A 534 VOLUME 113 | NUMBER 8 | August 2005 • Environmental Health Perspectives

Environews Spheres of Influence

ContinentalDivideWhy Africa’s

Climate Change BurdenIs Greater

A frica can easily be said to contributethe least of any continent to globalwarming. Each year Africa produces

an average of just over 1 metric ton of thegreenhouse gas carbon dioxide per person,according to the U.S. Department of Energy’sInternational Energy Annual 2002. The mostindustrialized African countries, such as SouthAfrica, generate 8.44 metric tons per person,and the least developed countries, such asMali, generate less than a tenth of a metric tonper person. By comparison, each Americangenerates almost 16 metric tons per year. Thatadds up to the United States alone generating5.7 billion metric tons of carbon dioxide peryear (about 23% of the world total, making itthe leading producer), while Africa as a wholecontributes only 918.49 million metric tons(less than 4%). It is a cruel irony that, in manyexperts’ opinion, the people living on the conti-nent that has contributed the least to globalwarming are in line to be the hardest hit by theresulting climate changes.

“The critical challenge in terms of climatechange in Africa is the way that multiple stres-sors—such as the spread of HIV/AIDS, theeffects of economic globalization, the privatiza-tion of resources, and conflict—converge withclimate change,” says Siri Eriksen, a seniorresearch fellow in sociology and human geogra-phy at the University of Oslo. “It is where sev-eral stressors reinforce each other that societiesbecome vulnerable, and impacts of climatechange can be particularly severe.” She cites theexample of the 2002 drought-triggered faminein southern Africa, which affected millions due

partly to populations’ coping capacity beingweakened by HIV/AIDS.

“Climate change could undo even the littleprogress most African countries have achieved sofar in terms of development,” says AnthonyNyong, a professor of environmental science at theUniversity of Jos in Nigeria. With climate changehas come an increase in health problems such asmalaria, meningitis, and dengue fever, he says. Thismeans that the few resources these poor countrieshave that would have been channeled into essentialprojects to further economic development mustinstead be put toward health crisis after healthcrisis, providing emergency care for the people.

Models of Change

Africa may already be feeling the effects of globalwarming, says Isaac Held, a senior research scien-tist at the National Oceanic and AtmosphericAdministration (NOAA) Geophysical FluidDynamics Laboratory, and more marked effectsare likely to come, according to models devel-oped by climate scientists around the world.Projected effects of global warming on precipita-tion throughout the world can be summarized ina single sentence, according to Held: areas thatalready get a lot of rainfall—such as the equatori-al and subpolar rain belts—will get more, andareas that get little—such as the subtropical dryzones—will get less.

Climate models suggest that subtropicalAfrica south of the equator will follow this trend,and a plausible case can be made that globalwarming has already reduced rainfall in thatregion. In a paper published in the September2004 issue of the International Journal ofClimatology, NOAA scientist Pingping Xie andcolleagues wrote, “Large decreasing rainfall trendswere widespread in the Sahel from the late 1950s

Environmental Health Perspectives • VOLUME 113 | NUMBER 8 | August 2005 A 535

Spheres of Influence | Continental Divide

Ham

ish

Wils

on/P

anos

Pic

ture

s

Winds of change. A Somalian girl searches for edibleseeds among the dust. Increasing droughts are one ofthe most devastating effects of climate change.

to the late 1980s; thereafter, Sahel rainfallhas recovered somewhat through 2003, eventhough the drought conditions have notended in the region.” The study also foundthat major multiyear oscillations haveappeared to occur more frequently and to bemore extreme since the late 1980s.

About 300,000 people died in a pro-longed drought in the Sahel during the1970s. Until recently the scientific commu-nity attributed that drought to the severeloss of vegetation accompanying such factorsas overgrazing and overpopulation; accord-ing to this model, the reduction in vegeta-tion meant greater reflectivity of the Earth’ssurface and less moisture being returned tothe atmosphere, with a net drying effect.But now, Held says, “we think of thatdrought as having been driven by changes inthe ocean temperatures.”

New climate models posit that precipita-tion changes are occurring because of alter-ations in the temperature gradient betweenthe Southern and Northern hemispheres.“When the [ocean] waters are warmer in theNorthern Hemisphere, rains are attractedfarther north, and when they are warmer inthe Southern Hemisphere, it doesn’t get asfar north,” Held explains.

