Urban Sprawl: Definition, Causes, and Solutions

Urban sprawl refers to a pattern of low-density, often poorly-planned development stretching away from an urban center. This trend of outward growth became prevalent in the United States after World War II when people started leaving densely-populated cities for new, peripheral suburbs. The rise of the suburbs led to fragmented communities connected by roads and dependent on cars. This trend, also known as suburban sprawl, generally comes with adverse environmental and social impacts, including traffic congestion, air pollution, loss of forest and agricultural lands, and communities that are more segregated by race and class. 

Characteristics

Migration from cities to expanding peripheral developments called suburbs came about in part due to federal legislation and policies in housing, transportation and banking from the 1930s through the 1950s—first aimed at alleviating economic impacts of the Great Depression, and later to accommodate GIs returning from World War II whose growing families needed affordable homes. Mass production also helped make housing affordable for millions.

During the postwar economic boom, American suburbs grew exponentially around cities like Los Angeles, Chicago, Houston, Phoenix, and many others. Massive federal highway projects also facilitated this outward expansion. Together these policies transformed cities and created suburban communities with distinct features.

Low-Density, Single-Family Homes

In the post-WWII era, developers marketed cookie-cutter, single-family homes with a garage, driveway, and grassy yards as the attainment of the American Dream. The new suburbs were an escape from congested city centers to quiet streets and spacious homes outfitted with all the modern amenities.

But huge tracts of low-density single-family homes and scattered, haphazard commercial districts also became hallmarks of sprawl. The houses kept getting bigger: today, an average American home is nearly double the size of those in mid-century suburban neighborhoods.

Dispersed, Single-Use Developments

Historically, developers sought open space further out in the countryside rather than vacant land next to already-developed areas. Known as “leapfrogging,” this gobbled up larger amounts of land and led to disconnected, car-dependent neighborhoods interspersed with fragmented open space. 

It also led to “ribbon” developments: alternating residential areas and business zones extending out from city centers along roads and highways. Strip malls are a classic feature of ribbon developments, with large parking lots and associated congestion and traffic hazards. Both development approaches were strongly influenced by predominant Euclidean zoning policies, which designate developments as solely residential or business rather than mixed use. 

Roads and Congestion

As suburban neighborhoods multiplied, public transportation infrastructure failed to keep up. Instead, transportation in the suburbs centered around road construction to accommodate automobile traffic rather than connecting neighborhoods with bus and rail systems or providing alternative options like cycling lanes and pedestrian paths. 

Thanks to zoning and transportation priorities that emphasized roads and single-use developments, residents increasingly relied on cars to get to work and obtain basic goods and services.

Segregation

Not everyone had an equal shot at the American suburban dream. Exclusionary zoning and housing and banking discrimination led to suburban communities that were whiter and wealthier, while people of color were often stuck in urban centers. As tax revenue flowed to outlying suburbs, disinvestment in urban neighborhoods led to neglect and "blight."

Highway construction, which significantly reshaped cities and supported suburban growth, also contributed to deterioration of many urban communities and increased segregation—often intentionally.

Impacts

From pollution to safety hazards, the consequences of urban sprawl development only grew with time.

Increased Pollution

Increased use and dependence on cars causes more air pollution and fossil fuel emissions. In addition, inefficient energy consumption in ever-larger single-family homes means more demand on electricity and gas systems, and more burning of fossil fuels. 

More impervious surfaces (paved roads, parking lots, and sidewalks that don’t absorb water) also leads to water pollution, as toxic chemicals, oil, and bacteria accumulate in stormwater runoff and eventually flow into natural water bodies. Studies suggest that suburban development is associated with high levels of harmful contaminants. 

Loss of Open Space

As land is paved over with housing, roads, and shopping centers, critical wildlife habitat is destroyed. This disruption and fragmentation of habitat through land use change can lead to a decrease in biodiversity, and more negative, even dangerous, encounters between humans and wildlife.

In addition, loss of open space contributes to declining air and water quality by degrading or eliminating ecosystem services like flooding and pollution mitigation. As extreme weather events intensify with climate change, these natural services will become increasingly important for community resilience in the face of flooding, wildfires, sea level rise, and heat.  

