Where Do We Stand?How healthy are the earth’s ecosystems? Will they continue to

provide the food, water, shelter, and other necessities onwhich all life depends? These pressing questions have been receiv-ing attention from two international collaborations: The PilotAnalysis of Global Ecosystems (PAGE) was completed in late2000 and detailed in World Resources 2000–2001, the biennialreport of the World Resources Institute (WRI), and the upcomingMillennium Ecosystem Assessment (MEA) is due for completionin 2005.

The degradation of ecosystems is literally ancient history.Desertification—an enduring ecosystem degradation—gets muchof the blame for the decline of ancient civilizations in the MiddleEast. More recently, the severe soil erosion of the Dust Bowl inthe U.S. Great Plains during the 1930s started with unsustainablefarming practices and was exacerbated by drought. In total,according to a 2000 report by the United Nations EnvironmentProgramme (UNEP) titled An Assessment of Risks and Threats toHuman Health Associated with the Degradation of Ecosystems, deser-tification is now damaging 30% of irrigated areas, 47% of rainfedland, and 73% of rangelands.

Other examples of broad ecosystem degradation include thehypoxic “dead zones” in the Gulf of Mexico and other watersaround the world, the disastrous decline of Black Sea fisheries dueto the introduction of exotic species, and intensified flooding inBangladesh and Central America caused partly by deforestation.These and other such alterations reflect global-scale changescaused by human activities, particularly climate change andstratospheric ozone depletion.

Ecosystem assessments stand traditional environmental moni-toring on its head by examining an entire ecosystem, such as awatershed, mountain range, or coastline, rather than, say, a tractof land or an industrial sector. No longer, says David Rapport, aprofessor in the School of Rural Planning and Development at the

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University of Guelph in Ontario,Canada, is it sufficient to address prob-lems of agriculture, biodiversity, or freshwater in isolation, when the entire eco-logic fabric is getting ever more thread-bare. “Healthy organisms can only existin a healthy ecosystem,” Rapport says.“It’s becoming dysfunctional to the pointthat the basic needs for life—fertility ofthe soil, regeneration of fisheries, arable

land productivity, fresh water—all thesefundamental services, nature’s gifts, arebeing eroded.”

The PAGE is the most ambitiouseffort at worldwide ecosystem assessmentto date. Coordinated by the WRI, thePAGE got help from 18 players, includingthe World Bank, several United Nationsagencies, and organizations concernedwith food and the environment. ThePAGE was designed to serve as a pilotproject for the MEA, which will cover aneven more ambitious scope.

The MEA will document the condi-tion of ecosystems past, present, andfuture. Rather than prescribe changes forpolicy makers or dictate which problemsare most pressing, it will write scenarios toguide the actions of industry, government,and international agencies, says RobertWatson, chief scientist and director of theWorld Bank’s Environmental ly andSocially Sustainable Development Net-work, who is also cochair of the MEA’sboard of directors. These scenarios willpaint very broad pictures of how theworld’s ecosystems could change based oncertain uncontrollable variables. They cantherefore guide the actions of industry,government, and international agencieswithin their own spheres.

Scenarios are a departure from the tradi-tional approach to ecosystem management,points out Stephen R. Carpenter, a profes-sor of limnology at the University ofWisconsin at Madison, who will cochair theMEA scenarios group. He adds, “The clas-sic approach to decision making is to makea prediction and act on the probability

[of the various outcomes]. The problemwith projecting the world’s environment isthat we don’t know the probability distri-bution, and a very wide range of thingscan happen.”

Ecosystem Assessment: WhatPurpose Does It Serve?According to the description of thePAGE in the 2000–2001 WRI report,

ecosystem assessments have six maincharacteristics. They broadly evaluatehow humans affect the functioning andproductivity of ecosystems. They focuson an entire ecosystem rather than tradi-tional jurisdictions or sectors. They takea long view of ecological health. Theyexamine the entire productive potentialof an ecosystem. They stress relationshipsrather than individual sectors or outputs.And finally, they accept people as part ofecosystems.

The cross-sectoral approach is key,says Ashbindu Singh, a UNEP researcherwho cowrote An Assessment of Risks andThreats. He says environmental monitor-ing used to focus more on sectors such asforests or water. In contrast, the ecosystemapproach integrates all aspects of theecosystem, and by definition considershuman actions. “People are the biggestdrivers of change,” Singh says, “and needto be included in the assessment.”

