Thomas Dietz, Nives Dolšak, Elinor Ostrom, and Paul C. Stern
The “tragedy of the commons” is a central concept in human ecology and the study of the environment. The prototypical scenario is simple. There is a resource—usually referred to as a common-pool resource—to which a large number of people have access. The resource might be an oceanic ecosystem from which fish are harvested, the global atmosphere into which greenhouse gases are released, or a forest from which timber is harvested. Overuse of the resource creates problems, often destroying its sustainability. The fish population may collapse, climate change may ensue, or the forest might cease regrowing enough trees to replace those cut. Each user faces a decision about how much of the resource to use—how many fish to catch, how much greenhouse gases to emit, or how many trees to cut. If all users restrain themselves, then the resource can be sustained. But there is a dilemma. If you limit your use of the resources and your neighbors do not, then the resource still collapses and you have lost the short-term benefits of taking your share (Hardin, 1968).
The logic of the tragedy of the commons seems inexorable. As we discuss, however, that logic depends on a set of assumptions about human motivation, about the rules governing the use of the commons, and about the character of the common resource. One of the important contributions of the past 30 years of research has been to clarify the concepts involved in the tragedy of the commons. Things are not as simple as they seem in the prototypical model. Human motivation is complex, the rules governing real commons do not always permit free access to everyone, and the resource systems themselves have dynamics that influence their response to human use. The result is often not the tragedy described by Hardin but what McCay (1995, 1996; McCay and Acheson, 1987b; see also