Global Environmental Change: The Threat to Human Health

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Global Environmental Change:The Threat to Human Health

worldwatch in st i tute , wash ington , d c

WORLDWATCH REPORT 18 1

Suggested citation: Samuel S. Myers, Global Environmental Change: The Threat to HumanHealth, Worldwatch Report 181 (Washington, DC: Worldwatch Institute, 2009).

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© Worldwatch Institute, 2009ISBN 978-1-878071-92-7

The views expressed are those of the authors and do not necessarilyrepresent those of the Worldwatch Institute; of its directors, officers, or staff;

or of its funding organizations.

On the cover: A young girl in Gujarat, India, squats to get water from a hose hookedup to a pipeline that passes by the edge of her village.

Photograph © 2003 Shezeen Suleman, courtesy of Photoshare

Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Expanding the Focus of Environmental Health . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

A New Health and Environment Framework . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Environmental Change and Infectious Disease . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Environmental Change, Food, and Nutrition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Other Health Outcomes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Adapting to the Health Impacts of Climate Change . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Moving Forward in a Changing World . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Endnotes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

Figures, Tables, and Sidebars

Figure 1. World Population, 1850–2009 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Figure 2. Gross World Product Per Capita, 1700–2003 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Figure 3. Nitrogenous Fertilizer Consumption, 1962–2006 . . . . . . . . . . . . . . . . . . . . . . . . 10

Figure 4. Global Average Temperature at Earth’s Surface and Carbon DioxideConcentration in Earth’s Atmosphere, 1880–2008 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Figure 5. Complex Relationships Between Altered Environmental Conditionsand Human Health . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Figure 6. Proposed Relationship Between Resource Scarcity and Human Health . . . . . . . 13

Figure 7. Undernourished Population, Total and as Share of World Population,1990–2009 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Figure 8. Number of Category 5 Natural Disasters, 1980–2008 . . . . . . . . . . . . . . . . . . . . . 27

Table 1. Examples of Land Use Change and Increased Malaria Transmission . . . . . . . . . . 16

Table 2. Examples of Land Use Change and Increased Schistosomiasis Incidence . . . . . . 17

Table 3. Potential Ecological Constraints on Increased Global Food Production . . . . . . . 24

Sidebar 1. Health and Environmental Co-Benefits of Family Planning . . . . . . . . . . . . . . . . 32

Table of Contents

Acknowledgments

This report is adapted with permission from an article by Samuel S. Myers and Jonathan A. Patz inVolume 34 of the Annual Review of Environment and Resources. The Worldwatch Institute thanksthe editors of the journal for permission to publish parts of this paper in significantly revisedform. The author thanks Paul Ehrlich, Rosamond Naylor, David Lobell, and Gretchen Daily atStanford University, James McCarthy and Daniel Schrag at Harvard University, Felicia Keesing atBard University, Richard Ostfeld at the Cary Institute of Ecosystem Studies, Kristie Ebi at ESS,LLC, and Timothy Wirth at the United Nations Foundation for helpful comments on an earlierdraft of this manuscript. He also thanks Mary Sternitzky of the University of Wisconsin’s Centerfor Sustainability and the Global Environment for help creating the figures. The editors thankWorldwatch intern Brenda Voloshin for editorial, research, and graphical assistance.

Global Environmental Change: The Threat to Human Health www.worldwatch.org4

About the Author

Samuel S. Myers, MD, MPH is an Instructor of Medicine at Harvard Medical School and aResearch Fellow at the Harvard University Center for the Environment. He practices and teachesinternal medicine and serves as staff physician at Mount Auburn Hospital in Cambridge, MA.Dr. Myers is currently developing research into the health consequences of altered nutrient com-position of crops in response to high concentrations of atmospheric carbon dioxide. In additionto teaching clinical medicine, he teaches courses about the health impacts of large-scale anthro-pogenic environmental change at Harvard University. In the past year, Dr. Myers has been leadauthor of an article for the Annual Review of Environment and Resources on “Emerging Threats toHuman Health from Global Environmental Change” and has written several book chapters on thehuman health impacts of different types of large-scale environmental change, including land usechange, climate change, and ecosystem service disruption. Dr. Myers has also worked for the U.S.Agency for International Development and Conservation International and lived for two years ina village in Tibet, China, where he was field manager for an integrated conservation and develop-ment project focusing on population, health, and the environment. A graduate of HarvardCollege, Dr. Myers received his MD from Yale University School of Medicine and his MPH fromHarvard School of Public Health. He serves on the board of directors of the Worldwatch Institute.

Preface

he changes that human activities arecausing to the Earth’s basic physicaland biological systems have alwaysbeen much more than an environ-

mental issue. But the world is only slowly wak-ing up to the reality that environmental changethreatens human health on an unprecedentedscale—and in ways for which we are unpre-pared. Indeed, climate change combined withother types of large-scale, human-caused envi-ronmental change is increasingly recognized asone of the greatest public health challenges wehave ever faced.

Human health and the health of the envi-ronment are intimately connected. Both arenecessary to satisfy basic human needs. Theenvironment is a key factor in determining thehealth of people. At the same time, investmentsin human health can help improve the healthof the environment and ecological systems.

Both human health and the environment areunder greater pressure than ever before. Up toone-third of the 25,000 child deaths that occurevery day are due to dangers present in the envi-ronments where children live. Environment-related illnesses kill the equivalent of a jumbo-jet full of children every 30 minutes. This is atragedy of immense dimensions, yet there is farless focus on the problem than it deserves. Andit is the poor who bear the main burden.

While the challenges are greater than ever,we now have the ability more than ever beforeto secure good health for every individual andcommunity. In this report, Dr. Myers empha-sizes that most of the emerging health threatsassociated with large-scale environmentalchange are preventable. As such, the report is acall to action.

The knowledge that we canmake a differ-ence means that we have a large responsibilityto act. By fighting ignorance, inaction, andinequity, we can create the conditions underwhich health threats can be averted. Mostimportantly, we must take targeted collectiveaction to reduce the vulnerability of the poor-est people on the planet to threats they playedlittle role in generating.

Mitigation and adaptation are the two keystrategies we need to follow. First, we mustreduce emissions of greenhouse gases to aminimum in order to limit climatic disruption.A more stable climate will reduce vulnerabilityto the emerging threats that Dr. Myers high-lights in this report: the spread of infectiousdiseases, increasing scarcity of food anduncontaminated fresh water, natural disasters,and widespread population displacement.

Second, we must help the poorest countriesadapt to the consequences of environmentalchange.We must improve capacity to deal withthe major emerging health threats on whichthis report focuses. Health systems and theeconomies that support them must bestrengthened to withstand natural disastersand to detect and respond to changes in thedistribution of infectious diseases. At the sametime, we must broaden our focus beyond thetraditional health sector to evaluate, and planfor, widespread changes in access to freshwater, agricultural production, and migration.

We must build capacity, at the national level,to perform risk assessments to identify themost important regional threats and developinterventions to reduce vulnerability to them.In addition to these specific efforts at adapta-tion, we will need to bolster general support for

www.worldwatch.org Global Environmental Change: The Threat to Human Health 5

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6 Global Environmental Change: The Threat to Human Health www.worldwatch.org

Conference of the Parties to the UnitedNations Framework Convention on ClimateChange, to be held in Copenhagen, Denmark.The health of the world, and particularly of thepoor, hangs in the balance as we seek a globalagreement to halt the human-caused alterationof our planet’s climate. Human activity mustbe brought into balance with the Earth, onwhich our development and wellbeing ulti-mately depends.

—Gro Harlem Brundtland,Special Envoy on Climate Change to UnitedNations Secretary-General Ban Ki-moon;Director-General Emeritus,World Health Organization;former Prime Minister, Norway

socially and environmentally sustainablegrowth. As living standards rise, people will beless likely to be swept aside by the next extremeweather event, epidemic, or crop failure.

More than two decades ago, I had the honorto chair the World Commission on Environ-ment and Development.Our Common Future,the Commission’s report released in 1987,helped introduce the concept of sustainabledevelopment into the vocabulary of the globaldebate. It is thus with great pleasure that I jointhe Worldwatch Institute and the UnitedNations Foundation in helping to launch thepublication of this report. I hope it will bewidely distributed, closely read, and quicklyheeded by climate negotiators, governments,and the people they represent.

The report comes on the eve of the 15th

Preface

Summary

ver the past two-to-three hundredyears, humanity’s ecological foot-print has ballooned to such anextent that we are now funda-

mentally altering the planet.We have trans-formed the Earth’s land surface and altered thefunction of its ecosystems, and we are trigger-ing the rapid loss of both terrestrial and marinelife.We are also profoundly changing ourplanet’s climate. It is increasingly apparent thatthe breadth and depth of the changes we arewreaking on the environment are imperilingnot only many of the other species with whichwe share the ecological stage, but the healthand wellbeing of our own species as well.

Global climate change threatens humanhealth in numerous and profound ways. Largesegments of the population will experiencemore heat waves, altered exposure to infectiousdisease, and more-frequent natural disasters.Most significantly, climatic disruption threat-ens the adequacy of the core “building blocks”of health for large populations around theglobe: sufficient food and nutrition, safe waterfor drinking and sanitation, fresh air tobreathe, and secure homes to live in. As climatechange dismantles these central elements ofhealthy societies, people with fewer resourceswill be forced to migrate in large numbers tolands where they may not be welcome. A likelyresult of all of these processes will be increasedcivic instability and strife.

Even if the global climate were stable,humans would still be converting more land,water, and ecosystem services for their ownuse. The environmental changes from theseactivities are combining to magnify severalpublic health threats to the extent that they

now endanger health and wellbeing globallyand on scales never experienced in human his-tory. These threats include: exposure to infec-tious disease, air pollution, water scarcity, foodscarcity, natural disasters, and population dis-placement. Taken together, they represent thegreatest public health challenge of the 21st cen-tury. We need to wake up to the danger and actwith urgency to reduce ecological disruption asmuch as possible while simultaneouslystrengthening the resilience of populations towithstand the impacts of unavoidable environ-mental change.

Populations vary dramatically in their vul-nerabilities to these emerging health threats, inpart because the environmental changes thatare triggering these threats are not uniform.Rapid glacial melting on the Tibetan plateauthreatens the dry-season water supply for morethan 1 billion people living and growing irri-gated crops in Asia’s great river basins. In sub-Saharan Africa, droughts and increasedtemperatures caused by climate change willinteract with existing soil degradation, nutrientloss, and water scarcity to further reduce cropyields and constrain food supplies. The triplethreat of more-severe storms, rising sea levels,and degraded coastal barriers—such as man-grove forests, coral reefs, wetlands, vegetateddunes, and barrier islands—will pose signifi-cant risks to low-lying coastal populations.

But vulnerability is not determined only bya population’s exposure to health threats; it isalso determined by the ability to adapt in theface of such threats. Many of the threats associ-ated with global environmental change can bemitigated by means of trade, technology, infra-structure, behavior change, philanthropy, and


O

governance. Populations with the resources—both economic and socio-cultural—to engagethese mechanisms will suffer less than thosewithout such resources. As a consequence, cli-mate change threatens to further accentuatethe divide between rich and poor, both acrossnations and within them.

Because the impacts will depend in largepart on a population’s location and socioeco-nomic status, it is critical that all countriesconduct rigorous, location-specific risk assess-ments to identify which populations are athighest risk for which threats. Governmentsand other stakeholders will also need to mobi-lize substantial financial resources, technicalcapacity (both in assessment and appropriatetechnologies), and new partnerships that canhelp build capacity over the long term.

The health impacts of climate change pres-ent an opportunity as well as a challenge. Theinternational community increasingly recog-nizes the moral imperative to help the poorreduce their vulnerability to climate change—a threat that developing countries have had lit-tle role in generating. At the same time, thereis renewed emphasis on achieving the UnitedNations’ Millennium Development Goals, aswell as increasing attention in the UnitedStates to reforming foreign assistance. In thiscontext, climate change may help to shine alight on some of the most entrenched chal-lenges to human health in the poorest coun-tries—including poverty, malnutrition, andinfectious disease.

For many years, the industrialized world hasdone less than it could to relieve sufferingamong the global poor. Now, it will need tovigorously reframe its development assistance

to address the impacts of climatic disruption—impacts for which it is largely responsible.With the upcoming climate talks in Copen-hagen, Denmark, the year 2009 may be a defin-ing moment in human history: a year in whichthe historical injustice of human-induced cli-mate change could fuel an international effortto reduce vulnerability and simultaneouslyaddress some of the longest-standing scourgesto human health.

Our challenge, for the rest of this centuryand beyond, will be to work to mitigate envi-ronmental change (for example, by reducinggreenhouse gas emissions) and to increase theresilience of populations to the impacts of anychanges that we are unable to mitigate (such assea-level rise triggered by past emissions). Nei-ther task should detract from the other; wemust pursue both simultaneously and withequal fervor and strategic creativity. Along theway, there will be substantial opportunities toidentify co-benefits, whereby a single interven-tion can both mitigate environmental threatsand improve human health.

Addressing the health impacts of globalenvironmental change needs to be a priorityfor the public health community, environmen-tal scientists, and natural resource managers, aswell as for governments and intergovernmentalbodies such as the United Nations and multi-lateral development banks.What we need mostare political will and financial resources.Whilethese resources will need to be large, they aresmall compared to the cost of ignoring theimpacts of large-scale change and trying toaddress the overwhelming problems of famine,epidemic disease, massive population displace-ment, and civil strife that may ensue.


Summary

* Endnotes are grouped by section and begin on page 38.† Units of measure throughout this report are metricunless common usage dictates otherwise.

9www.worldwatch.org Global Environmental Change: The Threat to Human Health

than 45,000 large dams and some 800,000smaller dams around the world, altering thenatural flow on roughly 60 percent of theworld’s rivers.8

• As a result of habitat loss, invasive species,

s a species, we humans have beenremarkably effective at rearrangingthe natural world to meet our ownneeds. This transformation has

allowed for both rapid population growthand rapid economic development over thelast few centuries—particularly over the last50 years.*1 (See Figures 1 and 2.) Thesetrends, in turn, have placed acceleratingdemands on the ecological goods and servicesthat make our lives possible.

