Tragedy of the Commons

The Tragedy of the Commons

© Eric R. Pianka

Over 40 years ago, in a setpiece of rational thought that deserves much more attention than it has so far received, Garrett Hardin [Science 162: 1244 (1968) Download Hardin's article] perceived a fly in the ointment of freedom, which he explained as follows:
"The tragedy of the commons develops in this way. Picture a pasture open to all. It is to be expected that each herdsman will try to keep as many cattle as possible on the commons. Such an arrangement may work reasonably satisfactorily for centuries because tribal wars, poaching, and disease keep the numbers of both man and beast well below the carrying capacity of the land. Finally, however, comes the day of reckoning, that is, the day when the long-desired goal of social stability becomes a reality. At this point, the inherent logic of the commons remorselessly generates tragedy.

As a rational being, each herdsman seeks to maximize his gain. Explicitly or implicitly, more or less consciously, he asks, "What is the utility to me of adding one more animal to my herd?" This utility has one negative and one positive component.

1) The positive component is a function of the increment of one animal. Since the herdsman receives all the proceeds from the sale of the additional animal, the positive utility is nearly +1.

2) The negative component is a function of the additional overgrazing created by one more animal. Since, however, the effects of overgrazing are shared by all the herdsman, the negative utility for any particular decision-making herdsman is only a fraction of -1.

Adding together the component partial utilities, the rational herdsman concludes that the only sensible course for him to pursue is to add another animal to his herd. And another; and another . . . But this is the conclusion reached by each and every rational herdsman sharing a commons. Therein is the tragedy. Each man is locked into a system that compels him to increase his herd without limit in a world that is limited. Ruin is the destination toward which all men rush, each pursuing his own interest in a society that believes in the freedom of the commons. Freedom of the commons brings ruin to all."
Hardin's logic is compelling: overgrazing of public lands, overfishing of the oceans, pollution of the atmosphere and oceans all serve as ample testimony to its accuracy. He extends his argument to pollution and unlimited reproduction, noting that the "tragedy of the commons" theme recurs and underlies these and other serious human problems. Hardin suggests that a commons is acceptable only at low population densities and that we can no longer afford to have commons. But it is not so easy to escape from this trap: the Earth and its atmosphere and oceans themselves constitute commons that all humans must share whether we like it or not.

Examples include the rush to catch the last of the great whales and the ongoing destruction of earth's atmosphere (ozone depletion, acid rain, carbon dioxide enhanced greenhouse effect, etc.). Global weather modification is a very real and an exceedingly serious threat to all of us, as well as to all other species of plants and animals struggling to continue their existence on this beleagured planet.

Last updated 3 September 2014 by Eric R. Pianka