By Jonathan F. P. Rose and Peter Calthorpe

Truly great urban places have the potential to be the most environmentally benign form of human settlement and are at the heart of a sustainable future. Cities affect our lives in profound, self-reinforcing ways: they can be a source of economic innovation, a pathway for poverty reduction, a brake on logarithmic demographic growth, and a solution to climate change—or they can underscore economic isolation, heighten environmental impacts, and foment social strife. They generate 80 percent of global economic output and 70 percent of total energy and greenhouse gas emissions. One of the key drivers of those GHG emissions is sprawl in its varying forms around the planet—land-use patterns that separate activities, isolate jobs, exacerbate traffic, isolate affordable housing and create environments that are downright dangerous to walk or bike in.

Yet, cities and urban places can produce the smallest carbon footprint on a per capita basis.¹ New Yorkers, for example, emit just a third of the GHG of the average American.² Low-carbon cities can be a climate change antibiotic and our most affordable solution to the carbon-based global economy. They are, in fact, our single most potent weapon against climate change, overpopulation, poverty, and environmental degradation.

Today, cities are home to half of the world’s population, and an estimated 70 percent by 2050. The developing economies of the world will account for the vast majority of urban growth in the next half-century. Over 90 percent of urban growth is occurring in the third world, adding an estimated 70 million new residents to urban areas each year, much of it in the world’s poorest regions. However, it is the growth of the global middle class within our cities that is driving the growth in carbon emissions, not the poor: 86 percent of energy-based carbon emissions come from middle and upper-income populations. Therefore, as our cities grow, it is the well-off that must adjust the way they live and the kinds of cities they inhabit. Cities transitioning to a higher standard of living in the developing world must lay the groundwork for sustainable, low-carbon futures. Low-carbon urban forms—places that are compact, mixed-use, walkable, and transit oriented—are essential to both reducing climate change and creating more equitable societies.³

Countries across the globe have differing greenhouse gas emission profiles, which are deeply related to urban form and the way they shape the transport and building GHG sectors. Globally, buildings and transport account for 68% of energy-generated GHG while in California it amounts to 77%. It is clear that in addition to renewable sources of energy or conservation techniques, urban form can significantly reduce emissions by shaping cities that are less auto-dependent, less land-intensive and have greater building efficiencies through density. A California study comparing its historic sprawl to compact, walkable and mixed-use communities in 2050 cut GHG gases by 30% percent while at the same time reducing average household costs, infrastructure investments, land consumption, water use, and energy needs. The low-carbon future also created better health outcomes and balanced city budgets. We call these co-benefits: the cluster of positive outcomes that complement urban forms that reduce GHG emissions.

There are three types of sprawl affecting the globe. The first of these is high-income sprawl. We need only look to North America for the classic version of this type of sprawl with its low densities, isolated uses and auto-dominated transportation system made up of the familiar landscape of subdivisions, malls and office parks.

Typical in China is high-density sprawl, which is based on disconnected towers in single-use superblock patterns that compromise local connections, walkability and transit. Finally, there is low-income sprawl. This takes the form of low-income housing at the metropolitan edge, isolating the poor from access to jobs and services, while the wealthy remain in the urban center along with the concentrations of jobs and economic opportunity.

While each city is unique, there are common challenges and opportunities across each. High-density or low, high-income or low, sprawl in all of these differing forms increases auto dependence, compromises health, increases infrastructure costs, marginalizes the poor, consumes agricultural lands, destroys natural habitat and, of course, increases CHG emissions.

High-income sprawl is well known. It is the low-density, auto-oriented pattern that surrounded and eviscerated cities in the West after World War II. In U.S., Canada, and Austria it was driven by a middle class exodus from older urban neighborhoods, subsidized by public investment in highways, underwritten by biased housing finance, and reinforced by social and media norms. Since 2008, it is ironically less and less affordable to the middle class it was created for. Its challenges and pathologies are well-documented—isolated uses, segregated incomes, congestion, and complete auto dependence to name a few. It results in average per capita carbon emissions twice the rate of transit-oriented European cities and five times the rate of developing regions.

China’s form of city-making is connected to the single largest reduction in poverty in human history, as the nation moves its rural poor to cities where jobs, services, health care and education is more accessible, although not equally distributed. But the urban form deployed is unsustainable. Just like low-density sprawl, the new superblocks generate environments where uses are isolated, commutes grow long, congestion and air quality impacts are rising, and the traditional street life is lost. Its congestion is striking even in cities with only 30% auto ownership rates. Here, density adds to ill effects, not to the vitality that cities normally depend on.

Low-income sprawl is perhaps the worst of the three because its negative environmental impacts are matched by its painful social realities. The poor, either living in slums and informal settlements or in social housing at the metropolitan edge, are disconnected from the economic opportunity of the city just as they are starved for basic services. The city sprawls outward along ribbons of undersized roads in low-rise shantytowns often without sewer, water, power, internet or decent transit. These are low-carbon communities by necessity.

The solution to all three types of global sprawl is to develop mixed-use, mixed-income communities, whose urban form encourages transit, walking and biking. Density and mixed use makes mass transit with frequent service more viable just as shortening the distance between home, work, shopping, and other activities makes walking and biking convenient. A regional job/housing balance reduces commute distances while enhancing economic accessibility for lower-income populations. Higher-density housing naturally reduces heating and cooling costs through compact forms and current green-building standards can easily reduce energy use by 30%, with emerging passive house strategies of super insulation reducing energy usage by 75% over current practices. Deploying dispersed renewable energy sources and moving to more local, distributed co-generation systems and micro-grids of energy, heat and water can double the distribution efficiency and halve impacts when compared to centralized systems, as well as increasing resilience. In the end low-carbon urban forms support social equity and affordability while reducing emissions.

Great urban places are defined by the coherence of their public places, the integration of a diverse population, and the opportunity they create for our collective aspirations. If they fail and become matrixes of gridlock, poisonous air, economic segregation, and environmental pollution, the planet will surely follow. If they succeed in lifting the next generation into growing opportunity, integrating immigrants and working families into the next economy and living lightly on the land, they will contribute significantly to a low carbon and sustainable future. If cities can address a range of social, economic and environmental challenges, urban form will become our most cost-effective Drawdown strategy—a platform of lifestyles that inherently demand less of the planet.


  1. The Center for Neighborhood Technology has done extensive research revealing that urban dwellers commute shorter distances and rely on public transit more often. Their per capita emissions, as well as spending on transportation, are consistently lower than that of the average American.
  2. Office of Long-Term Planning and Sustainability, “Inventory of New York City Greenhouse Gas Emissions” (New York: Mayor’s Office of Operations, 2007), 6.
  3. 90 percent from “Systems of Cities: Harnessing urbanization for growth and poverty alleviation,” The World Bank, 2009; 86 percent from Chris Busch and CC Huang “Cities for People: Insights from the Data,” Energy Innovation: Policy and Technology, LLC, April 2015; “Better Growth Better Climate; The New Climate Economy Report, The Global Report,” World Resources Institute, 2013.

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