[T]hat which is common to the greatest number has the least care bestowed upon it. Every one thinks chiefly of his own, hardly at all of the common interest; and only when he is himself concerned as an individual. For besides other considerations, everybody is more inclined to neglect the duty which he expects another to fulfill.
he American ecologist Garrett Hardin (1915-2003) realized that actions that might seem sensible and harmless on an individual level could in a free society have disastrous cumulative results. He called this concept the tragedy of the commons. To explain the concept, he envisioned a pasture shared by several herdsmen.
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. …As a rational being, each herdsman seeks to maximize his gain. …[T]he 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 best interest in a society that believes in the freedom of the commons. Freedom in a commons brings ruin to all.
Hardin was concerned with overpopulation, but the concept applies to overdevelopment, over fishing, pollution, global warming, and any domain where resources are openly shared.
A morality suited to the modern age needs to take into account the individual’s responsibility for preventing such tragedies. Here religion-based morality has fallen short, mostly just because population levels were relatively small when the world’s major religions were formed. In those days it wasn’t important for herdsmen to consider the tragedy of the commons, for as Hardin said, “tribal wars, poaching, and disease [kept] the numbers of both man and beast well below the carrying capacity of the land.” No commandment on environmentalism was necessary during the Bronze Age or in medieval times, but we need one now.