How Green are Cities?

Ed Glaeser writes:

Manhattan, not suburbia, is the real friend of the environment.  Those
alleged nature lovers who live on multiacre estates surrounded by trees
and lawn consume vast amounts of space and energy.  If the environmental
footprint of the average suburban home is a size 15 hiking boot, the
environmental footprint of a New York apartment is a stiletto-heeled
Jimmy Choo.  Eight million New Yorkers use only 301 square miles, which
comes to less than one-fortieth of an acre a person.  Even supposedly
green Portland, Ore., is using up more than six times as much land a
person than New York.

New York’s biggest environmental
contribution lies in the fact that less than one-third of New Yorkers
drive to work.  Nationwide, more than seven out of eight commuters drive.

I get the point but I don’t quite buy this.  Manhattan sells services, most notably finance and entertainment, to the rest of America, and in turns draws upon industrial outputs, which of course include steel and glass.  It is also no accident that Gary, Indiana is near Chicago and those rather aesthetically thrilling factories off the New Jersey Turnpike are right outside New York City.  Try the other boroughs as well, they don’t call Staten Island a big garbage dump for nothing.  Praising Manhattan is a bit like looking only at the roof of a car and concluding it doesn’t burn much gas.  Manhattan supports its density only by being surrounded by a broader load of crud.

Perhaps a better question concerns the margin.  If we tax Peoria and subsidize Manhattan an extra bit, and induce some migration, does the total environment footprint of mankind go up or down?  For instance building up rather than out saves space but it also costs more construction energy and attracts more commuters and leads to more surrounding crud. 

If you think the big problem is humans grabbing more and more space, you might prefer to tax suburbs and subsidize cities.  If you think the big problem is humans using more and more energy, the opposite conclusion might follow.  Suburbs are bad for burning gas, but they are an especially efficient place to work, buy things, and raise children. 

A subsidy to 5th Avenue is also a subsidy to Port Newark.  Think of Manhattan as a place which outsources its pollution, simply because land there is so valuable.