Edward L. Glaeser is an economics professor at Harvard.
In Dr. Seuss’ environmentalist fable, “The Lorax,” the Once-ler, a budding textile magnate, chops down Truffula to knit “Thneeds.”
Over the protests of the environmentally sensitive Lorax, the Once-ler builds a great industrial town that despoils the environment, because he “had to grow bigger.” Eventually, the Once-ler overdoes it, and he chops down the last Truffula tree, destroying the source of his income. Chastened, Dr. Seuss’s industrialist turns green, urging a young listener to take the last Truffula seed and plant a new forest.
Some of the lessons told by this story are correct. From a purely profit-maximizing point of view, the Once-ler is pretty inept, because he kills his golden goose. Any good management consultant would have told him to manage his growth more wisely. One aspect of the story’s environmentalist message, that bad things happen when we overfish a common pool, is also correct.
But the unfortunate aspect of the story is that urbanization comes off terribly. The forests are good; the factories are bad. Not only does the story disparage the remarkable benefits that came from the mass production of clothing in 19th-century textile towns, it sends exactly the wrong message on the environment. Contrary to the story’s implied message, living in cities is green, while living surrounded by forests is brown.
By building taller and taller buildings, the Once-ler was proving himself to be the real environmentalist.
Matthew Kahn, a U.C.L.A. environmental economist, and I looked across America’s metropolitan areas and calculated the carbon emissions associated with a new home in different parts of the country. We estimated expected energy use from driving and public transportation, for a family of fixed size and income. We added in carbon emissions from home electricity and home heating. We didn’t try to take on the far thornier issues related to commercial or industrial energy use.
This exercise wasn’t meant to be some sort of environmental beauty contest, but an estimate of the environmental costs and benefits associated with living in different parts of the country. In a recent City Journal article, I gave a brief (and somewhat polemical) synopsis of the results.
In almost every metropolitan area, we found the central city residents emitted less carbon than the suburban counterparts. In New York and San Francisco, the average urban family emits more than two tons less carbon annually because it drives less. In Nashville, the city-suburb carbon gap due to driving is more than three tons. After all, density is the defining characteristic of cities. All that closeness means that people need to travel shorter distances, and that shows up clearly in the data.
While public transportation certainly uses much less energy, per rider, than driving, large carbon reductions are possible without any switch to buses or rails. Higher-density suburban areas, which are still entirely car-dependent, still involve a lot less travel than the really sprawling places. This fact offers some hope for greens eager to reduce carbon emissions, since it is a lot easier to imagine Americans driving shorter distances than giving up their cars.
But cars represent only one-third of the gap in carbon emissions between New Yorkers and their suburbanites. The gap in electricity usage between New York City and its suburbs is also about two tons. The gap in emissions from home heating is almost three tons. All told, we estimate a seven-ton difference in carbon emissions between the residents of Manhattan’s urban aeries and the good burghers of Westchester County. Living surrounded by concrete is actually pretty green. Living surrounded by trees is not.
The policy prescription that follows from this is that environmentalists should be championing the growth of more and taller skyscrapers. Every new crane in New York City means less low-density development. The environmental ideal should be an apartment in downtown San Francisco, not a ranch in Marin County.
Of course, many environmentalists will still prefer to take their cue from Henry David Thoreau, who advocated living alone in the woods. They would do well to remember that Thoreau, in a sloppy chowder-cooking moment, burned down 300 acres of prime Concord woodland. Few Boston merchants did as much environmental harm, which suggests that if you want to take good care of the environment, stay away from it and live in cities.
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