Mexico City from the air. Source: Doug Kelbaugh

An international lens on sprawl

As cities around the world are enveloped in sprawl, its health and sustainability problems are going global.

Note: This is Part 2 of a two-part series that was written for Doug Kelbaugh's upcoming book THE URBAN FIX: Resilient Cities in the War against Climate Change, Heat Islands and Overpopulation, due out in April of 2019. Here's the link to Part 1.

According to MIT’s Center for Advanced Urbanism, “While statistics demonstrate that the world population in metropolitan areas is rapidly increasing, rarely is it understood that the bulk of this growth occurs in the suburbanized peripheries of cities. By 2030, an estimated half a million square miles of land worldwide will become suburban.”i Major metro areas in the developing world are now spreading out and decentralizing. In the last decade, population densities in Chinese cities have declined by a quarter on average.ii If rural migrants to cities end up in suburban settlements, their carbon footprints will climb higher than if they had moved to a dense city. City-dwelling must be planned and made more attractive and affordable, or environmental gains will be lost as more people move to the suburbs to live more consumptive lifestyles. The environmental advantages of cities—namely walkability, transit, and smaller, multi-family and shared dwellings—will disintegrate. The developing world needs to beware the ever-tantalizing appeal of suburbia. 

The Metropolitan Regional Containment Index, published by London’s Philipp Rode in 2012, shows cities tend to spread out less if they are denser to begin with. For instance, Stockholm, Brussels and Helsinki have contained sprawl more effectively than Dallas, Washington, Houston and Prague.iii And cities with strong green belts, like London, or Urban Growth Boundaries, like Portland, have also better resisted the spread of sprawl. However, the typical low-density American pattern is resistant to densifying and retrofitting. Nonetheless, Ellen Dunham-Jones’ and June Williamson’s ongoing research and seminal book Retrofitting Suburbia shows more and more examples of “grayfield” redevelopment. Marginal malls have been converted into mixed-use, bus-served and sometimes rail-served centers, often open-air. Though urbanizing a suburban mall is usually a positive step, it may just become "an al fresco pedestrian treadmill where visitors can window-shop and stroll in circles—constrained on all sides by parking lots, malls, and an eight-lane road. This, like other developments scattered across our suburbs, may boast a ‘Live, Work, Play’ lifestyle, but the reality is more in line with ‘Commute, Work, Netflix.’”iv And the typical self-contained, cul-de-sac subdivision is even more physically resistant to both densification and connection to the larger circulation network.

As big cities in the developing world spread out and suburbanize, residents with long commutes spew more CO2, because jobs—especially for the middle and upper classes—remain in the central city, including service jobs for poor commuters to support the rich. There are exceptions to this trend: In countries like Bangladesh the garment industry is opening factories on the periphery. Although the poor try to move to where the jobs are, jobs sometimes move to where the workers are. Sprawl is not the only societal problem: As more rural residents leave the farms for employment in the city, there is also the potential danger that food supply might decrease below the growing demand for it. This danger particularly threatens low-lying countries like Bangladesh, where rising sea level, amplified by stronger monsoons, makes the soil salty. Indeed, food shortages, even famine is potentially a problem throughout the developing world.

In addition to emission costs, there are the well-known health costs of the automobile, particularly injuries and deaths in auto-dominated sprawl. Americans are over 500 times as likely to die in an automobile collision than in a terrorist attack.v These fatalities make living in suburbia on average more dangerous than living in the American inner city—even when homicides of strangers are included—because suburbanites drive more miles and drive faster. This means that the generation that took their families to suburbia actually exposed them to more danger than in the city! There are also respiratory ailments associated with automobile pollution, most notably asthma. A less-dissected cost of vehicles is the spatial one. When compared to a pedestrian, the typical car takes up about twenty times as much space, weighs about twenty times as much, and likes to move at about twenty times as fast on streets that are much wider than sidewalks. It’s simply not spatially possible to make good urbanism when there are so many of these mechanical behemoths roaming and parking in a city. 

