“The commons” has long been a pivotal idea in environmental studies, and the resources and institutions described by that term have long been recognized as central to many environmental problems, especially problems of global environmental change. Since its birth in 1989, the Committee on the Human Dimensions of Global Change of the National Research Council has recognized the importance of commons and commons research (Global Environmental Change: Understanding the Human Dimensions, National Academy Press, 1992). Not only is the topic important in its own right, the commons is also a central theme in studies of international cooperation, environmental decision making, and the design of resource management institutions. Its importance is highlighted in the International Human Dimensions Programme’s science plans on Land Use and Land Cover Change (www.uni-bonn.de/ihdp/lucc) and Institutional Dimensions of Global Environmental Change (www.dartmouth.edu/~idgec) . So the commons is at the center of the international research agenda on the human dimensions of global change.

The importance of the topic is one reason the National Research Council has undertaken a review of knowledge about the commons at this time. Another reason is that it has been 15 years since the Council completed the work of its Panel on the Study of Common Property Resource Management. That work, as discussed in Chapter 1, marked a turning point in the history of research on commons—it marked the emergence of a self-conscious interdisciplinary and international research community focused on understanding commons. After 15 productive years of research since that early synthetic effort, we felt it appropriate to reexamine and reintegrate what had been learned.