possible.

5. Scientific names: peregrine falcon (Falco peregri-nus anatum), California brown pelican (Peleca-nus occidentalis californicus), light-footed clap-per rail (Rallus longirostris levipes), Californiablack rail (Laterallus jamaicensis cotumiculus),

California least tern (Sterna antillarumbrotvni), Belding's savannah sparrow (Passer-culus sanwichensis beldingi), San Franciscogarter snake (Thamnophis sirtalis tetrataenia).

6. Of the actual loss of coastal wetlands between1954 and 1974, more than 90 percent was dueto human activities related to dredging for portdevelopment, filling related to the spread ofurban areas, and disposal of dredged material.However, the causes of coastal wetland lossdiffered considerably among states. Sixty-threepercent of wetlands loss in Delaware and 43percent in Virginia was due to urban develop-ment. In contrast, the primary cause of wet-lands loss in Maryland was coastal impound-ments, dredging projects, and rising sea level,which accounted for 73 percent of the wet-lands lost over this period. In coastal Loui-siana, the overwhelming cause of wetlands lossrelates to the drowning of wetlands due to thecombination of land subsidence and reducedmarsh accretion rates.

7. New Jersey was losing coastal marshes at a rateof 3,097 acres per year prior to passage ofstate coastal wetlands protection laws, and therate dropped to only 50 acres per year subse-quently. Similarly, in Maryland, rates of lossdropped from 1,000 acres per year to 20.

8. However, in some cases significant organic ma-terial returns to wetlands through this sameprocess, since anadramous fish, which live asadults in salt water but breed in freshwater, re-turn large quantities of nutrients when they re-turn to spawn and often to die.

9. In part, the recent decline is exacerbated bymore stringent harvest restrictions put intoplace as the population declined.

10. The study also analyzed west coast marshes,but due to apparent errors in determination ofelevations the estimates of wetlands loss werehighly uncertain.

11. Not all coral reefs were unable to keep pacewith these rates of sea level rise. One study ofcoral reefs in Papua New Guinea suggests thatgrowth kept pace with a 13 mm/yr relative sealevel rise over a span of 1000 years followingthe Pleistocene deglaciation (Chappell andPolach 1991).

41

12. The total for the five states does not equal thesum of the totals in Table 5 because some ofthe listed species are found in more than oneof the states. The coastal fringe refers to thearea below the 10-foot contour.

13- The choice of 5-foot and 10-foot contour ele-vations in this discussion is dictated by theavailability of data. The mapping of species oc-currences is accurate only to these ranges. Thiscoastal band slightly exceeds the area that willbe affected by sea level rise in the next century(1-6 feet) but is, in fact, the band at greatestrisk from the combined pressures of develop-ment and sea level rise.

14. A community is an integrated group of speciesinhabiting a given area. The organisms within acommunity influence one another's distribu-tion, abundance, and evolution.

15. These species fall into categories SI, S2, S3,and SH as used by The Nature Conservancy.The number corresponds to the G-ranksdescribed in Note 4, but refers to distributionand status at the state rather than global level.SH indicates a species of historical occurrencebut not verified in the past 20 years, thus itmay be either critically imperiled or extinct.

16. Almost no studies have examined the impactsof sea level rise on ecosystems other thancoastal wetlands, such as barrier beaches, man-groves, or coral reefs.

17. Discounting is an economic concept that ac-counts for the time value of money (or otherassets). Most individuals would prefer to re-ceive any given amount of money today ratherthan ten years hence, and would even be will-ing to accept less money if they could get itright away. The amount of difference a personis willing to accept will depend both on thelength of time involved, and on the specificbenefit they perceive by receiving the paymentimmediately rather than tomorrow (their dis-count rate).

18. Although economic discounting clearly biasesthe decision-making process against taking ac-tions that impose significant immediate costseither on the landowner or the government,the principle of economic discounting may beable to be turned to the advantage of wetlandsconservation under certain scenarios. Purchas-ing the discounted rights to land that mightlater be submerged, for example, should inprinciple be quite inexpensive. This option isdiscussed later in the text.

19. The Intergovernmental Panel on ClimateChange estimates that 1 meter rise in global sealevel would require defense of 360,000 km of

coastline around the world at a cost of close to$500 billion dollars over and above existingcosts associated with coastal protection aroundthe world. In the United States the cost is putat $106.2 billion, or $306 per person. This isequivalent to 0.03% of GNP for the UnitedStates, a seemingly modest figure. (IPCC1990b)

20. In the case of a landowners' interest in coastalproperty, he or she may feel that what hap-pens to the property in 50 or 60 years is ofrelatively little practical interest, and thatevents that far in the future are unlikely to sig-nificantly affect short-term real estate prices.As a result, he or she may be willing to simplyaccept the regulation, or may be willing totake a modest payment today in exchange forgiving up certain rights to protect their proper-ty if it eventually becomes threatened by sealevel rise.

21. The perceived robustness of this policy optionis dependent on one's own perceptions of howthe political and legal systems are likely tofunction in a situation in which large numbersof affluent landowners are suddenly faced withloss of their coastal property. Some observersargue that regulations or agreements imple-mented decades before are unlikely to be suc-cessfully challenged (Fischman 1991, Titus1991), and that the regulations and agreementscan be specifically tailored to minimize suchrisks. Indeed, there are many cases where con-ceptually similar provisions are successfully im-plemented, as in the case of conditional leaseswithin National Parks. Nevertheless, the ques-tion as it applies to the coastal zone, whereproperty loss could be dramatic and suddenunder some scenarios, will in some sense re-main open until it is actually tested.

22. To the extent that it is considered a right, suchrestrictions may be considered a taking.

23. The 1988 Beachfront Management Act pro-vided for a "deadzone" in which no new con-struction would be allowed, and in which de-stroyed buildings could not be replaced. Thelaw would have prevented rebuilding approxi-mately 20 of the 150 coastal structures dam-aged by the hurricane. Amendments to the lawin June, 1990 eliminated the "dead zone" andprovided for variances to other provisions ofthe law including construction setbacks. Someregulators argue that the 1990 incorporation ofthe variance process into the law, along withstronger provisions prohibiting bulkhead con-struction or rebuilding, actually made it possi-ble to more effectively implement the law than

42

had previously been the case. Nevertheless, example of legislation to eliminate such subsi-elimination of the "deadzone" and the de- dies. The goal must be to ensure that no feder-velopment of variance procedures will certain- al subsidies encourage development in areas uply increase the political pressure for shoreline to the limit affected by relative coastal sea lev-protection in future years as sea levels rise. el rise under the most likely scenarios of cli-

24. The Coastal Barriers Recovery Act (CBRA) is an mate change.

43

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The destructive effects of poor resourcemanagement on economic development and thealleviation of poverty in developing countries; and

The new generation of globally importantenvironmental and resource problems that threatenthe economic and environmental interests of theUnited States and other industrial countries and thathave not been addressed with authority in theirlaws.

The Institute's current areas of policy researchinclude tropical forests, biological diversity,sustainable agriculture, energy, climate change,atmospheric pollution, economic incentives forsustainable development, and resource andenvironmental information.

WRI's research is aimed at providing accurateinformation about global resources and population,identifying emerging issues, and developingpolitically and economically workable proposals.

In developing countries, WRI provides fieldservices and technical program support forgovernments and non-governmental organizationstrying to manage natural resources sustainably.

WRI's work is carried out by an interdisciplinarystaff of scientists and experts augmented by anetwork of formal advisors, collaborators, andcooperating institutions in 50 countries.

WRI is funded by private foundations, UnitedNations and governmental agencies, corporations,and concerned individuals.