In Defense of Density

Judge Glock’s recent article “Sprawl Is Good: The Environmental Case for Suburbia” provides a much-needed suppressant for the most feverish of pro-density ambitions. Glock’s core arguments are that low-density development aligns better with many Americans’ preferences than densification and that low-density development—sprawl, in other words—is not the environmental calamity urbanists make it out to be. Each of these points conveys important truths.

As Glock documents with data on commuting patterns and American cities’ relative population growth in the last half century, the suburban lifestyle has enduring pull. Moreover, as technology advances, the environmental costs associated with that lifestyle are falling. Glock recommends that urban advocates and policy makers take heed of such trends.

Strong though Glock’s piece is, his environmental claims in favor of sprawl may go too far and risk unduly tilting policy makers toward the suburbs. Contrary to Glock’s intentions, doing so could undermine people’s pursuit of their preferred lifestyles and would potentially leave us worse off environmentally as well.

Sprawl Marches On

Judging by the tenor of YIMBY meetups, one may deduce that the only appropriate way for human beings to live is to share walls with their neighbors, shop in the market on the ground floor, and take public transit when destinations fall out of walking distance. To deviate from this lifestyle of frequent social interaction may beget anomie, just as isolation in suburban enclaves may admit xenophobia. This conception of the suburbs, however, is wound up in the American experience and ignores millennia of urban sprawl around the world.

While the train and automobile accelerated modern suburbanization, the phenomenon is as old as cities themselves. Indeed, as University College London scholar Laura Vaughan has described, a 2,500-year-old carved stone relief of the ancient Persian city of Madaktu shows a clear distinction between the city itself and the manicured suburban villas outside its walls. Then as now, our decisions to live in the city or outside involve a complex, personal, and subjective triangulation among living space, cost, and convenience.

Some people willingly compromise on space and cost to live in happening neighborhoods. As Glock notes, dense urban settings like Manhattan, San Francisco, and Washington, DC abound with professional and social opportunities and, as a result, are engines of innovation. Other people, particularly if they choose to form families, view the trade-offs differently and compromise on convenience and economic and social opportunities in order to get more space at lower per-foot expense.

To stress a point Glock makes, cities like Austin, Nashville, and Phoenix are growing faster than places like New York and San Francisco, and they have been given a significant boost by the COVID-induced work-from-anywhere revolution. According to Zillow, in 2022, the hottest housing markets in the country will be low-density cities in Sun Belt states like Florida, North Carolina, and Texas. Not one city in the Northeast or on the Pacific Coast makes the top 10 list.

Another of Glock’s points is that the advancement of technology has brought down the energy requirements of modern living and the environmental costs of a low-density lifestyle. To cite a few broad trends, both per-capita electricity use and per-capita vehicular emissions are on the decline. After rising an average of 3 percent each year from 1960 to 2010, US residential per-capita electricity use has fallen by 5 percent in the last decade. Since 1975, the per-mile carbon dioxide emissions of the average car in the United States has been cut almost in half. And taking into account all on-road vehicles in the United States, greenhouse gas emissions were lower in absolute terms in 2019 than in 2005, despite total vehicle miles traveled having climbed by 9 percent.

These trends are consistent with the wonder of “dematerialization” that MIT researcher Andrew McAfee celebrates in his 2019 book, More from Less. As McAfee writes, “we’re now able to improve the human condition while also treading more lightly on the world: consuming fewer resources, using less cropland, reducing pollution, bringing back species we’d pushed to the brink of extinction, and so on.” Glock brings these points to the fore.

Wrong Turns

Nevertheless, Glock makes several claims to support sprawl that go beyond the data or omit key information.

