Collapse_ How Societies Choose to Fail or Succeed - Jared Diamond [266]
One particular form of clashes of interest has become well known under the name “tragedy of the commons,” in turn closely related to the conflicts termed “the prisoner’s dilemma” and “the logic of collective action.” Consider a situation in which many consumers are harvesting a communally owned resource, such as fishermen catching fish in an area of ocean, or herders grazing their sheep on a communal pasture. If everybody over-harvests the resource, it will become depleted by overfishing or overgrazing and thus decline or even disappear, and all of the consumers will suffer. It would therefore be in the common interests of all consumers to exercise restraint and not overharvest. But as long as there is no effective regulation of how much resource each consumer can harvest, then each consumer would be correct to reason, “If I don’t catch that fish or let my sheep graze that grass, some other fisherman or herder will anyway, so it makes no sense for me to refrain from overfishing or overharvesting.” The correct rational behavior is then to harvest before the next consumer can, even though the eventual result may be the destruction of the commons and thus harm for all consumers.
In reality, while this logic has led to many commons resources becoming overharvested and destroyed, others have been preserved in the face of harvesting for hundreds or even thousands of years. Unhappy outcomes include the overexploitation and collapse of most major marine fisheries, and the extermination of much of the megafauna (large mammals, birds, and reptiles) on every oceanic island or continent settled by humans for the first time within the last 50,000 years. Happy outcomes include the maintenance of many local fisheries, forests, and water sources, such as the Montana trout fisheries and irrigation systems that I described in Chapter 1. Behind these happy outcomes lie three alternative arrangements that have evolved to preserve a commons resource while still permitting a sustainable harvest.
One obvious solution is for the government or some other outside force to step in, with or without the invitation of the consumers, and to enforce quotas, as the shogun and daimyo in Tokugawa Japan, Inca emperors in the Andes, and princes and wealthy landowners in 16th-century Germany did for logging. However, that is impractical in some situations (e.g., the open ocean) and involves excessive administrative and policing costs in other situations. A second solution is to privatize the resource, i.e., to divide it into individually owned tracts that each owner will be motivated to manage prudently in his/her own interests. That practice was applied to some village-owned forests in Tokugawa Japan. Again, though, some resources (such as migratory animals and fish) are impossible to subdivide, and the individual owners may find it even harder than a government’s coast guard or police to exclude intruders.
The remaining solution to the tragedy of the commons is for the consumers to recognize their common interests and to design, obey, and enforce prudent harvesting quotas themselves. That is likely to happen only if a whole series of conditions is met: the consumers form a homogeneous group; they have learned to trust and communicate with each other; they expect to share a common future and to pass on the resource to their heirs; they are capable of and permitted to organize and police themselves; and the boundaries of the resource and of its pool of consumers are well defined. A good example is the case, discussed in Chapter 1, of Montana water rights for irrigation. While the allocation of those rights has