Urban sprawl, also called sprawl or suburban sprawl, the rapid expansion of the geographic extent of cities and towns, often characterized by low-density residential housing, single-use zoning, and increased reliance on the private automobile for transportation. Urban sprawl is caused in part by the need to accommodate a rising urban population; however, in many metropolitan areas it results from a desire for increased living space and other residential amenities. Urban sprawl has been correlated with increased energy use, pollution, and traffic congestion and a decline in community distinctiveness and cohesiveness. In addition, by increasing the physical and environmental “footprints” of metropolitan areas, the phenomenon leads to the destruction of wildlife habitat and to the fragmentation of remaining natural areas.
Environmental costs
One of the most obvious environmental effects of widespread building construction is the destruction of wildlife habitat. To make way for human dwellings and their associated infrastructure, natural land is plowed under, graded, and paved. Slow-moving streams are often channeled to provide more efficient drainage for housing tracts and commercial areas. Although small areas of wildlife habitat remain, they may be too small to support all the native species that lived there before or may be widely separated from one another. This arrangement often forces wildlife to cross dangerous human-dominated landscapes to find food or mates.
Exurban low-density neighbourhoods consume more energy per capita than their high-density counterparts closer to the city’s core. (An exurb is an affluent residential community located beyond the suburbs in a metropolitan area.) Energy for heating, cooking, cooling, lighting, and transportation is largely produced by burning fossil fuels (such as gasoline, home-heating oil, natural gas, and coal), a process that contributes to air pollution and global warming. To reach their jobs in the city or other employment areas, many suburban workers must commute by automobile. By the early 21st century the average to-work commute time for Americans was 26.9 minutes, and the bulk of this was done by automobile. In addition, trips to grocery stores or other retail establishments in the suburbs must also be done by automobile. Air pollution produced by gasoline-powered automobiles can combine with other pollutants from industry to form photochemical smog.