Using a gallon of gas produces about twenty-two pounds of carbon dioxide, if you factor in the carbon used in refining and distributing gasoline. An average family in the United States buys about a thousand gallons of gas a year, which is associated with about ten tons of carbon dioxide. It may be easier to imagine American families buying more fuel-efficient cars than giving up on car-based living altogether, but historically the bulk of variation in gas usage among various people over various periods of time comes from total miles traveled, not from fuel efficiency. Cars now get, on average, about 22 miles per gallon, and the big difference is whether you drive three hundred miles per year or thirty thousand, which depends on whether you live in a city or a suburb.
Kahn and I found that area density and distance to the city center are both strongly associated with gasoline usage. The average household living in a census tract with more than ten thousand people per square mile uses 687 gallons of gas per year, while the average household living in an area with fewer than one thousand people per square mile (about one household per acre) uses 1,164 gallons of gas per year. The density of one’s home neighborhood matters because most car trips aren’t commutes downtown. People drive millions of miles to buy groceries, to go out to eat, and to pick their children up at school. The density of stores and schools in an area determines the average distance of those trips. In a city, you often walk to a restaurant. In a low-density area, eating out might entail a twenty-five-minute drive each way.
Holding family income and size constant, gas consumption per family per year declines by 106 gallons as the number of residents per square mile doubles. These estimates suggest that if the average Northeastern household moved from living at one family per acre to five families per acre, then that family would consume 350 fewer gallons. These facts remind us that mass transit isn’t the only way to lower gas consumption. If people lived in denser areas, they’d travel far fewer miles and burn much less gas, even if they still drove to work.
Public transportation emits carbon too, but most forms of public transit are a lot more energy efficient than driving vast distances in our own personal gas burners. For example, the New York City Transit system uses 42 million gallons of diesel fuel and 14.8 billion megawatts of electricity each year to deliver 2.6 billion trips to its riders. That works out to an average of 0.9 pounds of carbon dioxide per trip—a tenth as much as the nine pounds of carbon dioxide emitted in an average car trip.
Kahn and I predicted the amount of gas that an average family with about $60,000 of income would consume in every census tract and every metropolitan area in the country. While every other area in our sample was associated with more than 1,000 gallons of gas per year, the average household in the New York metropolitan area was connected with fewer than 850 gallons of gas per year. While people in the United States as a whole are more than fifteen times as likely to drive themselves to work as to use public transportation, New York City residents are more than twice as likely to take mass transit as to drive to work.
Throughout the country, big cities mean less driving. On average, when population doubles, per-household carbon dioxide emissions due to driving decline by almost a ton per year. Southern cities have particularly high driving levels, and over 75 percent more gasoline usage than New York. Sunbelt cities like Greenville, South Carolina, Nashville, Tennessee, and Oklahoma City were built at low densities and have widely dispersed employment, and their residents use the most gas.
In almost every metropolitan area, city dwellers consume a lot less gas than suburbanites. Predictably, some of the biggest city-suburb gaps are in older areas, like New York, where the average urban family consumes more than three hundred fewer gallons of gas per year than its suburban counterpart. But some of the largest gaps between cities and suburbs also occur in places like Atlanta and Nashville. It isn’t that central Nashville or Atlanta has so little driving, but that people drive so much in their suburbs. These facts suggest that city density reduces carbon emissions in the older areas of the Northeast, but also in the newer areas that are growing fastest.
Cities are also greener than suburbs because urbanites use less electricity. Electrical appliances account for two thirds of residential energy use. The main factor that explains the difference in energy use among various metropolitan areas is summer heat. Everybody runs refrigerators and appliances, but air conditioning really drives the differences from place to place. The rise of the American Sunbelt in the postwar period owes much to the availability of cheap, cool air. Who would want to put up with Houston’s ninety-nine 90-degree days a year without air conditioning?
