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This paper is adapted and condensed from the book Once There Were Greenfields: How Urban Sprawl Is Undermining America's Environment, Economy and Social Fabric, by F. Kaid Benfield, Matthew D. Raimi, and Donald D.T. Chen (New York: Natural Resources Defense Council, 1999).

Make no mistake about it: to expand metropolitan areas into the countryside at rates many times faster than population growth, as we have been doing over the past five decades, is not good for the environment. Whether we can improve the pattern in the coming decades will be critical because, in the first half of the 21st century, the U.S. population is expected to grow by half. That anticipated growth of some 130 million people is equivalent to the current population of France and Germany combined. Where will these new citizens live, work, and shop? How important is it that we, as environmentalists who care about sustainability, bring resources to bear on the shape of America's future urban development?

Spreading out

Consider that the Maryland Office of Planning projects that, from 1995 to 2020, more land will be converted to housing in the region surrounding the Chesapeake Bay than in the past three and one-half centuries. In greater Chicago, in the two decades from 1970 to 1990, the consumption of residential land grew an amazing eleven times faster than the region's population. Over the same period, the Chicago region's consumption of land for commercial and industrial uses grew 74 percent, eighteen times faster than population. In greater Cleveland, land consumption has been growing even while population has been declining: since 1970, the regional population has declined by 11 percent, while the amount of urbanized land has grown by 33 percent.

In the Sun Belt, the prototype "city" of the future, if present trends continue, may well be metropolitan Phoenix, which is reported to be developing open land at the rate of 1.2 acres per hour. Indeed, the geographic reach of Phoenix is now said to be equivalent in size to Delaware. Another Sun-Belt candidate to represent the metropolis of the future is Atlanta, which has grown in population at an average annual rate of 2.9 percent since 1950, with almost all of the growth in the suburbs. Real estate analyst Christopher Leinberger holds that "it is altogether probable that in terms of land area Atlanta is the fastest-growing human settlement in history."1

And one of the most daunting aspects of our rapid development of new land is its permanence: every acre of natural or open space paved over for sprawl -- every acre claimed by a new subdivision or shopping center on the fringe of a Chicago, Phoenix, or Atlanta -- represents an acre lost forever. Barring heroic measures, farmland and other open space cannot be reclaimed.

These patterns of development portend serious consequences for our nation's land, air, and water, each of which we discuss below. Although as a society we have made great environmental progress in the last few decades, it is becoming increasingly clear that we cannot continue to do so if we do not change the way we grow.

From Old MacDonald to the new McDonald's

While the United States continues to enjoy the appearance of abundant farmland, the best of that land is being lost at an amazing rate. At the conclusion of exhaustive research on the subject, the American Farmland Trust has reported that from 1982 to 1992 we lost to urban and suburban development an average of 400,000 acres per year of "prime" farmland, the land with the best soils and climate for growing crops. This translates to a loss of 45.7 acres per hour, every single day. During that same period, we lost an additional 26,600 acres per year -- three more acres per hour, every single day -- of "unique" farmland, used for growing rare and specialty crops. Put another way, for each acre of prime or unique farmland that is being saved by various farmland protection programs across the county, three acres are lost to development.

To make matters worse, there is an unfortunate congruence between that land most suited and productive for farming and that land most in danger of urban encroachment. As Professor Reid Ewing has put it, the "lands most suitable for growing crops also tend to be most suitable for 'growing houses.' " 2 This is because inland urban settlements in the United States have tended to situate in river valleys and other fertile areas that are also highly productive for farming.

Perhaps as a result, most of the country's prime farmland is located within the suburban and exurban counties of metropolitan areas. Such "urban-influenced" counties currently produce more than half the total value of U.S. farm production; their average annual production value per acre is some 2.7 times that of other U.S. counties. Yet, ominously, their population growth is also disproportionately high, over twice the national average. Those counties with prime and unique farmland found to be threatened by particularly high rates of current development collectively produce some 79 percent of our nation's fruit, 69 percent of our vegetables, 52 percent of our dairy products, and over one-fourth of our meat and grains. Among the farming regions most seriously endangered by sprawl are California's Central Valley, the Northern Piedmont near Washington, DC and Baltimore, and the Northern Illinois Drift Plain near Chicago.

