Urban sprawl (Encyclopedia of Environmental Issues, Revised Edition)
Urban growth and development are usually controlled by two forces. First, municipal government authorities regulate growth through urban planning, zoning, and a variety of land-use ordinances. Second, social and economic forces combine to encourage outward growth of the urban area in one of three consistent patterns, described as concentric circle, sector, and multinuclear patterns. Urban sprawl, which is neither controlled nor regulated, often involves some break in this historic pattern. The unplanned nature of urban sprawl often results in a mix of incompatible land uses placed adjacent to one another on the same developed physical area.
The challenges presented by urbanization and urban sprawl are likely to intensify during the decades to come. In mid-2009 the world population officially became more urbanized than rural—of the earth’s 6.83 billion people, 50.1 percent were found to be living in urban areas; 75 percent of the inhabitants of the more developed regions lived in urban areas, while such areas accounted for only 45 percent of the people living in less developed regions. According to United Nations projections for the year 2050, the world’s population growth will continue to be concentrated within urban areas; of that increase, most is expected to be within the cities and towns of developing nations. By 2050 the number of people inhabiting urban areas is expected to be roughly 6.3 billion—the size of the total...
(The entire section is 228 words.)
Problems Caused by Sprawl (Encyclopedia of Environmental Issues, Revised Edition)
Sprawl results in discontinuous leapfrog or checkerboard patterns of development and strip development along transportation corridors, with skipped areas remaining undeveloped. This creates inefficiencies in providing urban services to the sprawl area. Sprawl also results in less-than-maximum utilization of existing developed land in the urban center. Instead of converting existing developed land to new uses, developers establish new developments on less expensive land in suburban areas adjacent to the existing urban area.
Urban sprawl generally increases the total amount of land affected by human activity, the amount of natural areas converted to recreational uses, the amount of wasteland, and the residential, industrial, institutional, and infrastructure uses of land. Wasteland is land disturbed by humans to such an extent that natural uses cannot be restored and future development on the land is restricted. Wastelands include soil borrow pits (areas where soil has been dug out to be taken to other locations), quarries, debris landfills, and construction material storage sites. Urban sprawl generally decreases agricultural uses and timber uses of land and decreases the amount of natural barren or rocky lands, river and stream floodplain areas, and native timber- and grasslands.
Sprawl is encouraged by a variety of social and economic forces. First, it is often a consequence of increasing heterogeneity of...
(The entire section is 369 words.)
Environmental Impacts (Encyclopedia of Environmental Issues, Revised Edition)
The first significant impact of urban sprawl on the environment is the abnormal greening of the physical area. In most cases, total greening is reduced through destruction of forests, grasslands, and floodplains to make way for development. This decreases the number and variety of species able to occupy the space and creates microclimate effects, such as regional warming. However, in some cases total greening is increased through irrigation and the introduction of cultivated lawns, orchards, and other plantings in areas that are naturally arid or barren. This results in the introduction of new species into the environment, increased pollen counts, and a variety of microclimate effects, such as increases in regional humidity. In either case, the presprawl natural ecology is dramatically changed, with resulting negative impacts on plant and animal species displaced by or unable to adapt to the new environment.
In the course of sprawl development, existing natural ecosystems are destroyed while presprawl plants and animals are killed, displaced, or replaced. Most presprawl wildlife retreats in the face of development. However, some species are able to adapt to the sprawl environment and find the mix of land uses, the dispersion of human activities, and the residue of human activity conducive to their survival. Among the wildlife that benefits are scavengers, such as pigeons, rats, raccoons, and opossums; vermin hunters,...
(The entire section is 360 words.)
Impacts on Air and Water Resources (Encyclopedia of Environmental Issues, Revised Edition)
Other consequences of urban sprawl include increases in noise, light pollution, land area devoted to highways and roads, and public-utility impacts as land is cleared for underground water, sewer, and utility pipes and for aboveground utility cables.
The impact of sprawl on air and water resources is both negative and positive. The increase in human population that accompanies sprawl increases the concentration of significant amounts of unnatural substances in the soil, water, and air and also produces abnormally high concentrations of natural substances at levels that may cause undesirable health effects, corrosion, and ecological change. However, studies also indicate that the population dispersal associated with sprawl actually reduces air pollution by dispersing both the mobile and stationary sources of pollutants. Increases in air pollution from automobiles associated with sprawl may be less than the air pollution produced by traffic gridlock, mass-transit buses, and trains in denser urban areas.
Subsurface water supplies and surface watercourses are less affected by sprawl than by denser patterns of development. Denser urban development increases the demands on water resources, runoff and the possibility of flooding, and the likelihood that watercourses will be channeled and hardened by concrete and other construction materials. Denser urban development, and the increase in paved surfaces that...
(The entire section is 220 words.)
Limiting Sprawl (Encyclopedia of Environmental Issues, Revised Edition)
Many municipalities attempt to limit sprawl by refusing to extend essential services such as water lines, sewer lines, and road systems outside their municipal boundaries. Rural areas may attempt to limit sprawl through zoning restrictions on development, farmland protection ordinances, environmental impact regulations, and special development-impact fees levied on new development to recover the public costs associated with constructing roads, schools, and other facilities necessary to provide services to the newly developed areas.
In North America, a movement toward “smart growth” has emerged as a sustainable middle ground between sprawl and zero growth. Smart growth emphasizes high-density neighborhoods and reduced car use. It occurs not on a city’s periphery, but at its heart, where urban land is redeveloped to provide a mix of residential, retail, and office uses. The intent of this clustered development is to enable residents to work and shop near their homes. Reduced travel distances between people’s residences and their workplaces and the sites of their leisure activities enable city dwellers to walk, bike, or use public transportation to reach their destinations.
