Hardin illustrated his fundamental argument by describing people who herd animals in a common pasture. Adding another animal to the pasture clearly benefits the animal’s owner by the full value of the animal; however, the negative component of such an addition, increased grazing of a limited resource, is spread over all herders. Since only a small fraction of the negative component accrues to the person adding the animal, a strictly scientific analysis says that each herder should seek to add as many animals as possible. But this leads to overgrazing the pasture, which destroys the resource for all. Hardin used the word “tragedy” to mean inevitable development of a system toward an undesired result. The potential for tragedy arises when people benefit individually from use of a shared resource whose depletion affects everyone, and when the population using the resource becomes large enough to endanger the viability of the resource. Pollution of the air, water, or land, removal of habitat required by plants or animals, depletion of mineral resources, and many other environmental problems fall within this general category. Hardin argued further that increasing population was the driver of all tragedies of the commons, and that population could only be controlled by what he termed, “mutual coercion mutually agreed upon”.

In the December 12, 2003 issue of Science, one day short of 35 years after publication of “The Tragedy of the Commons”, a special section included nine articles related to Hardin’s landmark paper. In addition, in the issues from November 14 through December 5, Science provided a “State of the Planet” series—a comprehensive overview of the issues facing Planet Earth over the next 50 years (3). Articles discussed population, biodiversity, soils and food security, fisheries, freshwater resources, energy resources, air quality, and global climate change—just the sort of issues where Hardin predicted tragedy might occur. Both collections of articles make excellent reading for students and teachers alike.

To say that many problems cannot be solved by science and technology alone is not to say that science and technology cannot play a major role in solving such problems. Rather it implies that scientists and engineers will need to collaborate with social scientists, lawyers, politicians, and many others. Maintaining effective communication among groups with such diverse approaches to the world requires major efforts on the part of all. An example is given by the last paper in the Tragedy of the Commons series (4). Oliver Houck of the Tulane Law School describes vividly the difficulty of applying science to the problem of reducing contamination of air and water. As scientists, we approach the problem by setting concentration standards that could be checked by chemical analysis and enforced by locating sources of contamination and causing them to cease contaminating. As Houck points out, because appropriate concentrations differ for each use, such as drinking, swimming, or maintaining an ecosystem, setting standards quickly exceeds the bounds of science and becomes political. Another set of issues arises when extrapolating from studies of toxicity in animals to toxicity in humans, where scientific consensus is difficult to achieve. As a result, even good environmental laws often achieve only 50% compliance.

To be prepared to deal with problems such as these, students should be learning to collaborate even more broadly than they now do as members of interdisciplinary graduate research programs. Mitigating many of the world's most pressing problems requires interdisciplinary teams that go far beyond scientific and engineering disciplines, and our students should be preparing to contribute to such teams and learning how to do so. How best to structure a curriculum to achieve this goal is far from obvious, but it behooves us to make the attempt.

Literature Cited

1. Hardin, Garrett Science 1968, 162, 1243–1248.
2. Wiesner, J. B.; York, H. F. Sci. Amer. 1964, 211(4), 27.
3. To see all papers in the “Tragedy of the Commons” series and the “State of the Planet” series, go to this Web site (accessed Mar 2004). This page also includes links to other Web sites that provide additional information.