A less direct but also disturbing cost is the increase in obesity and diabetes among suburbanites whose every trip is by car, not infrequently to a fast-food outlet for a high-calorie meal. Obesity rates in the U.S. are among the world’s highest, and climbing to perhaps as high as 50 percent. Sugar is now a greater danger than gunpowder, because it causes more deaths than The nation currently spends as much on treating obesity and related health problems as it does on national defense!vii A study by Oxford University and the University of Hong Kong showed that areas of with about 7 homes per acre had the greatest rates of obesity and lowest rates of exercise, and the best health came in areas with more than 14 units/acre. It also found in over twenty British cities that people living in built-up residential areas had lower levels of obesity and exercised more than residents in scattered homes.viii The study goes on to note that the densities of the popular London neighborhoods of Georgian townhouses are about four times that dense, enough to support trams and subways, while 14 units/acre is barely enough to support bus service. Jane Jacobs recommended considerably higher densities, at least 100 units/acre and even up to 200, in her Manhattan, the densest of American urban centers.

There are other costs of sprawl worth mentioning. For starters, it gobbles up open space, destroying farm land and habitat for plants and animals. The superhighways that empty the central city every evening rush hour allow low-density development to leap-frog into the countryside. This carpet of sprawl requires expensive infrastructure to build and maintain, increasingly more than the local governments can afford. Tax revenue “at low suburban densities isn’t nearly enough to pay the bills … property taxes at suburban densities bring in anywhere from 4 cents to 65 cents for every dollar of liability. Most suburban municipalities … are therefore unable to pay the maintenance costs of their infrastructure, let alone replace things when they inevitably wear out after 20-25 yearsThe only way to survive is to keep growing or take on more debt, or both.ix It seems likely that the next round of municipal bankruptcies will be in suburbia.

And the suburbs are getting poorer as low-income urban residents move out to first-ring suburbs, which have become less expensive as middle-class incomes and employment have stagnated due to automation and offshoring of jobs. What Yuval Noah Harari has labeled the economically “useless class” tends to settle there.  Scott Allard points out in his new book Places in Need: The Changing Geography of Poverty, “there are more poor people living in suburbs today than in cities. What’s worse is that suburbs don’t have the government and nonprofit infrastructure to deliver assistance to those in need. Without the appropriate fiscal policy tools, suburbs will continue to struggle just as central cities did 30 years ago.”x Professor Dunham-Jones corroborates the point: “Since 2005 more Americans in poverty live in suburbs than in cities and they have less access to social networks and cushions.” One can easily imagine extensive suburban slums of the future, with subdivided McMansions poorly maintained by absentee landlords and with their large lawns strewn with broken down cars and appliances. With warped wood studs and sagging sheetrock, they will not age as well as the old brick and plaster urban mansions that were once subdivided to accommodate poor residents in declining cities. As well as decayed, crowded houses, there will also be abandoned areas, which will be a cheap, blank slate for redevelopment, with much less political opposition and NIMBYism seen in more desirable locations.

The true and full cost of sprawl is as approximate as it is immense. According to a 2015 report by the London School of Economics and the Victoria Transport Policy Institute, the annual cost in the U.S. is about $1T!xi The economic and fiscal disadvantages of sprawl have become more and more apparent. It’s verging on a sort of unintended Ponzi Scheme that requires ongoing growth to cover the high cost of servicing an extensive area with sewer, utilities, garbage collection, and fire and police protection. Worth proclaiming again: the whole suburban experiment is a conspiracy of good intentions—government policy-makers, planning officials, bankers, transportation engineers, traffic engineers, fire marshals, code officials all trying to make it a better, safer, more affordable, more convenient place to live, but adding up to compounding costs that have often been hidden.

Another cost of sprawl has come to light more recently, one that is very relevant to CC. It has to do with combustion at a much larger scale—forest fires. These calamitous events happen more and more at the “wilderness-urban-interface,” (WUI) where suburbs are developed on the previously unbuilt edges of cities. This development makes for a volatile mix of buildings and flammable vegetation. As combustible as the suburban-exurban edge is, when developments leap-frog into exurbia and are completely surrounded by nature, this “intermix” version of WUI is even more fiery than “interface” WUI. In the U.S., almost 4 in 10 houses in the country are located in these zones, and 10 million new housing units were built in them during the decade leading to 2010. A report from the Center for Insurance Policy and Research reports that approximately two million, or 15 percent, of California homes are in WUIs. Texas and Colorado also have significant WUIs.xii

Wildfire has been an under-appreciated if episodic aspect of sprawl that directly contributes to UHIs when the wind pushes the extra heat into the city. It also contributes to and is exacerbated by CC: the slow increase in ambient temperature, which in turn dries out vegetation, making it more flammable; and there is less rainfall due to the warmer temperatures during the CC-revved-up dry season that further desiccate vegetation, making all the more fuel for wildfires.Then more rainfall in the CC-induced wet season often over-corrects for the preceding droughtwith additional precipitation that tends to increase vegetative growth, amplifying the next cycle. This classic case of positive feedback is anything but positive for the humans, not to mention plant and animal species, that are ravaged by wildfires. Nowhere is this trend more obvious than in California since 1980, with spring and summer temperatures warming by 5.4°Fxiii and larger wildfires burning hotter.

