If you want to fight global warming, one good way could be to live in a more compact neighborhood - with more neighbors and jobs close by, and where mass transit, biking and walking are accessible alternatives to the car.
That's a main conclusion of a study out this week by the National Research Council, a unit of the authoritative National Academy of Sciences. The study used Portland as a case study for how denser development coupled with mass transit can reduce gasoline consumption and greenhouse gas emissions.
"The evidence indicates that Portland's policies to steer growth into more compact, mixed use development have paid off, not only in revitalizing the downtown and many of its neighborhoods, but also in changing travel behavior, the primary concern of this study," the report says.
Portland-area residents drive 17 percent less than the U.S. average, because denser development provides shorter travel distances and higher mass transit use reduces driving. From 1993 to 2003, the region's mass transit ridership grew 55 percent and housing density grew 18 percent, while the population grew 21 percent.
The Congressionally mandated report's findings include:
• Making denser residential and employment areas is likely to reduce driving and fuel consumption.
• Doubling residential density across a region could reduce driving by 5 to 12 percent - or as much as 25 percent if accompanied by more employment, mass transit and mixed-use development.
• Obstacles to more mixed use development include reluctance by local governments to zone for it and a lack of state and regional-level involvement in land use planning.
• Americans' preference for low-density suburban homes also challenges the potential for denser neighborhoods.
But how much of a difference could denser development make in the growth of greenhouse gas emissions? A little or a lot?
It could cut emissions by 1 to 11 percent by 2050. That depends on whether the next generation of neighborhoods is built more compact than the dominant trend of sprawl across the nation.
The Research Council's panel, which included Metro Planning Director Andy Cotugno, could not agree on how much denser neighborhoods will be in the next 50 years, so it called for more study on that and related issues.
-- Dylan Rivera; firstname.lastname@example.org