America’s lowest electricity-using metropolitan areas are in coastal California and the Northeast. San Francisco and San Jose have the coolest summers in our sample of metropolitan areas, and they’re two of the places that use the least electricity. By contrast, the hot, humid cities of Houston, New Orleans, and Memphis lead the pack in electricity consumption. In these places, the summer months are almost unbearable without an artificial climate.
Warm Julys aren’t the only force driving up electricity usage. Bigger, denser cities, where people own smaller homes, use less electricity. The average single-family detached home consumes 88 percent more electricity than the average apartment in a five-or-more-unit building. The average suburban household consumes 27 percent more electricity than the average urban household. When we standardize for income and family size, we find that central-city residents use less electricity in forty-four out of the forty-eight metropolitan areas that we analyzed. More centralized metropolitan areas, such as New York, Boston, and even Las Vegas, use less electricity than more sprawling places, like Dallas or Phoenix.
In warmer areas of the country, electricity is sometimes used for heating, but natural gas is America’s primary source of warmth, and it is responsible for almost a fifth of residential carbon emissions. Home heating has actually gotten a lot greener over time. We started off burning wood, which emits plenty of carbon, and then moved on to coal, which darkened the skies of American cities until after World War II. Gradually cities started forcing people to switch away from coal, and luckily, just as coal was being phased out, natural gas from the American West became far more available (and George Mitchell made his fortune). Fuel oil, an older source of heat, still accounts for almost a tenth of residential carbon emissions, despite the fact that it is rarely used, because fuel oil emits much more carbon than natural gas.
Home heating emissions make the Snow Belt look less green than temperate California. Detroit and Grand Rapids, Michigan, lead our sample of metropolitan areas in natural gas consumption. Buffalo, Chicago, and Minneapolis are close behind. By contrast, Florida consumes hardly any natural gas. Miami is still pretty warm in January, even at night.
To form a total estimate of household carbon emissions, we just add together the emissions from driving, electricity, and heating, and add public transit. By now, it should be no surprise that cities are greener than suburbs. But the differences between metropolitan areas are even larger than the differences between individual cities and their suburbs. Coastal California is by far the greenest part of the country. The Deep South is by far the brownest. The five greenest metropolitan areas in the country are San Diego, San Francisco, Los Angeles, San Jose, and Sacramento. The five places with the highest carbon emissions per home are Houston, Birmingham, Nashville, Memphis, and Oklahoma City. The gap between these two extremes is dramatic. A household in San Francisco emits 60 percent less carbon than its equivalent in Memphis.
Older places in the Northeast and Midwest lie at various points between these extremes. They use more electricity than California but less than Houston, and they use plenty of energy for heating. New York is one of the greener cities, because of its density. Detroit, being the Motor City, has much higher emissions.
The Unintended Consequences of Environmentalism
So how should we interpret all this data? Simply put, if we wanted to reduce emissions by changing our land-development po
licies, more Americans should live in denser, more urban environments. More Americans should move to coastal California and fewer should live in Texas. California is blessed with a splendid natural climate that doesn’t require much cooling in the summer or heat in the winter. Living in Houston or Atlanta requires a lot more energy for habitability, so then why aren’t more Americans living in California?
The answer certainly isn’t overcrowding. California’s coastal areas are remarkably open. The drive along Route 280 through the heart of Silicon Valley is like a drive through an open Eden. There are about 2 people living on each acre in Santa Clara County. Marin County, just north of the bay, has more than one-and-a-quarter acres per person. By contrast, Montgomery County in Maryland has about 3 people per acre. Cook County, Illinois, has almost 9 people per acre. Manhattan has 111 people per acre, and that isn’t counting the vast crowd of workers that comes and goes each day.
Coastal California could house many millions more than it already does, but the growth in these coastal regions has fallen dramatically from its postwar heyday. Between 1950 and 1970, the population of Santa Clara County more than tripled, from fewer than three hundred thousand to more than one million. But between 1990 and 2008, Santa Clara County grew by only 17.8 percent, less than the national average, from 1.5 million to 1.76 million. Over the last seventeen years, Silicon Valley has been one of the most productive places on the planet, but its population growth has lagged behind the rest of the nation’s.