Last, there is the architectural and landscape mediocrity of sprawl. The suburban arterial strip has become an aesthetic blight, especially during daylight. The strips look better at night, when they are simplified to a sea of glowing electric signs and look less visually chaotic. If modern cities have skylines with tall, free-standing buildings competing for attention like so many perfume bottles on a shelf, the suburbs have second- and third-rate low-rise boxes with aggressive signage fighting for attention. New Urbanist James Kunstler has colorfully described the suburban detritus as having the architectural presence of a collection of “muffler shops,” even criticizing them as a place for which American soldiers may not continue to want to proudly lay down their lives.xiv

It is fair to say that in the country of origin as well as many others, the American “suburban experiment” has generally been an environmental failure. On top of the fiscal issues of low tax revenue per acre, sprawling infrastructure is more expensive to construct and maintain. Roads are wider, with more paving to install and maintain. Water and sewage capital and service costs are higher. Emergency services are costlier because more fire stations and police stations are needed per capita to keep response times down. Children’s busing distances to school are further, as are most trips in suburbia. “One study by the Denver Regional Council of Governments found that conventional suburban development would cost local governments $4.3 billion more in infrastructure costs than compact, ‘smart growth’ through 2020, only counting capital construction costs for sewer, water, and road infrastructure. A 2008 report by the University of Utah’s Arthur Nelson estimated that municipal service costs in low-density, sprawling locations can be as much as 2.5 times those in compact, higher-density locations.”xv There are exceptions, like the older, more compact and walkable railroad suburbs radiating out from what were once the country’s four largest cities—New York, Philadelphia, Boston and Chicago.

A major overhaul of suburbia is needed. The basic geometric pattern is dendritic, meaning the circulation network is too hierarchical, with cul-de-sacs and collector roads feeding into arterials and limited-access freeways. This branching, tree-like geometry leads to bottle necks and very wide arterials, which are unfriendly to pedestrians and bicycles. With too few intersections, there aren’t enough places to turn left, necessitating left turn lanes and signals, which essentially double the time sitting at intersections. The mostly low-rise buildings on arterials are set back to provide convenient customer-friendly parking in front, diluting any sense of spatial containment or human scale. Parking lots dominate all the suburban pods, whether retail, office or institutional. It’s an auto-dominated, sprawling and endless carpet of architectural and urban mediocrity. We need a paradigm shift like the City Beautiful Movement, which American cities embraced a century ago. The popular reform movement “turned the centers of many American cities from muddy cowtowns and squalid factory towns into places with picturesque parks, public plazas, and grand boulevards. These civic spaces were dotted with elegant, neoclassical government buildings, as well as museums, libraries, pavilions and bandshells, all artfully sited in public gardens, and among fountains, lakes, and lagoons.”xvi We need not revive neoclassical architecture, but attention to high quality design and construction is essential.


Center for Advanced Urbanism, MIT, 2/11/16

ii New Climate Economy, WRI, 2014

iii Raven, J., et al., ibid, p. 149

iv Robert Steuteville, quoting Daniel Harris in “Genuine change or lipstick on a pig?” Public Square,         9/22/17

Jeff Speck, plenary talk, CNU27, Savannah, 2018

vi Yuval Noah Harari, “Nationalism in the 21st Century,” youtube, 2018

vii Doug Farr, “Sustainable Nation,” plenary talk, CNU 25, Seattle, WA, 2017

viii “Inner-city living makes for healthier, happier people, study finds,” The Guardian, 10/5/17

ix Leigh Gallagher, Time, 7/28/14

Justin Marlow, “Tax Battle Lines Shift in Cities and Suburbs,” Governing, October, 2017

xi Steve Gleydura, “Lands’ End,” Cleveland Magazine, 10/16/17

xii Adam Rogers, “The West Is on Fire. Blame the Housing Crisis,” Science, 7/18/17

xiii Ben Geman, “Generate,” Axios, 8/15/18

xiv James Kunstler, The Geography of Nowhere, 1993,Home from Nowhere, 1996

xv Leigh Gallagher, quoting Charles Marohn, The End of the Suburbs, 2013, p. 60

xvi Doug Kelbaugh, “City Limits,” Architecture, 2008, p. 363

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