New York has a smaller carbon footprint than LA. Now I can't prove that but I betcha it is true. True not only overall but per capita. Why? The subway system. And the hybrid bus system. And the commuter train system.
Being a daft American, I hadn't really made the connection between sustainability and cities until I went to three of the dozen or so sessions on urbanism at the World Economic Forum in January. There was a string of sessions on sustainability and another string of sessions on the Urban Age. Yes, I know that architects, from Corbu to Koolhaas, have been writing about the wonder of making cities dense (or verticle--skyscrapers take up verticle, not horizontal, space) to make lots of room for parks and wilderness (OK, architects are not much into wilderness and prefer parks but it's the same idea).
But sustainability--living, growing, creating culture with fewer resources--is a different kind of connection to make. If you build the right kind of cities, you can cut down on energy and commodity usage tremendously. And you can shape the environments for greater innovation and creativity. And you can restore the rest of the land to natural places where we can rest, play and connect to something bigger than ourselves.