We must begin with the African elephant. This animal is very big. It is the largest land mammal on Earth; in fact, it’s a bogglingly massive and dense megalopolis of cells. The number of cells that make up this giant creature far surpasses the number of stars in this galaxy—around 400 billion. There is, however, an unexpected consequence to this enormous size, a consequence that breaks with the logic of intuition: A single cell in an elephant uses energy more efficiently than, say, a mouse. The reason for this is that the larger an animal is, the slower its rate of metabolic processing.
A leading thinker of this scientific idea, known as “metabolic scaling theory,” is the British-born physicist Geoffrey West. Around the beginning of the last decade, West, who had studied scaling and elephants, turned his attention to cities. Were there any comparable laws governing the properties of cities? The answer turned out to be Yes.
The larger a city is, the more efficiently it uses resources and energy.
West and his colleagues, according to The Economist, “found that cities scale much like organisms. Just as an elephant is, roughly speaking, a larger but more energy-efficient version of a gorilla, big cities are thrifty versions of small ones.” The reason for this is a metropolis uses shorter electric cables, has fewer gas stations and road surfaces, and so on. The result? When a city doubles in size, each individual’s burden on the infrastructure falls by about 15 percent.
Although West was comparing volume to surface area, the fact is that density still plays an obvious role in improving a city’s energy efficiency. The reason is, simple: more people are sharing the same infrastructure, i.e. the same stuff. This is clearly the case with transportation. Public transportation is practically useless in rural areas or the suburbs because the area covered is larger and the population sparser than in a city’s core. The benefits of public transportation are only meaningful when lots of people share a bus or train over a very small area. It is for this and other reasons that, as David Owen explained in Green Metropolis: Why Living Smaller, Living Closer, and Driving Less Are the Keys to Sustainability, the inhabitants of Manhattan have on average the smallest carbon footprint in the US. He writes: “The average New Yorker…annually generates 7.1 metric tons of greenhouse gases, a lower rate than that of residents of any other American city, and less than 30 percent of the national average, which is 24.5 metric tons; Manhattanites generate even less.”
Indeed, none of the super green fixtures and materials of Seattle’s new and celebrated Bullitt Center can compare with the simple greenness of its location: Capitol Hill, a dense neighborhood that’s serviced by lots of buses and soon, light rail. You can make a building with nothing but environmentally horrible materials, and it would still be green if located here. And similarly, you can make a home with every green thing you can buy, but it will still be an environmental nightmare if it is located in neighborhoods north, of say, Marysville. Green isn’t found in products but in location, population size, and the sharing of infrastructure. Giving up lawns for parks, cars for buses and trains, and so on—sharing is what really counts most.
Also, this is not just limited to dense Capitol Hill. Take Columbia City: old and planned for trolleys, which is why Link fit so easily. The suburbs of the early 20th century were massively accessed by public modes of transportation; in their DNA we find very little that’s similar to the suburbs that emerged after World War II. As a consequence, Columbia City is more urban than, say, Issaquah. Those who live in neighborhoods within the city’s limits utilize an older and established infrastructure and, as importantly, don’t need a car to survive.
New developments in the suburbs often require new services, amenities, waste management facilities and roads. And these additions are often paid for not by private investors but by the public. But the main benefit of living in or very close to the dense core is that walking becomes a practical mode of transportation. Those who live in dense cities tend to be healthier and live longer than those who live in the suburbs. Indeed, it is not a surprise that Hong Kong, one of the densest cities in the world, also has one of the highest life expectancies of anywhere.
As Americans, we have been raised to believe that happiness and prosperity are essentially found in the rural way of life—land, a single-family home, and distance from others. But this way of life is likely at odds with who we actually are: a highly social animal that has evolved to be a supreme walker. These defining attributes are certainly more at home in the dense city than in the sparser, car-dependent areas outside of it.