Landscapes lost

To add insult to injury, what is being plopped down on our nation's lost farmland and open space is not pretty, to say the least. The changes that sprawl is bringing to the character of our landscape have been summarized graphically by writer James Howard Kunstler:

We drive up and down the gruesome, tragic suburban boulevards of commerce, and we're overwhelmed at the fantastic, awesome, stupefying ugliness of absolutely everything in sight -- the fry pits, the big-box stores, the office units, the lube joints, the carpet warehouses, the parking lagoons, the jive plastic townhouse clusters, the uproar of signs, the highway itself clogged with cars -- as though the whole thing had been designed by some diabolical force bent on making human beings miserable. And naturally, this experience can make us feel glum about the nature and future of our civilization. 3

The impacts go beyond the annoyance of visual clutter, of course, to our deeper senses of place and history, and to our ever-more-tenuous connection as human beings to the mysteries of the natural world.

For example, there is plenty of evidence that we place a high value on exactly those benefits that we are losing. Writer Tony Hiss describes research documenting strong human preferences for green landscapes with water, winding paths, long and sweeping vistas, and hidden natural places. Similarly, in a recent public opinion poll, 63 percent of respondents cited "the beauty of nature" as a reason for wanting to protect the environment. A New Jersey survey reported that 78 percent of respondents supported changes in development patterns in order to preserve farmland. In still another study, citizens shown slide images gave the lowest approval rating to images of "cookie cutter" subdivisions and complexes, highway strip development, and shopping plazas with large front parking lots, while they gave the highest rating to natural areas, farmland, woodlots, parks and streams.

In addition to the findings with regard to preference, there is evidence that ugly development is not good for us. Research at Texas A & M and the University of Delaware indicates that humans' reactions to visual clutter may include elevated blood pressure, increased muscle tension, and impacts on mood and work performance. Recovery from stress has been measured as faster and more complete when we are exposed to natural outdoor environments. At least one study indicates that travel along unattractive suburban corridors may make people feel that they are driving for longer periods of time than they actually are.

Although the loss of a sense of place that accompanies sprawl is sometimes hard to quantify, it is real. Writing in The Washington Post about a developing area in nearby Maryland, reporter Todd Shields expresses something many of us have felt at one time or another:

The bulldozers came along and flattened a couple of acres of pine trees near Waldorf. As I drove home one evening, I was suddenly disoriented. Where did I miss a turn? Then the lack of trees registered. I realized that it was simply that the picture had been altered, as if someone had pulled down a new backdrop on a movie set. 4

Moreover, the loss of undeveloped landscapes threatens economic as well as psychological values. Over 130 million Americans enjoy observing, photographing, and feeding wildlife and fish, thus supporting a nature-oriented tourist industry in excess of $14 billion annually. The National Survey of Fishing, Hunting, and Wildlife Associated Recreation found that 77 percent of the U.S. population enjoys some form of wildlife-related recreation, and a 1987 poll sponsored by the President's Commission on Americans Outdoors found that "natural beauty was the single most important criterion for tourists selecting outdoor recreation sites." Independent of recreation and tourism, proximity to open spaces has been found to raise the value of residential property by as much as a third in some cases, raising property tax revenues as well.

But sometimes the impacts of sprawl on the landscape can only be described as deeply personal. Take the case of Minnie Johnson, 74, a resident of Howard County, Maryland, in the fast-developing corridor between Baltimore and Washington. When her story was reported in The Washington Post in 1997, Johnson was being forced to watch the rise of a $15 million warehouse that will isolate the small cemetery that for more than 100 years has been the resting place for her family, one of the largest African-American families in the county. Pursuant to state law, the cemetery itself will be preserved, but it will soon be surrounded by concrete, with an Interstate highway on one side and the new warehouse on the other. The Post reports that hundreds of graves have been ruined or isolated by new development in Howard County alone in the last decade.

Gray skies and greenhouses

Current development patterns also bring substantial air pollution, largely because of the increased automobile dependence that is associated with sprawl. As we spread ourselves farther and farther apart, it becomes inevitable that we must travel longer distances to work, shop, enjoy recreation, and visit family and friends. The convenience store and even the playground may no longer be within walking distance. The bus stop may be farther away, too, even if we are fortunate enough to have a bus that goes anywhere close to our destination; in some places, there may be no bus service at all. Work may be on the other side of town or even in another town altogether.

The only good choice for most suburbanites is to drive, and to drive a lot. And that is exactly what we are doing. Motor vehicle use in America doubled from one to two trillion miles per year between 1970 and 1990. In the 1980s, vehicle miles traveled grew more than four times faster than the driving-age population and many times faster than the population at large. There are many reasons for this surge in driving, but a growing body of research makes it increasingly clear that sprawl comprises a large portion of the problem: people in spread-out locations drive more.