The result is that the entire ecosphere—oceans, land surface, atmosphere, and freshwa-ter systems—has been modified extensively byhuman activities. For example:• We now appropriate one-third to one-halfof global ecosystem production for humanconsumption.2

• More than half of the nitrogen cycle is nowdriven by human activities.3

• We have converted roughly 40 percent ofthe Earth’s ice-free land surface to croplandor pasture.4

• We use roughly half of the planet’s accessiblesurface fresh water.5

• Over the past 300 years, we have reducedtotal forest cover by between 7 and 11 millionsquare kilometers—an area the size of thecontinental United States.†6

• Three-quarters of monitored fisheries arebeing fished at or beyond their sustainablelimits.7

• To harness electricity, control flooding, andimpound fresh water, we have built more

Expanding the Focusof Environmental Health

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Figure 2. Gross World Product Per Capita, 1700–2003

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pollution, and climate change, we are drivingspecies extinct at roughly 1,000 times the nat-ural rate.9

Humans have also changed the planet’schemistry.We have altered global nutrientcycles by applying synthetic fertilizer to soil,much of which finds its way into nearby waterbodies and the oceans.10 (See Figure 3.) Wenow add more fixed nitrogen to the biosphereannually than all natural sources combined.These additions of nitrogen lead to biodiver-sity loss and changes in species compositionsin terrestrial and aquatic ecosystems, as well asto groundwater pollution, air pollution, and


acidification of soils and fresh water.11 As abyproduct of our energy consumption andland use, we have increased the carbon dioxide(CO2) in the atmosphere by roughly 30 per-cent over preindustrial levels, warming theplanet artificially and making the oceans moreacidic.12 (See Figure 4.)

Despite historical concerns that populationgrowth and increasing resource consumptionmight cause humanity to outstrip its ecologicalbase, there has been little evidence at a globalscale of a Malthusian collapse. To the contrary,from a human health perspective, our transfor-mation of the planet appears to have beenlargely a success. Since 1820, average per capitaincome has risen eightfold.13 In the year 1000,the average infant could expect to live about 24years; today, she can expect to survive 66years.14 Infant and maternal mortality havefallen steeply, and per capita food productionhas risen despite a more-than fivefold increasein human population since 1820.15

These global averages hide dramatic dispari-ties between rich and poor, and there remainlarge segments of the human populationwhose lives are curtailed by poverty, hunger,and disease. Nonetheless, by recruiting an everlarger share of the biosphere to meet humanneeds for food, water, fiber, building materials,and so on, a rapidly growing human popula-tion has largely prospered.

Expanding the Focus of Environmental Health

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Figure 3. Nitrogenous Fertilizer Consumption, 1962–2006

Yet at the same time, we have begun to iden-tify emerging threats to human health that aredeeply troubling. Accelerating changes to theEarth’s climate, terrestrial surface, and ecosys-tems threaten our future access to some of themost basic components of public health: ade-quate nutrition, safe water, clean air, and pro-tection from infectious disease and naturaldisasters. As access to these “building blocks” ofhealth becomes more constrained, the healthconsequences for billions of people could befar reaching.

These changes justify a broadening of theconcept of environmental health. Traditionally,this field has focused on analyzing the risks tohumans associated with exposures to air andwater pollution and to environmental toxins,such as heavy metals, radiation, and chemicalsthat mimic hormones or disrupt their balancein the body.With more than 100,000 manufac-tured chemicals now pervading the Earth’sland, water, and soil—many of which are nearlyubiquitous in human bodies—policy change inthis area is critical. But we also need to con-sider the broader health implications of thehuman transformation of the natural world.

Expanding the focus of environmentalhealth would bring greater awareness to themajor threats associated with large-scale,human-caused changes to the natural environ-ment. Specifically, changes in land use, climate,and the function of ecosystems act synergisti-cally to alter exposure to infectious disease andnatural disasters, while curtailing access tofood, clean air, and clean water and increasingthe likelihood of population displacement andcivil strife.

The broader health impacts of environmen-tal change are difficult to study using tradi-tional approaches because they are complex,caused by multiple factors, and often occurover very large scales. The effects are some-times delayed significantly in time, and themomentum of past forces and alterations often

remains powerfully influential in the present.However, collaborative research into these rela-tionships is gaining momentum by drawing ona variety of disciplines, utilizing new tools andmethods, and developing innovativeapproaches to determining causality.16

Increasingly, some professional scientificsocieties are emphasizing the need for cooper-ative thinking across a range of natural, med-ical, and other social disciplines. These hybridspecialties go by such names as “eco-health,”“conservation medicine,” and the concept of“one health,” whereby healthy people, wildlife,and environments are considered parts of awhole. Regardless of the terminology, it is clearthat a new framework is needed for conceptu-alizing the connections between global envi-ronmental change and human health.



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A New Health andEnvironment Framework

umanity relies on the naturalworld to provide many of the cor-nerstones of health: adequatenutrition, clean water, clean air,

and protection from infectious disease andnatural disasters. Unfortunately, the combina-tion of rapid land use change and acceleratingclimate disruption is reducing the capacity ofecosystems to continue providing these andother “services” at their historic capacities, andrates of depletion are accelerating.1

As ecosystem services degrade or becomeless available, human health is likely to suffer.2

This seems intuitive, yet most studies exploringthis association have underestimated the com-plexity of the relationship, with some findingno immediate correlation between the loss ofecosystem services and adverse health out-comes.3 One reason for this conclusion is thatmost of us have the luxury of being blissfullyunaware of how much we rely on the servicesthat nature provides, since we tend to be insu-lated from the direct impacts of ecosystemservice degradation by a variety of mitigatingfactors, from regional or international marketsto effective infrastructure and governance.4

(See Figure 5.)Most societies rapidly externalize their “eco-

logical footprint” beyond the local ecosystemswhere they live, making it hard to measure adirect correlation between ecological disrup-tion and negative health outcomes. People whohave access to regional or international mar-kets can generally procure the food, fuel, fiber,and building materials they need. Most of useven buy water this way—in the form of thewater required to produce imported grain,meat, or other food products. In this way, we

insulate ourselves from the effects of localresource scarcity.5 In contrast, people with lit-tle or no access to wider markets—particularlyfor food—are especially vulnerable to ecologi-cal degradation.6

A second reason that studies may missimportant correlations between ecosystemdegradation and adverse health is that othersocial, political, and economic factors—such asinfrastructure and technology—can protectpopulations from the consequences of resourcedepletion.7 The loss of wetlands and theirwater-filtering capacity, for example, is lesslikely to cause disease among downstreampopulations that have access to water-filtrationtechnology. Meanwhile, the loss of coastal bar-riers such as mangroves, coral reefs, or vege-tated dunes can increase vulnerability toextreme storms among residents who cannotafford to build sea walls and whose housingcannot withstand high winds or storm surges.

Behaviors learned from family membersand the broader culture can also protect peoplefrom ecosystem change. Communities threat-ened by increased exposure to infectious dis-ease as a result of altered environmentalconditions may reduce their vulnerabilitythrough behaviors such as treating their drink-ing water, preparing foods in protective ways,or reducing exposure to disease-transmittingorganisms by wearing protective clothing,using bed nets and screening, and stayingindoors during certain hours. Because cultur-ally determined behaviors often evolve overmany generations and resist change, however,they may be less adaptable to rapidly changingenvironmental conditions.

Governance is another mediating factor. A

H


government’s capacity and commitment todeliver resources such as food, water, andenergy can prevent local resource scarcity fromcausing human suffering. Most of the faminesof the 20th century, for example, were drivenmore by failures of governance and resourcedistribution than by absolute food scarcity.8

International philanthropy may be the finalsafety net in settings where there is no access tointernational markets and where governancehas failed, yet even access to philanthropicefforts varies widely by location and can bestymied by unreceptive governments, as wasseen in Myanmar immediately followingTyphoon Nargis in 2008.

The relationship between resource scarcityand health outcomes is likely linear only to acertain point.9 (See Figure 6.) When resourcessuch as food or clean water are limited,increases in access to them can bring signifi-cant health improvements. But once peoplehave adequate access to these resources, the

relationship between increased access andhealth gains becomes much less pronounced.Further increases in access may lead to mar-ginal improvements in health status, butoveruse of resources may lead to reduced


A New Health and Environment Framework

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CHANGES IN LAND USE AND COVERDeforestation, dams and irrigation, agricultural

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Figure 5. Complex Relationships Between Altered Environmental Conditionsand Human Health

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Figure 6. Proposed Relationship Between ResourceScarcity and Human Health

health status, as with excess food consumptionand obesity.

The causal chain between global environ-mental change and health impacts can bequite complex and can occur over long timescales that obscure the connections. Both landuse and climate change, for instance, caneither threaten human health directly, or theycan produce indirect threats by degradingecosystem services relevant to health. (SeeFigure 5, page 13.) These environmentalthreats may or may not lead to poor health

outcomes, depending on the vulnerability ofthe populations they affect.

What makes populations vulnerable? Forone, a population must be at a critical thresh-old of resource consumption, below whichthere will be significant health impacts. Thepopulation must depend heavily on its localresource base and be unable to meet its needsby accessing a regional or global market.Finally, the population must lack the infra-structure, adaptive behaviors, governance, oraccess to international philanthropy that mightotherwise protect it from the impacts of envi-ronmental degradation. Unfortunately, thesequalities describe many of the populations ofthe developing world.

To avoid missing crucial connections, wemust apply a new framework for analyzing therelationship between environmental changeand health that includes not only the growingthreats associated with accelerating environ-mental change, but also the presence orabsence of insulating factors that can deter-mine a population’s vulnerability to thesethreats. Among the most worrisome relation-ships between environmental change andhuman health are those associated with infec-tious disease, food and nutrition, water scarcityand quality, air pollution, and greater vulnera-bility to natural disasters and forced migration.



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Environmental Changeand Infectious Disease

here is ample evidence that humandisruption of ecological systems ischanging the distribution of infec-tious disease.1 Most studies show an

increase in disease transmission as a result ofaltered environmental conditions, but there arealso examples of such disruption decreasingtransmission. (Draining wetlands where mos-quitoes breed, for example, could eliminate alocal source of malaria, although it could alsoreduce water quality and increase exposure todiarrhea and other waterborne diseases.)

Global land use and climate change drivenew patterns of infectious disease exposurethrough a variety of mechanisms. Theseinclude changes to: the density or presence ofdisease-related organisms; exposure pathways(the way organisms, including humans, inter-act with each other); the genetics of patho-gens; the life cycles of pathogens and vectors(typically insects such as mosquito, fleas, orticks that transmit diseases by biting humans);and species composition within a communityof organisms.

Infectious diseases that are transmitted by avector or that have a non-human host or reser-voir, such as malaria, dengue fever, schistoso-miasis, and Chagas disease, are particularlysensitive to these types of changes.2 Given thatsuch diseases affect more than half the humanpopulation, alterations in their transmissioncan have significant impacts.3

Changes to Habitats and the Densityof Disease-related Organisms

Collectively, changes in land use and climateare altering the biological composition, struc-ture, and complexity of much of the global

land surface. They change temperature, precip-itation patterns, soil moisture, biogeochemicalcycles, nutrient concentrations, surface-waterchemistry, and exposure to sunlight. Theseparameters are often fundamental in definingthe range and breeding habitat of numerousvectors, hosts, and pathogens. As they change,we can expect changes in the density or pres-ence of these organisms.

Malaria offers a good case study because ofits high death toll and its resistance to efforts ateradication and long-term prophylaxis. Each


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A health worker checks standing water for mos-quito larvae in a disturbed landscape in Dar esSalaam, Tanzania.


been shown to increase roughly fivefold duringthe year following an El Niño event whenmonsoons are particularly extreme.8 Similarassociations have been shown between malariaoutbreaks and El Niño-related climate variabil-ity in Botswana.9

It is worrisome that the relationshipbetween malaria and rising temperature doesnot appear to be linear. Just a half-degreecentigrade increase in temperature can trans-late into a 30–100 percent increase in mosquitoabundance as a biological threshold appears tobe crossed, allowing successful breeding andsurvival of the vector.10 In addition to malaria,clear effects of climate change have been estab-lished for cutaneous leishmaniasis, cholera,plague, and dengue fever.11

Schistosomiasis provides another example ofthe numerous ways that a common infectiousdisease may be sensitive to climate or land usechanges. Schistosomiasis is caused by parasiticworms that spend part of their life cycle in

year, there are roughly 500 million cases ofmalaria and more than 1 million people(mostly children under the age of five) diefrom the disease, primarily in Africa.4 Malariais transmitted by a wide variety of location-specific mosquito species within the genusAnopheles. Many of the most pervasive types ofland use change, such as deforestation, dams,and agricultural development, affect the den-sity of different Anopheles vectors, leading toincreased disease transmission.5 (See Table 1.)

There is still active debate about how manymore people will become infected by vector-borne diseases as a result of climate change;however, there is little doubt that climatechange will alter the geographic distributionand seasonality of many of these diseases,including malaria.6 In the highlands of EastAfrica, a warming trend from 1950 to 2002coincided with increases in malaria incidence.7

In India’s Punjab region, malaria epidemics arestrongly associated with precipitation and have

Environmental Change and Infectious Disease

Table 1. Examples of Land Use Change and Increased Malaria Transmission

Land Use Change Examples

Deforestation In deforested areas of the Peruvian Amazon, biting rates of Anopheles darlingiare almost 300 times higher than in intact forest, controlling for differencesin human density across varied landscapes. Similar associations have beenobserved in sub-Saharan Africa. In Asia, deforestation favors some vectors overothers but frequently leads to increased transmission.

Dams Microdams in northern Ethiopia increase the concentration of the local Anophelesvector and are associated with a sevenfold increase in malaria in nearby villages.

Irrigation projects In India, irrigation projects in the 1990s improved breeding sites for A. culcifaciesand led to endemic “irrigation” malaria among roughly 200 million people.

Agricultural In Trinidad in the 1940s, the development of cacao plantations caused a majordevelopment malaria epidemic. Nurse trees shading the cacao provided ideal habitat for epi-

phytic bromeliads that, in turn, created excellent breeding sites for A. bellator,the principal local vector. The epidemic was not controlled until the nurse treeswere reduced and plantation techniques changed.

In Thailand, both cassava and sugarcane cultivation reduced the density of A.dirus but created widespread breeding grounds for A. minimus, with a resultingsurge in malaria.

Wetland drainage In Uganda, the drainage and cultivation of papyrus swamps caused higherambient temperatures and more A. gambiae individuals per household thanfound in villages surrounding undisturbed swamps.

