Making the Link POPULATION REFERENCE BUREAU HEALTHY PEOPLE NEED HEALTHY FORESTS— POPULATION AND DEFORESTATION eforestation worldwide continues at a net rate of 9.4 million hectares a year, posing D a serious threat to human communities and natural ecosystems at the outset of the 21st century.1 This Emerging Policy Issues in Population, Health, and the Environment brief examines how deforestation threatens human and ecological health and highlights the underlying causes of deforestation, while paying special atten- Photo removed for tion to the role of human population dynamics in copyright reasons this process. Today, forests cover about 27 percent of the world’s land area, compared to roughly 50 percent 10,000 years ago.2 In Europe and South America, forests extend over roughly half the land, com- pared to less than one-fourth in Africa, Asia, and Oceania. Of the forested land that remains today, Deforestation continues to threaten human and ecological 55 percent is found in less developed countries.3 well-being throughout the world. During the 1990s, human activities resulted in the gross deforestation of an area roughly the size of Colombia and Ecuador combined (146 shown that, on average, precipitation is 30 percent million hectares, or 563,709 square miles). lower and temperatures are 1 degree Celsius high- During that same time period, 52 million hectares er in deforested areas of the Amazon than in were regained due to reforestation efforts and nat- forested areas.5 Ironically, deforestation can also ural regrowth. Rates of net deforestation (gross lead to increased flooding, even if rainfall is deforestation less reforestation, natural regrowth, reduced. Forests regulate runoff from precipita- and plantation growth) were highest in South tion, buffering against widespread flooding and America and Africa, while high rates of gross landslides. The removal of trees, especially in hilly deforestation in Asia were offset by expanding for- or mountainous areas, impairs the ability of the est plantations (see Table 1, page 2). In general, soil to absorb and retain water and release it slow- the 1990s saw forest cover expand in temperate ly over time. less developed countries, decline in tropical less I Loss of food, medicine, and fuel—Forests, developed countries, and remain relatively stable which have the highest species diversity of any ter- in more developed countries.4 restrial ecosystem, serve as important and depend- able sources of food, medicine, and fuel for Critical Impacts of Deforestation surrounding communities. Tropical forests, where Deforestation, and related forest degradation, can the majority of deforestation takes place, provide have harmful and even deadly consequences for habitat for up to two-thirds of known terrestrial both people and the environment: species.6 As forests are destroyed, degraded, or I Less precipitation, higher temperatures, fragmented, many of these valuable species of greater flooding—As trees that normally help plants and animals—any number of which con- induce precipitation in an area are removed, the tain precious genetic resources that could lead to area’s climate becomes increasingly arid, often new pharmaceuticals or provide important tradi- leading to desertification. Recent research has tional medicines—are threatened or lost forever. 2 PRB Making the Link 2001 Table 1 diseases such as typhus and rabies can spread. Top Gains and Losses of Forest Cover by Country, Migrants to recently deforested areas typically do 1990–2000 not have the immunity to these diseases that Net Forest Net Forest indigenous forest dwellers have built up over time. Country Loss (ha) Country Gain (ha) In addition, as deforested watersheds lose the ability Brazil 23,093,000 China 18,063,000 to provide adequate amounts of water consistently, Indonesia 13,124,000 United States 3,880,000 reduced flows lead to stagnation and falling per Sudan 9,589,000 Belarus 2,562,000 capita supplies of water. These conditions are ripe Zambia 8,509,000 Kazakhstan 2,390,000 for the spread of cholera and dysentery. Mexico 6,306,000 Russia 1,353,000 I Exacerbating climate change—As trees grow, Dem. Rep. of Congo 5,324,000 Spain 860,000 they absorb carbon from the atmosphere and store Myanmar 5,169,000 France 616,000 it in their tissues. When forests are cleared or Nigeria 3,984,000 Portugal 570,000 burned, this carbon is released back into the atmos- Zimbabwe 3,199,000 Vietnam 516,000 phere as carbon dioxide, which traps the sun’s ener- Argentina 2,851,000 Uruguay 501,000 gy and raises global temperatures. Forests contain Australia 2,820,000 New Zealand 390,000 40 percent of all stored carbon, more than any Peru 2,688,000 India 381,000 other terrestrial ecosystem, and thus help buffer 8 ha= hectares against global warming. The Intergovernmental NOTE: The FRA 2000 recalculated the 1990 forest cover figures, using the same definitions Panel on Climate Change, a UN-sponsored consor- and methodologies used for calculating the 2000 figures, in order to make the comparison tium of leading scientists, found that land-use between 1990 and 2000 