Here's a hypothetical discussion I'd like you consider, not because it could ever happen but because I think it makes an interesting thought experiment.
Imagine we're sharing a cup of coffee with Edward Glaeser and we make them the following proposal: let's take a large metropolitan area in the South or West and just zone the hell out of that puppy, set aside huge swathes of land right through the middle of the city, allow no development whatsoever, not even any roads except for a couple of elevated highways.
I predict that Glaeser would object strenuously to the suggestion. He would probably start things off by waxing eloquently on the evils of zoning, then decry the inefficiency of wasting land that could potentially house millions of city dwellers.
Suitable chastised we drop that idea and change the subject, asking him what cities in the South or West we should look to as models. I'll make a second prediction: he would cite either Seattle or San Francisco (and possibly both), praising them for their density, walkability and lack of sprawl.
The trouble is that all of these appealing aspects are pretty much a direct result of large swathes of undeveloped land that cover large parts of these area, swathes that can be driven across only by way of a handful of elevated highways.
Of course, it's awfully easy to be unfair to someone when you're writing his dialogue for him. It's quite possible that I've misrepresented Glaeser's positions on one or both of my predictions. Still, when I read Glaeser, I can't shake the impression that he's not just suggesting policy changes that can make things better; he's talking about a utopian product of libertarian ideals.Because of this I get the feeling that a city building around a body of water is fundamentally different than a city building around a piece of zoned land, even if the end result is the same. (Is it even possible for the end result to be the same? That's a topic for another post)
None of this makes Glaeser's analyses bad or diminishes any of his many good ideas, but when it comes to setting policy, utopianists always make me nervous.