The volume describes the earth as a unified system--exploring the interactions between the atmosphere, land, and water and the snowballing impact that human activity is having on the system--and presents perspectives on policies and programs that can both develop and protect our natural resources. It discusses why such seemingly diverse issues as historical climate change, species diversity, and sea-level rise are part of a single picture--and how human activity is the critical element in that picture. The book concludes with practical examinations of economic, security, and development questions, with a view toward achieving improvements in quality of life without further environmental degradation.