The metabolic efficiency of animals is directly proportional to body mass. Cities are the same.
Yahoo may have named Hastings, NE the greenest city in America, but a new study proves them wrong;. bucolic little towns like Hastings or Bedford Falls or Grover's Corners are less green that good old New York City. It appears that cities are like mammals, conforming to the phenomenon of "biological scaling"- the larger the organism, the more efficiently it uses energy. The elephant is far more efficient than the mouse.
Analyzing various data including electrical use, gas consumption, and lengths of roads, Geoffrey West and his team at the Santa Fe Institute found that "regardless of size and location, cities conform to certain universal dynamics—just like biological organisms."
Lance Hosey of William McDonough + Partners writes in Architect Magazine:
In terms of per capita consumption, New York is much greener than Hastings. Although the Big Apple didn't make Yahoo!'s list, it is in fact more energy efficient per person than any other American city—and even many states. The reason is density; more people per square foot equals lower average waste. Carbon emissions in NYC are less than a third of the national average, and typical electricity use is 75 percent lower than in Dallas. Because walking and public transit are popular, gasoline consumption approximates U.S. levels from the 1920s. When it comes to saving the planet, it doesn't take a village—it takes a metropolis.