"Further, in 1972, the California Supreme Court handed the state’s environmental movement a stunning victory in Friends of Mammoth v. Board of Supervisors of Mono County, requiring large numbers of private developments to undergo environmental impact reviews. The reviews are fundamentally one-sided: they consider only the impact on the local environment if the development occurs, not the impact on the national or global environment if the development fails to occur. In principle, all environmental reviews in the Golden State should consider the fact that if building doesn’t occur in coastal California, then it is likely to occur someplace with considerably higher carbon emissions."

- From a great E.L. Glaeser column in City Journal from Winter 2009

This is a great point about urban density. People who choose to live in cities choose not to live in other areas. And absent a few log cabins with wood stoves, that will mean large houses supplied by large amounts of heating fuel and electricity, and reachable by automobiles. If we’re interested in creating greener, more sustainable societies, we need to acknowledge that - counterintuitively - bigger, taller, more imposing cities will be a huge asset.