Urban sprawl

Urban sprawl, also called suburban sprawl or urban encroachment, describes the rapid expansion of cities and towns. It is a specific form of urbanization that changes how land and people are organized.

Sprawl is often defined by low-density residential housing and single-use zoning. This means different parts of a city are kept strictly separate. For example, one area might only have houses, while another only has shops. This separation forces an increased reliance on private automobiles for transportation. Because these areas are spread out, walking or bicycling becomes impractical for most people.

The mechanism of sprawl relies on how land is used and how people move. In a sprawling system, residential, commercial, and industrial zones do not mix. This creates a pattern where people live far from where they work or shop.

One specific type of growth is called leapfrog development. This occurs when new developments are built in patches, leaving vacant land in between. This creates a discontinuous landscape rather than a solid, connected urban area. Another pattern is strip development, where buildings follow major roads in long lines. These patterns often lead to inefficient resource utilization and higher transport costs.

Researchers identify several distinct characteristics to define this phenomenon. One key indicator is residential density, which measures how many housing units exist per acre. Another is decentralization, which is the spread of a population without a clear center. Some experts, like Reid Ewing, suggest using "accessibility" and the "lack of functional open space" as better indicators. He argues that using specific indicators is more flexible than just looking at negative characteristics. This helps distinguish between simple suburbanization and true, unplanned sprawl.

The history of this term is tied to debates about land use. The term was frequently used in letters between Lewis Mumford and Frederic J. Osborn between 1938 and 1970. They used the term to condemn the waste of agricultural land and natural landscapes. In 1955, the term appeared in The Times to criticize the outskirts of London. Today, the term is highly politicized and usually carries a negative connotation. It is often used as a rallying cry by those wanting to manage urban growth more effectively.

Significant data illustrates the scale of land development in the United States. According to the National Resources Inventory, about 100,000 square kilometers of land was classified as developed between 1982 and 2017. This is an area roughly the size of Kentucky.

While the 2000 Census showed that only 2.6 percent of U.S. land is urban, the footprint of development is much larger. In 2002, 37 large urbanized areas supported about 40% of the American population. Even in Europe, cities like Amsterdam, Brussels, and Munich saw population losses in urban centers alongside the expansion of sprawl between 1970 and 1990.

There are many surprising examples of how sprawl manifests in different ways. Los Angeles is a major example because it is both sprawling and very dense.

Unlike New York or Chicago, which have dense cores and very thin edges, Los Angeles has a more uniform density across its large area. This makes it the densest major built-up urban area in the U.S. despite its car culture. In contrast, China shows a phenomenon called "high-density sprawl."

In these areas, massive residential superblocks are surrounded by giant roads, making them unfriendly to pedestrians.

Urban sprawl connects to complex economic and social systems. One major issue is job sprawl, where employment moves from the central business district to the suburbs.

This can lead to a "spatial mismatch." This occurs when low-income or minority citizens cannot easily reach new jobs because they lack transportation. Economic studies show this trend is growing; for instance, in 2006, 45.1% of jobs in large U.S. metropolitan areas were located in the outer ring, 10 to 35 miles from the center. This movement of jobs and people continues to shape the environmental and social landscape of modern nations.