Source: See Endnote 5 for this section.


freshwater snails and then leave the snails topenetrate the skin of people who enter con-taminated water. The disease can damage theliver, lungs, intestines, and bladder and infectsroughly 200 million people worldwide.12

A variety of land use changes have beenassociated with increased incidence of schisto-somiasis, including deforestation, dams, irriga-tion projects, overfishing, and livestockdevelopment projects.13 (See Table 2.) Defor-estation, for example, changes the ecology offreshwater snail populations by increasing sun-light penetration, encouraging vegetativegrowth, and changing water levels and flowrates. Many snail species do not survive thesechanges, but those that do tend to be betterhosts for the parasitic worms.14

The rapid proliferation of dams and irriga-tion projects worldwide has contributed


greatly to the surge in global schistosomiasis,as these projects generate new habitat for snailsthat are well adapted to the altered environ-ments and to hosting schistosomes. In additionto schistosomiasis and malaria, other diseasesassociated with water projects include Rift Val-ley Fever, filariasis, leishmaniasis, dracunculo-sis, onchocerciasis, and Japanese encephalitis.15

Although most large-scale water projects arerequired to undergo economic and environ-mental assessments, health impact assessmentshave generally been insufficient or non-existent.

Marine systems are also affected by globalenvironmental change. Rising sea-surface tem-peratures and increased application and runoffof fertilizers that cause nutrient enrichment ofwaterways have resulted in a surge in harmfulalgal blooms.16 Such blooms can lead to mas-sive fish kills, shellfish poisonings, disease and

Table 2. Examples of Land Use Change and Increased Schistosomiasis Incidence

Land Use Change Example

Deforestation In Cameroon, deforestation led to an upsurge in schistosomiasis as one typeof freshwater snail (Bulinus forskalii) was displaced by another (B. truncatus)that was better suited to cleared habitats. B. truncatus was an effective host forSchistosoma haematobium, a primary cause of urinary tract schistosomiasis.

Dams Construction of Egypt’s Aswan dam in 1965 created extensive new habitat for B.truncatus. As a result, S. haematobium infection in Upper and Middle Egypt rosefrom about 6 percent before construction of the dam to nearly 20 percent in the1980s. In Lower Egypt, intestinal schistosomiasis rose to an even greater extent.

Irrigation projects In Kenya’s Tana River region, the Hola irrigation project led to the introductionof snail vectors where they had never been before. Between 1956, when theproject began, and 1966, the prevalence of urinary schistosomiasis in childrenin the region went from 0 to 70 percent. By 1982, it was 90 percent.

Overfishing In Lake Malawi, evidence suggests that overfishing contributed to the recentsurge of schistosomiasis around the Nankumba Peninsula. Studies found that aspopulations of snail-eating fish declined, the B. globosus snail proliferated in areasthat used to be free of it. This relatively sudden surge in host density has beenassociated with a spike in schistosomiasis in an area historically free of the disease.

Livestock In China’s Yunnan Province, an economic development project attempted todevelopment raise local incomes by giving villagers cows—which also happen to be a key

reservoir of S. japonicum in the region. As the cows spread, they shed schisto-some eggs into waterways, where the parasites could infect local snails. Diseaserates surged, infecting up to 30 percent of some villages and correlating directlywith cattle ownership.


death of marine mammals, and human illnessand mortality.Worldwide, roughly 60,000 indi-vidual cases and clusters of human intoxicationfrom algal blooms occur annually.17 Healthimpacts range from acute neurotoxic disordersand death to subacute and chronic disease.

Cholera outbreaks in Asia and South Amer-ica have been associated with rising sea-surfacetemperatures, altered rainfall patterns, andnutrient loading from agricultural runoff.Copepods, a type of zooplankton, are a reser-voir of Vibrio cholerae, the bacterium thatcauses cholera. High nutrient loads and warmwater temperatures cause blooms of these zoo-plankton and can lead to the transformation ofV. cholerae from a quiescent to a virulent form.18

Changes in Exposure Pathways

In addition to changing the density or pres-ence of disease-related organisms, globalchange is also altering routes of infectious dis-ease exposure. Some of these new exposurepathways have little to do with changes in thenatural world—such as increases in trade andtransportation that facilitate the rapid move-ment of disease-related organisms around theglobe. However, many types of human-causedenvironmental change also lead to new expo-sure pathways.

Land use changes are often associated withthe movement of non-immune workers intoareas where they are exposed to infectious dis-eases with which they have little experience. Inareas of the Amazon that are being cleared foragriculture and infrastructure development,farmers, road-building crews, and other work-ers often create forest edge that is ideal habitatfor the mosquito species A. darlingi, drivingthe phenomenon known as “frontiermalaria.”19 Similarly, in Côte d’Ivoire, the culti-vation of coffee and cacao plantations createsexcellent habitat for the tsetse fly, a transmitterof African sleeping sickness (trypanosomiasis),and non-immune agricultural workers rapidlybecome infected by this vector.20

A second exposure route results fromdirect human incursions into wildlife habitat.In Central Africa alone, some 1–3.4 milliontons of bushmeat (meat from wild animalspecies) is harvested annually for food andother purposes.21 Bushmeat hunters whoreported direct contact with the blood orbody fluid of non-human primates have con-tracted simian foamy virus, a retrovirus thatis endemic in most Old World primates.22

This finding provides further support for thealready compelling hypothesis that the retro-virus causing HIV/AIDS was likely a mutatedsimian virus contracted through bushmeathunting.23

Human infection with Ebola virus alsolikely had its origin in bushmeat hunting.Between 2001 and 2003, five human Ebolaoutbreaks were reported in the forest regionbetween Gabon and the Republic of Congo.In each instance, the human outbreaks werepreceded by outbreaks in wildlife, andresearchers concluded that every case ofhuman Ebola transmission was the result ofhandling infected wild animal carcasses.24

Bushmeat hunting itself appears to bedriven by the need of growing populations tosupplement their protein intake. In Ghana, forexample, there are strong correlations betweena shrinking local fish supply and increasedbushmeat hunting over a 30-year period.25

Heavy fishing by European Union ships inWest African waters resulted in 20-fold



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increases in EU harvests in the region and inconsequent reductions in fish available in localmarkets. Reduced access to this importantsource of dietary protein was identified as acritical driver of bushmeat hunting in Ghana’sinterior. Overfishing by heavily subsidized EUfleets, then, appears to be one of the drivingforces behind increased bushmeat hunting andexposure to infectious disease, at least inGhana and probably elsewhere in Africa.

Human incursions into wildlife habitat alsostem from the expansion of settlement andfarming, potentially increasing exposure tozoonotic disease (infectious diseases in animalsthat can be transmitted to humans). Researchdone around Kibale National Park in Ugandasuggests that the transmission of pathogensbetween humans and non-human primates isrelated not to bushmeat hunting but to otherfactors including population growth, forestfragmentation, crop raiding, interaction withdomesticated animals, and direct interaction ofpeople and wildlife through farming, landclearing, scientific research, ecotourism, andconservation activities.26

Urbanization, an important land use trendand a central demographic trend of the early21st century, also provides new pathways forinfectious disease exposure. Humanity isbelieved to have become half-urban around2008, and this share is projected to reach two-thirds by 2050.27 Much of the rapid urbaniza-tion occurring today takes place in urban orperiurban slums that lack quality housing andhave few services for clean water provision,sewage disposal, or solid waste manage-ment.28 In these settings, pools of contami-nated water and piles of municipal waste andrefuse that are capable of holding water (suchas old tires) create excellent habitat for a vari-ety of rodent hosts and arthropod vectors,particularly those that transmit dengue fever,malaria, filariasis, Chagas disease, plague,leptospirosis, and typhus.29

In addition, rural-to-urban migrationbrings people from different disease-endemicregions together in high density, providing asource for new infection as well as non-immune hosts. Migration can also erode social

capital, which creates an obstacle to buildinginfrastructure to prevent disease transmissionand can change disease-related behaviors aswell.30 Poor-quality housing that does notprovide an effective barrier to mosquitoes,rodents, or fleas contributes further to thespread of vector-borne disease in slums.Finally, increased human population densityand size both increase the likelihood of infec-tious disease becoming established in an urbanpopulation.31

One example is dengue fever, which hasspread rapidly out of Southeast Asia and thePacific and become endemic throughout thetropics.With roughly 50 million cases in morethan 100 countries each year, dengue is themost common mosquito-borne viral disease inthe world.32 It is transmitted by the bite ofinfected Aedesmosquitoes, which feed selec-tively on humans and often breed in human-made containers that collect rainwater, such asjugs, tires, metal drums, discarded plastic foodcontainers, and other items. These characteris-tics make the insects well adapted to urbanareas, and dengue is primarily a disease ofurban communities.33

A final way in which global change can affectroutes of exposure to infectious disease is byaltering the fate or transport of disease patho-gens. Warmer temperatures in Europe, for



Children in the Central African Republic watch as their fatherbutchers bushmeat, including duikers (a local antelope) and amoustache monkey.

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example, correlate with increased incidence offood poisoning. The relationship is strongestfor the period one week prior to illness, is lin-ear, and has been reproduced in multiple Euro-pean cities. Presumably, warmer temperaturesallow the pathogen (the strongest relationshipwas seen for Salmonella enteritidis) to surviveand multiply in higher numbers.34

Changes in land use can affect the fate andtransport of pathogens as well. Agriculturaland livestock practices lead to exposure towaterborne disease through direct contamina-tion of water supplies. Protozoan parasitesincluding Cryptosporidium parvum and Giar-dia lamblia are shed in the feces of domesti-cated livestock. During periods of heavyprecipitation, they are washed into waterwaysand then into drinking water supplies. Sixty-four percent of farms studied in Pennsylvaniahad at least one cow infected with Cryptosporid-ium. On 44 percent of the farms, all bovinestool samples tested positive. On these farms,the cattle had full access to waterways that couldbe contaminated by their feces.35

This combination of land clearing andgrazing ruminants with no buffer zones toprotect waterways provides a widespreadavenue for human infection. In Milwaukee,Wisconsin, in 1993, despite a new water filtra-

tion system, more than 400,000 peoplewere estimated to show symptoms of cryp-tosporidiosis, and 54 died following a periodof heavy rainfall and runoff.36

A study of all-cause waterborne disease out-breaks in the United States found a strongassociation with heavy precipitation, with two-thirds of the outbreaks following exceptionallyrainy months.37 The combination of more-extreme precipitation patterns associated withclimate change and the continued expansion ofanimal husbandry may be a setup for growingnumbers of waterborne disease outbreaks, par-ticularly in parts of the world where there islittle water filtration infrastructure to insulatepopulations from this risk.

Genetic Alterations

Other livestock management practices areaffecting infectious disease occurrence by facil-itating genetic alterations. The intensificationof livestock management, with larger numbersof animals held in higher densities in closerproximity to other species, has allowedpathogens to proliferate and to develop geneticmodifications more rapidly. These modifica-tions can affect both pathogen infectiousnessand virulence. Exposure of livestock to largequantities and varieties of antibiotics hasdriven the proliferation of antibiotic-resistantstrains of Campylobacter, Salmonella, andEscherichia coli, all of which can cause serioushuman infections.38 In Malaysia, high-densitypig farming proved to be the critical factor inallowing Nipah virus to jump from bats to pigsand then to humans, ultimately causing over100 fatalities.39

Smaller-scale, backyard livestock manage-ment systems can also lead to genetic exchangeand alteration of pathogens. Influenza A virusesare highly infectious respiratory pathogens thatinfect a wide variety of species. Because swineare susceptible to both avian and humaninfluenza viruses, they can serve as genetic“mixing vessels,” leading to novel reassortmentviruses that have the potential to cause pan-demic influenza from strains to which humanpopulations have little immunity.40 It is increas-ingly clear that the H1N1 influenza strain that



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caused the 2009 pandemic—a strain that hasbeen shown to contain DNA from avian, pig,and human influenza types—had its origins inthis sort of genetic exchange between pigs,birds, and humans.

Close confinement of pigs and fowl, forexample in Asian “wet markets” and Chinesepig-duck farms, fosters this type of geneticexchange.41 The SARS epidemic is likely tohave resulted from crowding of animals in live-animal markets in China. In this case, thespecies at the center of the epidemic werehorseshoe bats and palm civet cats as amplify-ing hosts, with a possible role for raccoon dogsand Chinese ferret badgers as well. Most of theearly cases of SARS were among people whoworked with the sale or handling of these ani-mals.42 These practices, combined with theincursion of people into wildlife habitat, mayhelp to explain why roughly 75 percent ofemerging infectious diseases are zoonoses.43

Changes in Life Cycle of Vectors or Pathogens

Environmental change can directly alter the lifecycle of disease-related organisms. In experi-ments in the western Kenya highlands, investi-gators showed that by reducing shading,deforestation raises the average temperaturein homes by 1.8 degrees Celsius (°C) and innearby aquatic habitats by 4.8–6.1 °C. AmongAnophelesmosquitoes, these ambient tempera-ture changes are associated with gonotrophiccycles (the interval between egg-laying epi-sodes) that are nearly 60 percent shorter, amore rapid developmental period from larvato adult, and increased larval and adult sur-vivorship. All of these, not surprisingly,increase the capacity of mosquitoes to causemalaria and the risk that exposed populationswill be infected.44

Local deforestation has also been shown toincrease the geographic range of less-abundantmosquitoes—in this case A. arabiensis—intohigher altitudes. As a result of warmer ambienttemperatures in deforested areas, A. arabiensishas a 49–55 percent higher adult life span anda reproductive rate about twice that in forestedareas. It has been suggested that a combinationof deforestation and climate change may facili-

tate the establishment of A. arabiensis as animportant cause of malaria in the highlandsof Kenya.45

Changing Species Composition

Complex changes in the types of organismsthat make up whole ecological communitiescan have dramatic impacts on infectious dis-ease exposure. In Belize, for example, theapplication of fertilizer to higher-elevationagricultural lands has been found to increasemalaria exposure downstream. The influx ofphosphorus and other nutrients causes short,sparse wetland vegetation to be replaced bydenser, thicker vegetation dominated by cat-tails—a breeding habitat favored by females ofthe species A. vestitipennis over A. albimanus.46

The result is a higher density of A. vestitipen-nis, a significantly more effective malaria vec-tor.47 Nor is Belize an isolated example. In arecent survey of 41 different pathogens on sixcontinents, nutrient enrichment led to ecologi-cal changes that increased disease exposure 95percent of the time.48

