In 2001, Scott Bernstein, at the Center for Neighborhood Technology in inner-city Chicago, produced a set of maps that are still changing the way we think about our country. In these maps, remarkably, the red and the green switched places. This reversal, perhaps even more than the health discussion, threatens to make walkability relevant again.

By red and green, I am referring to carbon emissions. On typical carbon maps, areas with the greatest amount of carbon output are shown in bright red, and those with the least are shown in green, with areas in between shown in orange and yellow. Basically, the hotter the color, the greater the contribution to climate change.

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Historically, these maps had always looked like the night-sky satellite photos of the United States: hot around the cities, cooler in the suburbs, and coolest in the country. Wherever there are lots of people, there is lots of pollution. A typical carbon map, such as that produced in 2002 by the Vulcan Project at Purdue University, sends a very clear signal: countryside good, cities bad.

For a long time, these were the only maps of this type, and there is certainly a logic in looking at pollution from a location-by-location perspective. But this logic was based on an unconsidered assumption, which is that the most meaningful way to measure carbon is by the square mile. It isn't.

The best way to measure carbon is per person. Places should be judged not by how much carbon they emit, but by how much carbon they cause us to emit. There are only so many people in the United States at any given time, and they can be encouraged to live where they have the smallest environmental footprint. That place turns out to be the city -- the denser the better.

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For this reason, when Bernstein replaced carbon per square mile with carbon per household, the colors simply flipped. Now the hottest areas in each American metropolitan area -- and their web site shows hundreds, from Abilene to Yuma -- are inevitably the outer suburbs. The coolest are smack-dab in the center of town.

To be accurate: Bernstein's maps have a limitation. They do not show full carbon output; they only show CO2 from household automotive use -- data that are much easier to collect. But this limitation turns out to be useful, for several reasons: first, because it causes us to confirm that automobile use is not only the single greatest contributor to our total carbon footprint, but also a reliable indicator of that total; and second, because limiting our greenhouse gas emissions, for many, is a much less pressing issue than our dependence on foreign oil.

You can't spell carbon without car

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At last measure, we are sending $612,500 overseas every minute in support of our current automotive lifestyle. Cumulatively, over recent decades, this has amounted to a "massive, irreversible shift in wealth and power from the United States to the petro-states of the Middle East and energy-rich Russia." This cash transfer, which is quickly working its way up to a third of a trillion dollars each year, is building some truly stunning metrorail systems in Dubai and Abu Dhabi -- our cars are buying their trains. Add to this amount the significant chunk of our $700 billion military budget that is used to protect these questionable foreign interests, and it's easy to see how our oil appetite could undo us economically long before the oil begins to run dry.

Do electric cars present an answer to this challenge? Certainly hybrids don't. Their marginally improved gas mileage mostly offers a feel-good way to drive more miles in increasingly larger vehicles. I always get angry when I see a "Hybrids Only" municipal parking space, knowing that it welcomes a 21-mpg Chevy Tahoe Hybrid but not a conventional 35-mpg Ford Fiesta. You could (theoretically) drive two 1990 Geo Metros at once and still beat the Tahoe.

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In contrast, the all-electric car seems to hold some real promise for curtailing our foreign oil addiction -- but at what environmental cost? In most of the United States, an electric-powered car is essentially a coal-powered car, and "clean coal" is of course an oxymoron. Both in its extraction and its combustion -- replacing a hydrocarbon with a pure carbon -- coal can make oil look positively green.

To be perfectly accurate, electric cars are currently a bit greener than gasoline cars -- per mile. Driving one hundred miles in a Nissan Altima results in the emission of 90.5 pounds of greenhouse gases. Driving the same distance in an all-electric Nissan Leaf emits 63.6 pounds of greenhouse gases -- a significant improvement. But while the Altima driver pays 14 cents a mile for fuel, the Leaf driver pays less than 3 cents per mile, and this difference, thanks to the law of supply and demand, causes the Leaf driver to drive more.

How much more? We don't know. But we do know what happened in Sweden, where aggressive government subsidies have led to the world's highest per-capita sales of "clean" cars. The results are in, and, shockingly, "greenhouse gas emissions from Sweden's transportation sector are up." As reported by Firmin DeBrabander:

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But perhaps we should not be so surprised. What do you expect when you put people in cars they feel good (or at least less guilty) about driving, which are also cheap to buy and run? Naturally, they drive them more. So much more, in fact, that they obliterate energy gains made by increased fuel efficiency.

