Robert E. Manning is a professor in the Rubenstein School of Environment and Natural Resources at the University of Vermont, where he teaches park and wilderness management and environmental history and philosophy, and conducts a program of research for the U.S. National Park Service.

The Tragedy of the Commons

Freedom in a commons brings ruin to all.

In 1968, a haunting paper—"The Tragedy of the Commons"—was published in the prestigious journal Science (Hardin 1968). Now a foundational piece of the environmental literature, this paper identified a set of environmental problems—issues of the "commons"—that have no technical solutions but must be resolved through social action. Hardin's ultimate prescription for managing the commons was "mutual coercion, mutually agreed upon": without such collective action, environmental (and related social) tragedy is inevitable.

Hardin began his paper with an illustration using perhaps the oldest and simplest example of an environmental commons, a shared pasture:

Picture a pasture open to all. It is expected that each herdsman will try to keep as many cattle as possible on [this] commons.... What is the utility of adding one more animal? ... Since the herdsman receives all the proceeds from the sale of the additional animal, the positive utility [to the herdsman] is nearly +1.... Since, however, the effects of overgrazing are shared by all the herdsmen, the negative utility for any particular ... herdsman is only a fraction of–1. Adding together the ... partial utilities, the rational herdsman concludes that the only sensible course for him to pursue is to add another animal to [the] herd. And another; and another.... Therein is the tragedy. Each man is locked into a system that [causes] him to increase his herd without limit—in a world that is limited.... Freedom in commons brings ruin to all. (1244)

Hardin went on to identify and explore other examples of environmental commons, ultimately addressing human population growth. However, one of his examples of the tragedy of the commons—one that resonates more urgently each year—is national parks and protected areas:

The National Parks present another instance of the working out of the tragedy of the commons. At present, they are open to all without limit. The parks themselves are limited in extent—there is only one Yosemite Valley—whereas population seems to grow without limit. The values that visitors seek in the parks are steadily eroded. Plainly, we must soon cease to treat the parks as commons or they will be of no value to anyone. (1245)

The tragedy of the commons has become one of the most compelling and powerful ideas in the environmental literature. The original paper has been republished in over one hundred environmental and public policy–related anthologies and has stimulated an enormous body of research and writing. A recent bibliography on papers related to issues of managing environmental and related commons includes over thirty-seven thousand citations (Hess 2004). This work has been applied to a growing list of commons-related resources and issues, including wildlife and fisheries, surface and ground water, range lands, forests, parks, the atmosphere, climate, oil and other energy resources, food, biodiversity, and population. The conceptual foundation of the tragedy of the commons has even been extended to a growing array of public resources that are not necessarily environmentally related, such as education (J. Brown 2000), medicine (R. Lewis 2004), and the infosphere or cyberspace (Greco and Floridi 2004). Recognizing the importance of common property resources and the issues identified by Hardin's 1968 paper, a special issue of Science was published in 2003 commemorating the thirty-fifth anniversary of publication of "The Tragedy of the Commons" and assessing the growing scientific and professional literature it has spawned.

Hardin and others have noted that the issue of managing common property resources has a long history. In fact, nascent interest in the "commons" was expressed by Aristotle, who wrote, "What is common to the greatest number gets the least amount of care. Men pay most attention to what is their own: they care less for what is common" (quoted in Hardin and Baden 1977, xi). The first modern expression of the commons issue is generally credited to Lloyd (1833) who published two lectures in England titled On the Checks to Population, which suggested the environmental degradation caused by unfettered population growth and the associated inability of the Earth to support very large numbers of humans. More contemporary, scientifically based explications of the commons were first offered in the 1950s in the context of ocean fisheries (Gordon 1954; Scott 1955).

Common property resources can be defined technically as having several characteristics (Ostrom et al. 1999; Feeny et al. 1990; Ostrom and Ostrom 1977; Greco and Floridi 2004). First, as the term suggests, ownership of the resource is held in common, often by a large number of owners who have independent rights to use the resource. Second, control of access to the resource is problematic for several potential reasons, including the large size or area of the resource, its pervasive character, its migratory nature, or its political intransigence. Third, the level of exploitation by one user adversely affects the ability of other users to exploit the resource. Hardin (1968) and others have noted that in addition to conventional common property resources in which tangible (e.g., forage, fish) and intangible (e.g., enjoyment) benefits are extracted from a resource, there are also "reverse" commons in which pollution is deposited into a resource that is owned in...