Lyme disease exposure in the northeasternUnited States also has a complex ecology. Lymedisease is caused by infection with the bac-terium, Borrelia burgdorferi. In the northeast-ern United States, it is transmitted by the bite



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of the blacklegged tick. The most competentreservoir of Lyme disease is the white-footedmouse. The abundance of these mice is a goodpredictor of the number of infected ticks.Because acorns are this mouse’s most impor-tant food source, the density of mice isstrongly associated with the abundance ofacorns in the prior fall. Not surprisingly, theabundance of infected ticks is also tightly asso-ciated with acorn abundance, although there isa two-year lag as a result of the long life cycleof the tick.49

But Lyme disease exposure depends onmore than the number of acorns available. Italso depends on the species composition of theentire mammalian community in northeasternforests. Because most other mammals are muchless competent reservoirs of Lyme disease, thepresence of more non-mouse mammals, onwhich ticks may feed, reduces the likelihood ofa tick becoming infected.50 This effect of biolog-ical diversity reducing disease transmission—known as the “dilution effect”—has beendescribed in a variety of other diseases includ-ing West Nile virus encephalitis, hantaviruspulmonary syndrome, and bartonellosis.51

In a final example, human outbreaks of St.Louis encephalitis (SLE) have followed wetsummers after dry springs. To cause mosquitoinfection rates sufficient to drive human epi-demics, SLE must be amplified in avian hosts.In South Florida, drought conditions in thespring cause Culex nigripalpus—the mosquitovector—to restrict its activity to densely vege-tated, wet, “hammock” habitats. Nesting wildbirds also make use of these habitats in thespring, and it appears that drought drives themosquitoes and birds into close contact. Thisforced contact provides for rapid amplifica-tion of the SLE virus in the infected birds.Subsequent wet conditions cause both birdsand mosquitoes to disperse and favor breedingand feeding by C. nigripalpus. With a criticalmass of wild birds already infected, newlyhatched mosquitoes can be infected by feedingon birds that still carry live virus loads, thus

maintaining the transmission cycle. The epi-demic of SLE among human residents ofIndian River County, Florida, in 1990appeared to depend on this complex ecologyof interactions among land cover, climate,wild birds, and mosquitoes.52

One theme emerging from research on suchinteractions is the complexity of relationshipsbetween land use, climate phenomenon,species diversity, and disease transmission.Directly stemming from this complexity is asecond theme: the unpredictability of diseaseoutcomes.Who would have predicted, basedon logic alone, that a disease that stops oaktrees from producing acorns might reducehuman exposure to Lyme disease, or that moreefficient use of fertilizers on mountain slopesof Belize might reduce malaria exposure hun-dreds of kilometers away?

A third emerging theme is the extent towhich ecological disturbance appears to favorrather than diminish disease transmission.More often than not, disruption of historicalland cover through deforestation, dams andirrigation, agricultural practices, and livestockmanagement practices seems to boost the riskof disease exposure. Both nutrient enrichmentand reductions in species diversity are addi-tional causes of increased disease exposure inmost systems that have been studied.

The reasons why degradation of ecologicalsystems would favor increased disease trans-mission are not obvious. Some researchersbelieve that pathogens may have evolved witha preference for infecting generalist species,such as rats, crows, and sparrows. By doing so,they would have access to host species in awide variety of ecological settings. Becauseecological disturbance also tends to favor thesegeneralist species (which are flexible in theirhabitat preferences), such an adaptationwould explain the link between ecological dis-ruption, increased prevalence of generalistspecies, and increased exposure to diseasescaused by these pathogens.53



Environmental Change,Food, and Nutrition

lthough the relationships betweenenvironmental change and infectiousdiseases are the best studied, theymay not in fact be the most impor-

tant health impacts of environmental change.Scarcities of food and water and greater vul-nerability to natural disasters and forcedmigration could lead to higher human deathrates and disease burdens than increased infec-tious disease exposure. At the same time, foodand water scarcity, natural disasters, and dis-placement all contribute to infectious diseaseas a result of both weakened immunity andincreased exposure.

The ecosystem service perhaps most essen-tial to human health is food production. Ade-quate nutrition—not just a full complement ofenergy-storing calories, but also protein andessential vitamins, minerals, and othermicronutrients—is vital to life. Yet today, anestimated 1.02 billion people—nearly a sixth ofthe global population—are undernourished,the highest number ever recorded.1 (See Figure7.) By some estimates, at least a third of thedisease burden in poor countries is due to mal-nutrition, and roughly 16 percent of the globaldisease burden is attributable to childhoodmalnutrition.2 Health impacts associated withnutritional shortfalls include impairments incognitive development and learning, metabolicand endocrine functioning, reproductivehealth, prevention and fighting of infectiousdisease, and overall vigor.

As the human population grows by roughly2.5 billion people by 2050, and as more pros-perous people across the globe add more meatto their diets, world agricultural productionwill need to roughly double over the next 50

years to keep up with projected demand.3 Oneof the central public health questions of thiscentury is whether we can meet this demand orwhether ecological constraints will stymie us.

This question must be answered at twoscales, local and global. Because most of thechronically hungry people in the world are alsoamong the over 1 billion people who live inabsolute poverty, global food production isonly partly relevant. Most of these people aretoo poor to access global food markets, andconsequently depend on local production. Forthem, local ecological constraints can drivehunger, disease, and death, even while globalfood production exceeds demand.

In many parts of the world, rapidly grow-ing populations are already encountering eco-logical constraints to local food production.Over the past 30 years, severe soil-nutrientdepletion in 37 African countries has led to


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allow a doubling of global output.7 However,each of these elements may be ecologicallyconstrained.8 (See Table 3.)

Two other global trends are likely to affectfood supplies. On the demand side, the accel-eration of biofuels production has stimulateda new, non-food market for cereals thatamounted to nearly 5 percent of global cerealproduction in 2009.9 For the first time, hungrypeople are competing directly with motorvehicles for the same grain, a development thathas potentially ominous consequences for thehungry poor.

On the supply side, climate change is certainto affect food production by altering biophysi-cal conditions.10 The Intergovernmental Panelon Climate Change projects with “high confi-dence” that many semi-arid areas (for exam-

significant soil impoverishment and reducedoutput.4 Similarly, water scarcity is necessitat-ing grain imports in all but two of the 34countries in Africa, Asia, and the Middle Eastthat have annual per capita runoff levelsbelow 1,700 cubic meters, a condition knownas water stress.5 With the number of peopleliving in water-stressed countries in theseregions projected to rise from 470 million tomore than 3 billion by 2025, regional waterscarcity is likely to affect local food produc-tion quite significantly.6

Increasing agricultural output at the globalscale may be limited by ecological constraintsas well. Some analysts are optimistic that a10–20 percent increase in land under cultiva-tion, combined with more widespread use ofirrigation, fertilizer, and new crop strains, will

Environmental Change, Food, and Nutrition

Table 3. Potential Ecological Constraints on Increased Global Food Production

Factor Ecological Constraint

Arable land Existing arable land already suffers degradation and outright destruction from soil ero-sion, salinization, desertification, and conversion to other uses, including rapid urban-ization. As farmers increase production, approaches that may have been sustainable inthe past are essentially “mining” soils unsustainably, resulting in dramatic net reduc-tions in fertility. Tillage agriculture is estimated to cause erosion at rates that exceedsoil formation by 1–2 orders of magnitude.

Irrigation Doubling agricultural output will require roughly an additional 2,000–3,000 cubic kilo-water meters of irrigation water per year—the equivalent of over 110 Colorado Rivers and a

more than tripling of current demand. Yet the three largest grain producers are miningaquifers faster than they can be recharged. In the North China Plain, where half ofChina’s wheat is grown, water tables are falling by more than 1 meter per year. In India, 15percent of grain production depends on water mined unsustainably from fossil aqui-fers, and blackouts are frequent in states where half of all electricity is used to pumpwater from as deep as 1 kilometer. In the United States, the water table below parts ofTexas, Oklahoma, and Kansas has dropped more than 30 meters in the past century.

Fertilizer Humans already release more nitrogen and phosphorus to terrestrial ecosystems thanall natural systems combined. Doubling food production by 2050 will require increasingapplications of both inputs by roughly 2.5 times, exacerbating already-serious impactsincluding eutrophication of marine ecosystems, biodiversity loss, groundwater and airpollution, and acidification of soils and fresh water.

Crop yields In many large grain-producing areas, crop yields per hectare are approaching biologicallimits that leave little room for significant gains. In sub-Saharan Africa, where big yieldgaps remain, the diversity of agro-climatic conditions makes disseminating high-yieldingseeds particularly challenging. And while new crop strains may provide greater resistanceto stress, there is little evidence that they provide significant gains in yield potential.



mum, certain agricultural regions are likely tosee significant overall reductions in food pro-duction, particularly in sub-Saharan Africaand South Asia—the regions where food inse-curity has often been the highest.17 Someresearchers believe that climate change couldreduce agricultural yields by up to 40 percentacross much of the tropics.18

Climate change will create an additionalobstacle to meeting global nutritional needs.There is strong evidence that grain grown at550 parts per million of carbon dioxide (a levelanticipated by 2050) contains 15–30 percentless protein, zinc, and iron than grain grown attoday’s levels. Already, some 3 billion peopleworldwide have zinc and iron deficiencies, anda large share of the more than 1 billion peoplesuffering from chronic malnutrition have pro-tein deficiencies.19 The main source of thesenutrients, particularly for women and childrenin the developing world, is grain because thereis so little meat in their diets. Further reduc-tions in access to protein and micronutrients islikely to cause a significant rise in the overallburden of disease. Thus, climate change is likelyto affect not only the quantity of food avail-able, but also the nutritional quality of food.

ple, the Mediterranean basin, western UnitedStates, southern Africa, and northeast Brazil)will suffer a decrease in water resources.11 Cli-mate change is already causing rapid meltingof glaciers that supply dry-season flow to manyof the world’s great rivers—including glacierson the Tibetan plateau that supply water tomore than a billion people downstream.12

Sea-level rise, weakened coastal barriers,and more-intense storms will lead to morecoastal flooding and to inundation of coastalfreshwater aquifers and fertile soils with saltwater.Winter snowpack is expected to meltearlier in the year, disconnecting water supplyfrom the height of the growing season in someareas.Warmer temperatures will also lead togreater evaporation from soils and plants andincrease irrigation requirements for crops. Allof these dynamics will further limit already-constrained access to fresh water for irrigation.

In addition, temperature rise has directimpacts on crop yields. Having been developedto maximize yields under current climate con-ditions, most cultivars now in use are grown ator near their upper limits of temperature forgrowth. A rule of thumb among crop ecolo-gists is that a 1 °C rise in the minimum tem-perature during the growing season leads to a10-percent reduction in yields of rice, wheat,or corn.13 This was recently confirmed by atime-series analysis from 1979 to 2003 at theInternational Rice Research Institute.14

Numerous modeling studies project similarsensitivities of the major grains to a 1 °C rise intemperature, with a yield change ranging from+3 percent to -17 percent depending on theregion and crop.15

Such extreme temperature sensitivity couldresult in major reductions in crop yields inmany of the most important food-producingregions, including the North China Plain,India’s Gangetic Plain, and the U.S. CornBelt.16 While the net impact of climate changeon global agricultural productivity is stilldebated, there is agreement that, at a mini-


Rice cultivation in Mali, with its demanding irrigation requirements,may not be sustainable in the future.

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Other Health Outcomes

n addition to affecting exposure to infec-tious disease and access to adequate nutri-tion, human-caused environmental changeadversely affects health through many

other pathways. These include: water scarcityand unsafe water supplies, natural disasters,increased air pollution, and population dis-placement.

Water and Sanitation

One ecosystem service critical to human healthis the provision of clean water. Each personneeds roughly 50 liters of uncontaminated

fresh water per day to meet basic needs rangingfrom food preparation to drinking water, sani-tation, and hygiene.1 Inadequate access todrinking water, sanitation, and hygiene is esti-mated to cause 1.7 million deaths annually andthe loss of at least 50 million healthy life years.Half of the urban population of Africa, Asia,and Latin America and the Caribbean suffersfrom one or more diseases associated withinadequate water and sanitation.2

Water is already scarce and getting scarcer.Humanity now uses roughly 40–50 percent ofthe available fresh water on the planet.3 Ratesof increase in water use relative to accessiblesupply from 1960 to the present have beennearly 20 percent per decade globally, withrates for individual continents rangingbetween 15 percent and more than 30 percent.

As with food, our ability to meet futurewater needs faces constraints on both the sup-ply and demand sides. On the supply side, fur-ther intensification of agriculture and livestockwill generate additional runoff of nutrientsand wastes, causing groundwater contamina-tion and pollution of freshwater systems.4

Urbanization and the growth of manufactur-ing continue to drive both biological andchemical contamination. And climate change isalready leading to physical changes that arelikely to further reduce access to fresh water.On the demand side, population growth, con-tinued economic development, and rapidlygrowing manufacturing and agriculture willcontinue to place additional demands onglobal freshwater supplies.

The health impacts of reduced access toclean fresh water depend on a variety of medi-ating factors.Wealthy populations, such as in

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Children collect water to take back to their villagein the Volta region of Ghana.