Electric vehicles are clearly the right answer to the wrong question. This fact becomes even clearer when we note that tailpipe emissions are only one part of the footprint of motoring. As described by the strategic consultant Michael Mehaffy, this footprint includes "the emissions from the construction of the vehicles; the embodied energy of streets, bridges and other infrastruture; the operation and repair of this infrastructure; the maintenance and repair of the vehicles; the energy of refining fuel; and the energy of transporting it, together with the pipes, trucks, and other infrastructure that is required to do so. These add an estimated 50 percent more pollution to the atmosphere than emissions alone.

But that's just the beginning. A much larger multiplier effect comes from the way that all of our other nonautomative consumption patterns expand as we drive. In "Green Metropolis," David Owen puts it this way:

The real problem with cars is not that they don't get enough miles per gallon; it's that they make it too easy for people to spread out, encouraging forms of development that are inherently wasteful and damaging ... The critical energy drain in a typical American suburb is not the Hummer in the driveway; it's everything else the Hummer makes possible -- the oversized houses and irrigated yards, the network of new feeder roads and residential streets, the costly and inefficient outward expansion of the power grid, the duplicated stores and schools, the two-hour solo commutes.

So, while I have gone to great efforts to explain how the way we move is more important than the way we live, it turns out that the way we move largely determines the way we live.

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Missing the forest for the trees

When we built our new house in Washington, we, too, did our best to clear the shelves of the sustainability store. We put in bamboo floors, radiant heating, double-thick insulation, dual-flush toilets, a solar water heater, and a 12-panel, 2.5 kilowatt solar photovoltaic system. A pine log crackling in our high-tech wood-burning stove supposedly contributes less pollution to the atmosphere than if it were left to decompose in the forest.

Yet all these gadgets cumulatively contribute only a fraction of what we save by living in a walkable neighborhood. It turns out that trading all of your incandescent lightbulbs for energy savers conserves as much carbon per year as living in a walkable neighborhood does each week. Why, then, is the vast majority of our national conversation on sustainability about the former and not the latter? Witold Rybczynski puts it this way:

Rather than trying to change behavior to reduce carbon emissions, politicians and entrepreneurs have sold greening to the public as a kind of accessorizing. "Keep doing what you're doing," is the message, just add another solar panel, a wind turbine, a bamboo floor, whatever. But a solar-heated house in the suburbs is still a house in the suburbs, and if you have to drive to it -- even in a Prius -- it's hardly green.

We planners have taken to calling this phenomenon "gizmo green"; the obsession with "sustainable" products that often have a statistically insignificant impact on the carbon footprint when compared to our location. And, as already suggested, our location's greatest impact on our carbon footprint comes from how much it makes us drive.

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This point was pounded home in a recent EPA study, "Location Efficiency and Building Type -- Boiling It Down to BTUs," that compared four factors: drivable versus walkable location; conventional construction versus green building; single-family versus multi-family housing; and conventional versus hybrid automobiles. The study made it clear that, while every factor counts, none counts more than walkability. Specifically, it showed how, in drivable locations, transportation energy use consistently tops household energy use, in some cases by more than 2.4 to 1. As a result, the most green home (with Prius) in sprawl still loses out to the least green home in a walkable neighborhood.

It is important that the EPA is doing its best to share the good news on how location trumps building design, but who is listening? Certainly not the EPA. A mere month after releasing the above study, the agency announced that it was relocating its 672-employee Region Seven Headquarters from downtown Kansas City to the new far-flung suburb of Lenexa, Kansas. Why are they moving 20 miles out of town into a former Applebee's office park? Well, because the building is LEED (green) certified, of course.

Kaid Benfield, a long-serving environmental watchdog at the National Resources Defense Council, did some numbers, and he found that while "an average resident in the vicinity of the current EPA Region Seven headquarters emits 0.39 metric tons of carbon dioxide per month ... the transportation carbon emissions associated with the new location are a whopping 1.08 metric tons per person per month ... one and a half times the regional average."

These numbers are, of course, just a stand-in for the actual increased carbon footprints of the EPA's staffers, most of whom will probably not move from their current homes. Presuming these employees' houses are distributed around Kansas City in the normal manner, the vast majority will have their commutes lengthened, many by 20 miles or more each way. Those who need to take transit to work will now have to get on the highway.

