The suburbs are putting green cities in the red.
Suburban sprawl has been squashing cities' green initiatives, California researchers have found, wiping out the carbon savings from mass transit and other greenhouse gas-reducing boons that come with high-density living.
Researchers at the University of California, Berkeley examined census, household and weather data to develop carbon footprint maps for neighborhoods in more than 31,000 ZIP codes across the country. They resemble Technicolor camouflage, with cities such as New York and Washington, D.C. – which have comparatively small carbon footprints – glowing a healthy green while their surrounding suburbs burn an angry red and orange.
"Metropolitan areas look like carbon footprint hurricanes," Christopher Jones, a doctoral student who assisted professor Daniel Kammen on the project, said in a statement. "Unfortunately, while the most populous metropolitan areas tend to have the lowest carbon footprint centers, they also tend to have the most extensive high-carbon footprint suburbs."
As Kammen described, "Cities are not islands: They exist in a complex landscape."
Suburbs contributed half of all household greenhouse gas emissions across the 31,000 regions researchers looked at, even though they accounted for less than half the population. With residents living in larger houses and driving far more often, researchers determined, the suburbs' emissions were as high as twice the average, while households at the center of dense cities were instead about 50 percent below average.
"A number of cities nationwide have developed exceptionally interesting and thoughtful sustainability plans," Kammen said. "The challenge, however, is to reduce overall emissions."
And a solution won't be one-size-fits-all. California, Kammen pointed out, has low emissions when it comes to electricity usage, but has large emissions from driving. By comparison, parts of the Midwest that get their electricity from coal-fired power plants are the opposite.
The key is "tailored climate strategies," Jones said. "People need to act within their own spheres of influence, where they feel they can make the most difference."
To look up a map of your neighborhood's greenhouse gas emissions, click here.
The study, funded by the National Science Foundation and the California Air Resources Board, was published in the journal Environmental Science & Technology.