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Israel, have developed highly efficient irriga-tion technologies, sanitation systems thatrequire little water, and the economic capacityto import water in the form of grain (about1,000 tons of water are used to grow 1 ton ofgrain). Poorer populations, however, are lesscapable of insulating themselves with technol-ogy and infrastructure and lack the purchasingpower to replace locally constrained resourceson the international market. Lacking suchresources, they are vulnerable to local waterscarcity just as they are vulnerable to local foodscarcity. Such vulnerability varies by socioeco-nomic status as well as by gender and age;women, for example, suffer disproportionatelyas a result of water shortages.5

Natural Disasters

Increasing vulnerability to natural disasters isyet another area where changing environmen-tal conditions may affect human health andwellbeing. Since 1980, the number of Category5 (devastating) natural disasters worldwide hastrended upward, with a record 40 such disas-ters registered in 2008.6 (See Figure 8.) All butone of these events—which included Hurri-cane Gustav in the Atlantic Ocean; monsoonalfloods in India, Bangladesh, and Nepal; andTyphoon Fengshen in the Philippines—wereweather-related.7

Human vulnerability to disasters dependson such factors as where people live, the qual-ity of their housing, disaster preparedness, theavailability of early-warning systems, and envi-ronmental conditions. 8As both the number ofdisaster events and vulnerabilities to them haveincreased, so too have the associated impacts.9

Twice as many people were affected by naturaldisasters in the 1990s as in the 1980s.10 Averageannual losses for all disasters in the 1990scomprised 62,000 deaths, 200 million peopleaffected, and $69 billion in economic losses.12

Data limitations make it difficult to evaluatethe contribution that environmental changehas played in increasing vulnerability to fires,floods, storms, tidal waves, landslides, andother natural disasters. Model simulations andempirical observations indicate that damagefrom the Indian Ocean tsunami of 2004 was

exacerbated by earlier destruction of coralreefs.13 Additional studies have shown thatareas where mangrove forests had beendestroyed suffered disproportionate damage.14

Compounding these changes in land useand cover are current and anticipated changesresulting from climatic disruption. The IPCChas expressed “high confidence” that a warm-ing of up to 2 °C above 1900–2000 levels (onthe lower end of most projections for 2100)would increase the risk of extreme eventsincluding severe tropical cyclones, floods,droughts, heatwaves, and fires.15 There is con-siderable uncertainty about the amount of sea-level rise this century, but recent estimatessuggest between 0.8 and 2.0 meters, althoughhigher levels are possible.16 Higher seas willmake coastal areas, where more than a third ofthe human population lives, particularly vul-nerable.17 The rapid destruction of coastal bar-riers such as mangrove forests, coral reefs,vegetated dunes, and wetlands, combined withsea-level rise and increasingly intense storms,represents a triple threat that is likely to causesignificant morbidity, mortality, and popula-tion displacement.

Natural disasters can cause death or illnessas a result of heat stress, acute injuries, ordrowning. In addition, severe storms canresult in pollution or biological contamina-tion of water supplies, and air quality may



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Figure 8. Number of Category 5 Natural Disasters,1980–2008

suffer as a result of fires or of mildew inhomes following flooding. Loss of homes andthe resulting population displacement hasnumerous health impacts as well. (See page29.) And we are only just beginning to under-stand the significant mental-health impacts ofdisasters. Survivors of Hurricane Katrina, forexample, suffered twice the rate of mental ill-ness as a similar population in New Orleansprior to the hurricane.18

Air Pollution

Extensive research documents the negativehealth impacts of both indoor and outdoor airpollution.19 Most of this work falls into therealm of traditional environmental health,which addresses the local impacts of exposureto toxic pollutants. But in some regions, airpollution has become so extensive that it is lit-erally blotting out the sun, altering regionalweather patterns, affecting agriculture produc-tion, and accelerating glacial melting.20

Atmospheric brown clouds (ABCs), com-posed primarily of the combustion products offossil fuels and biomass (including wood anddung used in household cooking stoves), causean estimated 337,000 excess deaths from heartand respiratory disease annually in China andIndia. In addition to these direct health effects,ABCs prevent sunlight from reaching the

Earth’s surface, thereby reducing agriculturalyields. ABCs are contributing to reductions inthe Indian summer monsoon rainfall and toshifting rainfall patterns in eastern China.21

Soot deposition from ABCs onto glaciers, par-ticularly the Hindu Kush-Himalayan Tibetanglaciers and snowpacks, is further acceleratingmelting, with worrisome consequences for thewater security of South and East Asia. All ofthese impacts of ABCs pose challenges to agri-cultural production and may explain in partthe declining annual growth in harvests of rice,wheat, maize, and sorghum throughout Asia,from 3.5 percent during 1961–1984 to 1.3 per-cent during 1985–1998.22

Global environmental change is affecting airquality in other ways as well. Ground-levelozone is strongly associated with increasedillness and death from cardiorespiratory dis-ease.23 The application of nitrogen-containingfertilizers to agricultural lands produces nitrousoxide (as does fossil fuel combustion), which isan important precursor to ozone formation.Of even greater concern, ground-level ozoneformation rises with temperature, with a par-ticularly strong association found at tempera-tures above 32 °C. Studies modeling climatechange project increased concentrations ofground-level ozone with consequent increasesin respiratory sickness and death as a result ofhigher temperatures.24

In addition, warmer temperatures andhigher CO2 concentrations are associated withlonger pollen seasons and increased pollenproduction for many allergenic plants. Forexample, ragweed that is grown at the concen-tration of CO2 anticipated for 2050 hasroughly 60 percent more pollen than ragweedgrown at current levels.25 This trend will causeadditional allergic respiratory disease, particu-larly asthma, which is already associated with aquarter-million deaths annually.26

Population Displacement

Population displacement and violent conflictcould become common outcomes as large,vulnerable populations suffer amplified expo-sure to water scarcity, hunger, and naturaldisasters. Already in 2008, an estimated 42



Two women commiserate amid the rubble of buildings destroyedby severe flooding in Balochistan province, Pakistan.

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million people worldwide were consideredrefugees or displaced persons, the majority ofthem in sub-Saharan Africa and Asia.27

The United Nations High Commissioner forRefugees estimates that between 250 millionand 1 billion additional people will be dis-placed by climate change alone between nowand 2050.28 Sea-level rise and more-extremestorms will make some low-lying coastal areasand islands untenable for habitation. (Coastalareas less than 10 meters above sea level repre-sent only 2 percent of the world’s land area, yetthey house 10 percent of the world’s popula-tion.29) Similarly, altered precipitation patternsare likely to turn already-marginal agriculturallands into deserts that cannot support localpopulations. Local scarcities of food and watermay drive populations out of resource-poorregions. These forces, working in concert, maylead hundreds of millions of people with fewresources and many needs to seek new homes.30

Population displacement is associated withnegative health outcomes for a variety of rea-sons. Non-immune populations migrating intodisease-endemic areas are more susceptible tomany infectious diseases.31 Poor housing, sani-tation, and waste management infrastructure,combined with unsafe drinking water andpoor nutrition, can lead to epidemics of infec-tious disease, particularly diarrheal diseases,measles, and acute respiratory infections. Pro-tein-energy malnutrition increases mortalityfrom these communicable diseases and con-tributes independently to illness and death.Prevalence rates of acute malnutrition havereached up to 50 percent in refugee popula-tions in Africa.32

In addition to malnutrition and communi-

cable disease, displaced people suffer high lev-els of violence, sexual abuse, and mental ill-ness. One study found symptoms and signs ofpost-traumatic stress disorder in 30 to 75 per-cent of resettled refugee children and adoles-cents.33 Overall, crude mortality rates as highas 30 times the baseline are not unusual fol-lowing an acute movement of refugees, withmuch of the mortality occurring in childrenunder the age of five.34

Added to the burden of suffering and dis-ease associated with population displacementitself is the risk of violent conflict. Already,resource scarcity has played an important rolein generating such conflict, and the prospect ofsignificantly larger numbers of resource-con-strained people seeking new homes in already-settled lands raises concern for greater conflictin the future.35



Shanghai smog in 2005, from the Oriental Pearl Tower.

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Adapting to the HealthImpacts of Climate Change


make things worse instead of better.But the fact that climate change is a threat

magnifier—and not, primarily, a source ofentirely new public health challenges—mayrepresent an opportunity as well as a challenge.If the international community accepts themoral imperative to help lower-income coun-tries reduce their vulnerability to the healththreats from climate change, it will also behelping those countries take strides towardaddressing entrenched threats that have been alongstanding scourge to the health of theireconomies and people.

Approaches to Adaptation

Efforts to adapt to the health impacts of cli-mate change must take three important char-acteristics into account:• Many health impacts are likely to be large,affecting hundreds of millions, possibly evenbillions, of people;

• The magnitude, timing, and location ofimpacts are inherently unpredictable. Thethreats are not likely to be new, although theirsize may be unprecedented. Rather, they willbe amplifications of existing health threats.

• The impacts will be experienced disproportion-ately by vulnerable populations in resource-constrained, low-income countries.From these characteristics, several key con-

cepts emerge. One is that there is a moralimperative for the wealthy world to assistlower-income countries with adaptation, giventhe size of the health threats, their preventabil-ity, and the disproportionate vulnerability oflower-income countries to them.

A second principle is the need to define“no-regrets” solutions. Despite improvements

nternational discussions about climatechange, its impacts, and how best to reducevulnerability cannot afford to ignore thelinkages between climate change and

human health. The disruption of our climaterepresents an accelerating destabilization of analready fundamentally unstable relationshipbetween humanity and its natural resourcebase. Because climate change is a new and rap-idly accelerating source of human-inducedglobal environmental change, there is a specialurgency to address it.

Climate change is a threat magnifier. It willmagnify water scarcity in areas that alreadyface unsustainable water use, and create newscarcities elsewhere. It will affect crop yieldsand generate obstacles to meeting global nutri-tional needs. It is also likely to cause more-fre-quent and severe natural disasters, alter thedistribution of infectious diseases, and reducethe air quality across large parts of the globe.And—as a result of all of these effects and oth-ers—it is likely to cause large-scale populationdisplacement and migration to a degree thathumans have not before witnessed.

In a cruel irony, the suffering that willresult from these impacts will occur mostlyamong the world’s poorest populations—those who have made the least contributionto climate change. Many of these people livein countries that are already overwhelmed byexisting public health challenges that stemfrom treatable conditions, such as malnutri-tion, diarrhea, acute respiratory infections,malaria, and other infectious diseases. Divert-ing limited personnel and resources awayfrom these ongoing problems to addressfuture threats from climate change could

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dictable, it would make sense to pool risk anddevelop insurance strategies whereby countriesagree to help whichever populations absorbthe greatest impacts. Before the victims of nat-ural disasters, coastal flooding, droughts, cropfailures, or acute water shortages have beendefined, such insurance agreements could beput into effect.

A fourth principle is the importance of sur-veillance. Because even the most sophisticatedclimate change models will be incapable ofpredicting biophysical changes in specificlocations with great accuracy, surveillancebecomes increasingly important. We knowthat conditions are likely to change, some-times fairly rapidly. It will be important togather and analyze information about fieldconditions across a variety of sectors. Surveil-lance of crop productivity, in-stream flowrates and water tables, food consumption andrates of malnutrition, and population move-ments will be as important to track as chang-ing distributions of vector-borne disease,water-related disease, or other infectious dis-eases. These types of surveillance will be animportant part of improving early warningsof climate impacts so that resources can betargeted to address emerging threats beforethey become humanitarian crises.

in climate change science, there will continueto be significant uncertainty about the loca-tion, timing, and magnitude of health impacts.At the same time, the impacts are most likelyto be experienced by people living in countrieswith few resources to address already-existingpublic health threats. Given these realities, andthe fact that climate change will magnify exist-ing threats more than generate entirely newones, adaptation strategies should be based on“upstream” interventions that will yield bene-fits regardless of the timing and location ofspecific climate-related events.

Examples of such “no-regrets” strategies are:improving public health infrastructure; devel-oping more-diverse crop strains that are toler-ant to a variety of different conditions (heat,drought, salt, etc); bolstering social capital andresilience, particularly in developing-countrymegacities; increasing storage capacity for freshwater by building reservoirs or rechargingaquifers; creating early-warning systems andpreparedness plans; and bolstering disease sur-veillance. We should design these types of activ-ities with climate change in mind, but they willprovide benefits independent of the preciseimpacts of climate change in a given setting.

Such an approach will help to avoid thedanger of diverting limited resources in devel-oping countries away from existing threats thatare already responsible for large disease bur-dens. Many of these interventions may beundertaken within the context of ongoing for-eign assistance. Indeed, there is a pressing needto contextualize the international conversationabout the effectiveness of foreign aid and theachievement of the United Nations’ Millen-nium Development Goals with an understand-ing of the impacts of climate change (andother types of global environmental change)and the need to reduce vulnerability to them.The challenge, then, is to focus developmentassistance so that it addresses existing threatsindependent of climate but simultaneouslybolsters resilience to the amplification of thesethreats that we anticipate from climate change.

A third principle is the need to employinsurance strategies. Because the impacts ofclimate change in a specific location are unpre-

Adapting to the Health Impacts of Climate Change

In the aftermath of torrential flooding in Assam, India, people arereduced to foot travel on the remains of a washed-out road.

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Finally, there is an urgent need for moreresearch to model the health impacts of cli-mate change in specific locations, to evaluateapproaches to reducing vulnerability, and toperform cost-effectiveness analyses on differ-ent adaptation approaches. There are manyoutstanding questions about how best to man-age the relocation of millions of people or howto improve social capital and communityaction in developing-country megacities where70 percent of the populations live in slums.There is a need to combine long-range weatherforecasting with modeling of ecosystem serv-ices such as food and water generation and

A fifth principle is the importance ofaddressing demographics. Human populationgrowth will increase vulnerability to many ofthe most worrisome health impacts of climatechange. Food scarcity, water scarcity, vulnera-bility to natural disasters, and population dis-placement are all exacerbated by havinggrowing populations relying on limited landand resources. One upstream intervention thatshould play a central role in both reducinggreenhouse gas emissions and reducing vulner-ability to health impacts of climate change isreducing the unmet need for family planningservices.1 (See Sidebar 1.)