A prime motivation for the MEA, saysCarpenter, is three global treaties on wet-lands, biodiversity, and desertification thatrequire the scientific community to pro-vide a coherent information base that theconvention secretariats can use to makedecisions. “There was a recognition withinthe scientific and policy communities thatthese [treaties] had pretty strongly over-lapping information needs,” he says.“Given that the community of scientiststhat can do this globally is pretty smalland the cost is pretty large, why not doone scientific effort?”

Another reason to look globally is thegrowing intensity of human use of the

biosphere. According to Walter Reid, aformer official of the WRI who was actingscience director for the MEA, by 2020world demand for rice, maize, and wheatwill grow by 40%, and livestock produc-tion by 60%. By 2025, humans areexpected to use 70% of the freshwaterrunoff from snow- and rainfall. “Thesegrowing demands for ecosystem goods andservices can no longer be met by tapping

unexploited re-sources,” Reid wrotein the Spring 2000edition of Issues inScience and Technol-ogy. “A nation canincrease food supplyby converting a for-est to agriculture,but in so doingdecreases the supplyof goods that maybe of equal orgreater importance,such as clean water,

timber, biodiversity, or flood control.” Carpenter also believes that from a

decision-making standpoint perhaps thebiggest mistake that could be made is leav-ing out important possibilities. For exam-ple, he says, i f the Ross Ice Shelf inAntarctica breaks loose from the oceanfloor, the sea level could rise by 10 metersvirtually overnight. Thus, he says, suddenchanges will become the basis for someMEA scenarios.

The scenarios will rest on data fromthe physical sciences, such as studies ofglobal warming. Social and political con-ditions, Carpenter says, will play a keyrole in future conditions. “Will the worldby 2050 be largely globalized, with . . . avery flexible international exchange ofgoods and services?” he asks. “Or willthere be vast areas where democracy andthe rule of law fail and the open marketcannot function? Those two worlds havehugely different implications for the wayecosystems and the environment willoperate.” Because the probability of anyone scenario coming to pass is uncontrol-lable and unpredictable, Carpenter says,the group will try to forecast their ecologicimpact without necessarily evaluatingtheir likelihood as starting points.

However, the MEA’s data may helpother organizations set priorities, saysKenneth Kassem, a conservation specialistat the World Wildlife Fund who alsoworked on the PAGE. Because the MEAconsiders biodiversity an essential benefitof healthy ecosystems, its results will helpgroups refine their evaluations of conser-vation status around the world.

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Healthy organisms can only exist in a healthyecosystem. It’s becoming dysfunctional to the

point that the basic needs for life—fertility ofthe soil, regeneration of fisheries, arable land

productivity, fresh water—all these fundamentalservices, nature’s gifts, are being eroded.

–David Rapport, University of Guelph

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Ecosystem assessments elucidate a lotof interesting relationships. Water is thebasis of several surprising interactions. Forexample, a recent study published in the15 May 2001 online version of Proceedingsof the National Academy of Sciences of theUSA by Daniel Rosenfeld, a professor inthe department of atmospheric science atthe Hebrew University of Jerusalem inIsrael, linked dust from the Sahara Desertwith reduced rainfall. Although raindropsmust condense on dust or some othernucleus, the desert dust produced toomuch of a good thing; many waterdroplets formed in the atmosphere, butthey were too small to drop out as rain. Ifconfirmed, such a destructive feedbackloop could intensify desert i f icat ion.Drought and overgrazing would causedust and then more drought, thus damag-ing the rangeland further and causing yetmore desertification.

Consideration of ecosystem effectscould help forecast the consequences ofhuman actions and prevent the kind of sur-prises that followed a World HealthOrganization malaria control program thatsprayed the pesticide dieldrin in Borneo inthe 1950s. Accordingto Jonathan Patz,who is director of theProgram on HealthEffects of GlobalE n v i r o n m e n t a lChange at the JohnsHopkins BloombergSchool of Publ icHealth, the mosquitopopulation declinedas desired, but other,unexpected problemstook their place,including thatched roofs that began fallingin and a major typhus epidemic. Lizardsdied from eating poisoned insects mosqui-toes, and cats died from eating the poi-soned lizards, allowing rats to run rampant,covered with fleas that carried typhus. Theinsecticide also killed wasps that formerlykept the caterpillar population in check,and the caterpillars ate the thatched roofs,which then fell in. “By trying to do adirected treatment, they ended up withproblems worse than they started with,”Patz says. The story, he says, is a “classicexample of how everything is interrelated.”

