Westerners are all too familiar with the phenomenon of "urban sprawl," as development creeps farther from city limits and eats up more land. A study released by the nonprofit Numbers USA offers new insight into the causes of sprawl, emphasizing the contribution of population growth to changes in land use.


Weighing Sprawl Factors in Large U.S. Cities analyzes the relative contributions of land-use decisions and population growth to sprawl in the nation's 100 largest urbanized areas. Using data from the Census Bureau and U.S. Department of Agriculture from 1970 to 1990 - during which 9 million acres of natural habitat and farmland were converted to suburbs - Roy Beck and Leon Kolankiewicz found that while about half of urban sprawl in these cities can be attributed to increases in land consumed per person, increases in population are responsible for the other half. In the Mountain West and Desert Southwest, population growth is the "overwhelming" contributor to sprawl, accounting for 81 to 100 percent of newly developed land.


"Most studies and reporting about sprawl don't touch on population growth," says Beck, because most environmental groups have shied away from the controversial issue of immigration, the largest contribution to population growth in the United States.


You can get the study online at www.SprawlCity.org.