Continued Urban Sprawl Threatens U.S. Coasts

Daniel McGrath, Coastal Business and Environmental Specialist for Illinois-Indiana Sea Grante, has been studying the urban sprawl patterns of the top 20 coastal metropolitan regions ranked by population. Using population statistics from the 1990 U.S. Census and urban land area data from the past five decades, McGrath has arrived at a forecast for the year 2025. Assuming the current trends in average population density and land use continue, the forecast doesn't look good.

McGrath predicts, "Given that the nation's top 20 oceanic and Great Lakes coastal metropolitan regions are likely to increase their population by an additional 32 million people, by the year 2025 the 'urban footprints' of these 20 regions are likely to expand by 46 percent, or from about 20,000 square miles to about 29,000 square miles." That's an additional 9,000 square miles, or about 5.8 million acres, of land that today is either agricultural land or open space.

The reality of urban sprawl over the next 25 years is even worse since Portland and Los Angeles were excluded from McGrath's final forecast. These two cities have factors which make their future difficult to predict. "Portland has a tight urban growth boundary in order to limit development," says McGrath, "and Los Angeles has the physical barrier of the mountains as well as restrictions on land development which put endangered species at risk."

It's also important to note that McGrath's forecast does not include the nearly 100 smaller coastal metropolitan regions currently experiencing a boom in growth as well, nor does it include the many large, non-coastal cities in the U.S. like Atlanta, Denver, and Nashville, for example.

Increases in real income (income which has been adjusted for inflation) and advances in the technology of transportation over this past century are major factors contributing to urban sprawl, according to McGrath. On average since 1950, U.S. coastal cities are twice as large as they would have been if there had been no changes in real wealth and transportation technology that determine urban land area. Put another way, since 1950, nearly half of urban land area growth has been determined by technology factors rather than by population.

"We've spread out further, continuing to make the trade-offs between urban amenities and the cheaper land that suburban locations provide because we have had the means to do so-both in terms of wealth and technology," says McGrath. Stated simply: people want to live and work in or near cities; and, because of better, faster transportation options today, people can continue to demand semi-rural residential locations while still maintaining a reasonable commute-time to work.

McGrath fears that even a comprehensive strategy is unlikely to make a dent in the wave of urbanization facing U.S. metropolitan regions. "The private development industry will likely continue to take advantage of cheaper land opportunities at the urban fringe as it has since World War II," continues McGrath, "subsequently putting more farmland and open space at risk."

McGrath doesn't sugar coat the future either. He says that if an effort to change this trend in urban sprawl does not happen soon, "Metropolitan regions will continue to fight to fix the problems imposed by unbalanced, market-driven urbanization after the fact, and "we'll wind up losing our natural capital and species diversity forever." McGrath concludes, "If cities continue to sell land to the highest bidder and undervalue our natural capital, they'll always be trying to solve problems post-mortem."

The Illinois-Indiana Sea Grant College Program is one of 30 National Sea Grant College Programs. Created by Congress in 1966, Sea Grant combines university, government, business and industry expertise to address coastal and Great Lakes needs.