Other Health and Safety Impacts

In car-dependent communities, the rates of accidents and traffic-related mortalities increase. Traffic safety measures often don’t keep pace with rapid development, thus sprawl is associated with less walking and cycling as people avoid them due to safety concerns, contributing to more sedentary lifestyles. Combined with the increased risks posed by air pollution, this can exacerbate health conditions like respiratory illness, cardiovascular disease, obesity, and diabetes. 

Social Inequities

Jobs and other economic opportunities left urban centers, contributing to poverty and by extension, chronic health conditions. Discriminatory housing policies and racism relegated many Black Americans and other people of color to only narrow slices of cities and suburbs, harming their economic opportunities and their health. 

Highways that connected suburbs with city centers were often intentionally routed through poor neighborhoods, as was the siting of heavy industry along those roads. Highways and industry destroyed formerly vibrant neighborhoods, their residents either displaced or exposed to hazardous waste and harmful pollutants.

Solutions

Even in the 1950s people were aware of adverse impacts of sprawl. Over time, citizens and local governments sought to address those concerns, and eventually a movement emerged in response to unbridled sprawl.

Smart Growth

In the 1970s, Portland, Oregon became one of the first cities to apply smart growth strategies. Over time, the city concentrated population growth in the urban center rather than expanding suburbs. Today, it reflects many smart growth principles: diverse housing options, plentiful green space, mixed-use developments, preservation of ecologically important areas, and multiple transportation options including both public transit and accessible walking and biking infrastructure. 

Smart growth also encourages and facilitates community involvement in decision making and collaboration among stakeholders to ensure that plans consider everyone’s needs, regardless of wealth or influence. It is often used interchangeably with the terms sustainable development and new urbanism. Although not identical, these approaches all seek more equitable and environmentally sustainable development. 

Today, cities around the world are adopting these principles to combat pollution and climate change, conserve open space, energy and other natural resources, and generally improve the well-being of citizens. 

Ditch the Car

Many of the fundamental changes revolve around transportation—specifically, investing in “multi-modal” transportation systems that offer convenient, affordable alternatives to driving while limiting car traffic. Terms like 15-minute city, walkable city, and sustainable city reflect strategies to make cities greener, less polluting, and less carbon-intensive while ensuring that residents’ basic needs can be met within a short walk of home. 

There’s evidence to suggest that such investments, if implemented equitably, could also address sprawl. Shifting investment from roads to multi-modal transport systems, for example, is a means of limiting sprawl and increasing equity and health.

Diversify Housing, Avoid Gentrification

A recent report from the National Association of Homebuilders shows that, post-pandemic, a new wave of suburban migration is underway. Can the latest suburban boom avoid unsustainable development patterns of the past? One remedy to sprawl and housing shortages involves diversification of housing stock. 

For years there’s been a trend toward increasing housing density, but the 2020 pandemic revealed drawbacks to ultra-dense apartment blocks. An alternative concept known as distributed density challenges single-use zoning laws and allows construction of multi-family homes or low-rise residential buildings, which take up less space and consume less energy than single-family homes. It can also mean locating denser housing along public transportation corridors for increased access while preserving public green space.

A caveat: Sustainability measures, both in city centers and suburbs, carry the risk of green gentrification. As property values increase according to housing scarcity and improved neighborhood amenities like parks and transportation access, the availability of affordable housing can end up decreasing. Portland, for example, has worked to accommodate population growth without sprawl by focusing on density. But as housing costs rose, so did displacement of low-income residents.

In California, some cities are looking to undo decades-old zoning laws that restrict residential lots to one single-family home in order to generate more housing stock, combat skyrocketing housing costs, and address housing discrimination. To be truly sustainable, social justice must be addressed alongside environmental objectives. 

In 1950, when suburbs were ascendant, about 30% of people lived in and around urban areas. By 2050, more than two-thirds will, according to the United Nations. How cities and their suburbs are organized will have important impacts on climate change, social equity, health, and the economy. True remedies for chaotic, poorly-planned development patterns respond to all of these and consider everyone affected by sprawl—whether they live in the ‘burbs or not.