Population Density and the Environment

Somehow I have started reading too much of The Atlantic Cities, and books like Green Metropolis, or Triumph of the City. I have been quite convinced that higher population density is the easiest way to make cities more green.

This chart of average yearly electricity usage in kilowatt hours is pretty impressive:

So I am glad there is a building boom of towers going on at the moment. Still, I don't see a good way to fight the NIMBY's who block the construction of these buildings and make them useless by forcing cities to have lower population density. If cities like New York City and San Francisco were to pull out the stops and go on a building spree, they could easily suck a few million people from states like Texas which is about the best thing anyone could do for the environment.