This translates directly into growing emissions of greenhouse gases and the continued inability of our metropolitan areas to cleanse themselves of unhealthy air. In particular, transportation in the United States already contributes some 450 million metric tons of carbon dioxide - the inevitable by-product of fossil-fuel combustion - each year, around 32 percent of total U.S. carbon emissions, to the atmosphere. The federal Department of Energy projects that total U.S. carbon emissions will continue to grow at an average rate of 1.0 percent per year, with transportation sources growing 20 percent faster than the average. And DOE's projections are conservative; many experts predict the rate of growth could be much greater, precisely because of continued increases in automobile and truck emissions due to sprawl-induced driving.

So far, the effects on our quality of life from rising accumulation of greenhouse gases in our atmosphere have not been dramatic. But they could become so. While it is beyond the scope of this paper to document the likely patterns and consequences of global warming, the Intergovernmental Panel on Climate Change developed a range of projections of future climate trends in 1995, all of them indicating that average rates of warming probably will be greater than any seen in the last 10,000 years. The IPCC's mid-range, "best estimate" forecast is for an additional 2?C (3.6? Fahrenheit) warming in the 21st century. The "best estimate" scenario also forecasts an additional sea level rise of about 50 centimeters (20 inches) during the same time period.

The resulting impacts on human health and ecosystems could be widespread and quite serious. While the American responses to international agreements negotiated in Rio de Janeiro and Kyoto to contain greenhouse gas emissions are still being formulated, under any scenario it will be difficult to meet our obligations if emissions from the transportation sector continue to rise so dramatically.

The news on other air pollutants from sprawl-induced traffic is only slightly more encouraging. A recent government publication summarizes the situation:

Despite considerable progress, the overall goal of clean and healthy air continues to elude much of the country. Unhealthy air pollution levels still plague virtually every major city in the United States. This is largely because development and urban sprawl have created new pollution sources and have contributed to a doubling of vehicle travel since 1970. 5

In particular, cars and other highway vehicles continue to emit some 60 million tons of carbon monoxide per year, about 62 percent of our national inventory of that pollutant; cars and other highway vehicles continue to emit some seven million tons per year, almost 26 percent, of our volatile organic compounds (VOCs), which constitute a major precursor to ozone smog; and they emit around eight million tons per year, about 32 percent, of our nitrogen oxides, another ozone precursor. Motor vehicles also emit as much as 50 percent of our carcinogenic and toxic air pollutants, such as benzene and formaldehyde. And heavy vehicles, particularly diesel-powered buses and freight trucks, constitute a significant source of soot and other unhealthy fine particles that, when inhaled, lodge in and damage human tissue.

EPA research indicates that, notwithstanding continuing improvements in emission control systems, the total national inventory of hydrocarbon emissions from gasoline vehicles could reverse direction and begin to increase again in the early part of the 21st century, because of increased driving. Total nitrogen oxide emissions from motor vehicles already are at a higher level than they were two decades ago, despite improvements in the emissions performance of individual vehicles. Ozone and particulate pollution are both projected to rise, and some observers believe that, by 2015, carbon monoxide will also be on a rising trend.

These ingredients make for a nasty soup. Exposure to carbon monoxide is associated with visual impairment, reduced work capacity, reduced manual dexterity, poor learning ability, and difficulty in performing complex tasks. At sustained high levels, it can be fatal. Ozone, the principal component of smog, damages lung tissue, aggravates asthma and other respiratory disease, and leads to choking, coughing, and stinging eyes. It also inhibits plant growth and can cause widespread forest and crop damage, around $40 million worth each year in Maryland alone. Health threats from diesel soot and other particulate pollution include a variety of cardiac and respiratory symptoms, such as impaired breathing, damage to lung tissue, increased asthma attacks and emergency room visits, cancer, and premature death, particularly among the elderly and children.

Runoff run amok

Haphazard sprawl development also brings runoff water pollution to more and more watersheds, degrading streams, lakes, and estuaries. Natural landscapes, such as forests, wetlands, and grasslands, are typically varied and porous. They trap rainwater and snowmelt and filter it into the ground slowly. When there is runoff, it tends to reach receiving waterways gradually. Cities and suburbs, by contrast, are characterized by large paved or covered surfaces that are impervious to rain. Instead of percolating slowly into the ground, stormwater becomes trapped above these surfaces, accumulates, and runs off in large amounts into waterways, picking up pollutants as it goes.

It is now thoroughly documented that, as the amount of impervious pavement and rooftops increases in a watershed, the velocity and volume of surface runoff increases; flooding, erosion and pollutant loads in receiving waters increase; groundwater recharge and water tables decline; stream beds and flows are altered; and aquatic habitat is impaired. As a result, there is a strong correlation between the amount of imperviousness in a drainage basin and the health of its receiving stream.

