The world is increasingly urban, with cities projected to gain 2.5 billion more residents by 2050 – mostly in Asia and Africa. As we face escalating global crises such as climate change, chronic disease, poverty, inequity and homelessness, popular opinion often reflects the stereotypes of urban living as a major contributor. This cliché contrasts smoggy skylines, traffic-choked streets and sedentary city dwellers with clean, verdant, suburban or rural communities with active and fit residents.
In fact, to fight the 21st century’s global problems, sustainable urbanization can be a powerful tool to support health and well-being while reducing harm to the environment. The evidence is clear: Compared with sprawling suburbs, well-designed cities can be better for both individuals and the environment.
We’ve learned this after generations of urbanization – especially in wealthy countries – based on car-centric planning approaches, the harmful effects of which cities now struggle to reverse. Unfortunately, knowledge of what makes a city healthy isn’t being translated to rapidly urbanizing areas in the low- and middle-income countries where most global population growth and economic development is occurring.
What about climate change? It is true that cities account for most of the world’s growing greenhouse-gas emissions, but urbanization is not the cause of more emissions. Rather, growing economies and populations are raising energy consumption and urbanization in parallel.
In fact, the available evidence shows that in wealthy countries, cities have lower per capita greenhouse-gas emissions than corresponding national averages. There is a different pattern in some cities in low- and middle-income countries, such as China, where it appears that higher incomes among city residents, rather than urban lifestyles, are driving more consumption and emissions.
Globally, cities have a vast range of per capita energy use, carbon emissions, land use and transportation systems. This variation has been used to identify the types of urbanization that support sustainability and active lifestyles.
At the top of the list of what works: cities that are compact and have mixed land use, with dense residential and commercial development clustered near public and active transportation corridors. These cities are much more efficient than those that are characterized by urban “sprawl” or low-density development, with commercial and residential uses separated by distances that are not walkable.
Transportation and energy policies that favor affordable public transit over low motor-fuel prices augment the efficiency of transit-friendly urban form. Living in compact cities requires fewer and shorter car trips for errands, outings and commuting, and dwellings in these cities tend to be smaller attached homes or apartment buildings that require less energy to heat or cool.
Guiding urbanization toward a compact, efficient form could be a powerful tool for reducing greenhouse-gas emissions. According to one study, the projected global growth in urban greenhouse-gas emissions through 2050 could be reduced by 37% compared with current trends through urban-planning approaches reinforced by transportation taxes. The greatest benefits would occur in rapidly developing low- and middle-income countries, and more than half of this “urban mitigation wedge” could be realized in Asia.
Fortunately, the same types of cities and urban neighborhoods that reduce greenhouse-gas emissions can also promote a healthy lifestyle.
Mixed land uses (residential, commercial and parkland) in close proximity encourage exercise by providing residents destinations within walking or cycling distances. Public transit in a neighborhood is also associated with physical activity due to the need walk or cycle to and from transit stops as part of daily commutes.
A city with the right layout and transportation system can make daily physical activity a default choice for many without depending on people having the willpower or time for purposeful exercise. Regular physical activity is a powerful prescription for health, reducing the risk of cardiovascular disease, obesity, diabetes, cancer, osteoporosis, depression and dementia.
Compact, transit-friendly urbanization has multiple other benefits for people and the environment. For example, low-sprawl urbanization can place more jobs within affordable commuting range, supporting economic mobility and opportunity. Compact cities support more people and economic activity on less land, which means less sprawl to undeveloped land that can then support ecosystems, farming or watershed protection.
To be sure, urbanization – compact or sprawling – can create many health risks and environmental problems that need to be managed. Foremost among these is exposure to air pollution, which is a leading cause of global deaths and is growing.
In many rapidly growing cities in low- and middle-income countries, growing emissions from modern sources such as motor vehicles and electric-power generation are added to pollution from traditional sources, such as the substantial proportion of households still using solid fuels such as coal charcoal or for cooking or heating, as well as trash burning and cottage industry.
Managing urbanization is highly complex, combining actors at multiple levels of government and outside stakeholders such as energy-industry and other powerful forces. Complexity, politics and the speed of growth are significant challenges, and global data suggest that investments and policies to manage urbanization are falling short.
Urban sprawl is growing and progress against air pollution is slow or non-existent in many cities. And other barriers to managing urbanization are popular misconceptions, for example that urban density, bus lanes or bike lanes cause traffic or that widening urban roads can relieve congestion. Examples abound of community opposition to higher-density urban development, fuel taxes or dedicated road lanes for public buses.
This is where public-health experts – often a missing piece of urban-planning efforts – can help. Public-health data can demonstrate that dense, green cities are not just good for the global environment, but can drive substantial gains in the health and quality of life of city residents.
Communication techniques used in other public-health efforts, such as tobacco control, can be used to convey the real health damage caused by poor planning, building public support that can buoy the political will necessary to bring together disparate partners. We have seen the damage that omitting the public-health perspective can do, for instance subsidizing diesel fuels that may be good for reducing greenhouse-gas emissions but have other emissions that are terrible for people.
Cities can be engines powering a healthier and greener global future. Each must find its own way forward, but the blueprint and lessons are there, pulled from numerous cities that have successfully managed urbanization or are recovering from poorly managed growth.
We have an opportunity to help the fastest-growing cities avoid the mistakes of the past. Public-health experts must be among the voices in that effort to help manage urbanization in a way that supports the health of people and the planet.