As of last year, more than half the world’s population was living in cities. By the end of this decade, it’s estimated that three out of five people will live not only in cities, but in megacities.

Cities are often hailed as saviours for many of the world’s environmental woes. These green metropolises, with their compact buildings in close proximity to infrastructure and public transportation, increase efficiencies and reduce energy use. Cities, which are responsible for higher per-capita economic and social activity, consume fewer resources per capita. We are told that density equals efficiency, and efficiency equals sustainability.

The idea that cities are inherently sustainable is being promoted by a group calling themselves the “eco-modernists.” This influential group of scholars recently issued an “Ecomodernist Manifesto,” an approach to sustainability that recommends “decoupling” humanity from nature and “intensifying many human activities — particularly farming, energy extraction, forestry and settlement — so that they use less land and interfere less with the natural world.” Economic development, they suggest, is an indispensable precondition to preserving the environment.

Economic development, however, is not without its environmental consequences. The average New Yorker, for example, consumes almost 25 times more energy than someone in Kolkata, India (population 4.6 million). This is to be expected, but it also demonstrates the wealth paradox: as economic activity of a city increases, resource-efficient infrastructure is created — but people begin to consume more stuff, discard more waste, and use more energy (and often at a pace that is quicker than the population growth). This ultimately has negative environmental consequences.

A paper recently published in Proceedings of the National Academy of Sciences lead by Chris Kennedy, a professor of civil engineering at the University of Toronto, sheds further light on the assumption that megacities are inherently sustainable. The researchers looked at 27 of the world’s largest cities and analyzed their “urban metabolism” — the flow of energy and materials through the city. They found that while these “megacities” (cities of 10 million people or more) account for almost 7 per cent of the world’s population, they also consume 9 per cent of its electricity, 10 per cent of its gasoline, and produce almost 13 per cent of global waste. So what happened to the efficiency that we are told is an inherent result of density?

It turns out that while density does equal efficiency, “megacity” does not necessarily equal density. Megacities do encompass those places that we typically associate with dense and culturally vibrant urban centres: New York City, Tokyo, London. But what’s not often taken into account is the fact that to keep them running, these cities also require surrounding areas such as industrial lands, ports, suburbs. In other words, the environmental benefits of a city’s dense urban core can be outweighed by the resource-inefficient, yet essential, areas on its periphery. They are, in fact, two sides of the same coin.

An area of focus that Kennedy’s research didn’t explore, but which potentially has an impact on resource use, is the psychological impact that increased urbanization has on sustainability. As people retreat from rural areas into cities, their interaction with nature also decreases. This is particularly true for the developing world. National Geographic’s annual Greendex Survey which measures nations’ consumption habits and attitudes, shows that people who are more connected with the environment demonstrate more sustainable behaviour; the more urbanized, the more unsustainable the behaviour. As author George Monbiot points out, this leads to a vicious circle: the richer we are, the more we consume, the more harm we do to the environment, the less we empathize with the natural world, the more we try to fill the void by buying more stuff.

What this research shows is just how complex urban sustainability issues really are. Rather than simply praising the benefits of increased urbanization, then, perhaps we need to start thinking about what it all really means.
____

Note: This article appears in the Summer 2015 issue of Sustainable Building & Design magazine.

Photo credit: Pablo Lopez Luz