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The Tragedy of the Commons

The game of tic-tac-toe has simple rules, a limited number of moves, and equal chances for both sides. If both players understand the game, it is almost impossible to avoid a draw. As ecologist and philosopher Garrett Hardin noted in his 1968 paper The Tragedy of the Commons, tic-tac-toe has "no technical solution." Sure, there might be ways to win by thinking outside the box:

I can win only by giving a radical meaning to the word "win." I can hit my opponent over the head; or I can drug him; or I can falsify the records. Every way in which I "win" involves, in some sense, an abandonment of the game, as we intuitively understand it. (I can also, of course, openly abandon the game—refuse to play it. This is what most adults do.)

But these are not "wins" in the traditional sense of the word. In his paper Hardin introduced this example as evidence that there are indeed problems for where there is no technical solution. Having shown that this class of problems does exist, Hardin then suggests that population growth is one of these problems.

The problem is that as the population grows even by a small percentage annually, the ability of the planet to produce enough resources for the population decreases. At some point, the population will become unsustainable—we won't be able to produce enough food for everyone. Population growth will stop as people starve. This is inevitable even if we are able to use technology to improve food production. Increasing the food supply will only postpone that day; we cannot prevent it.

Ideally we would want to limit our use of finite resources to a consistently sustainable level, so we don't reach that tipping point. Unfortunately, unlike the hidden incentives in the academic exercise known as the prisoner's dilemma, the tragedy of the real-life commons is that individuals have every incentive to exploit the system and harm their neighbors in the process.

Hardin pictures a scenario where ranchers graze their cattle on public lands. As long as the pasture produces more grass every year than the cattle eat, the system is sustainable. With sustainable grazing lands, it makes sense for each rancher to increase the size of their herd. More cattle means more income. But at some point, the grass eaten by the cattle reaches the full capacity of the land. "At this point," says Hardin, "the inherent logic of the commons remorselessly generates tragedy."

The tragedy is that even one rancher adding one animal creates a state of overgrazing, where the land cannot regrow enough grass to replace what was consumed during the year. In this state, eventually all the grass will be consumed and the pasture cannot feed the cattle.

However, while the pasture is in an overgrazed state, a selfish rancher can benefit by increasing his herd size. The rancher gains all the income from the sale of the extra animals, but the cost of reduced grass supply is shared by all.

A governing agency can attempt to prevent this by setting grazing limits and imposing fees or fines to reduce the benefits of gaming the system, but a rancher can still find ways to benefit individually from the commons while forcing their unwitting neighbors to share the costs. Nevada rancher Cliven Bundy defaulted on more than a million dollars of grazing fees over the course of two decades, leading to a standoff between armed militamen and federal officals, and later a takeover of an Oregon wildlife refuge by Bundy supporters.

Hardin offers pollution as a second example of individuals exploiting a common resource, to the detriment of all. When the cost to a manufacturer of dumping waste into the water—or pumping toxins into the air—is less than the cost of cleaning up, profit-conscious businesses have no incentive not to pollute.

Researchers soon found real-life examples of the scenarios Hardin described.

The Grand Banks region off the coast of Newfoundland has long been one of the world's best places to fish for cod. But technological advances were already rippling through the fishing industry when Hardin wrote his essay, and before the next decade was over, the Grand Banks cod supply had collapsed. By 1992 the cod supply was so low that the Canadian Minister of Fisheries and Oceans declared a moratorium on cod fishing in the region. It would be more than a decade before researchers saw the first signs of recovery of cod stock, and even now—a quarter of a century into the moratorium—cod have not recovered to historical levels.

Researchers have also found real-life examples of water pollution leading to tragedy, once more with serious consequences for the fishing industry. Chemicals from farmlands and suburban backyards are washed into rivers, and from there to the Gulf of Mexico. These chemicals, designed to spur plant growth, are consumed by blue-green algae in the Gulf. As the algae remove oxygen from the water, they create an inhospitable environment for fish and other sea life. As of 2018, the Gulf of Mexico dead zone continues to grow.

The tragedy of the commons is the inverse of the prisoner's dilemma. Rather than a scenario where cooperation benefits everyone, this is a situation where cheaters prosper for a time, to the ultimate detriment of all.

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