Sustainable cities

In the last chapter we looked at two conditions for successful cities: smart growth and neighbourhood renewal. In this final chapter we explore three final conditions: environmental sustainability; mixing existing communities; and changing ways of running cities. These five conditions redirect our energies away from grand, sweeping plans to something more finely tuned, more careful, more respectful of what is already there and what the wider environment can support.

Human greed has put us on nature's warning system and sheer stupidity threatens our survival. London's flood risks are greatly increased by allowing millions of suburban homeowners to concrete over their front gardens to park their cars in. This trivial negligence then channels rainfall, not into the ground as in the past to water trees and grass, over a vast catchment and then into the Thames, but into the drains that lead into the London sewer system. The flow is so fast at times of heavy rain, including August 2004 and 2005, that, partly as a result of the destruction of humble front lawns and flowerbeds, the sewer system overflows into the river. The very drainage we so ingeniously built a century and a half ago to remove sewage from the Thames is the victim of its own success. If London's river has again become a relief sewer under pressure, what of less prosperous cities?

Yet Rees argues there is great potential for cities to contribute to global sustainability. Compared to more dispersed forms of human organisation, cities are relatively compact and adaptable; they could offer efficiency gains by grouping together so many people in one place. Cities are also by-products of nature, built by human creatures, using many natural if processed resources, home to large living as well as inanimate agglomerations. Developed societies use far more than their global share of finite environmental resources but cities per se emit less carbon per head of population than the average for the whole population, partly because cities depend on a wide hinterland for food, materials, energy and waste disposal.