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This would be funny if it weren't so sad. The carbon saved by the new building's LEED status, if any, will be a small fraction of the carbon wasted by its location. This type of missing the forest for the trees is what David Owen calls "LEED Brain." Many governments and corporations -- and they are to be congratulated -- have committed themselves to LEED-rated building construction, including the federal government, New York, Chicago, San Francisco, the District of Columbia and a boatload of others. The list is getting longer every day, and it seems to have reached a tipping point where you can't get hired as an architect without becoming LEED accredited.

Urban location is indeed one of the factors that contributes to a building's LEED building rating, but it is only one of many factors, such that the overall carbon savings created by downtown locations are almost always undercounted. And because it's better than nothing, LEED -- like the Prius -- is a get-out-of-jail-free card that allows us to avoid thinking more deeply about our larger footprint. For most organizations and agencies, it is enough. Unfortunately, as the transportation planner Dan Malouff puts it, "LEED architecture without good urban design is like cutting down the rainforest using hybrid-powered bulldozers."

Manhattan as Mecca

If -- in America -- dense, transit-served cities are better, then New York is the best. This is the clear and convincing message of David Owen's "Green Metropolis," certainly the most important environmental text of the past decade. The book deserves a bit more of our attention, so profound is the revolution in thinking it represents.

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As Owen himself notes, the environmental movement in the United States has historically been anti-city, as has so much American thought. This strain traces its roots back to Thomas Jefferson, who described large cities as "pestilential to the morals, the health and the liberties of man." Not without a sense of humor, he went on: "When we get piled up upon each other in large cities, as in Europe, we shall become as corrupt as in Europe, and go to eating one another as they do there."

Given that the U.S. population in 1780 was less than 1 percent of its current total, it is easy to understand why Jefferson did not see anything but good in its dispersal. With what must have seemed to be both infinite land area and resources, there was no reason not to stretch our legs, especially since the greatest by-product of transportation was fertilizer.

Unfortunately, over the next 200 years, the American anti-urban ethos remained intact as everything else changed. The desire to be isolated in nature, adopted en masse, led to the quantities and qualities we now call "sprawl," which somehow mostly manages to combine the traffic congestion of the city with the intellectual culture of the countryside. Now that the full environmental impacts of suburban development are being measured, a new breed of thinkers is finally turning the old paradigm on its head. These include David Owen -- like Jane Jacobs, a mere writer -- and the economist Ed Glaeser, who puts it this way: "We are a destructive species, and if you love nature, stay away from it. The best means of protecting the environment is to live in the heart of a city."

And no American city performs like New York. Owen's back, which was originally to be called "Green Manhattan," is stuffed full of astounding data. The average New Yorker consumes roughly one-third the electricity of the average Dallas resident, and ultimately generates less than one-third the greenhouse gases of the average American. The average resident of Manhattan -- New York at its most New Yorky -- consumes gasoline "at a rate that the country as a whole hasn't matches since the mid-1920s." And so on.

New York is our densest big city and, not coincidentally, the one with the best transit service. All the other subway stations in America put together would not outnumber the 468 stops of the MTA. In terms of resource efficiency, it's the best we've got. But why stop there? Other places, with a variety of densities and transit options, do much better. Sure, New York consumes half the gasoline of Atlanta (326 versus 782 gallons per person per year). But Toronto cuts that number in half, as does Sydney -- and most European cities use only half as much as those places. Cut Europe's number in half, and you end up with Hong Kong. If 10 Hong Kongers were to move to New York with the goal of keeping their gasoline consumption unchanged, nine of them would have to stay at home.

These numbers become especially meaningful as we consider the impacts of peak oil prices in the years ahead. What city, or country, is likely to be the most competitive in the face of $200-per-barrel oil? Paris is one place that has determined that its future depends on reducing its auto dependence. The city has recently decided to create 25 miles of dedicated busways, introduced 20,000 shared city bikes in 1,450 locations, and committed to removing 55,000 parking spaces from the city every year for the next 20 years. These changes sound pretty radical, but they are supported by 80 percent of the population.

Happy urbanism

Stories and numbers like these are truly intimidating and potentially demotivating. Why even bother trying when other countries are so far ahead?