possible. SOURCE: Food and Agriculture Organization of the United Nations (FAO), “Forest Resources change—of which tropical deforestation is the most Assessment (FRA) 2000, Forest Cover Change” (www.fao.org/forestry/fo/fra/index.jsp, accessed significant component—was responsible for rough- Aug. 13, 2001). ly 20 percent of human-induced carbon emissions during the 1990s.9 If left unchecked, global warm- ing could melt polar ice caps, raising sea levels by I Declining crop yields, loss of vital soil nutri- several feet and threatening low-lying countries. ents, and degradation of surrounding ecosys- Such a development would be devastating for many tems—Trees serve as barriers to soil erosion and countries. For example, if the sea level were to rise ensure that vital nutrients are naturally returned by 150 centimeters, Bangladesh could lose up to to the soil. In many tropical areas, valuable soil 16 percent of its land area, displacing 34 million erodes and crop yields can quickly decline when people.10 trees are cleared to make way for agriculture or I Loss of aesthetic value and natural beauty— livestock. Eroded soil often ends up in streams Many people view forests as natural treasures and and rivers, leading to siltation, contamination, areas of beauty that lose spiritual and aesthetic and stagnation. These processes, in turn, disrupt value when destroyed through deforestation and aquatic ecosystems, often killing fish and other forest degradation. aquatic organisms. I Spreading tropical diseases, reduced quantities Drivers of Deforestation of safe water—The spread of some potentially fatal Deforestation is directly attributable to humans tropical diseases (including malaria, hemorrhagic clearing land for agriculture or pasture, building fever, filariasis, leishmaniasis, and cholera) often fol- roads, logging, and extracting forest products. lows paths of deforestation.7 Mosquitoes thrive in These direct causes of deforestation are them- recently deforested areas as the number of stagnant selves symptoms of underlying demographic, bodies of water (pools, culverts, pits, and streams social, and economic interactions. While patterns clogged by felled trees) needed for breeding of deforestation vary, its four main essential caus- increase. As some forest animal species such as birds es have been summarized in the phrase, “people, and bats disappear from an area, insect populations poverty, plunder, and policy.”11 The relationships swell, facilitating the transmission of disease. and interactions among these forces are often Deforestation and hunting also remove the natural very complex, challenging our ability to under- predators of rodents. As their numbers multiply, stand this critical phenomenon. 3 PRB Making the Link 2001 PEOPLE: The Complex Role of Population Although disagreements exist over the connections Growth An increase in population density, whether due to natural between population and deforestation, at some increase or migration, heightens the probability of defor- level demographics do matter. estation in any given area. For each additional person, there are additional resource demands (food, fuelwood, shelter, land, etc.), resulting in increased pressure on forest tions led Jacques Diouf, director general of the Food and resources. The impact of each additional person will vary Agriculture Organization of the United Nations (FAO), to depending on their particular needs and the availability of state that, “These differences [among countries] cannot be employment opportunities outside the agriculture and explained by population pressure on forests alone, rather forestry sectors. In one study of deforestation in Costa they are apparently the results of economic developments at Rica, doubling the number of potential cultivators in an large, and national forest or land use policies.”15 area adjacent to forested land increased the likelihood of While many analysts believe that population growth deforestation in the area by 37 percent.12 does contribute to deforestation in one way or another, While the connection between population growth and there are disagreements over the precise role that it plays. deforestation often seems clear when examined at the local Some believe that population dynamics—growth, density, level, the links are less obvious at higher levels. First consider and migration—are the primary drivers of deforestation, a regional example. Population pressure on forests is while others assert that these dynamics merely exacerbate arguably much greater in Asia or alleviate more fundamen- than in any other region of tal causes (poverty, land-use the world (see Figure 1, page policies, and resource con- 4). Yet rates of net deforesta- sumption). To differing tion in Africa and South degrees, both of these views America (7.8 percent and 4.1 affirm the value of policies percent, respectively) were that attempt to preserve much higher during the forests by slowing popula- 1990s than in Asia (0.7 tion growth, such as provid- percent).13 ing access to voluntary Nor is the connection family planning or restrict- clearer at the national level.