This Tuesday I attended the “Earth Day Rollout” of a new book detailing the relationship between urban development and climate change.

Intuitively, it would seem logical to conclude that compact cities release less greenhouse gasses on a per capita basis than low density ones. We might hypothesize compact cities shorten distances between destinations, encourage walking and biking for short trips, and encourage public transportation use. It may also be more energy efficient to heat and cool the housing in more compact cities.

Amazingly, many scholars disagree. Just one year ago UCLA professor Randall Crane stated on his blog “how discretionary land use decisions can best address global warming is virtually unknown.” Crane is co-author of a 240-page research survey on the relationship between urban form and travel. At the root of the issue is the difficulty of disentangling person preferences, culture, and the physical environment. Even if urban residents use much less energy per capita, it may be because of socio-economic or so-called “self selection” factors. This scholarly ambivalence has left the planning profession at the sidelines of the global warming debate. Despite a striking cover on last September’s Planning magazine (found in the mailboxes of most American urban planners) the articles inside were sadly disappointing, with few meaningful strategies presented. As a sign of the profession’s state, one reader wrote in to complain “other theories also explain the same observed data,” contrasting modern global warming theory with urban renewal theories of the 1950s. Another letter expressed disappointment over the lack of an article summarizing recommendations about what to do.

There are signs this is changing. A draft policy guide currently being considered by the American Planning Association on climate change features as its first two policy findings that land use patterns play a “significant” role in reducing vehicle miles traveled (VMT), and that parking and transportation policies can be employed to “discourage” private auto use.

This is precisely the case Ewing and his co-authors make in Growing Cooler. In essence, they argue that even if alternative fuel vehicles are phased in aggressively and the gas mileage of vehicles is increased to 50 miles per gallon, the U.S. will be far from meeting its goal of reducing CO2 emissions. The reason is that travel growth is expected to continue to grow rapidly along with rising population and economic growth. They find that people living in compact neighborhoods drive roughly 20 to 40 percent less than the residents of sprawling areas. They define compact neighborhoods by five criteria — the five D’s — density, diversity of land uses, design, destination access, and distance to transit. In the aggregate, a national smart growth policy could cut transportation CO2 emissions by 7 to 10%. Since transportation is only responsible for 33% of total U.S. CO2 emissions the role of Smart Growth is modest, but significant factor.

The authors point out compact development is a particularly attractive strategy to combat climate change because the emissions savings are permanent, it also results in public health and environmental gains, and may result in additional greenhouse gas savings through more energy-efficient homes. We know people buy smaller houses in compact communities, and even if the size of their units don’t decrease, row homes and condos are more energy efficient to heat and cool than freestanding homes. (Indeed, my neighbor told me his heating bill dropped significantly when our row house was remodeled after being vacant for many years.) Chapter 9 on “Policy and Program Recommendations” offers a wide range of suggestions, from a reformed federal transportation policy in the form of a “Green-TEA” law and national cap-and-trade system, to a variety of proposals at the regional, state, and local levels to create compact development patterns. I’m happy to see the very last proposal listed “Invest in Civic Engagement and Education.” Recognizing that “successful planning requires the meaningful engagement of people who live and work in the affected community,” the authors call on “planners and decision makers [to] actively seek out public input early in the planning process.” After all, under our urban planning system local communities have the biggest role to play determine the form of our cities. This book makes the case their decisions will play a critical role in our effort to combat global warming.

> ULI: Growing Cooler
> Smart Growth America: Growing Cooler: The Evidence on Urban Development and Climate Change