Some time ago someone asked me if it is better for the environment to live in a city, or out in the country. I didn’t have an answer at the time, but I do now…
In the August 2007 issue of SEED Magazine Jonah Lehrer writes about the metabolism of cities and their similarity to living organisms. And, if you think about it, it’s true. Resources enter the city, are consumed, and waste flows out, much like any living organism whether it’s a single-cell or a Blue Whale. The article, entitled “The Living City,” talks about Max Klieber who, in the 1930′s, discovered that the metabolism (energy used per unit of mass) of virtually all animals is related to their mass. In fact, he was able to define this relationship as the mass of the animal to the 3/4 power (or “the metabolic rate increases on a scale three-quarters that of mass”). So, due to massive economies of scale, a large whale uses less energy per kg of mass than a mouse.
Lehrer goes on to talk about the work of Geoffrey West, Luis Bettencourt (physicists from Los Alamos National Labs), Jim Brown, and Brian Enquist (ecologists from the University of New Mexico) to apply the same ideas to the metabolism of cities. By analyzing resource consumption data for cities they were able to determine that the same relationship exists for cities. As the population of a city increases, its resource use increases by a power of 0.8. So, if a city doubles its population size it does not double its resource use as well.
Lehrer explains that city inhabitants use have as much electricity as those living outside the city. Also, city dwellers tend to live in smaller apartments. Smaller apartments require less energy to illuminate and they may only have one exterior wall to lose heat to. City inhabitants often have access to public transit and car-sharing programs and are less likely to own a car. And city inhabitants probably walk more as well.
So it appears that we need more massive cities to combat our even more massive energy appetite. But big cities are rarely, if ever, self sufficient and have a footprint that is much more massive than their direct land area. Populations require almost 1 acre of farm land per person (exact estimates vary and are dependent on meat/dairy consumption) to grow/raise food. As cities get larger and larger their requirements for farm land grow too. This means that food will need to be supplied from farther and farther away. While city residents that participate in 100-mile diet initiatives are doing a great thing for the environment (or less bad), it is probably not feasible for everyone in a given city to “eat local.”
Despite this issue, the benefits of city living are clear. Economies of scale make living at higher densities much more economical from an ecological perspective. If our economic system properly understood the true costs of everything, and internalized those costs, it might actually be reflected in lower living costs in the city.
Pablo P√§ster, MBA