JUL 24, 2012
One need not look far to find a passionate argument that the compact city is the green city. Having more people in a smaller area results in less energy use for transportation purposes, lower greenhouse gas emissions, and greater efficiencies in the use of various resources. Cramming more people into a smaller space makes our cities more sustainable. Or does it? New research published in the spring issue of the Journal of the American Planning Association finds that – unlike today's dominant narrative of the green city – urban form may actually have very little impact on energy use and other measures of sustainability.
Researchers from the universities of Cambridge, Newcastle, and Leeds looked at three English metropolitan areas of various sizes and ran them through computer models that imposed three different urban forms over the course of 30 years. Each area was modeled as a hyper-dense city with tight restrictions on land use, an urban growth boundary and prioritized transit development, a sprawling, market-driven urban form that had few restrictions on land use, and a middle ground based on English new towns, or those planned suburban-style developments on the outskirts of larger cities. Each urban form – compaction, dispersal, expansion – was modeled on the three areas between the years 2001 and 2031 and evaluated on the basis on 26 different measures of sustainability – from pollution levels to degradation of water systems to the energy consumption of buildings and people. The models showed only very slight differences between the three urban forms.
"To our surprise, if you compare the compact form versus the current trend, the difference in reduced transport by automobile is very minor. And if you allow the city to expand, the increase in the use of the car is only marginal," says Marcial Echenique, a professor at the University of Cambridge Department of Architecture and one of the authors of the report. "If you make the city more compact, it doesn't mean that people will abandon their car. Only 5 percent of people abandon the use of the car. Ninety-five percent carries on using the car, which means there are more cars on the same streets, therefore there is much more congestion and therefore there is much more pollution and no great increase in the reduction of energy."
Echenique says he and his team have been working on this research for about 4 or 5 years, and continued modeling and analysis has only backed up their findings.
"We are not very convinced of the idea that compacting cities will make very much difference in terms of environmental quality. But it will have severe consequences in terms of economics and social issues," Echenique says.
Of particular concern for these researchers is that restricting development to only high-density, urban locations could greatly increase the cost of land and housing, causing both the cost of living and the cost of doing businesses to skyrocket. Echenique worries this will cause cities to become less competitive over the long term.
In terms of reducing the environmental impacts of human development and lifestyle, Echenique says his numbers indicate that we might be better off focusing our effort on improving technology and energy efficiency. He says we'll have a much better chance of reducing the negative impacts of modern living by focusing on automobile technology and reduced energy usage in buildings. He and his team are currently working on research on the effectiveness of focusing on the technology side. Results are expected to publish later this year.
"We believe that we can reduce by 50 percent or more the use of energy in a fairly short time, within the next 20 years or so," he says. "It's much more effective than compacting or dispersing cities, because there's only a five percent difference either way."
Echenique argues and his research indicates that greater gains can be achieved by making more efficient cars or better insulation for buildings than by trying to reshape the urban landscape.
"Technology offers a much better future than trying to constrain behavior of the market," he says.
The result of this work will likely be somewhat frustrating for urban boosters arguing for an increased emphasis on density and city living. Echenique recognizes that urbanization is underway, especially in developing countries, and that density will likely be the development paradigm in many of these places. But he also observes that urbanization is happening on a metropolitan scale, and that means development is occurring at a variety of densities within a region. Valuing one over the others as the sustainable model is unwise, he argues. He says this research shows that creating sustainable places has little to do with what they look like and far more to do with their energy use.