But it is a subject of debate, he says,whether the changes in temperature gradientthat caused the Sahel drought were due tonatural variability of the oceans or werepartly the result of man-made changes in thecomposition of the atmosphere. There is asyet no consensus among climate modelerson the most likely future trend of Sahel rain-fall, he emphasizes.

Still, climatologists agree that warming ishappening. In Climate Change 2001:Impacts, Adaptation and Vulnerability, theIntergovernmental Panel on ClimateChange Working Group II reported, “Thehistorical climate record for Africa showswarming of approximately 0.7°C [1.3°F]over most of the continent during the twen-tieth century; a decrease in rainfall over largeportions of the Sahel . . . and an increase inrainfall in east central Africa.”

Accompanying the Sahel droughts hasbeen an increase in dust storms, althoughwhether these storms are a result of thedroughts or a cause has been a subject ofcontroversy. Research published in the 22May 2001 issue of the Proceedings of theNational Academy of Sciences, for example,presents an analysis that demonstrated thatthe particles in Sahel dust storms weren’table to absorb much water. As a result, theydid not form cloud condensation nuclei, asis usually expected in such dust particles,and so they suppressed rainfall and exacer-bated the droughts. In addition to effectson weather, dust motes averaging less than

2.5 micrometers in diameter are in the rangeof particles that research shows may haveserious health consequences. Such dust cancarry with it a variety of hitchhikers includ-ing bacteria, fungi, and chemical pollutants,all of which may adversely affect health.

Food Stock FailureOn any continent crop failure means trou-ble, but in Africa it’s a catastrophe. About40% of the gross national product ofAfrican countries flows from agriculture,and about 70% of African workers areemployed in agriculture, most of them onsmall plots of land. “Africa is full of poorpeople who are very highly dependent onclimate-related issues for their livelihoods,”says Bob Scholes, an ecologist at the Councilfor Scientific and Industrial Research inPretoria, South Africa. “They are subsistencefarmers in often very marginal environ-ments.” African governments are frequentlychaotic, ineffective, unstable, and corrupt,adding to the people’s precarious existence.

Land ownership changes, less restrictivetrade policies, commercialization of the agri-cultural sector, and increasing impoverish-ment, along with population growth, havepushed people into farming in dry areas,such as savanna, that not long ago wereopen to cattle and wildlife grazing, saysJennifer Olson, regional coordinator forland use with the LUCID (Land Use,Change, Impacts, and Dynamics) project atthe International Livestock ResearchInstitute in Kenya and a geography professorat Michigan State University. Faced withshrinking open grasslands, once solely pas-toral people are settling down and plantingcrops of their own to supplement their live-stock. New farmers tend to be poor, Olsonsays, and their farms, set in these dry areas,are usually small and thus especially vulnera-ble to droughts, floods, and other weatherhazards associated with climate change.

“Rainfall is the biggest variable for cropand animal production here,” Olson says.“Everything goes up and down dependingon how the rainy seasons are going, so cli-mate change is going to have a huge impactwith the expansion of the number of peopledoing cropping in the more marginal areas.These tend to be the people on the edge ofdoing well anyway because there’s notenough rainfall for them to be productive.”

According to Robert Mendelsohn, a pro-fessor at the Yale School of Forestry andEnvironmental Studies, small farmers inAfrica are especially vulnerable to changes inprecipitation. Only a small number use irriga-tion or fertilizer of any kind. Larger growers,such as the commercial farms of parts of EastAfrica, are better able to cope with weatherextremes, but they are in the minority.

People who depend on livestock will bejust as hard-hit as pastures go brown,Mendelsohn says. But in this case smallerspreads fare better than large ones. Big opera-tions are usually committed to herds of cattle,which demand plentiful water and easy-to-reach areas in which to graze. When water isscarce, large pastoralists are forced to movetheir herds southward to relatively wetterareas that are usually occupied by sedentaryfarmers, thus precipitating intergroup con-flicts. However, people who have just a fewanimals can switch to goats and sheep, ani-mals that tend to be more inventive when itcomes to finding food and water.

