possible by the technology. For levels of analysis at the local level, the inefficiency of Chinese energy use can be understood in terms of outmoded technology and lack of funds for replacing it; at the national level, low prices for coal and the system of production quotas appear as critical factors; at the world level, the entire system of command economies is implicated. All the relationships are equally real and important, yet answers derived at each level are incomplete.

IMPLICATIONS FOR RESEARCH

1. The highest priority for research is to build understanding of the processes connecting human activity and environmental change. Better studies focused on the driving forces and their connections to the proximate causes are necessary for effective integrative modeling of the human causes of global change. Quantitative models will be of limited predictive value, especially for the decades-to-centuries time frame, without better knowledge of the processes.

More is generally known about the causes of population growth, economic development, technological change, government policies, and attitudes and culture—the driving forces of global change—than about their interrelationships and environmental effects. This is so because study of the driving forces is supported by organized subdisciplines or interdisciplinary fields in social science, such as population studies, development studies, and policy analysis, whereas an interdisciplinary environmental social science—a field that examines the environmental effects of the driving forces—is not yet organized. There is a critical need for support of the research that would constitute that field. Research on the processes by which human actions cause environmental change should begin from the basic principle that the relationships are contingent: the effect of such variables as population on environmental quality depends on other human variables that change over time and place. This fact has three major implications for research strategy: understanding the human causes is an intrinsically interdisciplinary project; the important human causes of global change are not all global; and comparative studies to specify the contingencies are critically needed (see #2 and #3 below). Research at the global level is important but far from sufficient for understanding the human causes of global change.

2. Over the near term, research on the human causes of environmental change should emphasize comparative studies of glob-



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