Through the Global Environment Outlook series, the United Nations Environment Programme provides a comprehensive assessment of the state of the global environment, a review of policy responses, and an outlook on the future. The first Global Environment Outlook (GEO-1) was released in 1997, the second (GEO-2000) in 2000, and the third (GEO-3) in 2002. This background paper for GEO-3 provides a scenario-based approach to illuminate the challenges and appropriate responses over the coming decades. It addresses environmental trends in an integrated framework that included economic, social, and cultural factors that ultimately shape the ways in which human activity impacts nature, and it places regional analyses in the context of global patterns.