Sidebar 1. Health and Environmental Co-Benefits of Family Planning

Currently, more than 200 million women worldwide do not have access to the family planning servicesthey want or need, ranging from contraception to reproductive health counseling. Contraception allowscouples and women to decide for themselves whether, when, and how often to give birth. Providingthese services accomplishes three critical goals simultaneously: it reduces maternal and child mortality,it reduces vulnerability to many of the impacts of global environmental change by reducing pressure onlimited natural resources, and it mitigates climate change by reducing greenhouse gas emissions.Each year, some 80 million women worldwide become pregnant without intending to do so, result-

ing in high fertility rates in many parts of the world. This amounts to between one-third and one-half ofall pregnancies and is roughly equal to the amount that the world population grows each year (79 mil-lion). Widespread adoption of family planning enables populations to maintain fertility rates close toor below two children per woman. After two or more decades of such low fertility, populations (and theworld population as a whole) can stop growing and enter a period of improved stability.Family planning increases the intervals between pregnancies, directly benefiting the health and sur-

vival prospects of mothers and their children. A child’s survival is most likely when birth spacing is atleast 36 to 59 months—an interval that can be achieved consistently only through contraception.Women at high risk for problem pregnancies can benefit in particular from access to family planningand the broader reproductive health care that should accompany it. By reducing the number of preg-nancies and births, especially unplanned ones, the overall risk of death and poor health outcomes isreduced for each woman throughout her lifetime.A gradual ending and reversal of human population growth (currently at 1.1 percent annually) is

essential to long-term environmental sustainability. A smaller human footprint would ease pressure onnatural resources—freshwater supplies, forests, fisheries, and biological diversity—while making itmore feasible for global food production to feed the world while sustaining the planet. A smaller worldpopulation will also simplify the task of shrinking global greenhouse gas emissions in an equitablemanner, especially later in the century as more widespread economic development results in greaterequality in per capita emissions. Finally, slowing population growth is an adaptive strategy againstmany of the predicted impacts of climate change—food and water scarcity, natural disasters, and pop-ulation displacement—all of which will be exacerbated by larger populations needing access toresources, secure homes, and productive lands.Even in the absence of climate change, smaller, healthier populations would be a powerful compo-

nent of more resilient societies. No other intervention would provide more benefits across the healthand environmental sectors than providing global access to family planning services.



most vulnerable populations have been identi-fied, planners will be able to make specific pol-icy recommendations. A country facingsignificant risks from water scarcity mightemphasize the need to increase water storagethrough dams or recharging aquifers, or mightrecommend rapid adoption of more water-efficient irrigation or sanitation technology. Acountry confronting food shortages, and with-out the economic prospects to purchase foodon international markets, might emphasizeless-vulnerable forms of agriculture includingthe development of new drought- and heat-tolerant crop strains, more-efficient and wide-spread use of fertilizer, different approaches tosoil management, or new crop types altogether.Coastal regions may need to invest in restoringnatural coastal barriers, building infrastructurebetter capable of withstanding storm surge,developing early-warning systems for coastalflooding, or relocating populations entirely. Ineach location, the menu of interventions andpolicies that will be most effective at reducingvulnerability will be different.

land-cover analysis to provide early warningfor water scarcity, food scarcity, or epidemicdisease. These types of research will needaggressive support to have an impact.

National Adaptation Planning

While the general principles above are criticalto addressing the health impacts of climatechange, specific policy recommendations mustemerge from a careful analysis of local condi-tions. The most important truth about thehealth (and other) impacts of climate changeis that both the threats and the vulnerabilitieswill vary tremendously by location. For thisreason, it will be critical to perform national-level risk assessments that cut across disci-plines and sectors. Such assessments muststart with the best available projections of howlocal climate is likely to change, includingchanges in temperature, precipitation, sealevel, and natural hazards. They should alsoinclude assumptions about demographicchange, including population growth andmigration, and about economic growth andinfrastructure development.

Based on these projections, planners canmodel anticipated freshwater supplies, foodproduction, changes in air quality, altered dis-tribution of infectious disease, and future pop-ulation displacement. National plannersshould also identify those sub-populations thatare particularly vulnerable. These populationsmay be defined by ethnicity, gender, age,socioeconomic status, and geographic location.The threats in different places will be different.Some regions will highlight water scarcity orfood shortages as critical, while others willidentify coastal vulnerability or desertificationand migration as the highest-priority threats.Without doing this type of rigorous risk assess-ment, it will be impossible to target limitedresources to the highest-priority threats andthe most vulnerable populations.

Once the highest-priority risks and the


Women at the Women’s Skills Development Center in Pokhara,Nepal, receive family planning information.

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Moving Forward ina Changing World


initiatives such as India’s 150-million-stoveprogram, improved cook stoves are becomingmore widely distributed throughout thedeveloping world, with tremendous implica-tions for both reducing climate change andimproving health, particularly among womenand children. Meanwhile, farmers worldwideare turning to water-conserving technologiessuch as drip irrigation and to more-efficient“no-till” cultivation, a practice that savesboth time and energy while producing similaryields to conventional farming.2 Otherencouraging trends include the rising pro-liferation of low-interest microfinance loansfor the poor and self-employed (especiallywomen), “bus rapid transit” and otherimprovements in urban transport and design,and new technologies that have enabled thecosts of renewable energy to approach thoseof fossil fuels.3

In the health arena, inexpensive multime-dia and mobile communications technologiesare being applied in a concept called “m-health,” a public health practice supported bycell phones, patient monitoring devices, andother wireless equipment that sends real-timepatient data to health practitioners. As theexplosion of mobile phone use continues inthe developing world, telecommunicationstechnologies are an important component ofboth economic and social development,including health-systems strengthening.

Innovations like these are characterized bythe application of new thinking and evolvingtechnology to an understanding of environ-mental and social constraints. More suchinnovation will be required on a massive scaleto achieve true sustainable development and

he need to act goes beyond mitiga-tion of, and adaptation to, human-induced climate change. Acceleratingchanges to the planet’s land surface

and the functioning of its ecosystems are actingsynergistically with climate change to generateemerging threats to human health at a scalethat threatens the health and wellbeing of hun-dreds of millions—even billions—of people.

Collectively, these threats are likely to be thegreatest public health challenge of the 21st cen-tury. Responding to them effectively willrequire new approaches to economic andhuman development, new technologies, andnew research efforts, as well as new approachesto policy and decision making. Much of thehuman suffering likely to result from thesetrends is preventable—there is a tremendousamount that can be done.

Despite the increasing scale of environmen-tal degradation and the growing risks of climatechange and ecosystem disruption, there aremany positive trends that should encourage usas we seek to slow the pace of environmentalchange and to lessen its toll on health. One crit-ical factor is the size of the human population.Over the past four decades, the number of chil-dren born to each woman on average has fallenby nearly half, to only a fraction of a birthabove the “replacement” fertility of slightlymore than two children per woman. There isa strong possibility that human populationgrowth will peak and reverse this century,although the world is still projected to gain wellover 2 billion people before that occurs.1

There are other positive signs that we canreverse, or at least manage, some of the worstimpacts of environmental change. Thanks to

T

decouple current economic growth fromfuture ecological collapse.

Research and Decision Making

From a research standpoint, we need toimprove our understanding of the complexconnections between environmental changeand health. How do different types of human-caused change interact with local conditions togenerate each of these emerging threats? Whatare the characteristics of populations thatmake them particularly vulnerable or resilientin the face of such threats? Which populationsaround the globe are at greatest risk for eachtype of threat?

To answer these questions, we need to do amuch better job at integrating informationacross sectors and scientific disciplines. Thereis tremendous potential to advance our under-standing by tapping large existing sets of envi-ronmental and social-science data andidentifying relationships with human health.For example, a wealth of data is available fromnear-real-time environmental monitoringsatellite platforms. These data could be ana-lyzed with historical data on local and regionalland use, climate, and socio-demographic con-ditions to help us identify relationshipsbetween health and the environment.

In addition to integration at the researchlevel, we need better integration in the trainingof research scientists.4 Researchers in health,natural, and social sciences need trainingacross each other’s disciplines so that they canwork together collaboratively. Agencies andacademic institutions should augment awardsand promotion by developing criteria forscholarship in interdisciplinary pursuits, ratherthan the current incentives for reductionism inresearch endeavors. Government agencies likethe U.S. National Science Foundation and theNational Institutes of Health could worktogether to support more collaborativeresearch efforts, including funding for post-doctoral fellowships that emphasize workacross these disciplines.

While better integration and collaborationacross disciplines is a critical step to improv-ing our understanding of health-environment

relationships, we also need to fill severalimportant data gaps. There is an astonishinglack of reliable, high-resolution, and geo-graphically referenced data about population,health, and environmental conditions—or thehost of other factors that determine vulnera-bility. We know little about the incidence orprevalence of most infectious diseases, water-related diseases, or different types of malnutri-tion at sub-national scales. We lack fine-scaledpopulation data on key components of vul-nerability: resource availability, socioeco-nomic status, quality of infrastructure, humanbehavior, or governance.

Nor do we have good data on some of themost basic and critical questions pertaining toenvironmental conditions that have very sig-nificant health consequences. Scientists dis-agree on how much additional arable land isavailable for cultivation or how much addi-tional fresh water is available for sustainableuse. Global rates of deforestation are not wellestablished.We do not know how much arableland is becoming degraded by salinization, ero-sion, desertification, or nutrient loss. And wedo not know how fast many of these processes


Moving Forward in a Changing World

In West Bengal, India, a woman’s stove burnsmethane from a village biogas project.

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are occurring or to what extent they arereversible.Without such basic information, wehave little chance of making good decisionsabout policy or resource management.

But it would be misleading to imply that theonly constraints are related to data. One of themajor factors curtailing our understanding ofthe health impacts of global change is the sub-ject’s sheer complexity.While filling data gapsis key, it is also important to acknowledge thatthe complexity of some of these relationshipswill always make exact impacts of changingenvironmental conditions on human wellbeingdifficult to quantify. In this context, it is criticalto step-up efforts at surveillance so that we areable to detect changing patterns of infectiousdisease, malnutrition, heart and respiratorydisease, morbidity from natural disasters, andenvironmental migration.

The emerging threats associated withchanging environmental conditions alsorequire a reorientation of policy and decisionmaking. Public health practitioners cannoteffectively protect public health without mov-ing outside of the traditional health sector.Schools of public health and public health pro-fessionals need to expand their focus to include

health impacts from global environmentalchange. “Strengthening public health infra-structure,” a much repeated mantra, will notgo far enough. Health professionals need tojoin their colleagues in sectors that have tradi-tionally been considered unrelated to health todiscuss the health impacts of differentapproaches to energy generation, food produc-tion, land use management, urban design,transportation, and water resource manage-ment. These topics should be integral compo-nents of public health research and training.

Decision makers in non-health sectors willalso need to evaluate the impacts of their deci-sions through a public health lens. Decisionmaking should be fully integrated, with coor-dination across agencies, and include policy-makers involved in all aspects of economicdevelopment and societal wellbeing. Everydevelopment project—even relatively smalland local ones—will have trade-offs andshould require a Health Impact Assessment(HIA) in addition to requirements for environ-mental impact assessments. Treaty negotiationsand large-scale policy decisions should includeHIAs as well.

Sophisticated HIAs could provide answersto critical questions that would help us tailorour efforts to maximize health outcomes whileaddressing problems of global change. Forexample: How would varying approaches toreducing global CO2 emissions affect humanhealth, versus continuing with business asusual? How would widespread adoption ofimproved agricultural techniques or alteredmanagement of coastal zones affect health?How can ecosystems be managed to maximizetheir services while allowing for other uses?

One of the advantages of more widespreaduse of HIAs would be the identification of “co-benefits,” whereby actions taken to address oneproblem can significantly improve publichealth at the same time. Replacing coal-firedpower plants with solar or wind generationwould help reduce carbon emissions and alsosignificantly improve air quality and cardiores-piratory health.5 Widespread adoption ofcleaner-burning, more-efficient cook stoveswould dramatically improve indoor air quality



Deforested slopes erode above subsistence rice terraces on this hillin Madagascar. Once known for its lush growth, Madagascar is nowknown as the “Red Island” for the ruddy soil carried by its riversinto the Indian Ocean.

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produce energy more cleanly; break transmis-sion cycles of infectious disease; or support ahost of other interventions? To a large extent,our global society will decide how much suf-fering results from large-scale environmentalchange by the way it answers these questions.

Our inability to quantify current or pro-jected health impacts resulting from alteredenvironmental conditions should not be anexcuse for complacency. Even without exactestimates, we have ample cause for concern.Numerous infectious diseases are changingtheir distribution, exposure pathways, viru-lence, and infectiousness in response tochanges that we only partially understand—and new infectious diseases are emerging at anaccelerating rate. Huge segments of the world’spopulation already live without adequateaccess to food or water. Climate change repre-sents a further destabilization of this alreadytenuous relationship between human popula-tions and their resource base.

At present, all of the major types of human-caused environmental change—climatechange, changes in land use and cover, andecosystem service degradation—are accelerat-ing. In concert, these trends are producing sig-nificant and growing vulnerabilities for largesegments of the expanding human population.Many of these threats can be addressed withtechnology, infrastructure, policy, and eco-nomic development. However, with nearly halfthe world’s population living on less than $2per day, such development will require a levelof international assistance and cooperationthat is not currently evident.6 To reduce avoid-able human suffering, we must redouble ourefforts to slow the pace of environmentalchange, humanely reduce the rate of popula-tion growth, and reduce the vulnerabilities ofthose in harm’s way.

as well as reduce CO2 and black carbon, a sig-nificant greenhouse gas that is also acceleratingglacial melting. Designing urban areas toencourage walking and cycling would similarlyreduce emissions while improving air qualityand promoting exercise that has myriad directhealth benefits.

A final important element is to bring theseemerging public health threats to the attentionof political, corporate, and other leadersaround the world in order to encourage themto take strong action, both to reduce the paceof global environmental change and to helpthe populations at highest risk. Modeling thedynamics of each of the major public healththreats associated with large-scale human-induced change and mapping out which pop-ulations are at greatest risk for each of thesethreats would provide leaders with the infor-mation they need to convince their con-stituencies of the importance of such actionsand to target their resources in the most effec-tive way possible.

Confronting Environmental Change,Confronting Vulnerability

It is impossible to project how much sufferingwill result from infectious disease exposure,constrained agricultural production, waterscarcity, poor air quality, natural disasters, dis-placement, or civil strife without knowing theeffectiveness of mitigating factors that protectpopulations from these threats.Will economicdevelopment increase the capacity of theworld’s poorest people to access internationalfood markets? What degree of responsibilitywill the wealthy countries and internationalcommunity take for helping the poor reducetheir vulnerability? How rapidly will technol-ogy and infrastructure proliferate to makemore efficient use of water, soil, and fertilizers;


June 1998, at http://cdiac.ornl.gov/ftp/trends/co2/lawdome.smoothed.yr20; and on National Oceanic andAtmospheric Administration, data from 13 July 2009,available at ftp://ftp.cmdl.noaa.gov/ccg/co2/trends/co2_annmean_mlo.txt.

13. Maddison, op. cit. note 1.

14. Ibid.

15. United Nations Population Division, op. cit. note 1.

16. R. K. Plowright et al., “Causal Inference in DiseaseEcology: Investigating Ecological Drivers of DiseaseEmergence,” Frontiers in Ecology and the Environment,vol. 6, no. 8 (2008), pp. 420–29.


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4. Figure 5 is reprinted, with permission, from theAnnual Review of Environment and Resources, vol. 34(2009) by Annual Reviews, www.annualreviews.org.

