Here is Bruce Yandle  talking about the tragedy of the commons and the evolution of regulation of the environment. Particularly interesting is the role that common law played in preventing environmental damage. Most people seem to think that before 1970 you could dump garbage into the air and water. Not so. as Bruce points out, judicial decisions at the state level played a crucial role in improving the environment before the federal regulation of the 1970s. This is a wonderful introduction to the economics of the environment.