The dramatic increase in world population and industrial activities during the last century has given rise to concern that human activities are adversely affecting the environment at all geographic scales, Until the last decade or so, the key environmental issues were local, regional, or continental in scale and were primarily linked to air and water pollution. More recently, our concerns have increasingly focused on global-scale issues. In particular, there are three interrelated globalscale environmental issues that affect both human well-being and the quality of life and that also threaten the very foundation of sustainable development: stratospheric ozone depletion, loss of biological diversity, and climate change. The scientific community is coming under increasing pressure to improve humanity’s understanding of key processes, to estimate the potential impacts of global environmental change, and to evaluate technologies and strategies for dealing with such issues. This is providing new opportunities for research as well as increasing the responsibilities for participation in scientific assessments designed to provide timely information for decision-making.