5. A.T. Wolf, “Shared Waters: Conflict and Coopera-tion,” Annual Review of Environment and Resources, vol.32, no. 1 (2007), pp. 241–69.


1. Figure 1 from United Nations Population Division,World Population Prospects, 2008 Revision, annual datasetson CD-ROM, forthcoming. Figure 2 recreated fromAngus Maddison, Contours of the World Economy: Essaysin Macro-Economic History (Oxford, U.K.: OxfordUniversity Press, 2007).

2. P.M. Vitousek et al., “Human Appropriation of theProducts of Photosynthesis, “ Bioscience, vol. 36. no. 6(1986), pp. 368–73.

3. P.M. Vitousek et al., “Human Domination of Earth’sEcosystems,” Science, 25 July 1997, pp. 494–99.

4. J.A. Foley et al., “Global Consequences of Land Use,”Science, 22 July 2005, pp. 570–74.

5. S.L. Postel, G.C. Daily, and P.R. Ehrlich, “HumanAppropriation of Renewable Fresh Water,” Science, I9February 1996, pp. 785–88.

6. Foley et al., op. cit. note 4.

7. United Nations Food and Agriculture Organization(FAO), Review of the State of World Marine FisheryResources (Rome: 2005).

8. Large dams refer to structures roughly the size of afour-story building or larger. World Commission onDams, Dams and Development: A New Framework forDecision-Making (London: November 2000).

9. S.L. Pimm et al., “The Future of Biodiversity,” Science,21 July 1995, pp. 347–50.

10. Figure 3 from International Fertilizer IndustryAssociation, electronic database, at www.fertilizer.org/ifa/ifadata/search, viewed 10 August 2009.

11. Vitousek et al., op. cit. note 2.

12. Figure 4 from the following sources: temperature datafrom J. Hansen et al., “Global Land-Ocean TemperatureIndex in .01 C, base period 1951–1980 (January–December)”(New York: Goddard Institute for Space Studies), athttp://data.giss.nasa.gov/gistemp/tabledata/GLB.Ts+dSST.txt. Carbon dioxide is a Worldwatch calculation based onA. Neftel at al., “Historical CO2 Record from the SipleStation Ice Core” (Bern, Switzerland: Physics Institute,University of Bern, September 2004), at http://cdiac.ornl.gov/ftp/trends/co2/siple2.013; on D.M. Etheridge et al.,“Historical CO2 record derived from a spline fit (20 yearcutoff) of the Law Dome DE08 and DE08-2 ice cores,”


Endnotes

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7. B.L. Turner et al., “A Framework for VulnerabilityAnalysis in Sustainability Science,” Proceedings of theNational Academies of Sciences, vol. 100, no. 14 (2003),pp. 8074–79.

8. A.K. Sen, Poverty and Famines: An Essay on Entitle-ment and Deprivation (Oxford, U.K. and New Delhi,India: Clarendon Press, 1981).

9. Figure 6 is reprinted, with permission, from theAnnual Review of Environment and Resources, op. cit.note 4.


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Endnotes

Endnotes

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3. S.L. Postel, G.C. Daily, and P.R. Ehrlich, “HumanAppropriation of Renewable Fresh Water,” Science, 9


1. Figure 7 from United Nations Food and AgricultureOrganization (FAO), “Food Security Statistics,”www.fao.org/economic/ess/food-security-statistics/en,viewed 6 August 2009, and from FAO, “1.02 BillionPeople Hungry: One Sixth of Humanity Undernourished,More Than Ever Before,” press release (Rome: 20 June2009). Population figures from United NationsPopulation Division,World Population Prospects, 2008Revision, annual datasets on CD-ROM, forthcoming.

2. F. Keesing and R.S. Ostfeld, “Disease Ecology,” in J.C.Ingram, C. Rumbaitis Del Rio, and F.A. DeClerck, eds.,Integrating Ecology and Poverty Alleviation and Interna-tional Development Efforts: A Practical Guide (New York:Springer, in press); C.J.L. Murray and A.D. Lopez, “GlobalMortality, Disability, and the Contribution of Risk Fac-tors: Global Burden of Disease Study,” The Lancet, vol.349, no. 9063 (1997), pp. 1436–42.

3. N. Alexandratos, “World Food and Agriculture:Outlook for the Medium and Longer Term,” Proceedingsof the National Academy of Sciences, 25 May 1999, pp.5908–14.

4. P.A. Sanchez, “Soil Fertility and Hunger in Africa,”Science, 15 March 2002, p. 2019.

5. S.L. Postel, “Water for Food Production: Will ThereBe Enough in 2025?” Bioscience, vol. 48, no. 8 (1998), pp.629–37.

6. Ibid.

7. J. Bruinsma,World Agriculture: Towards 2015/2030,An FAO Perspective (London: FAO, 2003); C. Runge et al.,Ending Hunger in Our Lifetime (Baltimore: Johns HopkinsUniversity Press, 2003).

8. Table 3 derived from the following sources: arableland from K.G. Cassman et al., “Meeting Cereal DemandWhile Protecting Natural Resources and ImprovingEnvironmental Quality,” Annual Review of Environmentand Resources, vol. 28, no. 1 (2003), pp. 315–58, and fromA. Young, “Is There Really Spare Land? A Critique ofEstimates of Available Cultivable Land in DevelopingCountries,” Environment, Development and Sustainability,vol. 1 (1999), pp. 3–18; soil fertility from D.R. Mont-gomery, “Soil Erosion and Agricultural Sustainability,”Proceedings of the National Academy of Sciences, 14 August2007, pp. 13268–72; tillage from D.R. Montgomery, “PayDirt,” Scientific American, July 2008, p. 76; irrigationdemand from Postel, op. cit. note 5, and from M.W.Rosegrant, C. Ringler, and T. Zhu, “Water for Agriculture:Maintaining Food Security Under Growing Scarcity,”Annual Review of Environment and Resources, vol. 34 (inpress); North China Plain from J. Yardley, “BeneathBooming Cities, China’s Future is Drying Up,”New YorkTimes,” 28 September 2007; United States from L. Brown,“Could Food Shortages Bring Down Civilization?”Scientific American, May 2009, and from R.E. Kaspersonand K. Dow, “Vulnerable Peoples and Places,” in R.Norgaard and D. Rapport, eds., Ecosystems and HumanWell-being: Current State and Trends: Findings of theCondition and Trends Working Group of the MillenniumEcosystem Assessment (Washington, DC: Island Press,2005); nitrogen and phosphorus from P.M. Vitousek et

Endnotes


20. Ibid.; V. Ramanathan and G. Carmichael, “Global andRegional Climate Changes Due to Black Carbon,”NatureGeoscience, vol. 1, no. 4 (2008), pp. 221–27.

21. Ramanathan et al., op. cit. note 19; Ramanathan andCarmichael, op. cit. note 20.

22. P. Eilers and B. Groot, “Effects of Ambient ParticulateMatter and Ozone on Daily Mortality in Rotterdam, TheNetherlands,” Archives of Environmental Health, vol. 52,no. 6 (1997), p. 455.

23. M.L. Bell et al., “Climate Change, Ambient Ozone,and Health in 50 U.S. Cities,” Climatic Change, vol. 82(2007), pp. 61–76; K. Knowlton et al., “Assessing Ozone-Related Health Impacts Under a Changing Climate,”Environmental Health Perspectives, vol. 112. no. 15 (2004),pp. 1557–63.

24. P. Wayne et al., “Production of Allergenic Pollen byRagweed (Ambrosia artemisiifolia L.) Is Increased in CO2-enriched Atmospheres,” Annals of Allergy, Asthma andImmunology, vol. 88 (2002), pp. 279–82.

25. K.M. Shea et al., “Climate Change and AllergicDisease,” Journal of Allergy and Clinical Immunology, vol.122 (2008), pp. 443–53.

26. Office of the United Nations High Commissioner forRefugees, “UNHCR Annual Report Shows 42 MillionPeople Uprooted Worldwide,” press release (Geneva: 16June 2009).

27. L.C. Johnstone, “Planning for the Inevitable, TheHumanitarian Consequences of Climate Change,” presen-tation at “Linking Climate Change Negotiations andDisaster Risk Reduction,” Copenhagen, Denmark, 12November 2008.

28. G. McGranahan, D. Balk, and B. Anderson, “TheRising Tide: Assessing the Risks of Climate Change andHuman Settlements in Low Elevation Coastal Zones,”Environment and Urbanization, 1 April 2007, pp. 17–37.

29. J.D. Sachs, “Climate Change Refugees,” ScientificAmerican. June 2007, p. 43.

30. D.H. Molyneux, “Patterns of Change in Vector BorneDiseases,” Annals of Tropical Medicine & Parasitology, vol.91, no. 7 (1997), pp. 827–39.

31. M.J. Toole and R.J. Waldman, “Refugees andDisplaced Persons. War, Hunger, and Public Health,”Journal of the American Medical Association, 4 August1993, pp. 600–05.

32. L.A. McCloskey and K. Southwick, “PsychosocialProblems in Refugee Children Exposed to War,” Pediatrics,vol. 97, no. 3 (1996), p. 394.

33. M. Toole and R. Waldman, “The Public HealthAspects of Complex Emergencies and Refugee Situa-tions,” Annual Review of Public Health, vol. 18 (1997), pp.283–312.

34. T. Homer-Dixon, Environment, Scarcity, and Violence(Princeton, NJ: Princeton University Press, 1999);Michael Renner, The Anatomy of Resource Wars, World-watch Paper 161 (Washington, DC: Worldwatch Institute,2002).

February 1996, pp. 785–88; Vorosmarty, Leveque, andRevenga, op. cit. note 2.

4. D. Tilman, “Forecasting Agriculturally Driven GlobalEnvironmental Change,” Science, 13 April 2001, pp.281–84.

5. I. Ray, “Women, Water, and Development,” AnnualReview of Environment and Resources, vol. 32, no. 1(2007), pp. 421–49.

6. Figure 8 from Munich Re, Topics Geo: Natural Catas-trophes 2008–Analyses, Assessments, Positions (Munich:2009).

7. Petra Löw, “Devastating Natural Disasters ContinueSteady Rise,”Vital Signs Online (Worldwatch Institute),4 June 2009.

8. W.N. Adger et al., “Social-Ecological Resilience toCoastal Disasters,” Science, 12 August 2005, pp. 1036–39.

9. R.E. Kasperson and K. Dow, “Vulnerable Peoples andPlaces,” in R. Norgaard and D. Rapport eds., Ecosystemsand Human Well-being: Current State and Trends. Findingsof the Condition and Trends Working Group of the Millen-nium Ecosystem Assessment (Washington, DC: IslandPress, 2005).

10. Ibid.

11. Ibid.

12. C.M. Kunkel, R.W. Hallberg, and M. Oppenheimer,“Coral Reefs Reduce Tsunami Impact in Model Simula-tions,” Geophysical Research Letters, vol. 33 (2006), p.L23612; E. Marris, “Tsunami Damage Was Enhanced byCoral Theft,”Nature, 25 August 2005, p. 1071.

13. F. Dahdouh-Guebas et al., “How Effective WereMangroves as a Defence Against the Recent Tsunami?”Current Biology, vol. 15, no. 12 (2005), pp. R443–47; F.Danielsen et al., “The Asian Tsunami: A Protective Rolefor Coastal Vegetation,” Science, 28 October 2005, p. 643.

14. W.T. Pfeffer, J.T. Harper, and S. O’Neel, “KinematicConstraints on Glacier Contributions to 21st-centurySea-level Rise,” Science, 5 September 2008, pp. 1340–43.

15. Ibid.

16. More than a third of the human population lives incoastal areas and small islands (within 100 kilometers ofthe shore and less than 50 meters above sea level). E.B.Barbier et al., “Coastal Ecosystem-based Managementwith Nonlinear Ecological Functions and Values,” Science,18 January 2008, pp. 321–23.

17. R.C. Kessler, “Mental Illness and Suicidality AfterHurricane Katrina,” Bulletin of the World Health Organi-zation, vol. 84, no. 12 (2006), pp. 930–93.

18. K.R. Smith and M. Ezzati, “How EnvironmentalHealth Risks Change With Development: The Epidemi-ologic and Environmental Risk Transitions Revisited,”Annual Review of Environment and Resources, vol. 30,no. 1 (2005), pp. 291–333.

19. V.M. Ramanathan et al., Atmospheric Brown Clouds:Regional Assessment Report with Focus on Asia (Nairobi:United Nations Environment Programme, 2008).

Endnotes


Individualism,”Global Environmental Change, vol. 19(2009), pp. 14–20; adaptive strategy from United NationsFramework Convention on Climate Change, “NationalAdaptation Programmes of Action,” http://unfccc.int/cooperation_support/least_developed_countries_portal/submitted_napas/items/4585.php, viewed 11 April 2009.


1. United Nations Population Division,World Popula-tion Prospects: The 2008 Revision Population Database,available at http://esa.un.org/unpp/, viewed 13 July 2009.

2. L. Raffensperger, “A Fresh Green for No-Till Farm-ing,” Earth Trends (World Resources Institute), 19 Febru-ary 2008, at http://earthtrends.wri.org/updates/node/286.

3. Grameen Bank, “Microfinance in Action,” www.grameenfoundation.org/what_we_do/microfinance_in_action,viewed 13 July 2009.

4. H. Eakin and A.L. Luers, “Assessing the Vulnerabilityof Social-Environmental Systems,” Annual Review ofEnvironment and Resources, vol. 31, no. 1 (2006), pp.365–94.

5. J. Hess and S.S. Myers, “Climate Change and HumanHealth, in J.C. Ingram, C. Rumbaitis Del Rio, and F.A.DeClerck, eds., Integrating Ecology and Poverty Alleviationand International Development Efforts: A Practical Guide(New York: Springer, in press).