Ecosystem ChangesWith changes in land use and climate, someareas in East Africa have become drier,Olson says, and water sources are becomingintermittent or disappearing. Streams thatused to run year-round are now seasonal.The expansion of agriculture into savannasalso blocks migration routes for large ani-mals such as zebras, wildebeest, and ele-phants, she says.

As a result of climate-related ecosystemchanges, some wild sources of food are alsobecoming harder to find, says CatherineO’Reilly, an assistant professor of environ-mental science at Vassar College. The fishstock in the deep Rift Valley lakes of EastAfrica, for example, are decreasing as averageair temperatures rise. These lakes—a chainof fresh and brackish bodies including lakesMalawi, Tanganyika, and Victoria—containgreater biodiversity than any other of theworld’s freshwater systems, she says. Thatdiversity depends on algae that are suppliedwhen surface waters mix with nutrient-richdeep waters.

“With c l imate change,” O’Rei l lyexplains, “there is less of this mixing,because the [temperature-mediated] densitydifference between the surface waters andthe deep waters has gotten greater, and so ittakes more energy to mix deep water up tothe surface.” Less algae means less food forthe entire food web, and the result, shesays, is big decreases in fish catches in all ofthese lakes.

O’Reilly and colleagues reported in the14 August 2003 issue of Nature that climatechange had contributed to a 30% decline inLake Tanganyika fish stocks over the past 80years. Such declines can be disastrous for thevillages in the region, where the averageincome is less than US$250 per year, andwhere the people depend on the fish fromthese lakes for all of their protein.

When this important food source fades,every aspect of the regional environment isaffected. As fish yields go down, increaseddemands are put upon the land as some

A 536 VOLUME 113 | NUMBER 8 | August 2005 • Environmental Health Perspectives

Spheres of Influence | Continental Divide

fishermen switch to arable farming, O’Reillysays. This in turn leads to more intensifiedfarming, and thus more deforestation,increased erosion, and degradation of theshoreline. Degradation of the shorelinedestroys in-shore habitat and spawninggrounds for many fish species, furtherimpacting the fish population. “You get apositive feedback loop started,” she says,“whereby a small decrease in productivity inthe lakes can cycle through all these factorsand impact [yet] another aspect of the fishlife-history cycle.”

When food sources dry up, Africans alsoturn to wild game. This can put pressure onalready endangered species and potentiallyexpose diners to the diseases these exoticanimals carry. A report published in the 12November 2004 issue of Science showed thatdeclining fish stocks in Ghana—down by atleast 50% since 1970—corresponded with ademand for “bushmeat” that led to a 76%decline in the numbers of 41 species ofmammals, including buffalo, antelope, jack-als, monkeys, and elephants.

Insects—and with them the diseases theyharbor—have also been affected by new cli-matic conditions, says Jonathan Patz, a physi-cian and associate professor of environmentalstudies and population health sciences at theUniversity of Wisconsin–Madison. As Africahas warmed, he says, vectorborne diseases—those in which a pathogen is carried from onehost to another by pests such as mosquitoes—have increased their range. Malaria, for exam-ple, has moved into higher African latitudes ashighlands have warmed enough for mosqui-toes to breed. (However, other experts, suchas Marlies Craig, a malaria researcher at theSouth African Medical Research Council inDurban, believe that factors besides increasingtemperatures, such as increased resistance todrugs, are the cause of this vector spread.)Further, as malaria makes its way into higherlatitudes, it reaches people who didn’t developmalaria immunity as children. The result is anincrease in adult mortality.

Although some areas may become moresuitable for some diseases, others maybecome less so, Patz adds—disease vectorsdon’t universally seek warmer temperatures.Rather, each has optimum conditions inwhich it thrives. In North America, forexample, Patz says the warmer, wetter tem-peratures that foster some mosquito growthtend to worsen conditions for the tick thatcarries Lyme disease. Similarly, research by ateam from the Institut Français deRecherche Scientifique pour le Développe-ment en Coopération in Senegal, publishedin the March 1996 issue of the AmericanJournal of Tropical Medicine and Hygiene,indicated that tickborne borreliosis extendedits range out of the Sahel and into West

Africa most likely because of the Saheldrought of the 1970s.

