Most of us have heard the story of the "tragedy of the commons." But have we heard the ecological version, or the ideological one?
The basic yarn posits a pasture used in common by herdsmen for their mutual benefit. But eventually, as people keep introducing more cattle, the pasture is degraded by overgrazing. People can't help trying to maximize their own wealth, even when it becomes clear that their individual actions are destroying the very pasture they all depend on.
Conservatives like to give the story an anti-socialism slant, saying that it proves the futility of collective ownership. Only individuals who own their land will take care of it properly.
This version appears not to be true. If it were, how could so many Middle-Ages collectives have succeeded for so many hundreds of years? There is indirect evidence in the historical record that success was the norm: Records of civil lawsuits contain almost no evidence that people were sued for damaging the commons by overgrazing. It seems likely that local ordinances - and a strong dose of peer pressure - kept greedy herdsmen in line.
Of course, the metaphor of the commons remains of vital ecological importance. I don't think I need to belabor all the ways that the Earth is under threat. Think of the commons not as a small pasture, but as the whole planet itself. And remember what Professor Eric G. Strauss of Boston College likes to point out: Around 1990, humans exceeded the capacity of Earth to support the demands we place on it.