6. Population Reference Bureau, “World PopulationData Sheet,” fact sheet (Washington, DC: August 2005).

Adapting to the Health Impactsof Climate Change

1. Sidebar 1 from the following sources: 200 millionfrom S. Singh et al., Adding It Up: The Benefits of Investingin Sexual and Reproductive Health Care (New York:Alan Guttmacher Institute, 2003); 80 million from AlanGuttmacher Institute, Sharing Responsibilities: Women,Society and Abortion Worldwide (New York: 1999); a thirdto one-half from Singh et al., op. cit. this note; 79 millionis a Worldwatch Institute calculation based on unpub-lished data from United Nations Population Division,personal communication of Robert Engelman withThomas Buettner (note that the two numbers, on unin-tended pregnancies and annual additions to world popu-lation growth, are not comparable, since many unintend-ed pregnancies end in abortion, and others displace preg-nancies that would have later been intended); 36 to 59months from S.O. Rutstein, “Effects of Preceding BirthIntervals on Neonatal, Infant and Under-Five YearsMortality and Nutritional Status in Developing Coun-tries: Evidence from the Demographic and HealthSurveys,” International Journal of Gynecology & Obstetrics,vol. 89 (2005), pp. S7–24; risk of death and poor healthfrom N. Prata et al., “Saving Maternal Lives in Resource-poor Settings: Facing Reality,”Health Policy, vol. 89, no. 2(2008), pp. 131–48; 1.1 percent from United NationsPopulation Division,World Population Prospects: The 2008Revision Population Database, available at http://esa.un.org/unpp/, viewed 13 July 2009; P.A. Murtaugh andM.G. Schlax, “Reproduction and the Carbon Legacies of

Endnotes


climate change, see also environ-mental change

call to action on, 5, 34characteristics of impacts, 15, 30confronting, 37disproportionate impact on

poor, 30food production impacts, 24–25health impacts, adaptation for,

30–33health impacts, complex rela-

tionships with, 13, 14, 22health threats from, 7, 13, 14,

15–22population displacement from,

28–29synergistic effects of changes,

11, 34, 37coastal regions

ecosystem services of, 12vulnerabilities of, 7, 25, 27, 29

collaborative research, 11cooking stoves, 34, 35, 36–37Copenhagen, Denmark, climate

talks in, 6, 8cows

Cryptosporidium and, 20schistosomiasis and, 17

crop yields, 24, 25air pollution and, 28

Cryptosporidium, 20Culex nigripalpus, 22cultural factors, 12cutaneous leishmaniasis, 16

Dams, 9malaria transmission and, 16schistosomiasis incidence and, 17

data gaps, 35–36decision making for future changes,

35–37deforestation

data gaps on, 35in Madagascar, 36malaria transmission and, 16

Acorns, Lyme disease and, 22adaptation, 5–6, 30–33

international assistance for, 37“no-regrets” solutions, 30–31

Aedesmosquitoes, 19, 20African sleeping sickness, 18agricultural development

area of land converted for, 9crop yields, 24, 25, 28malaria transmission and, 16movement of non-immune

workers, 18“no-till” cultivation, 34

air pollution, 28, 36–37algal blooms, 17–18allergic respiratory disease, 28Amazon basin, deforestation in, 16Anophelesmosquitoes, 16, 18, 21antibiotic resistant bacteria, 20arable land, 24, 35assistance, international, 8, 13, 37Aswan Dam, 17atmospheric brown clouds

(ABCs), 28

Bartonellosis, 22biological diversity, 22birds, as pathogen hosts, 22black carbon, 37Borrelia burgdorferi, 21–22Bulinus forskalii, 17Bulinus truncatus, 17bushmeat hunting, 18–19

Cacao plantations, 16, 18Campylobacter, 20carbon dioxide

concentration in atmosphere, 10concentration, influence on

nutrient content of foods, 25cell phones, 34Chagas disease, 15, 19child deaths/mortality, 5, 10cholera, 16, 18

Index

mosquito life cycles and, 21in past 300 years, 9schistosomiasis incidence and, 17

dengue fever, 15, 16urbanization and, 19, 20

diarrheal diseases, 29“dilution effect”, 22disease, see infectious diseasedracunculosis, 17drip irrigation, 34

E. coli, antibiotic-resistant, 20Ebola virus, 18economic growth, 9, 10ecosystem services

clean water, 26–27complex relationships of, 12, 13degradation of, 12, 13, 14, 37

encephalitisJapanese, 17St. Louis (SLE), 22

environmenthealth of, 9–11human modification of, 9–10new framework for, 12–14

environmental change, see also cli-mate change

adaptation principles andstrategies, 30–33

call to action on, 5, 34characteristics of impacts, 30complexity of relationships, 13,

14, 22, 36confronting, 37data gaps on, 35–36, 37food and nutrition and, 23–25framework for analysis, 14health threats from, 7, 11, 14,

15–22infectious disease and, 15–22mitigation of, 5–6, 8momentum/time scale of, 11new approaches to, 34–37other impacts on health, 26–29

research and decision makingfor, 35–37

environmental health, expandingfocus of, 9–11

Escherichia coli, antibiotic-resistantstrains, 20

Ethiopia, malaria in, 16extinction of species, 10extreme events and disasters, 27–28

Famines, 8, 13fertilizer, 10, 24, 28

malaria exposure and, 21runoff of, 17–18, 26

filariasis, 17, 19fisheries

declines in, 9overfishing, 17, 18–19

Florida, avian hosts in, 22food and nutrition, 23–25

constraints on increased foodproduction, 24

crop yields, 24, 25, 28malnutrition, 23, 25, 29nutrient cycles, 10

food poisoning, 20forests, see deforestationframework for environment and

health, 12–14

GDP (gross world product), 9generalist species, 22genetic alterations, infectious dis-

ease and, 20–21Ghana, bushmeat hunting in,

18–19Giardia lamblia, 20governance, as mediating factor,

12–13grains

crop yields and nutrient con-tent, 24–25, 28

use for biofuels, 24greenhouse gases, 10gross world product (GDP), 9ground-level ozone, 28

H1N1 influenza, 21habitat loss, 9–10hantavirus pulmonary syndrome, 22harmful algal blooms, 17–18health, see also health impacts;

health threats; infectiousdisease

air pollution and, 28core “building blocks” for, 7, 11environmental, 9–11expanding focus for, 9–11

food and nutrition, 23–25infectious disease, 15–22mobile communications and

(“m-health”), 34natural disasters and, 27–28new approaches to, 34–37new framework for, 12–14new specialties/concepts in, 11population displacement and,

28–29public health focus, 36–37resource scarcity and, 13–14water and sanitation and, 26–27

health impactsadaptation to, 30–33complexity of relationships, 13,

14, 22, 36differing vulnerabilities to, 7–8difficulty in quantifying, 37of ecosystem services

deterioration, 12, 13governance and, 12–13Health Impact Assessments

(HIAs), 36–37importance of addressing, 8, 36of malnutrition, 23, 25, 29planning for, 34–37risk assessments, 8time scales/delays in, 11

health threats, see also vulnerabilityfrom climate change, 7, 11,13, 14synergistic effects of environ-

mental changes, 11, 34, 37HIV/AIDS virus, 18human health, see healthhuman population, 9, 23, 34

displacement/migration of,19, 28–29

Hurricane Gustav, 27Hurricane Katrina, 28

Indiacook stove program, 34, 35malaria incidence in, 16

infectious disease, 15–22, 37antibiotic resistance and, 20biological diversity and, 22cholera, 18“dilution effect”, 22exposure pathways, 18–20, 37genetic alterations and, 20–21global prevalence of, 15habitats/density of disease-

related organisms, 15–21, 37land use changes and, 16, 17, 18life cycle of vectors/pathogens, 21Lyme disease, 21–22malaria, 15–16


Index

movement of non-immunepersons and, 18, 29

schistosomiasis, 16–17species composition changes,

21–22temperature rise and, 16, 21transmission decrease, 15transmission increase, 15,

16–17, 22unpredictability of outcomes, 22urbanization and, 19, 20zoonotic disease, 19, 21

influenza viruses, 20–21infrastructure, 7, 12, 14, 18, 31international assistance/

philanthropy, 8, 13, 37iron deficiency, 25irrigation projects

malaria and, 16schistosomiasis and, 17

irrigation water/requirements, 24,25, 34

Israel, water-use technologies in,26–27

Japanese encephalitis, 17

Lake Malawi, 17land use change, 11, 12, 18

fate/transport of pathogens and,19–20

infectious disease patterns and,15–21

malaria and, 16schistosomiasis and, 17

leishmaniasis, 16, 17leptospirosis, 19life expectancy, 10livestock development, 17, 20Lyme disease, 21–22

“M-health”, 34Madagascar, deforestation in, 36malaria, 15–16

fertilizer use and, 21“frontier malaria”, 18land use change and, 16, 18, 21temperature rise and, 16, 21urbanization and, 19

malnutrition, 23, 25, 29marine systems, health of, 17–18markets, access to, 12, 14, 23measles, 29mice, Lyme disease and, 22migration

infectious disease exposureand, 19

population displacement, 28–29


research and decision making,35–37

resource scarcity, health outcomesand, 13–14, 29, 37

respiratory diseases/infections,28, 29

retroviruses, 18rice yields, 25, 28Rift Valley Fever, 17risk assessments, 8runoff of fertilizer/nutrients,

17–18, 26

St. Louis encephalitis (SLE), 22Salmonella, antibiotic-resistant

strains, 20Salmonella enteritidis, 20sanitation, health impacts of, 26–27SARS epidemic, 21Schistosoma haematobium, 17schistosomiasis, 15, 16–17sea-level rise

coastal vulnerability and, 25,27, 29

estimates for this century, 27simian foamy virus, 18snails, schistosomiasis and, 17soil-nutrient depletion, 23–24soot (black carbon), 28, 37species composition, changes in,

21–22species extinction, 10surveillance, need for, 31, 36swine, infectious diseases and,

20–21synergistic effects of environmental

and health changes, 11,34, 37

Temperature, global surface, 10temperature rise

algal blooms and, 17–18cholera and, 18disease pathogen fate/transport

and, 19–20extreme events increased by, 27food production and, 25ground-level ozone and, 28malaria and, 16, 21

Tibetan plateau, water supply from,7, 28

ticks, Lyme disease and, 21–22trypanosomiasis, 18tsetse fly, 18tsunami, Indian Ocean (2004), 27Typhoon Fenshen, 27Typhoon Nargis, 13typhus, 19

rural-to-urban, 19Milwaukee, Wisconsin,

cryptosporidiosis in, 20mitigation of environmental

change, 5–6, 8mobile communications

technologies, 34monsoons, 16, 27, 28mosquitoes

Aedes, 19, 20Anopheles, 16, 18, 21Culex, 22temperature rise and, 16

Myanmar, Typhoon Nargis and(2008), 13

National Institutes of Health(U.S.), 35

National Science Foundation(U.S.), 35

natural disasters, 27–28Nipah virus, 20nitrogen cycle, 9nitrogenous fertilizers, 10, 28nitrous oxide, 28“no-regrets” solutions, 30–31“no-till” cultivation, 34nutrient cycles, 10nutrition, see food and nutrition

Ocean acidification, 10onchocerciasis, 17overfishing, health concerns associ-

ated with, 17, 18–19ozone, ground-level, 28

Pigs, infectious diseases and,20–21

plague, 16, 19policy making, 36pollen, 28poor populations

dependence on local food pro-duction, 23

disproportionate impacts on,27, 30

loans for, 34need for international assis-

tance, 8, 13, 30, 37population displacement, 28–29population growth, 9, 23, 26

possible peak and reversal of, 34protein deficiency, 25, 29protozoan parasites, 20public health focus, 36–37

Rainfall/monsoon patterns, 28, 29refugees, 28–29

Index

Ugandawetland drainage and malaria

in, 16zoonotic disease research in, 19

United Nations’ MillenniumDevelopment Goals, 8

urban transport, 34urbanization

infectious disease exposure and,19, 20

water contamination and, 26

Vector-borne diseases, 16–22Vibrio cholerae, 18violent conflicts, 28–29viruses, 18, 20–21, 22vulnerability, 7–8, 12, 14

of coastal regions, 7, 25, 27, 29confronting, 37cultural behaviors for

reducing, 12data gaps on, 35to natural disasters, 27–28

Waterconservation technologies, 34contamination, 26dams, impacts of, 9, 16, 17health impacts, 26–27irrigation, 24, 25, 34resources, decrease in, 24–25, 27supply, threats to, 7, 20, 26

water projects, infectious diseaseand, 16, 17

waterborne illnesses, 20West Nile virus encephalitis, 22wetland drainage, 16white-footed mouse, 22wildlife habitat, movement of

humans into, 18–19

Zinc deficiency, 25zoonotic disease, 19, 21


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On Climate Change, Energy, and Materials180: Red, White, and Green: Transforming U.S. Biofuels, 2009179: Mitigating Climate Change Through Food and Land Use, 2009178: Low-Carbon Energy: A Roadmap, 2008175: Powering China’s Development: the Role of Renewable Energy, 2007169: Mainstreaming Renewable Energy in the 21st Century, 2004160: Reading the Weathervane: Climate Policy From Rio to Johannesburg, 2002157: Hydrogen Futures: Toward a Sustainable Energy System, 2001151: Micropower: The Next Electrical Era, 2000149: Paper Cuts: Recovering the Paper Landscape, 1999144: Mind Over Matter: Recasting the Role of Materials in Our Lives, 1998138: Rising Sun, Gathering Winds: Policies To Stabilize the Climate and Strengthen Economies, 1997

On Ecological and Human Health174: Oceans in Peril: Protecting Marine Biodiversity, 2007165: Winged Messengers: The Decline of Birds, 2003153: Why Poison Ourselves: A Precautionary Approach to Synthetic Chemicals, 2000148: Nature’s Cornucopia: Our Stakes in Plant Diversity, 1999145: Safeguarding the Health of Oceans, 1999142: Rocking the Boat: Conserving Fisheries and Protecting Jobs, 1998141: Losing Strands in the Web of Life: Vertebrate Declines and the Conservation of Biological Diversity, 1998140: Taking a Stand: Cultivating a New Relationship With the World’s Forests, 1998

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On Food, Water, Population, and Urbanization176: Farming Fish for the Future, 2008172: Catch of the Day: Choosing Seafood for Healthier Oceans, 2007171: Happier Meals: Rethinking the Global Meat Industry, 2005170: Liquid Assets: The Critical Need to Safeguard Freshwater Ecosytems, 2005163: Home Grown: The Case for Local Food in a Global Market, 2002161: Correcting Gender Myopia: Gender Equity, Women’s Welfare, and the Environment, 2002156: City Limits: Putting the Brakes on Sprawl, 2001154: Deep Trouble: The Hidden Threat of Groundwater Pollution, 2000150: Underfed and Overfed: The Global Epidemic of Malnutrition, 2000147: Reinventing Cities for People and the Planet, 1999

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Global Environmental Change: The Threat to Human Health

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