Build more conveniently located homes in walkable neighborhoods and not only will people get more housing choices, drive times will shrink and that will reduce the nation's carbon footprint.

A carbon footprint isn't some forensic term for the imprint from a sooty sole, but a measure of the impact human activities have on the environment in terms of the amount of greenhouse gases produced.

Greenhouse gasses are caused, in part, by burning fossil fuels -- say gasoline in motor vehicles. The gasses contribute to global warming and, most scientists believe, climate change -- hotter summers, colder winters, more severe storms.

Residential development can substantially contribute to these potentially planet altering greenhouse gasses, for better or for worse, according to "Growing Cooler: The Evidence on Urban Development and Climate Change", a new book chronicling the review of dozens of studies conducted by the Urban Land Institute (ULI).

ULI and its publishing partners -- National Center for Smart Growth (NCSG); Smart Growth America (SGA), and the Center for Clean Air Policy (CCAP) say people who live in compact "green neighborhoods" with shorter drive times, are making a just as large, if not larger, contribution to the global warming fight as those who buy the most efficient hybrid vehicles, but remain in outer lying car-dependent areas.

Unfortunately, planning trends still favor sprawling, auto-dependent development in the hinterlands. If the trend continues fueling more drive time, the projected 59 percent increase in the total miles driven between 2005 and 2030 will erase expected gains from hybrid vehicle efficiency and low-carbon fuels, according to the study.

Hybrid boom or not, because of the growing number of people driven to live in sprawl, vehicle emissions of carbon dioxide would be 41 percent above today's levels, rather than well below 1990 levels as required for climate stabilization by 2050, according to the yet to be published book.

"Curbing emissions from cars depends on a three-legged stool: improved vehicle efficiency, cleaner fuels, and a reduction in driving," said lead author Reid Ewing, a research professor at the National Center for Smart Growth, University of Maryland. "The research shows that one of the best ways to reduce vehicle travel is to build places where people can accomplish more with less driving."

Like live-work environments, for example.

The new book is in line with the recently released Consumer Electronics Association report that says if a worker with a one-way commute of 22 miles, instead telecommutes five days a week, he or she would save about 320 gallons of gasoline and reduce CO2 emissions by 4.5 to 6 tons per year.

In a year, the individual's energy savings would amount to approximately 4,000 to 6,000 kilowatt-hours of electricity -- an amount comparable to the electricity consumed by an average household in 4 to 6 months.

Hybrids are a good idea. Driving at lot less, even with a hybrid is an even better idea.

Depending on several factors, from mix of land uses to pedestrian-friendly design, compact development reduces driving from 20 to 40 percent, and more in some instances, according to the study's authors. Typically, Americans living in compact urban neighborhoods where cars are not the only transportation option drive a third fewer miles than those in automobile-oriented suburbs, the researchers found.

Despite the every larger average sized home bandied about by developers, there is documented growth in demand for smaller homes and lots, townhomes, condos in areas where jobs and destinations are nearby.

The Urban Land Institute's "Lack of Affordable Housing Near Jobs," for instance.

In addition to seeking less expensive home near work, some of the demand is coming from dramatic demographic changes, shrinking households, rising gas prices, lengthening commutes and cultural shifts.

Shift 60 percent of new growth patterns to reduce sufficient carbon emissions and the shift could equate to a 28 percent increase in federal vehicle efficiency standards by 2020 (to 32 mpg), a standard currently debated in Congress.

It's not just about building green houses, but green communities.

"Clearly, the development industry has a key role in the search for solutions to offset the impact of climate change," said ULI Fellow William H. Hudnut, III, former mayor of Indianapolis.

"Whether close-in or in suburbs, well-planned communities give residents the option to walk, bike or take transit to nearby shopping, retail and entertainment. Being able to spend less time behind the wheel will benefit our health, our pocketbooks and the environment."

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