Stream degradation begins as impervious cover in a watershed exceeds 10 percent. This amount of imperviousness is typically achieved by the rooftops, streets, and driveways of even large-lot subdivisions whose density is one dwelling unit per acre or less. If one includes the arterial roadways and commercial parking lots and buildings typically surrounding such subdivisions, the threshold of 10 percent imperviousness in a watershed would be achieved even with much larger lots.

Above 10 percent imperviousness, fish species begin to decline. Brown trout, for example, may disappear altogether at around 10 to 12 percent imperviousness. When the watershed reaches 25 percent imperviousness, as it might with half-acre residential lots coupled with modest convenience shopping and arterial roadways, additional species may disappear. Indeed, at levels above 30 percent imperviousness, a watershed may be considered generally degraded. These levels are easily exceeded by sprawl: research indicates that commercial and shopping center development, for example, typically brings 75 to 95 percent imperviousness to its site.

The consequences of watershed degradation from development have been felt across the country. In the Puget Sound region of Washington state, for example, major floods that were 25-year events now occur annually; "the sponge is full," according to King County analyst Tom Kiney. Similarly, in Akron, Ohio, runoff from residential areas has been estimated at up to 10 times that of pre-development conditions, and runoff from commercial development has been estimated at 18 times that before development. In several Maryland, Pennsylvania, and Virginia watersheds that drain into the Chesapeake Bay, pollution from development has been found to exceed -- in some cases dramatically -- pollution from industry and agriculture. Even in counties that have enacted stormwater-management regulations, the pace of development is causing pollutant loads to increase.

Partly as a result, runoff pollution is now the nation's leading threat to water quality, affecting about 40 percent of our nation's surveyed rivers, lakes, and estuaries. Among the various pollution categories, urban runoff is the second-most prevalent source of impairments to our estuaries, affecting some 46 percent of the impaired estuaries in EPA's National Water Quality Inventory. It is tied for third-most-prevalent among sources of impairments to our lakes.

What to do?

Fortunately, smart-growth solutions -- those that reinvigorate our cities, bring new development that is compact, walkable, and transit-oriented, and preserve the best of our landscape for future generations -- work well for the environment. For example, a comprehensive New Jersey study found that, compared to a "current trend" scenario, a plan that channeled job and housing growth to preferred locations (but assumed that a majority of new homes would remain single-family and detached) would consume 28 percent less farmland, 43 percent less open space of all kinds, and an impressive 80 percent less environmentally fragile land, including valuable forests, steep slopes, and sensitive watersheds, all while accommodating a projected growth of 408,000 new households and 654,000 new jobs over 20 years.

Building smart-growth neighborhoods that are more compact can reduce traffic, too. Transportation research indicates that each doubling of average neighborhood density is associated with a decrease in per-household vehicle use of 20-40 percent, with a corresponding decline in emissions. This is one of the reasons that European cities typically exhibit only one-fourth the per-person emissions of carbon dioxide and other pollutants from transportation that are typical of American cities. Similar savings can be had in the effects of runoff water pollution: the New Jersey study, for example, found that, by directing growth to preferred locations and achieving modestly higher average residential densities, the state could lower pollutants in stormwater runoff by some 4,560 tons per year, a 40 percent reduction over that predicted for the "current trend" scenario.

In other words, we don't have to keep doing this to ourselves. Indeed, this is a time of great innovation in the development, architecture, planning, and land preservation communities. There may be no one magic, all-encompassing solution to sprawl, but many promising and successful alternatives are at hand.

For the environment, the task is to apply advocacy to all levels of government, local, state, and national, and to work with the private sector on forging and implementing the alternatives. The rewards can be great because, just as sprawl poses multiple environmental problems, its solutions promise multiple environmental benefits. The task is large, but also exciting. We dedicate ourselves to it.


1. Christopher B. Leinberger, "The Metropolis Observed," Urban Land, vol. 57, October 1998, pp. 28-33.

2. Reid H. Ewing, "Characteristics, Causes, and Effects of Sprawl: A Literature Review," Environmental and Urban Issues, Florida International University/Florida Atlantic University, p. 11 (1994).

3. James Howard Kuntsler, "Home from Nowhere," The Atlantic Monthly, vol. 278, September 1996, pp. 43-66.

4. Todd Shields, "On Edge," The Washington Post Magazine, February 16, 1997, pp. 23, 24.

5. Office of Mobile Sources, U.S. Environmental Protection Agency, Motor Vehicles and the 1990 Clean Air Act, Fact Sheet OMS-11, August 1994.

last revised 4/14/2000

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