ABSTRACT
The “tragedy of the commons” is a social dilemma arising from a situation in which members of a group make independent rational decisions that lead to the depletion of a natural resource, even though this will eventually result in a welfare loss for every group member. Garrett Hardin in his 1968 Science article stimulated this discussion and emphasized the increasing pressure on natural resources as a consequence, in particular, of population growth induced by a supportive welfare state (see Population sustainability). According to Hardin, these developments require a change in human values, ideas of morality, or rules instead of technological solutions. To shape his arguments he introduced the much debated parable of a pasture jointly used by a group of herders and implicitly assumed the absence of any coordination between the users. Each individual herder of the group of herders managing such an unregulated pasture will receive all of the profits from his own animals. Simultaneously, the negative consequences of pasture degradation caused by his animals will be shared by all group members. Imagine a local grazing area of limited size. The value of one additional cow grazing on it depends on the total number of grazing cows. With too many cows on the pasture competing for fodder, the animals will give less milk, lose weight, and the regeneration of the ecosystem will be disturbed. Thus, each additional cow generates a negative externality for the other cows as there is rivalry in consumption. Adding together the component of partial utilities, the rational herdsman concludes that the only sensible course for him to pursue is add another animal to his herd-and another, and another. This is the conclusion reached by each and every rational herdsman sharing a commons. Therein is the tragedy of the commons (Hardin 1968; see also Townsend and Wilson 1987). Hardin’s example of a social dilemma can be applied to overexploitation of various common pool resources such as fisheries or forests, as well as to the problem of maintaining and contributing to global public goods such as clean air.
