Global ChangeIntersection of Nature and Culture

Land consumption and open space loss across U.S. cities

Tuesday, March 2nd, 2010

The issue of land use change is a complex, with many factors being important historically, such as

• population growth (more land required for more people)
• technology (e.g., automobiles made suburban expansion feasible)
• economics (cheaper land and rents in suburbs compared to cities)
• policy (things like 30-yr mortgages, mortgage insurance, and FHA loans had a large impact on urban sprawl because they often made it cheaper to own rather than rent)
• cultural values (the romanticized notion of a detached home in a safe, pollution-free neighborhood with good schools)

In this week’s PLoS One, Robert McDonald and colleagues¹ examined land use change for 274 metro areas (figure 1) in the U.S. to determine tends across cities.

Their results were interesting (excerpts):

• 1.4 million ha of open space was lost, and the amount lost in a given city was correlated with population growth.
• American cities vary by more than an order of magnitude in their MSA-wide per capita land consumption. Generally large cities have small per capita land consumption, with the five smallest in 2000 being New York (459 m²/person), Miami (476 m²/person), Philadelphia (519 m²/person), Los Angeles (535 m²/person), and Washington, DC (536 m²/person). Conversely, many small cities have large per capita land consumption, with the five biggest in 2000 being Grand Forks, ND (5394 m²/person), Bismark, ND (3913 m²/person), Flagstaff, AZ (3381 m²/person), Enid, OK (3249 m²/person), and Cheyenne, WY (3073 m²/person).
• The per capita land consumption (m²/person) of most cities decreased on average over the decade from 1,564 to 1,454 m ²/person, but there was substantial regional variation and some cities even increased.
• Cities with greater conservation funding or more reform-minded zoning tended to decrease in per capita land consumption (scroll to table 1) more than other cities.
• The inequality of land consumption varied geographically, with less inequality on the East Coast compared to the West Coast (scroll to figure 4).

They provide a simplified snapshot of how development changes with history and geography (for a more-thorough yet readable treatment of land use in the U.S., check out Crabgrass Frontier by Kenneth Jackson):

The process of development plays out differently in cities with different socioeconomic histories. Moreover, cultural differences exist among and within many U.S. cities, leading to varying spatial patterns of development. However, a general historical pattern exists. In many U.S. cities, an urban core existed in the decades or centuries prior to the widespread use of the automobile, and these neighborhoods have high population density and small amounts of developed area per capita. The surrounding suburban and exurban areas, created predominately after WWII, contain residents living at lower population density and consume more land per capita. There are substantial economic links between these two zones, and in contemporary U.S. cities commuting occurs in both directions. Northeast U.S. cities that developed before the automobile typically follow this narrative. Many have a relatively dense urban core, but have adopted zoning policies that ensure contemporary suburban settlements occur at lower density. While they remain dense compared to other U.S. cities, they are getting less dense over time, as proportionally more of the population is in suburban areas. The declining manufacturing cities of the Rust Belt and the Southern Appalachians are an extreme example of this spreading out of population.

Southeastern U.S. cities, excluding Florida, are often newer and have less of a legacy of a dense urban core. They do not appear to be getting markedly denser, and the relatively fast population growth of these cities implies that their total impact on natural habitat in coming decades will be large. In contrast to the Southeast, Western cities appear to be getting denser, including those that do not have a historical legacy of a dense urban core such as Phoenix. These Western cities are often still growing quickly and consuming a great deal of land, but contemporary development is making these cities denser than they were previously. Many of these Western cities have a strong conservation culture, and the degree of conservation funding and reform-minded zoning correlates with how much denser they are getting. However, it should be noted that contemporary development in Western cities is still well below the densities found in the dense urban core of Northeastern U.S. cities, posing problems for designing effective public transit systems.

¹McDonald, R., Forman, R., & Kareiva, P. (2010). Open Space Loss and Land Inequality in United States’ Cities, 1990–2000 PLoS ONE, 5 (3) DOI: 10.1371/journal.pone.0009509

_____

Photo Credit:  http://www.flickr.com/photos/bobjagendorf/ / CC BY-NC 2.0