Maps: Urban Sprawl Steady Since 1976
Maps: Urban Sprawl Steady Since 1976
By Tracy Staedter, Discovery News
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May 12, 2006— An unprecedented survey of urban sprawl in the continental United States is challenging conventional notions about development.
The research, published in the May issue of the Quarterly Journal of Economics, offers a detailed view of how land use varies across the country and, for the first time, explains what may be causing the variation.
"There was a lot of talk about urban sprawl and there were no facts. We put this data set together so that we could get some facts," said Matthew Turner, associate professor of economics at the University of Toronto.
Turner conducted the study with Marcy Burchfield of the Neptis Foundation in Toronto, Hernry Overman of the London School of Economics, and Diego Puga, of the University of Toronto.
Questions and opinions about urban sprawl and its causes have been around for years. But according to Turner, the opinions and policies arising from these debates are based largely on speculation.
To produce meaningful data, the researchers merged high-altitude photography from around 1976 with satellite images from 1992 -- the most recent images available. They divided the space into 8.7 billion grid cells, each representing 900 square meters (a little less than a quarter of an acre).
The scientists pinpointed development by measuring the percentage of impermeable cover, such as that created by buildings and concrete, producing a sprawl index.
The higher the index, the more scattered a city. For example, among metropolitan areas with a population over one million, Atlanta has an index of 56 percent, while New York has an index of 20 percent.
When averaged for all American cities, the numbers reveal that the open space around a typical home did not change much in the 16-year time frame. In 1976, the average sprawl index was 42 percent and in 1992, 43 percent.
The researchers also found a direct relationship between the pattern of sprawl and a city's topography, climate and access to groundwater. In temperate climates, for instance, populations tend to spread out more. In hilly areas, populations extend to build on level ground. And development tends to be more expansive where groundwater is abundant.
"All of this is very useful and it's a great achievement," said Jan Brueckner, a professor of economics at the University of California, Irvine, and the editor of the Journal of Urban Economics. But, he said, "it doesn't get at the fundamental question of whether a city is too built up."
"My idea is it's the spatial size of cities that matter. Their idea is that it's the compactness of development that matters," said Brueckner.
Turner agreed, and in fact, said his team has such data and will be analyzing it extensively until this summer.
By Tracy Staedter, Discovery News
type size: [A] [A] [A]
May 12, 2006— An unprecedented survey of urban sprawl in the continental United States is challenging conventional notions about development.
The research, published in the May issue of the Quarterly Journal of Economics, offers a detailed view of how land use varies across the country and, for the first time, explains what may be causing the variation.
"There was a lot of talk about urban sprawl and there were no facts. We put this data set together so that we could get some facts," said Matthew Turner, associate professor of economics at the University of Toronto.
Turner conducted the study with Marcy Burchfield of the Neptis Foundation in Toronto, Hernry Overman of the London School of Economics, and Diego Puga, of the University of Toronto.
Questions and opinions about urban sprawl and its causes have been around for years. But according to Turner, the opinions and policies arising from these debates are based largely on speculation.
To produce meaningful data, the researchers merged high-altitude photography from around 1976 with satellite images from 1992 -- the most recent images available. They divided the space into 8.7 billion grid cells, each representing 900 square meters (a little less than a quarter of an acre).
The scientists pinpointed development by measuring the percentage of impermeable cover, such as that created by buildings and concrete, producing a sprawl index.
The higher the index, the more scattered a city. For example, among metropolitan areas with a population over one million, Atlanta has an index of 56 percent, while New York has an index of 20 percent.
When averaged for all American cities, the numbers reveal that the open space around a typical home did not change much in the 16-year time frame. In 1976, the average sprawl index was 42 percent and in 1992, 43 percent.
The researchers also found a direct relationship between the pattern of sprawl and a city's topography, climate and access to groundwater. In temperate climates, for instance, populations tend to spread out more. In hilly areas, populations extend to build on level ground. And development tends to be more expansive where groundwater is abundant.
"All of this is very useful and it's a great achievement," said Jan Brueckner, a professor of economics at the University of California, Irvine, and the editor of the Journal of Urban Economics. But, he said, "it doesn't get at the fundamental question of whether a city is too built up."
"My idea is it's the spatial size of cities that matter. Their idea is that it's the compactness of development that matters," said Brueckner.
Turner agreed, and in fact, said his team has such data and will be analyzing it extensively until this summer.
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