The Tragedy of the Commons (ToC) was coined by Garrett Hardin in his seminal paper of the same name in 1968.

What is the Tragedy of the Commons?

Hardin implores us to imagine a pasture open to all. Call this the commons. Within it, we may come to expect that the herdsmen who share it shall want to keep as many cattle on the commons as possible. As rational beings, Hardin imagines that each herdsman will ask himself, “what is the utility of adding just one more animal to my herd?”. The answer is as follows:

1. The positive utility of adding one more animal to his herd is +1, where this utility is derived from the functional increment of one animal.
2. The negative utility of adding one more animal to his herd is less than -1, where this disutility is derived from the functional detriment caused to the commons by one more overgrazing animal.

This asymmetry defines the ToC. Where the herdsman shall be the sole beneficiary of adding one more animal to his herd, he does not bear the cost of doing so as the commons is shared between all herdsmen in the vicinity. Rationally, then, the rational herdsman should certainly add an animal to his herd!

The ToC, more than half a century later, has seen considerable academic attention. This is due to the applicability that the ToC has on almost all ecological crises. Here’s a diagrammatic representation of how the ToC comes into play with ecological crises. I use “pollute” as a placeholder for “to contribute to an ecological crisis”. Let us postulate that to ‘pollute’ is in our personal best interests. For example, it maximizes my own utility to use single-use plastics because of the convenience that it comes with.

	I Do Not Pollute	I Pollute
Others Do Not Pollute	Not good for me, everyone benefits	Good for me, cost borne by community
Others Pollute	Not good for me, others benefit	Good for me, cost borne by community

From this table, we can see that the best way to “hedge” our bets — even if we accept that not destroying the environment is in everyone’s best interests — is to pollute.

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How does this figure into population growth, then?

It is uncontentious that human beings have an urge to reproduce. While we may speculate on the genesis of such urges (e.g., evolution), all we need to know for now is that this urge exists in human beings. Because this urge exists, I shall take the satisfying of such urges to be in one’s personal best interests. Furthermore, we even have reasons to believe that people desire genetically-related children (e.g., see Rulli, 2016; Gangestad & Simpson 2000).

Making children, however, increases the amount of people in the world. Increasing the amount of people in the world, in turn, increases the amount of resources required to sustain the population. This is because existence entails unavoidable ecologically harmful consumption. By the sole fact of existence, for instance, a human being naturally produces methane and carbon dioxide as organic waste matter. In the 21st century, it almost seems unimaginable that a person can exist without having to consume single-use plastics or other non-biodegradable matter that, in turn, exacerbate ecological crises.

Herein arises the ToC as it relates to childbearing — we, as human beings, have a personal investment to bear genetically-related children. The satisfaction of this urge, however, comes at a cost to the greater community (i.e., the world population).