Does a growing population contribute to urban sprawl? The relationship between population growth and sprawl appears obvious to some but is denied or minimized by just as many. What has been lacking is a systematic, comprehensive, consistent means of quantifying the role of population growth in sprawl in recent decades. A national study by NumbersUSA, “Weighing Sprawl Factors in Large U.S. Cities” does just that. The Chesapeake Bay Watershed is home to more than 3,000 species of plants and animals, and nearly 15 million people today. The restoration and long-term protection of the Bay depends on halting the urban sprawl that is threatening the biodiversity and water quality of the area.

To date, almost all efforts to combat sprawl have focused on “Smart Growth” strategies, which primarily seek to create denser settlement by changing land use practices. Our findings indicate this approach will have limited success in saving rural land from development because it fails to address a key reason for sprawl — population growth. Our calculations show that about half the loss of rural land in recent decades is attributable to increases in the U.S. population, while changes in land use account for the other half. New immigration and births to immigrants now account for more than three-fourths of U.S. population growth. Therefore, population growth and the immigration policies that drive it must be an integral focus of efforts to preserve rural land.

As opposed to the Smart Growth approach, this study takes a
“conservationist” approach, examining only the loss of rural land to new
development and not the quality of urban planning. We focus on state
increases in developed land between 1982 and 1997. We also analyze the
expansion of urbanized land in the nation’s 100 largest cities between
1970 and 1990.

At the most basic level, there can only be three reasons for sprawl:
either there is a rise in per capita land use, a rise in the population,
or a rise in both. Quantifying the relative role of population growth is
important because almost all anti-sprawl organizations have focused on
Smart Growth and have generally been dismissive of population growth’s
role. These groups are not alone. A New York Times editorial in 2000
called it “absurd” to suggest that population growth and the immigration
that drives it contribute significantly to sprawl. Our findings indicate
that this view is incorrect.

Among the study’s findings:

• The more a state’s population grew, the more the state sprawled (see
Figure A). For example, states that grew in population by more than 30
percent between 1982 and 1997 sprawled 46 percent on average. In
contrast, states that grew in population by less than 10 percent
sprawled only 26 percent on average.

• On average, each 10,000-person increase in state population resulted
in 1,600 acres of undeveloped rural land being developed, even
controlling for other factors such as changes in population density.

• Apportioning the share of sprawl that is due to increases in
population versus increases in per-capita land consumption shows that,
nationally, population growth accounted for 52 percent of the loss of
rural land between 1982 and 1997, while increases in per-capita land
consumption accounted for 48 percent.

• While population growth is a key factor driving sprawl, our findings
indicate that Smart Growth must also play a significant role in
anti-sprawl efforts because per-capita land use has been increasing.
Between 1982 and 1997, land use per person rose 16 percent from 0.32
acres to 0.37 acres.

• There is significant variation between states in the factors
accounting for sprawl. For example, population growth accounted for more
than half of sprawl in five of the 10 states that lost the most land,
while increases in per-capita land use accounted for more than half of
sprawl in the other five worst sprawling states.

• An examination of the nation’s largest urban areas reveals the same
pattern as in the states. Between 1970 and 1990, population growth
accounted for slightly more than half of the expansion of urbanized land
in the nation’s 100 largest cities.

• In the 1990s, new immigration and immigrant fertility accounted for
most of the 33-million increase in the U.S. population. Census Bureau
data from 2002 indicate that the more than 1.5 million legal and illegal
immigrants who settle in the country each year along with 750,000 yearly
births to immigrants are equal to 87 percent of the annual increase in
the U.S. population.

• Contrary to the common perception, about half the country’s immigrants
now live in the nation’s suburbs. The pull of the suburbs is even
greater in the second generation. Of the children of immigrants who have
settled down and purchased a home, only 24 percent have done so in the
nation’s central cities.

• The suburbanization of immigrants and their children is a welcomed
sign of integration. But it also means that they contribute to sprawl
just like other Americans.

In short, Smart Growth efforts to slow or stop the increase in per
capita land use are being negated by population growth.
Immigration-driven population growth, in effect, is “out-smarting” Smart
Growth initiatives by forcing continued rural land destruction.