(The entire section is 177 words.)
Further Reading (Encyclopedia of Environmental Issues, Revised Edition)
Frumkin, Howard, Lawrence D. Frank, and Richard Jackson. Urban Sprawl and Public Health: Designing, Planning, and Building for Healthy Communities. Washington, D.C.: Island Press, 2004.
Gillham, Oliver. The Limitless City: A Primer on the Urban Sprawl Debate. Washington, D.C.: Island Press, 2002.
Miller, Debra A., ed. Urban Sprawl. Detroit: Greenhaven Press, 2008.
Pugh, Cedric, ed. Sustainability, the Environment, and Urbanization. 1996. Reprint. Sterling, Va.: Earthscan, 2002.
Soule, David C., ed. Urban Sprawl: A Comprehensive Reference Guide. Westport, Conn: Greenwood Press, 2006.
Squires, Gregory D., ed. Urban Sprawl: Causes, Consequences, and Policy Responses. Washington, D.C.: Urban Institute Press, 2002.
(The entire section is 94 words.)
Urban Sprawl (Encyclopedia of Public Health)
Land use choices strongly affect public health. More or less direct effects on air and water pollution are well recognized, but other less direct but important impacts have only recently begun to reach public attention. "Urban sprawl" may be defined as development of low-population-density settlements around high-density cities, either by emigration from the core cities or by influx of new residents from elsewhere.
Sprawl results from thousands of personal decisions and from policies and subsidies that are outcomes of the electoral process. Special interests such as the highway and automobile lobbies spend vast sums to exert pressure; developers often state sincerely that they will build whatever the market demands. The fact that sprawl is in part subsidized by government policiesor example, building roads and sewers and supporting low gas prices partly at the expense of non-users, in effect providing greater subsidies for suburban than for low-income core-city housingurther emphasizing that the "choice" of living in sprawl development is not a simple free-market or quality of life option. In addition, in choosing sprawl over core city redevelopment, we are in effect incurring public health burdens.
RELATIVELY DIRECT EFFECTS OF SPRAWL ON PUBLIC HEALTH
Air Pollution. Life in sprawl developments demands up to three times as much driving as in high-density urban areas. Since high levels of the monitored pollutants can trigger loss of federal highway funds, affected metropolitan regions such as Atlanta are changing their development policies. Light rail and other forms of mass transit can reduce auto pollution in suitable situations but, in the absence of special planning, may not decrease sprawl.
Water Pollution. In 1998 the Environmental Protection Administration (EPA) reported that 35 percent of the nation's rivers and 45 percent of its lakes were polluted and not clean enough for swimming or fishing. Although some of the pollutants were from agricultural and industrial sources and landfills, many resulted indirectly from sprawl. For instance, increased bacteria come from overextended and overloaded sewer systems, overflows of "combined sewers," and leaking home septic systems. Road "runoff" of automobile oils and battery metals and road salt also contribute to water pollution and may affect public health.
Other Impacts of Increased Auto Usage. With increased mileage, higher speeds, and fewer sidewalks, pedestrian accidents have increased, especially among children and elderly, comprising some 13 percent of traffic accident fatalities in 1997 and 1998. Remarkably, 59 percent of pedestrian deaths occurred where there was no access to crosswalks, that is, in typical sprawl roadways. A related factor was the higher speeds prevalent in suburban (vs. urban) roads, since speed and fatality are highly correlated. If states were willing to spend highway funds on pedestrian safety, there are many shortterm measures (e.g., "traffic calming," more crosswalks) that could be taken, but at some point, slowing of traffic will encounter public resistance. Another impact in typical sprawl development is the loss of easy access of the elderly to medical care, social services, and shopping once they stop driving; since mass transit is not generally available. This problem is bound to become more severe as the elderly begin to comprise some 20 to 25 percent of our population by 2050.
INDIRECT EFFECTS OF SPRAWL ON PUBLIC HEALTH
A few examples illustrate that there are also some indirect impacts of urban sprawl on public health.
Duplication of Medical Infrastructure. As hospitals expand to meet the needs of the more affluent and growing population, they often cannot afford to maintain medical centers both in a population-depleted or relatively poor inner city and in the suburbs.
Quality of Life and Health. The stress of commuting and congestion decreases time and energy for quality parenting and relaxation. The conversion of open space to roads and developments creates an environment without ready access to parks and nature. Abandonment of traditional neighborhoods results in a loss of sense of community, which in turn may lead to less community-based caring for children, the elderly, the ill, and the disabled. Finally, abandonment of and disinvestment in urban core cities leads to concentration of poverty and both racial and economic resegregation.
There are strong and often compelling social reasons or perceptions why many Americans prefer low-density suburban to urban living, beyond the known or hidden subsidies that promote this population shift. However, to the greatest extent possible, the public health impacts need to be consciously factored into the public costs of sprawl so that provisions are made to minimize these costs to those (especially inner-city residents) who are negatively affected and to offer everyone more balanced choices of places to live and work. The so-called "Smart Growth" movement offers a variety of land use choices that minimize the negative public health impacts discussed here.
Jacobs, J. (1993). The Death and Life of Great American Cities. New York: Vintage Books.
Surface Transportation Policy Project (2000). Mean Streets 2000: Pedestrian, Health, and Federal Transportation Spending. Washington, DC: Author.
U.S. Congress, Office of Technology Assessment (1995). The Technological Reshaping of Metropolitan America (OTAH ETIH 643). Washington, DC: U.S. Government Printing Office.