Tragedy of the Commons and Common-sense Morality

I just listened to Joshua Greene talk about on Moral Tribes on EconTalk.

He starts off by describing the tragedy of the commons, discussed by Hardin in this very readable article. Wikipdia describes it as:

The Tragedy of the commons is an economic theory by Garrett Hardin, which states that individuals acting independently and rationally according to each's self-interest, behave contrary to the best interests of the whole group, by depleting some common resource.

In Hardin's parable, a bunch of herdsmen graze their cattle on a commonly owned meadow. Each herder has a "selfish" incentive to increase the size of his herd, and thereby increase his output. However, if they all simultaneously increase their herds, then the meadow gets over-grazed, and they will all be worse off in the long run.

Greene tacks on an interesting sequel to Hardin's parable.

So, imagine that there's this large forest. And all around this large forest are many different tribes. And these different tribes are all cooperative, but they are cooperative on different terms. 

So, on the one side you might have your communist herders who say, Not only are we going to have a common pasture; we're just going to have a common herd, and that's how everything gets aligned. Everything is about us. 

And on the other side of the forest you might have the individualist herders who say, Not only are we not going to have common herds; we are not going to have a common pasture. We are going to privatize the pasture, divide it up; and everybody's responsible for their own piece of land. And our cooperation will consist in everybody's respecting each other's property rights. As opposed to sharing a common pasture. And you can imagine any number of arrangements in between. 

He continues,

One hot, dry summer, lightning strikes and there's a forest fire and the forest burns to the ground. And then the rains come and suddenly there is this lovely green pasture in the middle. And all the tribes look at that pasture and say, 'Hmmm, nice pasture.' And they all move in. So now we have in this common space all of these different tribes that are cooperative in different ways, cooperative on different terms, with different leaders, with different ideals, with different histories, all trying to exist in the same space. And this is the modern tragedy. This is the modern moral problem.