One exceedingly complex issue thatecosystem assessments must try to tackle iscarbon storage—the removal of the green-house gas carbon dioxide from the atmos-phere. About 7.9 billion tons of carbonenters the atmosphere each year fromhuman activities, primarily burning fossilfuels, deforestation, and agriculture.

About 2.3 billion tons is dissolved in theocean or taken up by marine vegetation,so global warming is affected by condi-tions that alter marine ecosystems, includ-ing pollution, siltation, and introductionof exotic species. Terrestrial ecosystemstake up another 2.3 billion tons of carbonper year.

Carbon storage brings up countlessphysical, biologic, and economic issues.For example, fixation of organic nitrogeninto inorganic forms that are available toplants, largely through fertilizer produc-tion, hastens plant growth—leading tomore carbon storage—but also causesexcess and unhealthy growth in freshwaterand marine environments. Carbon isstored in soil as organic matter that helpssoil retain water, a process that is reversedby erosion and desertification, both ofwhich reduce carbon storage. Thus, agri-cultural and forestry practices are bothmajor determinants of carbon storage:they directly influence the amount of car-bon stored in vegetation and indirectlyinfluence soil storage. Ecosystem assess-ments must try to forecast the effects ofother actions that affect carbon storage,

such as nutrient management and the useof organic fertilizer and minimum tillage,but the challenge is daunting.

Lessons Learned from the PAGEThe results of the PAGE were neithersurprising nor encouraging. “The mes-sage was that ecosystems are in a precari-ous state,” Watson says. “They can besaved, but with business as usual, we’regoing in a direction that over the longhaul is not going to be able to supportthe goods and services we require.” Usingprimarily literature reviews rather thanoriginal research, the PAGE painted agrim picture of five ecosystems: agricul-tural, coastal, freshwater, marine, andforest systems.

Agroecosystems have allowed cropoutput to double since 1970, but a soar-ing worldwide demand for food will con-tinue to stress farmlands and rangelands.

About two-thirds of agricultural land hasbeen degraded over the past 50 years byerosion, salinization, soil compaction,nutrient depletion, biological degradation,and pollution.

Coastal ecosystems are being harmedby a growing human population—40% ofhumanity lives within 100 kilometers of acoast. Other harmful factors includeincreasing use of synthetic chemicals andfertilizers, overfishing, and destruction offish nurseries. Increases in hypoxia andharmful algal blooms and declines in fishharvests indicate the decreasing health ofthese ecosystems.

Freshwater systems have been dam-aged in most parts of the world by agricul-ture, industry, and urbanization. Peoplealready use about half of present riverflow, and the percentage is rising. About20% of freshwater fish species have goneextinct in recent decades, or are threat-ened or endangered. About half of all wet-lands were destroyed during the twentiethcentury for farming and development. Asa result of all these factors, 5 million peo-ple die each year from lack of adequatedrinking water and good sanitation.

Forest cover has been reduced by20–50% since preagricultural times andcontinues to decrease by 0.7% per year.The PAGE attributes forest loss to eco-nomic development and population pres-sures, and found that logging, mining, androad building all expose forests to settlers,hunters, fires, and invasive species.Deforestation can reduce rainfall, becausetrees return rainwater to the atmosphere aswater vapor, which then condenses intorain. Deforestation can also increase runoff,causing flooding and siltation downstream.Deforestation harms biodiversity, reducingthe variety of plants and animals availablefor drug discovery and crop breeding. Italso changes insect habitat, resulting in theexpansion of vectorborne diseases such asmalaria and dengue fever.

Grassland ecosystems cover 31–43% ofthe planet’s land surface and are home to17% of the human population. Grasslands

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The classic approach to decision making is to makea prediction and act on the probability [of the variousoutcomes]. The problem with projecting the world’senvironment is that we don’t know the probabilitydistribution,and a very wide range of things can happen.

–Stephen R. Carpenter, University of Wisconsin at Madison

are under threat from overgrazing, unwiseconversion to croplands, and fires used—and often misused—by farmers and ranch-ers to clear brush.

