Or so says Edward L. Glaeser, and then only if you live in them. Higher density residential districts have a much smaller carbon footprint, and not just because of the reduced driving. Electricity consumption and emissions from home heating are also significantly lower for urbanites than for exurbanites. In the type of puckishly contrarian statement economists like to make these days about everything but the actual economy, Glaeser writes, “Living surrounded by concrete is actually pretty green. Living surrounded by trees is not.”
Maybe so, but there are two caveats. First, Glaeser and his colleague Matthew Kahn, an environmental economist at UCLA, bracketed out “the far thornier issues related to commercial or industrial energy use.” I know people who produce two tons of unread PowerPoint printouts every year. Add to that all the discarded water bottles and empty bags of ranch-flavored Doritos and you’ve got the makings of a major ecological disaster.
Second, there has to be a point at which a residential building gets so tall that it reverses whatever positive environmental impact it may otherwise have. I would guess that one kilometer is about the height in which a skyscraper loses its green benefits.