Coastal California hasn’t grown because it hasn’t built much housing. Any area that doesn’t build much won’t grow much. Coastal California’s construction declines don’t reflect a lack of demand. In 2007, the National Association of Realtors median sales price passed $800,000 in both San Francisco and San Jose. Even after the crash, these places remain the two most expensive areas in the continental United States, with average housing prices around $600,000 in the second quarter of 2010. Prices in California are kept high by draconian limits on new construction, like the sixty-acre minimum lot sizes that can be found in Marin County. These rules are joined with a policy of pulling more and more land off the market as protected parks and wildlife areas. By 2000, one quarter of the land in the Bay Area has become permanently protected, that is, off limits to building.
Many environmentalists see the reduction of development in the San Francisco Bay region as a great triumph. The pioneers of the Save the Bay movement, which formed to block development around the water, have become iconic figures in American environmentalism. The Friends of Mammoth case, which imposed environmental reviews on all new California projects, is seen as a watershed victory. The advocates of California’s growth limitations are often put forward as ecological heroes. But they’re not.
The enemies of development in California are quick to point out that restricting construction is necessary because of the state’s sparse water supplies. Yet California would have more than enough water for its citizens if it didn’t use so much of it irrigating naturally dry farmland. California’s cities and suburbs use about 8.7 million acre-feet of water each year. California agriculture gets subsidized water and uses 34 million acre-feet of water each year for irrigation. America is filled with wet regions that can raise crops. By redirecting water from farm areas to cities, California could easily provide enough water to sustain much higher density levels, which would reduce America’s carbon footprint.
While limits on California’s growth may make that state seem greener, they’re making the country as a whole browner and increasing carbon emissions worldwide. Houston’s developers should thank California’s antigrowth movement. If they hadn’t stopped building in coastal California, where incomes are high and the climate is sublime, then there wouldn’t have been nearly as much demand for living in the less pleasant parts of the Sunbelt.
People who fight development don’t get to choose the amount of new construction throughout the country; they only get to make sure it doesn’t occur in their backyard. At the national level, a principle that could be called the law of conservation of construction appears to hold. When environmentalists stop development in green places, it will occur in brown places. By using ecological arguments to oppose growth, California environmentalists are actually ensuring that America’s carbon footprint will rise, by pushing new housing to less temperate climates.
The 1970 California Environmental Quality Act was a pioneering piece of legislation, which mandated that any local government project have an environmental impact review before it went forward. In 1973, an environmentally activist California Supreme Court interpreted this act to mean not only projects undertaken by local governments, but also projects permitted by local government, which means pretty much any large construction in the state. In 2008, California’s regulations generated 583 environmental impact reviews, considerably more than the 522 impact reviews that occurred nationwide in response to federal guidelines. These impact reviews add costs and delays to new construction, which ultimately make it even more expensive.
The great flaw of environmental impact reviews is their incompleteness. Each review only evaluates the impact of the project if it’s approved, not the impact if it’s denied and construction begins somewhere else, outside the jurisdiction of the California Supreme Court. The incompleteness of these reviews stacks the environmental deck against California construction and makes it seem as though it’s always greener to stop new building. The full impact would note that permitting building in California would reduce construction somewhere else, such as the once pristine desert outside of Las Vegas. Assessing the full environmental cost of preventing construction in California would make that state’s environmental policies look more brown than green.
