An urban center is an artificial environment in conflict with the natural environment. The natural surface of the soil is plastered over with concrete or asphalt. Air pollution, continuous light emissions, noise, vibrations, and a warmer and drier climate (thanks to air conditioning and the wind-break effect of build ings) together create a very particular kind of universe. And yet plants and animals (and not just cats and dogs) manage to thrive in this environment, which fosters a special kind of biodiversity. The green areas and patches of waste ground are home to a number of wild creatures: rats and cockroaches, for example, are prolific in urban areas, but so too are foxes and birds of prey. In some parts of Zurich, for example, the density of foxes is ten times greater than in the countryside.
A great many towns and cities have been built in defiance of the natural environment to some extent as if to demonstrate the resourcefulness of humanity. Skyscrapers climb ever higher, land is reclaimed from the sea, and cities spring up in the desert despite the shortage of water. BrasÌlia and Naypyidaw, the capitals of Brazil and Burma respectively, were built from nothing in the midst of savannah, on the one hand, and jungle on the other.
Our towns and cities actually occupy less than 5% of the planet’s continental land masses. Urban expansion eats up the countryside, however, and natural habitats are carved up by road networks. Our food and construction materials and the energy we consume in travel and transport require the use of agricultural lands, mines, etc. A city such as Los Angeles gets its drinking water from the Colorado River, 240 miles (390 kilometers) away. And as a result of world trade, the impact of an urban center extends far beyond its immediate environment.
Paradoxically, the concentration of human beings in a city, though directly responsible for pollution and other negative effects, actually limits our ecological footprint. It reduces the need for transport, while apartment blocks use less energy for heating and lighting. By contrast, a suburban or semi-rural lifestyle leads to the urbanization of further areas of countryside (due to road building and the extension of water and electricity supplies), and is generally accompanied by an increase in travel and transport and higher energy costs.