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Will slower population growth alleviate pollution and the degradation of the natural environment? The quality of the natural environment, including air and water, climatic conditions, and the number and abundance of species of plants and animals, has direct significance for the health, economic production, and aesthetics of human populations. In addition to being essential requirements for human life, air and water are direct inputs into many production processes and also provide an important economic service by absorbing the residuals of production processes (Smith and Krutilla, 1979~. Climatic conditions, of course, represent an important parameter in agricultural production. Climate remain-e Anal ~1~ ~ ~_:~1 ~ ^~ ,~ .. .. Us - w~un pram and animal species to create aesthetically appealing environments Mat can beta basis for tourism. And naturally occurring plant and animal species represent sources of genetic diversity that may be important in developing new products Trough biotechnology (Miller et al., 1986~. Production and consumption of industrial goods provide the primary link between population and environmental degradation, so the strength of the linkage may depend importantly on income levels. However, there are many processes of environmental degradation Hat depend more directly on population. For example, while most of the buildup of aunospheric carbon dioxide responsible for the emerging "greenhouse', effect is due to fossil fuel combustion, predominantly in He developed countries, some 23 to 43 percent is due to the burning of forests, primarily for land clearance, in developing countries ~Voodwell et al., 1983), which may well be linked to population increase. But because only a moderate proportion of the addition to atmospheric carbon dioxide is athibmable to activities in developing counties 35

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36 POP UI'ION GROWTH AND ECONOMIC DEYELOPMENT and because the sensitivity of this addition to changes in population size or growth is uncertain, the effect of population trends in developing countries on the carbon dioxide problem may be minor. Environmental resources are mostly renewable, but as with other renewable resources, human action can interfere with the renewal process in ways that produce permanent degradation. This possibility is most evident in the case of total species extinction, which is clearly an irreversible process. The atmospheric buildup of carbon dioxide and fluorocarbons as by-products of production has effects that are also so long term as to mimic irreversibility, as are effects of siltation of major water resources. Eutrophication of lakes and effects of acid rain are processes that can be reversed, but probably not in less than a generation. Reflecting their physical characteristics and seeming abundance, environ- mental resources typically have no property rights that govern access to them. Because of this common-propert~r aspect, many of these resources tend to be overexploited. For instance, when access to air and water is unregulated, polluters can impose substantial costs on other users, and in many cases, these costs are greater than the costs of pollution abatement. Thus, there would be a net gain to society if there were some institution- such as pollution taxes or a market in pollution nghts-that would allocate rights to the resource so as to balance costs and benefits. However, there are a number of barriers to setting up such institutions. It is both analytically and empirically difficult to determine the optimum levels of pollution taxes or to specify the conditions required for efficient markets in pollution rights. The use of either pollution taxes or markets in pollution rights has had relatively few applications (Starrett, 1972~. On a pragmatic level, imposing and enforcing new properq rights to previously unpriced resources is politically and administratively difficult. Vested interests that would suffer losses from the new assignment of property rights may oppose ~em, as has occulted in the United States (Portney, 1982). In developing countries, which may lack administrative resources, even if environmental quality measures are adopted, such measures may be difficult to police. And many environmental problems have an important international dimension, because many environmental resources extend beyond a single political jurisdiction so that regulations affecting their quality require a negotiated consensus. Win weak international cooperation in many fields, including use of resources, it may be unrealistic to expect environmental quality policies established in one country to adequately reflect the potential costs of degradation in another country. The vast abundance of environmental resources has provided little motive for regulation until relatively recently, when it became increasingly evident that human activity could significantly degrade the quality of environmental . .

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POLLUTION AND ENVIRONMENTAL DEGRADATION 37 resources. In response, the richer countries have instituted policies that have reduced levels and rates of pollution and degradation in most (though not all) major areas of air and water quality (Baumol and Gates, 1984~. These improvements reflect the fact Hat a clean environment is, in a sense, a "luxury good" insofar as the willingness to pay the required costs seems to increase with income levels. For developing countries, there are few systematic time series for measuring environmental quality, but it is clear that important instances of deteriorating quality are occurring (see below). In discussing the role of population growth in producing change in environmental quality, it is convenient to invoke a scheme used by Commoner et al. (1971~. This scheme considers the size of population, the level of per capita production, and the level of pollution produced per unit of production. Commoner and coauthors note that it is pollution per unit of output that has been quantitatively the most important in producing the rising U.S. levels of pollution they review. The second factor, rising levels of per capita production, can have immediate effects that increase pollution, but as noted above, it can also have advantageous effects that work through higher levels of personal income. It is difficult to envision equivalent advantageous effects for changes in population size. Eventually, population grown may increase pollution to the point that new forms of social intervention are introduced, but this possibility does not negate the direct negative effects of population growth. The most serious international issues reflect economic activity in the developed counties, including the buildup of atmospheric fluorocarbons, carbon dioxide from fossil fuel combustion, and the production of acid rain from sulfurous residues. Although some carbon dioxide accumulation is due to He burning of forests in developing countries, the most important environmental problems in developing countries are likely to be relatively localized, such as air and water pollution from human and industrial wash especially in cities-and siltation of water resources from erosion. The cumulative effect of localized environmental degradation is difficult to predict because natural processes can clean He air and water up to a certain threshold level, beyond which degradation may progress more rapidly. How important are these effects in developing counties? Would a developing nation be willing to forgo a small but nonnegligible share of its income or employment growth in order to coning or reverse environmental degradation? In many developing counties, air, water, and many species have been treated as free goods. The failure to institute restrictions on the use of these resources suggests either Hat there are severe technological and institutional barriers to resource control, or that pollution abatement has a low priority relative to a low-income country's other needs. As we noted earlier in the case of oil, as common resources become more scarce and hence more

