use of many materials has been declining in North America and western Europe for some time (Herman et al., 1989). Waste management based on recycling, redesign of production processes, and the treatment of the wastes of one process as raw materials for another can reduce the environmental impact of economic activity (e.g., Ayres, 1978; National Research Council, 1985; Haefele et al., 1986; U.S. Office of Technology Assessment, 1986; Friedlander, 1989). And an observed trend in the United States, in which the main source of pollution has shifted from production activities to consumption activities, has effects on the overall economy-environment relationship that are not yet clear (Ayres and Rod, 1986; Ayres, 1978).
The environmental effect of economic growth may also depend on forms of political organization. The comparison of emissions of CO2 and pollutants in Eastern and Western Europe suggests that democratic countries may be able to deal more effectively with the effects of wastes than nondemocratic countries. When people who feel the effects, or become concerned about the effects on others, have ready access to political power, their concerns may possibly have more influence on policy. If this hypothesis is correct, then political trends toward democracy, such as in Eastern Europe, will tend to reduce the amount of degradation resulting from economic growth there.
National policies also help determine the environmental costs of economic growth. In many developing countries, policies have favored extensive use of ''unused'' resources and "underpopulated" land to increase national power and improve the welfare of their citizens. Countries such as the United States, Canada, Argentina, and Australia had such policies during rapid development phases, and other countries have followed the example. This model of development through frontier occupation and rapid creation of wealth required cheap food and raw materials from rural areas, an infrastructure of roads and transport to open up these areas, and huge infusions of capital for enterprises and settlement. An alternative development model generates increased production per unit of land by agricultural intensification rather than by extensive land uses such as shifting agriculture or ranching (Boserup, 1990; Turner et al., n.d.). Development of this kind can be carried out in a sustainable manner (Conway and Barbier, 1990; Sublet and Uhl, 1990).
The effects of economic development on the proximate causes of global change appear to be contingent, among other things, on