The tragedy of the commons: twenty-two years later.

The authors take up the hypothesis originally proposed by Garrett Hardin that resources held in common, such as oceans, rivers, air, and parklands, are bound to be subject to massive degradation. Specifically, they "examine the accumulated evidence pertaining to common-property resource management and provide a critique of the conventional theory expounded by Hardin." They conclude that recent evidence suggests that users of such resources are able to restrict access to them and establish rules among themselves for their sustainable use.