If we assume global greenhouse gas emissions are a significant problem, as Glock indicates he does, we ought to recognize that despite efficiency improvements, the United States is still a prodigious per-capita emitter. The displacement of coal-fired electricity by natural gas and automobiles’ miles-per-gallon gains have made a real dent in the country’s cumulative greenhouse gas output, but Americans on average still emit nearly twice as much carbon annually as the average person in Japan or Germany. This discrepancy can largely be attributed to America’s sprawl; US per-capita road transportation emissions are 2.5 times higher than in Germany and three times higher than in Japan.

A specific environmental claim from Glock’s piece that merits scrutiny is the assertion that tall buildings “create more burdens on both the local and global environment than small ones.”

First, by comparing buildings, Glock overlooks the key metric of the households within them. Obviously, the costs—environmental and other—of a large, multistory building exceed the costs of building one house. But one house shelters one household, whereas one multistory building can shelter hundreds of them.

In terms of energy requirements for running the buildings’ systems and—crucially—new infrastructure demands, there is no contest between tall buildings and single-family homes: tall buildings are more efficient. By sharing walls, apartments insulate one another and thus use less energy for heating and cooling, the two biggest energy expenditures for residential buildings on average. “In 2015,” the US Energy Information Administration writes, “the average household living in a single-family detached home consumed nearly three times more energy than a household living in an apartment building that has five or more apartments.” Part of that difference can be explained by the size of homes, but relative household energy use shows an efficiency contrast as well. Heating and cooling account for more than half of detached homes’ energy consumption, while for apartments in buildings with five or more units heating and cooling account for a less than a third of energy consumption.

Second, between single-family homes and tall buildings are various forms of development that bridge the gap between detached houses and residential skyscrapers. Multifamily homes, duplexes, triplexes, low-rise apartment buildings, and the like provide a middle ground between hyperurban development and modern American sprawl. These forms of residential housing constitute what some urbanists call “gentle density.” Incremental densification consistent with local norms has serious potential for meeting housing demand and reducing environmental impact.

Third, low-density development requires substantially more public infrastructure than does dense development. Roads, sewers, fire and police departments, and much else require more investment when people’s homes are more spread out. The environmental and fiscal costs of construction and upkeep are typically borne not by the owners of those suburban homes, but by municipal governments and, by extension, their citizens as a whole—even those who don’t benefit from the new low-density development.

The infrastructure needs of low-density development offer a segue to another misstep in Glock’s article: misinterpreting suburbs’ superficial landscaping as development in harmony with nature. Paradoxically, the stark environments we describe as concrete jungles spare the natural environment outside the city, allowing it to flourish with less interruption from human use. Dense development reduces per-capita land use and thus permits more untrammeled natural growth. Suburbs, despite their natural veneer, are engineered environments that curtail ecosystems and reduce biodiversity. Simply as a matter of fact, density lowers impacts on the natural world, relative to sprawl.

Look, for example, to two of the modern world’s quintessential dense cities, Singapore and Hong Kong.

Singapore, an island city-state, has a population of almost 6 million people. Hong Kong has a population of 7.5 million and, while nominally larger by area than Singapore, faces both border constraints and the challenge of mountainous terrain. Each city has an urban core density on par with that of New York City. And, yet, each has been able to maintain a verdant ecosystem by building up, rather than paving over the entirety of their territories.

Glock’s discussion of the so-called demons of density also warrants debate. While water pollution and disease have historically plagued cities, technology has largely eradicated these problems for those of us fortunate enough to live in wealthy countries; it has done so even more effectively than technology has eradicated the environmental costs of sprawl. Frightening as life was in urban areas during the early stages of the COVID-19 pandemic, over the last two years the data have shown that the risk of density can be neutralized by effective public health measures. Japan’s Tokyo prefecture, with a population of about 14 million and density that exceeds that of any US metro area, had recorded fewer than 3,200 COVID deaths as of November 2021; the Phoenix metro area—one of Glock’s stars of sprawl—has now recorded almost 15,000 COVID deaths, despite its population numbering less than 5 million.

