Population growth is half the problem in sprawl

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:

(1) 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.

(2) Population Growth: The other half of sprawl is related to the increase in the number of residents.

What is Sprawl?


Although there are many definitions of sprawl, a central component of most definitions and of most people's understanding of sprawl is this:

Sprawl is the spreading out of a city and its suburbs over more and more rural land at the periphery of an urban area. This involves the conversion of open space (rural land) into built-up, developed land over time.

From the standpoint of urban planning institutions, the style of that conversion can sometimes be more important than the amount of the conversion. Organizations whose chief concerns involve urban planning goals may tend to emphasize qualitative attributes of sprawl -- such as attractiveness, pedestrian-friendliness and compactness.

But for those who are most concerned about the effect of sprawl on the natural environment and agricultural resources, the more important overall measure of sprawl is the actual amount of land that has been urbanized. Knowing the actual square miles of urban expansion (sprawl) provides a key indicator of the threat to the natural environment, to the nation's agricultural productivity and to the quality of life of people who live in cities and in the small towns and farms that are near cities.

Both the urban planning and environmentalist approaches to sprawl are valid ones for achieving sometimes differing -- although not necessarily competing -- goals.

NumbersUSA.com adopts the environmentalist emphasis. It uses the term "sprawl" to refer to the reduction of rural land due to the increase of the total size of the land area of a city and its suburbs over a particular period of time.

That definition of sprawl is certainly not the only one. But it is unequalled as a standard quantitative measure of rural urbanization in cities in all regions of the country. Sprawl City uses this definition because it is based on the unrivaled measurements of Urbanized Areas by the U.S. Bureau of Census. No other source so methodically and with such standardization measures the loss of rural land to urbanization.

This measurement by amount closely resembles the most common American understanding of sprawl. For example, if an Urbanized Area covered 10 square miles in 1980 and covered 12 square miles in 1990, it would be common to say that the city and its suburbs over that period of time "sprawled 2 square miles."

If 25 square miles of open spaces around a city are urbanized, most Americans would consider that to be 25 square miles of sprawl, regardless of whether it was developed tastefully or not. They might be more offended by the sprawl if it included ugly development than if it was 25 square miles of well-planned sprawl, but the amount of sprawl - and the number of rural acres lost - would be the same. Thus, using this measure, it is possible to have well-planned sprawl or chaotic sprawl, to have high-density or low-density sprawl, to have auto-dependent or mass-transit-oriented sprawl. But regardless of the quality of the sprawl, the amount of sprawl is measured by the square miles of rural land eliminated by urban development.

None of that is to say that the quality of sprawl doesn't affect the amount of sprawl. Generally, well-planned sprawl will result in fewer square miles of rural land being covered by urban development. And environmentalists are interested in the urban planning aspects of anti-sprawl work because they can reduce the amount of energy used by and pollution produced by residents. And better planned sprawl is likely to keep its residents happier and less likely to decide later to move even farther beyond the urban center.

Clearly, though, the amount of rural land lost to sprawl is the key issue from an environmentalist and agricultural perspective. The amount of rural land loss and urban expansion also is significant to the quality of life of urban dwellers. The larger an urban area, the more difficult it will be for the average resident to reach the open spaces beyond the urban perimeter; the increase in urban distances can also affect commuting time, mobility and a resident's feeling of being "trapped."

Population growth without Sprawl apparently not practicable

The virtual void of population-stabilization plans within the anti-sprawl programs around the country is related to a belief that population growth can be accommodated without causing sprawl.

Theoretically, that is possible – for awhile: All new residents would have to move into the existing urban area, and none of the previous residents could move to the edge of the city. Such an occurrence over any period of time could happen only through the continual demolition of existing housing to make room for higher-density cluster houses, condominiums or apartment buildings; the demolition of apartment buildings to build higher apartment buildings; higher occupancy rates in existing structures, including some structures not intended for residential use such as garages, and building on any remaining vacant land.

Even if Americans were to accept the escalating governmental regulations that would be required to handle each year's population growth within existing boundaries, such a success would not ease the massive "ecological footprint" on the rural areas of the country.

It is important to recognize that the per-capita-land-consumption figure upon which nearly all conventional anti-sprawl efforts focus includes only the land consumed by an average resident inside his/her own Urbanized Area. It does not include all the rural land in other parts of the country that is required to obtain the food, fiber, minerals and energy for that resident, and to dispose of that resident's wastes – termed the ecological footprint of the Area.

A study of sprawl nationwide released in March of 2001 failed to find any American community that has shown an inclination to adopt the regulations and make the personal behavior changes that would counteract the effects of population growth for even a few years, let alone in perpetuity – which essentially is what would be required if current national population policies stay in place.

Los Angeles is a prime example of the limits to how far Americans will go in packing additional people into their neighborhoods. No city in America may be a better model of the goal of attempting to restrain sprawl by channeling population growth into ever-denser settlements, both in the urban core and throughout the suburbs. Between 1970 and 1990, per capita land consumption fell until the L.A. Urbanized Area was the most densely populated in the country. Many people find this hard to believe because of Manhattan's skyline. But New York's suburbs are only 60% as dense as those of Los Angeles. No other Urbanized Area provided so little land per resident as Los Angeles (0.11 acre). Most American communities have refused to come anywhere near the L.A. densities.

Yet despite accepting the densest living conditions in the country, the Los Angeles Area sprawled across another 394 square miles of orchards, farmland, natural habitat and other rural land. The reason? The addition of another 3.1 million residents.

The necessity of addressing population growth

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.