Sprawl: a problem without a solution?

Dueling headlines cropped up in my newsreader today:

> More People, Less Driving: The Imperative of Curbing Sprawl (Smart Growth America)

Vs.:

> Forget Curbing Suburban Sprawl: Building denser cities would do little to reduce CO2 emissions, a new NAS report concludes (MIT Technology Review)

Both articles refer to the same study, conducted by a blue-ribbon panel for the U.S. Department of Energy. And both are pretty much right: the study does affirm the link between sprawl and carbon emissions, but it also strongly suggests that attacking sprawl is a tough way to curb energy use.

Despite the common-sense link between density and driving, establishing cause and effect in a rigorous manner remains difficult. The sheer number of variables tend to overwhelm the analysis. Nevertheless, empirical evidence does support a link between land use and vehicle miles traveled (VMT). The MIT Technology Review summarizes the study’s conclusion thusly:

> Even if 75 percent of all new and replacement housing in America were built at twice the density of current new developments, and those living in the newly constructed housing drove 25 percent less as a result, CO2 emissions from personal travel would decline nationwide by only 8 to 11 percent by 2050, according to the study. If just 25 percent of housing units were developed at such densities and residents drove only 12 percent less as a result, CO2 emissions would be reduced by less than 2 percent by 2050.

In other words, an enormous shift in land development trends yields a roughly 10% cut in emissions over 40 years. A more modest shift in land development trends yields a fairly anemic drop in emissions over 40 years. Vehicle fuel efficiency provides a much bigger lever for lowering emissions from transportation. This is what I was getting at the other day when I said, “If your car runs on electricity, and your electricity comes from the sun, and your McMansion is built to the Passive House standard, then your suburban lifestyle is suddenly looking a lot more benign.”

All that being the case, the study sensibly recommends a variety of policies to promote compact, mixed-use development. There are a number of good reasons to pursue smart land use policies, even if attacking sprawl isn’t likely to save us from climate change in the near- or even medium-term.

The first is that many anti-sprawl measures are just good policy in their own right. Carbon taxes, gas taxes, transit development, better zoning laws, etc., all make sense regardless of their immediate payback in reduced gasoline consumption. And, of course, sprawl has environmental impacts beyond just VMT.

The second is that we’re stuck with our built environment for a very long time, so if we want the future to look different than the past, we had better get started making some changes. As Ryan Avent reminds us, “Between now and mid-century, the country will very nearly have to build itself all over again to accommodate population growth. In addition to the 100 million homes now in America, somewhere between 62 and 105 million more will be built.” Examples such as Portland show that it is possible to buck the dominant trend in development. But it takes a few decades for the results to really show.

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  1. Woody - September 9, 2009

    Infinitely complex calculations using guestimated numbers will lead to inaccurate conclusions.
    K-I-S-S: Fewer people = fewer carbon emissions.
    Support family planning locally, nationally and worldwide while paring down CO2 emissions as well.

  2. Jeb - September 9, 2009

    Urban apartments and condos are also much more energy efficient and require less water than traditional suburban developments. The carbon benefits are not limited to just fewer VMT.

  3. michael - September 9, 2009

    I for one do not like computers, especially for my ecologically sentive job. However, computers may hold a place for many of us by allowing us to perform more work from home…but we have to look at our jobs in a different way…I know that I could shave 3 commuting days off my daily grind with a shift in thinking but management here is just plain afraid of “unknown limitations”. They’re extremely disruptive and do not plan well – but, can you imagine shaving three commuting days from your daily grind?
    The other benefit – in particular to my circumstances – is our offices are on many physical levels. If we share space on one level we do not need to heat and cool the other levels…while I am also heating and cooling my house at home.
    Chaning the physical look of our villages, towns and cities may prove to be too costly – in terms of money and added co2…habits have to change first.

  4. demockracy - September 10, 2009

    First of all, I doubt the study is going to be helpful unless it studies something besides density as a remedy to driving. There are plenty of sprawl proponents (Wendell Cox, for one) who will use such lies, damned lies and statistics to prove that sprawl is the only realistic way to build (and who will tell you sprawl is preferred by the market — another lie).
    Meanwhile, it’s pretty uncontroversial that 70% of U.S. petroleum consumption comes from transportation (just over 50% is commuting), so building neighborhoods that are more compact would, of necessity, reduce commuting distances at least.
    But what really reduces vehicle miles traveled and congestion is pedestrian-friendly mixed use (see http://www.dpz.com/transect.aspx for an illustration and lots more info). This is not exotic new knowledge; it’s how we built most cities before 1950.
    Of sprawl, urbanist Jane Jacobs says: “The pseudo science of planning seems almost neurotic in its determination to imitate empiric failure and ignore empiric success.
    “…to put it bluntly, [sprawl planners] are all in the same stage of elaborately learned superstition as medical science was early in the last century, when physicians put their faith in bloodletting.”
    The pedestrian-friendly, mixed-use alternative also happens to be preferred by the market to the point that actual buyers (not theorists) pay premiums to live in such neighborhoods.
    Depending on how the pedestrian-friendly mixed-use alternative is configured, VMT (vehicle miles traveled) declines by 1/3 to 2/3.
    Incidentally, viable transit is *only* possible when customers can walk to the stops (“pedestrian-friendly” means just that). So any alternative to the single-occupant auto has to include this alternative.
    We don’t need to invent a car powered by exotic fuels (radioactive cat farts?). We already have 100mpg cars. They’re called “buses.”
    Building such neighborhoods is a no-brainer, really, thwarted primarily by inertia, big-box stores, and sprawl-oriented studies that pretend they’re telling you the whole story when really all they promote are half truths.

  5. Ed - September 12, 2009

    I’ve read that the super-rich, who can afford to live anywhere, tend to live where there’s either abundant green space or water nearby. I would guess that the not-super-rich, if they have a choice, would make a similar decision. Which means that suburbs, with more green space than the central city, happen because that’s what people want. Which also implies that if the central city had more green space more people would choose to live there.
    For the last few years there have been a lot of For Sale signs in all parts of town. As the economy and housing market recover, it’ll be interesting to see where people choose to buy a house. My guess is that a lot will depend on the price of gas.
    It would also be swell if the city commissioners who decide on Urban Development Boundaries and Downtown Redesigns had the wisdom and foresight to plan for when they’re no longer in office, but I’m not holding my breath.

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