Week of 2/13/2005

Dear EarthTalk: What is "sprawl" and how do we keep it in check for the sake of the environment?

—G. Korchowsky, Yardley, PA

Sprawl is the tendency of cities to expand into outlying agricultural and rural lands, creating developed suburbs where there was once open space. The negative effects of sprawl include the loss of parks and farmland, clogged highways and urban decay as people abandon metropolitan centers. It is usually driven by human population increases and—ironically—people's desire to escape the "concrete jungle" to quieter and more natural surroundings.

According to Tim Frank of the Sierra Club, sprawl in fact destroys more than two million acres of parks, farms and other open space each year in the U.S. alone. Further, by spreading development out over large amounts of land, sprawl puts longer distances between homes, stores and job centers, making people more and more dependent upon driving. This reliance on driving in turn leads to more roads and highways that churn up natural landscapes and bring increased smog and pollution.

Staving off sprawl is a complex and often contentious endeavor, with real estate developers pitted squarely against preservationists. The good news is that an association of organizations called the Smart Growth Network (SGN) is working to promote development that boosts the economy while still protecting the environment and enhancing community vitality.

SGN was formed in 1996 by the U.S. Environmental Protection Agency in partnership with several other government agencies and non-profit organizations, including the Sierra Club. Promoting public transportation, keeping farms economically viable, preserving open space and restoring urban centers are key elements of SGN's fight against the negative impacts of sprawl. "What we are doing is carrying out activities to educate people about the consequences of sprawl and help them realize that steps can be taken to create smart growth,” says Frank.

Even the National Aeronautics and Space Administration (NASA) is lending a hand. The agency's NAUTILUS project provides city planners with satellite data to help with decision-making regarding zoning and development. In test regions throughout the northeastern U.S., city planners are working with NASA on developing growth projections based on satellite maps and historical growth trends.

Whether these efforts are any match for the frontier ethic that still dominates American culture is yet to be seen. And with many less developed nations building up their industrial infrastructures, on a global scale the sprawl problem is likely to get worse before it gets better.

CONTACTS: Sierra Club, www.sierraclub.org; Smart Growth Network, www.smartgrowth.org; NASA NAUTILUS program, http://science.nasa.gov/headlines/y2002/11oct_sprawl.htm.

Dear EarthTalk: Are there any environmental benefits to diesel-powered cars?

—Bill Darcy, Concord, NH

The high fuel economy of a diesel-powered vehicle, such as the Volkswagen Golf GL TDI, might seem like a no-brainer choice for anyone looking for a new car that will consume less gas and money. But although the TDI gets far better gas mileage than a similar gasoline-powered Golf, its diesel engine emits considerably more harmful pollutants into the air.

In fact, a Swedish study found that diesel-powered cars in India had twice the cancer potency level of gasoline-powered vehicles in that country, results supported by German research. And the Union of Concerned Scientists (UCS) reports that, in California, diesel exhaust accounts for 70 percent of the cancer risk from that state's polluted air. According to the U.S. Environmental Protection Agency (EPA), the particulates, or soot, in diesel exhaust cause a host of health problems, including: irritation of the eyes, nose and throat; heartburn; headaches and lightheadedness; and asthma and lung disease.

The EPA's Green Vehicle Guide rates cars and trucks on a scale of zero to 10 (10 being the best) based on their emissions of smog-forming pollutants per every 15,000 miles driven. While the gasoline-powered Golf received a rating of seven, emitting just under 12 pounds of pollutants, the Golf TDI got a one, spewing out 44 to 59 pounds over the same distance driven. The gargantuan Ford Excursion and Hummer H2—with gas mileage in the single digits—each received just a two.

Some diesel proponents claim that the increased fuel efficiency of diesel engines could significantly reduce the carbon dioxide emissions responsible for global warming. But, according to UCS, widespread adoption of diesel-powered cars would yield less than a five percent reduction in carbon emissions, while significantly increasing air quality problems.

Under current EPA regulations, diesel vehicles are allowed to emit 16 times more particulates into the air than gas vehicles. However, California is taking the lead in phasing out loopholes that allow diesel cars to out-pollute their gas-powered equivalents, and other states are sure to follow. While pollution from diesel cars has been cut by 80 to 90 percent over the past two decades, it must be reduced another 75 to 90 percent within the next few years just to meet pollution standards in California. Additionally, the federal government recently adopted new "Tier Two" tailpipe standards that will require significant cuts in diesel vehicle emissions nationally.

Drivers looking to minimize their pollution impact while maximizing fuel efficiency would be smarter to ignore diesel offerings and go for a gasoline-electric hybrid like the Toyota Prius or Honda Insight. And once auto makers can resolve refueling infrastructure issues, zero-emission hydrogen-powered fuel cell cars should provide another cost-efficient and environmentally friendly alternative to the gas-guzzlers dominating the road today.

CONTACT: U.S. Environmental Protection Agency Green Vehicle Guide, www.epa.gov/greenvehicles; Union of Concerned Scientists, www.ucsusa.org.