Species and Sprawl: Humans
Homo sapiens is particularly noted for its survival instinct, even when faced with some of the most perilous habitats on Earth. Consider Craig Mayhew, a long-time car commuter on the treacherous and tangled tarmac of the Baltimore-Washington metropolitan area. In 1997, Mayhew’s 56 km one-way commute along a toll road and the eight-lane beltway from Reston, Va., to Greenbelt, Md., usually took him 45 minutes. But as the 75-minute “bad days” grew more frequent, he began to telecommute two days a week, and then three.
In the last five years, Mayhew has had more opportunities than ever to employ his cunning, outwit the competition, and abandon the pack on his two weekly travel days. Around 1999, a new tech hub near Dulles Airport, including new headquarters for America Online and MCI, seemed to mushroom overnight. Development in a new suburb called Ashburn exploded to house the added workers. Loudon County, Va., saw its population hurtle from 57,000 in 1980 to nearly 222,000 in 2003, making it the fastest-growing county in the nation. “My commute grew to nearly two hours,” says Mayhew. He began hunting for alternatives to the highway, ferreting out labyrinths of local roads to avoid highway clogs. “I have become a master at interpreting traffic reports,” he says.
A move to a subdivision in Herndon, Va., 8 km further from work, required wilier tactics. One day, Mayhew abandoned his car for a 20-minute bus ride to a 1½-hour subway ride to a 45-minute local bus ride to a 10-minute walk to his office’s main gate. “Two hours, 45 minutes!” he fumes. “Impossible.” Two trials on his bicycle clocked in at two hours one-way.
“I can guarantee I’ll be out of my job by spring and out of the region by the end of 2005,” says Mayhew. “But does that mean I will contribute to and suffer from sprawl in another region?”
Given the current statistics on sprawl in the United States, it’s not unlikely.
For example, Mayhew could move to Phoenix, which is developing open land at a rate of 1.2 acres an hour. Or he could follow the masses to Atlanta, which, free from natural barriers to meandering development such as mountains or a limited water supply, expects to see its population double in the next 50 years. Odds are, Mayhew wouldn’t head to Cleveland—it’s been declining in population since 1970—but if he did, he could buy plenty of square footage; developed land in the city grew 33 percent during the same period.
Humans are shaping, and shaped by, sprawl—the rapid, poorly planned, low-density growth of homes and businesses far from urban centers. Sprawl is affecting Homo sapiens, just as it does many other species on this planet. It permanently alters our habitat, hampers our mobility, and diminishes our odds for survival. Here’s how:
An Altered Landscape
The desire for a safe habitat with ample food, shelter, protection from predators, and means of escape is instinctual for all living things. For many Americans, this instinct manifests itself as a single-family dwelling outside the city, with a patch of grass, a car in the driveway, and a mega-supermarket a few miles down the road. Yet each U.S. citizen today uses four to five times more land than he or she did in 1940. Construction of homes, pavement, and businesses is incurring a staggering, permanent loss of natural open land—more than 2 million acres of forest, prairie, desert, wetlands, and farmland are developed every year. Ecologically, economically, and aesthetically valuable wild lands such as the Midwest’s virtually vanished tallgrass prairie and Arizona’s diverse, fragile Sonoran Desert are at risk of disappearing or degrading completely.
Take the once pristine Chesapeake Bay, its shores not 80 km from Mayhew’s townhouse. Despite recovery efforts, the estuary remains severely polluted from its rapidly suburbanizing watershed. Sewage-treatment wastewater and fertilizer runoff prompt algal blooms that suffocate fish and blue crabs. Eroded sediment smothers oysters and blocks sun from vegetation. Chemicals from pavement runoff and vehicle and power plant emissions are proving toxic to the bay’s 3,000 species of plants and animals.
Developing on or near wetlands like the Chesapeake Bay is also changing the hydrologic cycle. When soil is topped by pavement or buildings, precipitation can no longer accumulate in wetland reservoirs or percolate gradually to underground aquifers. Instead, it runs off impervious surfaces haphazardly, bringing floods and pollution to both wild and metropolitan areas.
Today, 6.4 million km of public roads link our homes, businesses, and parking lots. In fact, sprawl could not exist without vehicles. In historic communities, businesses, stores, and services were within a walkable distance from residences. But Mayhew, for example, must walk 1.2 km—and back—to get a quart of milk. In 1960, 12.1 percent of Americans took public transportation to work, and 9.9 percent walked. Today, 4.7 percent use public transport, and 2.9 percent walk.
Ironically, the proliferation of roads, compounded with ineffective zoning and rapid, as-needed planning, has actually made it harder for people to get around. We drive farther, more frequently, and for longer periods than we used to. Research confirms Mayhew’s experience; in 1999, Washington, D.C., residents were driving 77 percent more than they were 1982. Nearly all the increase was due to sprawl and not simply population growth.
An Unhealthy Environment
Sprawl is also compromising human health. Motor vehicle exhaust contains carbon monoxide, smog precursors benzene and formaldehyde, and soot and other particles that are toxic to drivers and people living and working in airflow distance from well-trafficked roads. Recent sprawl studies are revealing surprising health connections, like the fact that children living near high-traffic roadways are more likely to be hospitalized for asthma and six times more likely to develop cancer. A recent report also found that increases in ozone levels from car, industry, and power-plant pollution were associated with increases in death rates in populous U.S. cities.
Choosing to drive versus walking or biking is also contributing to the nation’s obesity epidemic. A recent study in the American Journal of Health Promotion discovered that people living in sprawling communities are more likely to be overweight and have high blood pressure.
The day-to-day realities of sprawl and the scores of statistics that measure its effects are encouraging some humans to reverse the trend. Community planners nationwide are espousing policies of smart growth, a widely touted brake to accelerated sprawl. Smart growth favors creating neighborhoods with a combination of housing types, communities with services and stores in easy reach of homes, a multitude of clean and efficient transportation options, and preserved open space and critical ecological areas. Effectively implementing smart growth and fostering a more natural, navigable, and survivable habitat for all species, is perhaps one of Homo sapiens’ toughest environmental challenges.
Sierra Club: Stopping Sprawl
What you can do to fight sprawl.
Urban Advantage: Envisioning Smart Growth
Photo-realistic visualizations of how smart growth can transform communities.
Centers for Disease Control and Prevention: Designing and Building Healthy Places
A clearinghouse of information on land use and health.
More About This Resource...
Our innovative Science Bulletins are an online and exhibition program that offers the public a window into the excitement of scientific discovery. This essay was published in February 2005 as part of the Species and Sprawl: A Road Runs Through It Bio Feature.
- It opens with the story of a commuter who has seen his journey to work double in time because of development in the nation's fastest-growing county.
- It then explains how sprawl is affecting Homo sapiens as it does many other species: it alters our habitat, hampers our mobility, and diminishes odds for survival.
- The essay concludes with a look at how community planners are espousing policies of smart growth.
Supplement a study of biology with a classroom activity drawn from this Science Bulletin essay.
- Ask students to name the species affected by sprawl, the spreading outwards of a city and its suburbs.
- Have them read the essay (either online or a printed copy).
- Have students write a brief reaction to the essay, explaining in their own words how sprawl is affecting us just as it does many other species.