The tragedy of the commons

More tragic than we knew?

In 1832 William Lloyd, per the terms of his professorship in political economy at the University of Oxford, gave two public lectures. His topic was the controversial question of whether population would outstrip the means of sustenance. Would the English people grow poorer over time, as Thomas Malthus had predicted, or richer, as Adam Smith rejoined?

Lloyd asked his listeners to consider the case of an English village commons, the grazing area open to all inhabitants of the village, and to compare it with privately owned, enclosed pastures nearby. Observation showed that cattle did better in the latter spaces than in the former. Lloyd asked why. “Why are the cattle on a common so puny and stunted? Why is the common itself so bare-worn, and cropped so differently from the adjoining inclosures? No inequality, in respect of natural or acquired fertility, will account for the phenomenon. The difference depends on the difference of the way in which an increase of stock in the two cases affects the circumstances of the author of the increase. If a person puts more cattle into his own field, the amount of the subsistence which they consume is all deducted from that which was at the command of his original stock; and if, before, there was no more than a sufficiency of pasture, he reaps no benefit from the additional cattle, what is gained in one way being lost in another. But if he puts more cattle on a common, the food which they consume forms a deduction which is shared between all the cattle, as well that of others as his own, in proportion to their number, and only a small part of it is taken from his own cattle.”

Lloyd reached no firm conclusion, though he wasn’t hopeful. As matters turned out, his example had longer life than his overall argument. In 1968 Garret Hardin, an American ecologist, in an article titled “The Tragedy of the Commons,” employed Lloyd’s village commons as a metaphor for the global environment. “Picture a pasture open to all,” Hardin wrote. “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 herdsmen, 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 best interest in a society that believes in the freedom of the commons. Freedom in a commons brings ruin to all.”

Hardin’s phrase “the tragedy of the commons” entered the lexicon of ecologists, economists and others pondering the future of the planet. In the 1960s the most pressing problem appeared to be overpopulation; today it is climate change. Yet the dynamics now are the same as they were in Hardin’s—and William Lloyd’s—time. When a resource is held in common, whether a patch of village grass or the atmosphere of the earth, self-interest works against the measures required to protect that resource. If Country A reduces its carbon emissions, it will incur the whole cost of reduction but will share the benefits with every other country. The result for Country A will be a net loss. Every country will make a similar calculation, and few reductions will be made.

Hardin concluded that the only alternative to the tragedy of the commons was collective action—what he called “mutual coercion mutually agreed upon.” Individuals’ rights would have to be abridged, including the right to procreate. “The only way we can preserve and nurture other and more precious freedoms is by relinquishing the freedom to breed, and that very soon,” he declared. “It is the role of education to reveal to all the necessity of abandoning the freedom to breed. Only so, can we put an end to this aspect of the tragedy of the commons.”

Not surprisingly, Hardin’s program didn’t catch on in the United States or other democratic countries. Individuals there were not willing to vote away their right to procreate. But it did take hold in China, where overpopulation appeared a more immediate threat than in most other countries. The Chinese government adopted a one child per family policy and maintained it for decades. The policy worked too well, and in the late 2010s it was dropped.

Yet Hardin’s insight about the need for collective coercion against the collective threat remains pertinent. And this need poses the single most stubborn obstacle to meaningful action on climate change. Strikingly, to the extent that the world has democratized since the 1960s, the chances of meaningful collective action might well have diminished. In America, democracy has produced deadlock on nearly every important issue, even when all the benefits of a policy would be captured by Americans themselves. For Americans to take on costs for the benefit of non-Americans appears essentially out of the question. Many countries look to the United States for leadership on this issue, if only to spare themselves the exposure of getting out front. And the United States appears unlikely to provide such leadership.

So will it be left to the dictators to save the planet? Will the human race have to choose between personal freedom and collective survival?

It’s a grim thought. The tragedy of the commons may turn out to be more tragic than anyone knew.

Am I too pessimistic? I hope so. Please comment.