Summarizes the ecological concerns that threaten sustainability and discusses ways in which psychologists and other social scientists can help improve the situation. The most central factor producing environmental problems is the worldwide human population explosion. The rapid increase in population size, affluence, and use of advanced technology is largely responsible for the many other environmental threats. Psychologists and social scientists can help alleviate environmental problems through research on environmental behavioral processes and responses, proposal and execution of policies and social technology interventions, and evaluation of environmental policies once implemented. Examples of valuable social science research related to population control, global environmental change, energy conservation, and reducing and recycling solid wastes illustrate these attempts.