Wages of War When the apocalyptic horsemen of famineand pestilence appear, war can’t be farbehind. Decreasing pastoral lands, decreas-ing available tillable land, decreasing wildgame, and decreasing available water all addup to more strife, Scholes says. “Subtropicaldry, arid areas are going to be a huge sourceof conflict over the next half-centurybecause we still have very, very high popula-tion growth rates in those areas, very loweconomic growth rates, and deterioratingenvironment,” he says.

“Basically,” he adds, “not only are thespillover effects environmental, in terms ofdust storms and soil erosion and so forth,but there is also massive spillover of peoplemoving out of [more stressed areas] into bet-ter resourced areas.” In relatively developedcountries such as Nigeria and South Africa,30% or more of the population consists ofillegal immigrants.

Farmers, pastoralists, and the new agro-pastoralists are already competing for waterand suitable agricultural and grazing land,Olson says; regional warming and dryingcan only be expected to worsen the situa-tion. On occasion, she says, the conflictsthat result from this competition can turnviolent, although most are settled peacefully.

But according to Eriksen, extended peri-ods of increased violent raiding in parts ofEast Africa have led to loss of livestock andland, and have driven people into a state ofdestitution that makes them extremely vul-nerable to drought events. “Although manyconflicts are politically instigated and drivenby underlying economic inequities inresource access, rather than climate changeas such, increasing drought stress can exacer-bate conflict and violence,” she says.

Strategies for CopingAs a reaction to so much bad news, in July2005 the G8 countries—Canada, France,Germany, Italy, Japan, Russia, the UnitedKingdom, and the United States—approveda pledge to forgive about US$40 billion ofdebt owed by 18 nations, including 14African countries. These forgiven debts rep-resent about one-sixth of the total owed byAfrican nations to the G8 nations and inter-national lenders. According to Nyong, relieffrom these debts will allow these Africangovernments to spend more on local issuesrelated to climate change. The G8 leadersalso committed to double annual African aidfrom US$25 billion to US$50 billion.

But debt relief isn’t an instant cure. “Wereally have to spend some time exploringthe implications of [debt relief] for rural

economies and urban economies,” saysDavid Campbell, a geography professor atMichigan State University who has studiedEast African communities for more than 25years. It’s also important, he says, to deter-mine what investment should be made withfinancial aid to maintain the resilience ofsocieties, both urban and rural, in the face ofpotential increased climatic variability.

Industrialized nations bear anotherresponsibility, Nyong says: “Just as Africa istrying to adapt to these adverse impacts ofclimate change, the developed countries,particularly the G8 countries, should put inplace a mechanism to which they are com-mitted to substantially reducing their green-house gas emissions. [With Nigeria] havingsigned the Kyoto protocol, we want to seedefinite plans articulated to achieving thetargets set by the protocol.”

Mendelsohn lays out the bottom line:“As the net income of this land deteriorates,it’s not going to be able to sustain the num-ber of bodies that are on it anymore. So thequestion is, where will these bodies go?”One long-term answer is to try to increaseindustrialization in Africa to give peopleother alternatives, to move away from cli-mate-sensitive livelihoods and industriestoward those that are not climate-sensitive—ecotourism has been suggested as one possi-ble replacement for farm income.

In the meantime, Campbell says, “It’simportant that the G8 outcome be commit-ted over the long term to maintaining [finan-cial aid] policies.” This financial aid, he says,will be vital to the lives of Africa’s poor, whorepresent an ever increasing segment ofAfrican society. And climate change is likelyto accelerate such societal stratification, hesays. People who have at least some wealthwill be better able to switch to different crops,buy a different kind of livestock, or combinegrowing and herding. “Herders who hadtaken on farming appeared to be less vulnera-ble to drought than the people who hadmaintained themselves in terms of subsistingalmost entirely on herding,” Campbell says.“So that diversification showed itself to besuccessful in terms of allowing them to copewith prolonged drought.” However, thoseAfricans who don’t have sufficient wealth tobuffer the effects of increasing climatic vari-ability will plunge deeper into poverty.

But as much as financial aid is needed,Nyong says, the reality is that no amount ofmoney is going to stop climate change fromaffecting Africa in profound and unpre-dictable ways. Africa wasn’t able to preventthe buildup of greenhouse gases, he says;“What we are left to do now is to adapt tothe buildup.”

Scott Fields

Environmental Health Perspectives • VOLUME 113 | NUMBER 8 | August 2005 A 537

Spheres of Influence | Continental Divide