Back in 1991, the Sierra Club's John Holtzclaw studied travel habits in 28 California communities of widely varying residential density. He found, as expected, an inverse relationship between urbanity and driving miles. But, perhaps not expected, he also found his data points distributed around a pretty sharp curve, with most of the gains in efficiency occurring early on. Increasing housing density at the suburban end of the scale had a much greater impact than at the urban end, such that the vast majority of the driving reduction occurred in the switch from large-lot sprawl to densities of 10 to 20 units per acre. These densities represent a traditional urbanism of apartments, row houses, and, yes, some freestanding single-family homes. In contrast, the further concentrations of households at higher densities -- even above 100 per acre -- while helpful, produced less dramatic results.

He subsequently conducted similar studies in New York and Los Angeles, and found the data tracking along almost identical curves. In each case, increasing density from two units per acre to 20 units per acre resulted in about the same savings as the increase from 20 to 200. To students of urban form, these outcomes are not that surprising because 10 to 20 units per acre is the density at which drivable suburbanism transitions into walkable urbanism. There are, of course, some (rather horrid tower-in-the-parking-lot) exceptions, but most communities with these densities are also organized as traditional mixed-use, pedestrian-friendly neighborhoods, the sort of accommodating environment that entices people out of their cars. Everything above that is icing on the cake.

That means that while Americans might have a long way to go to match European or Asian sustainability, a little effort can get us a lot closer. But not every American is motivated by concerns about climate change or peak oil, and even among those of us who are, it is not always easy to turn that intention into action. Certainly, unless we hit a national crisis of unprecedented severity, it is hard to imagine any argument framed in the language of sustainability causing many people to modify their behavior. So what will?

The gold standard of quality-of-life rankings is the Mercer Survey, which carefully compares global cities in the 10 categories of political stability, economics, social quality, health and sanitation, education, public services, recreation, consumer goods, housing, and climate.

Its rankings shift slightly from year to year, but the top 10 cities always seem to include a bunch of places where they speak German (Vienna, Zurich, Dusseldorf, etc.), along with Vancouver, Auckland, and Sydney. These are all places with compact settlement patterns, good transit, and principally walkable neighborhoods. Indeed, there isn't a single auto-oriented city in the top 50. The highest-rated American cities in 2010, which don't appear until No. 31, are Honolulu, San Francisco, Boston, Chicago, Washington, New York, and Seattle.

The Economist magazine has its own ranking that, although it uses Mercer data, tends to turn out a bit differently. It has been criticized as favoring Anglophone countries, which -- although no help to the United States -- means that eight of its top 10 cities are in Canada, Australia, and New Zealand. But all are places that are better for walking than driving.

Whomever you want to believe, the message is clear. Our cities, which are twice as efficient as our suburbs, burn twice the fuel of these European, Canadian, and Aussie/Kiwi places. Yet the quality of life in these foreign cities is deemed higher than ours by a long shot. This is not to say that quality of life is directly related to sustainability, but merely that many Americans, by striving for a better life, might find themselves moving to places that are more like the winners -- or better yet, might try transforming their cities to resemble the winners. This sort of transformation could include many things, but one of them would certainly be walkability.

Vancouver, British Columbia, No. 1 in the Economist's ranking, proves a useful model. By the mid-20th century, it was fairly indistinguishable from a typical U.S. city. Then, beginning in the late 1950s, when most American cities were building highways, planners in Vancouver began advocating for high-rise housing downtown. This strategy, which included stringent requirements for green space and transit, really hit its stride in the mid-1990s, and the change has been profound. Since that time, the amount of walking and biking citywide has doubled, from 15 percent to 30 percent of all trips. Vancouver is not ranked No. 1 for livability because it is so sustainable; the things that make it sustainable also make it livable.

Quality of life -- which includes both health and wealth -- may not be a function of our ecological footprint, but the two are deeply interrelated. To wit, if we pollute so much because we are throwing away our time, money, and lives on the highway, then both problems would seem to share a single solution, and that solution is to make our cities more walkable. Doing so is not easy, but it can be done, it has been done, and indeed it is being done in more than a few places at this very moment.

Excerpted from "Walkable City: How Downtown Can Save America, One Step at a Time" by Jeff Speck, to be published November 13th by Farrar, Straus and Giroux, LLC. Copyright (c) 2012 by Jeff Speck. All rights reserved.