What Drives Urban Sprawl in the United States: Rising Population or Falling Population Density?
Updated: Oct 24, 2018
Senior Environmental Scientist
Environmental consultant to NumbersUSA
State College, PA
To neoclassical economists, urban sprawl represents economic growth and dynamism. To ecologists, in contrast, it represents unsustainable, environmentally-damaging appropriation and displacement of critical natural ecosystems. In biophysical terms, sprawldegrades or eliminates natural habitats and their ecological services as well as productive agricultural land; it also increases fossil energy consumption, climate-altering carbon emissions, water demand, and emissions of “criteria” air pollutants (VOCs, NOx, PM, etc.).
In a series of studies on urban sprawl spanning nearly two decades, researchers with Arlington, VA-based NumbersUSA examined the relative contributions of the two fundamental factors that drive sprawl: population growth and increasing per capita land consumption (or decreasing population density). Our findings in a number of studies contradict the conventional wisdom that falling population density – rather than population growth – is the main cause of sprawl. In our first national-level study of the 100 largest U.S. cities back in 2001, we found that while there was significant variation between cities and regions, in aggregate, population growth and decreasing density each accounted for about half of sprawl. Overtime, while the pace of sprawl has slowed somewhat, the percentage of sprawl attributable to population growth has increased. If current large population projections to 2050 and beyond for the U.S. are realized, development pressures on undeveloped rurallands will increase immensely in the years ahead.
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