What makes this study different from most of the research on sprawl is
its focus on the destruction of undeveloped rural land. While concern
over the loss of rural land is one of the central issues driving the
public’s desire to reduce sprawl, most studies in this field and most
anti-sprawl organizations have not focused on this problem. Instead,
they have evaluated the density of new development or the employment of
various urban planning techniques. This is true even of organizations
and researchers with an environmental orientation. While such studies
are valid for analyzing various aspects of sprawl, they fail as measures
for conservation goals; their approach has the distinct disadvantage of
making the actual loss of agricultural land and natural habitat largely
irrelevant because all of the emphasis is on the quality of the planning
or the density in the new development. By examining the actual loss of
undeveloped rural land, this study avoids this problem.

This study emphasizes the role of population growth because most
anti-sprawl efforts ignore it while focusing only on the urban planning
approach embodied by Smart Growth. To the extent that population is
discussed in the context of sprawl it has generally been dismissed as a
cause. It is often argued, for example, that since sprawl occurs where
there is no population growth, increases in population must be a minor
factor in sprawl. As a moment’s reflection should reveal, such
observations only make sense in reaction to an assertion that population
growth is the only factor generating sprawl. We make no such assertion.
Our findings show that population growth is a key factor, but it is by
no means the only factor. There are certainly individual places where
population growth played little or no role in sprawl, just as there are
places where population growth accounted for all of sprawl. But,
overall, our analysis shows that increases in population nationally
accounted for about half the loss of undeveloped rural land. Thus
reducing population growth by reducing immigration must become an
important part of any long-term effort to save rural land.

Our conclusion that population growth accounts for half of sprawl is not
only consistent with the available evidence, it is also consistent with
common sense. Those most directly involved in sprawl certainly believe
that population is one of main reasons for sprawl. In fact, the
president of the National Association of Home Builders chided the Sierra
Club for its 1999 sprawl report because it “…failed to acknowledge the
significant underlying forces driving growth in suburban America — a
rapidly increasing population and consumer preferences.” Homebuilders
and real estate developers are clearly pleased with the high rate of
U.S. population growth. But they, of course, have a very different point
of view from anti-sprawl organizations as well as most Americans.

Assuming population growth continues to drive about half of all sprawl,
as it has in recent decades, federal immigration policy would appear to
be the single largest factor in determining how much sprawl will occur
over the next 50-100 years. Population growth can only be dealt with
effectively on a national scale by reducing immigration because new
immigration and births to immigrants now account for most of the
increase in the U.S. population. Given the population pressure America
faces as a result of immigration, local efforts to discourage population
growth by, say, low-density zoning, will almost certainly result in
“leapfrog” development and legal challenges. Moreover, intensified Smart
Growth programs in the face of rapid population growth will require
increased governmental regulation which, in turn, will almost certainly
undermine political support for such programs. Absent population growth,
Smart Growth policies would be more successful and would encounter less
opposition.

While our conclusions may seem obvious to most readers, some may find
them controversial. Part of the reason most anti-sprawl organizations
ignore population growth is that they are unaware of its role. It is our
hope that this study will help correct this. However, some involved in
anti-sprawl efforts avoid dealing with population growth because they
know that doing so will inevitably lead to a debate over U.S.
immigration policy, making it seem as if immigrants are being “blamed”
for sprawl. This is something that anti-sprawl organizations (and the
authors of this report) understandably wish to avoid. But such concerns
seem misplaced since anti-sprawl organizations can make clear that
immigration must be reduced due to rapid population increase rather than
because of the characteristics of immigrants. It might also be helpful
for such organizations to indicate their support for policies designed
to help legal immigrants already here integrate into American society.
Moreover, advocating less immigration in the future for conservationist
reasons is likely to be politically popular given that public opinion
polls show most Americans, including minorities, want less immigration.

While significantly reducing immigration may be very helpful in reducing
sprawl, some may worry that doing so might harm the economy. The
available data suggest otherwise, however. A 1997 report by the National
Academy of Sciences entitled The New Americans concluded that the net
economic benefits from immigration are very small and are, in fact,
entirely outweighed by the fiscal drain immigrants impose on taxpayers.
The nation’s leading immigration economist, George Borjas of Harvard,
comes to much the same conclusion in his recent book Heaven’s Door.
Policymakers can reduce future immigration secure in the knowledge that
doing so will not harm America’s economy.

At present, about 11 million people are allowed to settle legally in the
United States each decade. Bringing this number down to three million,
coupled with increased efforts to reduce illegal immigration, still
would allow the United States to accept more immigrants than any other
country in the world. One may favor high immigration for any number of
reasons, but our study makes clear that those concerned about sprawl
must at least understand that dramatically increasing the size of the
U.S. population though immigration has enormous long-term implications
for the preservation of rural land. It is very difficult to see how it
could be otherwise.