Two Green Visions: The Prince and the Mayor
Environmentalism is hardly a tidy, well-ordered movement. In the United States, it includes the bird watchers of the Audubon Society and the activists of Greenpeace, the hikers of the Appalachian Trail and the drivers of Toyota hybrids. In Europe, the movement is even more successful and even broader. Any movement that diverse and that successful will inevitably attract individuals with wildly different worldviews, such as His Royal Highness, the Prince of Wales, and “Red” Ken Livingstone, the erstwhile Labour Party politician, who led London, first as head of the Greater London Council between 1981 and 1986 and then as London’s first citywide mayor from 2000 to 2008. Livingstone has said that “climate change caused by CO2 emissions” is “the single biggest problem facing humanity”; Prince Charles has declared climate change to be the “greatest threat to mankind.” They’re both doing their best to help the planet, but they share little else besides their views about mankind’s “biggest threat.”
The prince was born in 1948 in Buckingham Palace and promptly baptized by the archbishop of Canterbury. Livingstone was born three years earlier in Lambeth, the traditionally poor area of London that surrounds the Archbishop’s Palace. Prince Charles received more formal education than any British king, going to elite private schools and Cambridge. Livingstone’s education was spotty, and while still a teenager, he went to work as a lab technician, eventually, as the London Sunday Times reported, “cultivating tumors in the smaller rodents,” before he was elected to the Lambeth City Council in 1971.
While Livingstone spent the 1970s rising in the London-Lambeth Labour Party, Prince Charles was being a dutiful royal, serving in the Royal Navy, flying jets and helicopters, and eventually commanding his own boat, HMS Bronington . A media explosion surrounded the young prince’s Cinderella wedding in 1981 to Lady Diana Spencer. In the same year, Livingstone became head of the Greater London Council, which caused a tabloid known more for its Page Three pictures than for trenchant political analysis to blare the headline “Red Ken Crowned King of London.” Half the world was desperate to see the Prince and Diana’s marriage, but Ken Livingstone refused to attend.
In the 1980s, both men increased their involvement with urban planning. As “King of London,” Livingstone�
�s nascent environmentalism appeared in some areas but not others. Livingstone argued loud and long that low public-transit fares would keep people out of cars and reduce both congestion and pollution. He fought for more housing, but he opposed skyscrapers, especially Richard Rogers’s plans for a “Berlin Wall” of high-rise buildings on the south side of the Thames. At the same time, Prince Charles began to establish his public persona as a patron of sustainable agriculture and a foe of modernism. The Prince of Wales is also Duke of Cornwall, and his Cornish estates provided an opportunity to push for organic farming and reject the high yields of genetically modified food. Just as Prince Charles likes more traditional farming, he likes traditional buildings. In 1984, he made headlines with a tough attack on modernist architecture he delivered in what was expected to be a perfunctory address to the Royal Institute of British Architects.
Prince Charles offered a nostalgic vision that “London before the last war must have had one of the most beautiful skylines of any great city.” By contrast, a proposed modernist extension to the national gallery was “a monstrous carbuncle on the face of a much-loved and elegant friend.” The prince wanted to know “Why has everything got to be vertical, straight, unbending, only at right angles—and functional?” He joined the fight against a proposed Mies van der Rohe-designed modernist tower next to London’s magnificent eighteenth-century Mansion House. Prince Charles called the tower “a giant glass stump better suited to downtown Chicago.” Richard Rogers was one of the many architects supporting the tower (so was my father), but the prince won, sort of. There would be no Miesian tower in London.
Prince Charles’s fight for traditional British architecture continues unabated, as does his fight for his “model community” of Poundbury. In his agricultural estates in Cornwall, the prince is building his vision of an ideal English town, which has been described as looking like “an early Victorian market town, as if architecture stopped in 1830.” His royal patronage has given a great boost to Leon Krier, Poundbury’s planner, who is also one of the intellectual forces behind the New Urbanist movement. The New Urbanism “stand[s] for the restoration of existing urban centers and towns within coherent metropolitan regions, the reconfiguration of sprawling suburbs into communities of real neighborhoods and diverse districts, the conservation of natural environments, and the preservation of our built legacy.”
Triumph of the City: How Our Greatest Invention Made Us Richer, Smarter, Greener, Healthier and Happier Page 26