There’s an interesting post at the NYT’s economics blog about the environmental cost of living in a city:
In almost every metropolitan area, we found the central city residents emitted less carbon than the suburban counterparts.
cars represent … one-third of the gap in carbon emissions between New Yorkers and their suburbanites. The gap in electricity usage [is] about two tons. The gap in emissions from home heating is almost three tons [of a seven ton total].
The decreased carbon cost of transport and heating in cities is predictable, but there are still questions remaining here.
I’d like to know more about the carbon costs of construction in cities but that’s likely to be a small part of the lifetime carbon cost of a building. I’d also like to know about the cost of having concentrated emissions: in a city the emissions per capita may be lower, but the emissions per hectare are far higher. If the effects of pollutants are non-linear then the environmental cost of cities may still be higher.
Finally, as the BBC points out, the comparison depends on where you live. Moving from suburban Chicago to the Bay area may decrease your personal carbon emissions, but moving from rural Sichuan to Beijing probably doesn’t. Urbanisation is correlated with industrialisation and industrialisation massively increases our environmental impact.
I don’t mean to suggest that we should deny poor nations the opportunity to industrialise: I only mean to point out that this result isn’t, by itself, a sufficient reason to promote further urbanisation across the globe (although it may be a necessary condition of such promotion).
Update: Ed Glaeser’s article has some of the numbers.