Although global by nature,the PAGE also has local compo-nents (as will the MEA). Forexample, the PAGE looked atthe health of grasslands inMongolia, an area where forthousands of years nomadicherders have subsisted withoutcausing fatal harm to theecosystem. By collaborating inrotating animals over sharedpastures in prescribed ways,herders were able to secure theircountry’s economy without degrading itsecosystems. New social and economic prac-tices are threatening the rangeland, however.Smaller, more static livestock operations willrequire fodder crops, but half of Mongolia’slimited croplands are already degraded. Thechange from traditional, collective landtenure to private ownership of land andherds, the PAGE found, “has decreased flex-ible systems such as rotational grazing andaccess to shared grazing lands.”

The PAGE also examined case studies ofpromising solutions to ecologic problems.Many of its case studies were small, locallymanaged projects that were intended toserve people and nature at the same time. Amangrove restoration project in theCaribbean nation of St. Lucia, for example,showed how local input could help preservethese coastal trees, which protect tropical

coastlines from erosion and provide nurseryhabitat for finfish and shellfish. A 63-hectaretract of mangroves was being cut withoutrestriction by local charcoal makers. By theearly 1980s, a local nongovernmental orga-nization proposed to include the charcoalmakers in managing the mangroves for sus-tainable use. A new inland tree plantationaugmented the wood supply, and the man-groves’ health improved with little decline incharcoal output.

Assessing the AssessmentsWatson, who formerly directed theIntergovernmental Panel on ClimateChange (IPCC), the ongoing United

Nations–led effort to document globalwarming, says that, in an effort to securewide dissemination and acceptance, theMEA will borrow some of the techniquesof the IPCC, whose massive periodicreports are written by a broad range of sci-entists. The MEA will, for example, bewritten and reviewed by 1,000–2,000 sci-entists, assuring wide scientific awarenessof the product (the PAGE, by contrast, gotalmost no publicity). To further ensureacceptance, MEA organizers are talkingwith environment ministries, industryleaders, and international organizationssuch as the World Health Organizationduring the planning phase.

The carbon storage example points toone key hurdle of these assessments: thesheer complexity of global environmentalproblems. Carpenter says he hopes to deal

with that complexity in the MEA withoutgetting bogged down. “I intend to makehard-nosed, pragmatic decisions to keepcomplexity under control,” he says. “Youwill leave some important things out, butyou will actually get something done.” For aproject as ambitious as the MEA, he adds,“it would be disastrous to wallow in com-plexity and never develop a product.”

William Clark, a professor of interna-tional science public policy at HarvardUniversity’s Belfer Center for Science and

International Affairs, says rushing to judg-ment on large international scientificefforts such as the MEA is a mistake. Afteryears of study of the effectiveness of simi-

lar efforts, he found that even the mostinfluential reports tend to be less influen-tial when considered by themselves.Ecosystem assessments, he says, should beseen as part of a long-term process thatwill go on to produce future reports andactions. He points to the highly influentialIPCC, which has successfully positioneditself as the final authority on climatechange but which initially got little noticeoutside the field.

Clark dismisses the idea that the MEAand future assessments like it will becomejust another global ecosystem report gath-ering dust on the shelves of scientists andpolicy makers. Cynics, of course, wonderwhether these reports will really tell usabout how to reallocate resources. Willthey be dismissed as too ambitious or toocomplicated? Will they help in the

inevitable politicaland economic battlesover developmentand environment?And will the MEA,like its predecessorthe PAGE, disappearfrom view as soon asit’s finished?

Watson acknowl-edges the possibilityof that happening,but says the MEA isdetermined to makeits report count. The

goal, he says, is “not to tell us that worldecosystems are falling apart—we knowthat—but to identify the underlying causes.It’s not to have prescriptions, but todemonstrate what different choices willmean to meeting our needs for food, fiber,etc. The onus is on us that it’s not justanother book showing that we’re going tohell in a handbasket.”

David J. Tenenbaum

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The message [is] that ecosystems are in aprecarious state. They can be saved, but with

business as usual, we’re going in a direction thatover the long haul is not going to be able tosupport the goods and services we require.

–Robert Watson, World Bank Environmentally andSocially Sustainable Development Network

People are the biggest drivers of change and need to be included inthe assessment.

–Ashbindu Singh,United Nations Environment Programme