A major controversy in the efforts to halt rural land loss is whether land-use and consumption decisions are the primary engines of urban sprawl, or whether it is the nation's continuing population boom providing most of the power driving the expansion. A careful analysis of U.S. Census Bureau and U.S. Department of Agriculture data found that the two sprawl factors share equally in the blame:
- Per Capita Sprawl: About half the sprawl nationwide appears to be related to the land-use and consumption choices that lead to an increase in the average amount of urban land per resident.
- Population Growth: The other half of sprawl is related to the increase in the number of residents
Addressing national policies now destined – according to the Census Bureau – to expand the current population of 292 million (up from 203 million in 1970) to more than a half billion (571 million) this century is essential to stopping sprawl.
At the same time, cities which value their surrounding rural land and want to stop sprawl will need to address (a) local incentives that entice more people to move into particular cities and (b) state policies that attract residents from other states.
It is difficult, however, to conceive of many cities in America being able to stop their population growth for more than a short period if current demographic trends are allowed to continue and add nearly 300 million people to the nation this century.
The figure below shows how many square miles of the 100 largest Urbanized Area's sprawl over a 20-year period was related to the population growth of that time. Even if the cities had succeeded in eliminating all the sprawl related to the land-use and consumption factors behind per capita land growth, that still leaves 7,403 square miles of sprawl that was explained by population growth.