What’s more, sprawl has demons of its own that we ought not forget, with one of its gravest being vehicular deaths. Car-oriented development significantly increases the risk of people being injured or killed by people driving cars. The densest US cities tend to be the safest in this respect. Dense development lowers traffic speed and increases awareness and use of non-motor vehicle modes of travel. In terms of annual car deaths, New York City compares well to the safest cities globally. The same cannot be said of the more sprawling Los Angeles, which records around eight car deaths per 100,000 people annually. In fact, more Angelenos are killed by cars each year than New Yorkers in absolute terms, despite LA proper having half the population of the Big Apple.

On the subject of cars, Glock presents electric vehicles (EVs) as a silver bullet for sprawl’s costs. To state the obvious, EVs are only as green as the electric grid that powers them. Given our grid’s resource mix, we’re already oversubsidizing EVs. According to a back-of-the-envelope estimate by the Niskanen Center’s Nader Sobhani, the $7,500 tax credit the federal government gives EV buyers is about $5,500 too high based on the emissions they avoid.

Furthermore, tailpipe emissions aren’t the only pollution vehicles create. Non-exhaust emissions—the floating muck cars generate from the disintegration of their tires and brake pads—accounts for 85 percent or more of particulate matter from traffic. And because they are heavier than conventional vehicles, tomorrow’s EVs might even create more of this pollution than today’s average cars.

Seeking Common Ground

While I think Glock overstates the environmental case for sprawl, he and I agree broadly that public policy should respect people’s preferences, neither cramming them into dense spaces nor forcing them to the hinterlands.

We also agree that some of the prime offenders of this principle are the progressive municipalities of California. In an egregious 2021 case, for example, San Francisco’s city supervisors voted against a plan to turn a parking lot into 500 housing units.

Decisions like this have the grim ripple effects Glock describes. With too little housing in California’s coastal enclaves, people are pushed by policy, not preference, into California’s hotter interior or out of the state altogether. The result is more people driving cars to and from the city each day and more people living in climates like Nevada’s and Arizona’s where cooling and heating demands are much greater. Building more housing in California’s cities will give more people an opportunity to live near high-productivity economic hubs, will reduce upward price pressure on housing across the western United States, and will reduce energy usage and emissions. It will also lessen the cultural tensions that underpin much of our discussion of sprawl.

To stretch Glock’s argument a step further, the case against suburbia is increasingly rooted not in data, but in the dynamics of the American culture war. Today, political inclination and aesthetics often motivate the invective against the suburbs. In response, a certain segment of the American political right now treats the suburbs as if they’re a lesser-known inclusion in the Bill of Rights. By permitting more building in our cities themselves, we can reduce the pressure on suburban areas and give more people the freedom to live how they want, both in cities and outside of them.

Beyond building in our cities, governments need to establish clear rules that properly account for the environmental effects and infrastructure costs of development, not promulgate rules that prescribe a lifestyle. With clarity of that sort, people will be free to make choices that best align with their values and live the lives they want, but they’ll do so with better cost-benefit transparency. One specific policy swap that would fit with this principle is to institute road pricing and repeal gas taxes.

While the gas tax is viewed as something of a proxy for vehicle miles traveled, the proliferation of electric vehicles severs that link. With more EVs on the roads and fewer people paying the gas tax, the tax becomes a wealth transfer of the worst sort, giving yet another subsidy to rich EV buyers. As described above, EVs are not an environmental panacea and will perpetuate some of the worst ills of sprawl, like local air pollution and car deaths. By pricing road use independently of fuel source, we can more fairly account for the costs of driving.

With the title “Sprawl Is Good,” Judge Glock’s article was bound to ruffle many a feather, as it did my own. Tongue in cheek [ed note: or pushed by an editor] though it may have been, the proposition allows me to express a contrary, but not contradictory, view: sprawl is natural. Lower-density development is the organic consequence of our widely varying preferences as human beings. Rather than dogmatically railing against sprawl, we need to recognize the validity of the suburban preference, but—critically—we need to do so without ignoring or subsidizing its costs.