We have all been arguing it for years; David Owen in the Green Metropolis claiming that the denser the city, the lower the per capita energy use. Ed Glaeser declaring the Triumph of the City. Myself, arguing for a "Goldilocks Density." It was the accepted wisdom: the way to achieve sustainability is to stop sprawl and to pack people in tighter.
Maybe not. Nate Berg at Atlantic Cities points to a new study titled Growing Cities Sustainably that studied British cities with different development patterns, compact, dispersal and expansion, and found that in fact, it doesn't make much difference at all. Nate quotes one of the authors:
To our surprise, if you compare the compact form versus the current trend, the difference in reduced transport by automobile is very minor. And if you allow the city to expand, the increase in the use of the car is only marginal," says Marcial Echenique, a professor at the University of Cambridge Department of Architecture and one of the authors of the report. "If you make the city more compact, it doesn't mean that people will abandon their car. Only 5 percent of people abandon the use of the car. Ninety-five percent carries on using the car, which means there are more cars on the same streets, therefore there is much more congestion and therefore there is much more pollution and no great increase in the reduction of energy.
Just as Brian noted that in America, the exurbs are growing fastest, even in the compact Europe that we all admire (We'll always have Paris), cities everywhere "are converging to the same model in which the process of peripheral growth is diluting the importance of the center." All over Europe, "People and jobs are moving out and taking advantage of the emerging mobility to search for space at lower prices."
The study concludes:
The current planning policy strategies for land use and transport have virtually no impact on the major long-term increases in resource and energy consumption. They generally tend to increase costs and reduce economic competitiveness. The relatively small differences between options are overwhelmed by the impacts of socioeconomic change and population growth.
Smart growth principles should not unquestioningly promote increasing levels of compaction on the basis of reducing energy consumption without also considering its potential negative consequences. In many cases, the potential socioeconomic consequences of less housing choice, crowding, and congestion may outweigh its very modest CO2 reduction benefits.
The study basically concludes that we can't fight the car, so we might as well concentrate on technology, more efficient cars, more ground source heat pumps. Basically, urban design, density and walkability don't matter. Nate Berg says "this work will likely be somewhat frustrating for urban boosters arguing for an increased emphasis on density and city living"; that is a serious understatement.