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38 POPUl'7ON GROWIN AND ECONOMIC DEI{ELOPMENT valuable, rules for access to them tend to become better developed and more restnctive. Means do exist to control at the source the pollution of air and water from industrial processes and the pollution of water in urban areas by human waste. If these means are not implemented, which they apparently are not in Chinese cities, for example (Smil, 1984:100), population growth will likely exacerbate problems of pollution. But the fact that they have not been widely implemented suggests either Hat the problems are less important, relative to the many other problems of developing countries, or that there are severe technological and institutional bamers to resource control. The problem of siltation of water resources from soil erosion is exceptional because the means to control it, which originate in millions of actions taken over highly dispersed areas, are not obvious and probably not inexpensive. For example, they are not obvious and inexpensive enough to have been widely adopted in the United States. Crosson (1984) estimates that the off- farm costs of soil erosion in the United States exceed the on-fann costs, largely because of siltation. Crosson (1983) also implies that the same may be hue in developing countries, although the data are extremely poor. He cites many instances in developing countries in which the siltation of reservoirs has occurred at a rate far more rapid than anticipated, with a drastic shortening of He economic lives of the reservoirs because of unanticipated increases . . . In soil erosion. Species loss is another example of a problem difficult to control because of the highly dispersed actions that contribute to it. It is an international problem because the potential usefulness of a particular species is not confined to a single country or ecological area. And unlike many of the other resource problems with an international dimension, species loss is more acute in developing than in developed counties. Tropical areas are the home of about two-thirds of the known species of plants and animals (Hamngton and Fisher, 1982~. Data on the rate of loss are very poor (Simon and Wildavsky, 1984), but there is little question that the rate of loss has accelerated in recent years and little hope or Scion that the rate of loss in developing countries will diminish in the near future. The rate of loss is unlikely to be slowed because of the difficulty of enforcing preservation strategies and the tendency to heavily discount Heir aesthetic value as well as a future in which the disappearing species may acquire greater economic value-as food, fiber, building material, and drugs. Population grown, particularly by encouraging encroachment on forested areas, is surely contributing to He loss of species (Myers, 1980; Hamngton and Fisher, 1982~. Population may be a factor in climatic change at both He regional and global level. Overawing by the herds kept by nomad* peoples in the Sahel region of Africa, for example, apparen~dy led to the loss of ground cover,

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PORTION AND E~VIRONMENIAL DEGRADATION 39 which increased We sunlight reflected from the earth and reduced We level of rainfall, accelerating We process of desertification (World Meteorological Organization, 19831. The accumulation of atmospheric carbon dioxide and the emergence of the "greenhouse" effect, the economic implications of which are uncertain, depend in part on population growth (National Research Council, 1984~. Using the analytical scheme suggested by Commoner et al. (1971), and assuming continued growth in output per capita and dependence on technology based on energy from fossil fuel combustion, rapid population grown in the developing countries will contribute to the buildup. This buildup could hasten the global temperature increases and climatic change now predicted for the latter part of the next century (World Meteorological Organization, 1983~. Because forests convert carbon dioxide to oxygen through photosynthesis, the clearing of forest areas for settlement under population pressure also contributes to the greenhouse effect. CONCLUSIONS Because environmental resources are common property, they tend to be overexploited, leading to pollution and degradation. Controlling or reversing environmental damage seems to have a low priority in developing countries in view of the substantial fiscal and institutional requirements. Although population growth contributes directly and indirectly to environmental problems, it is important to emphasize that He common-property aspect of environmental resources also contributes to these problems. Damage is likely to continue in the developing countries until environmental resources become scarce enough that the countries are willing to bear the cost of environmental protection and until the corrective social and political institutions develop. It is necessary, of course, Mat such protection be undertaken before the resource is irreparably damaged. While the long-term solution to these problems will require socially negotiated access rules, slower population growth might allow somewhat more time for developing countries to implement the policies and to develop He institutions necessary to protect the environment.