To project the human consequences of global change, it is necessary not only to anticipate environmental change but also to take social change into account: social and economic organization and human values may change faster than the global environment, and people may respond in anticipation of global change. It is worthwhile to test projected environmental futures against projected human futures to see how sensitive human consequences may be to variations in the social future. But long-term forecasting is still a very inexact practice. The near-term research agenda should emphasize processes of human response to the stresses that global environmental change might present.

People may respond to experienced or anticipated global change by intervening at any point in the cycle of interaction between human and environmental systems. Mitigation—that is, actions that alter environmental systems to prevent, limit, delay, or slow the rate of undesired global changes—may involve direct interventions in the environment, direct interventions in the human proximate causes, or indirect interventions in the driving forces of global change. People can also respond by blocking the undesired proximate effects of environmental systems on what they value, for example, by applying sunscreens to the skin to help prevent cancer from exposure to ultraviolet radiation. They can make adjustments that prevent or compensate for imminent or manifest losses of welfare from global change, for example, famine relief or drought insurance. And people can intervene to improve the robustness of social systems by altering them so that an unchecked environmental change would produce less reduction of values than would otherwise be the case. For example, crop polyculture may not slow the pace of global change, but it is more robust than monoculture in the face of drought, acid deposition, and ozone depletion. If crop failure occurs, it will affect only some crops, making famine less likely. Many of these responses may indirectly affect the driving forces of global change. Consequently, the research agenda should include studies of both the direct and secondary effects of responses to global change, using the best available methods of evaluation research.

Global change is likely to engender conflict—about whether it is in fact occurring, whether any organized response is necessary, whether response should emphasize mitigation or not, who should pay the costs, and who has the right to decide. Such conflicts tend to persist because they are based in part on differing inter-

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