World Is Soon Half Urban

by Kai N. Lee with Lisa Mastny

The United Nations projects that sometime in 2008 more people will live in cities than in rural areas.1 Over the past half-century, the world’s urban population has increased nearly fourfold, from 732 million in 1950 to 3.15 billion in 2005.2 (See Figure 1.) People living in cities accounted for 49 percent of the total population of 6.46 billion in 2005.3

The bulk of future population increase— 88 percent of the growth from 2000 to 2030— is projected to occur in cities of the developing world.4 Asia and Africa, the most rural continents today, are set to double their urban populations to some 3.4 billion by 2030.5

Urbanization has slowed considerably in North America and Europe, where by 1950 more than half the population already lived in cities.6 Latin America, at 77 percent urban, has also gone through this demographic transition.7 Growth in that region’s “megacities”—urban agglomerations with more than 10 million inhabitants—has slowed, although large slum populations continue to grow, thanks to the world’s highest levels of economic and social inequality.8

Africa, currently only 38 percent urban, already has nearly 350 million city dwellers— more than the populations of Canada and the United States combined.9 (See Figure 2.) Urbanization there is more recent and more rapid because of higher population growth, rural poverty, and wars that drive people into cities.10 Lack of infrastructure for the poor, followed by rapid urban growth, has produced large slum populations at high risk of disease and environmental hazards like flooding.11 Worldwide, roughly 1 billion urban dwellers live in slums, defined as areas where people live without one or more of life’s basic necessities: clean water, sanitation, sufficient living space, durable housing, or secure tenure.12

Asia, the world’s most populous region, is roughly 40 percent urban.13 Pacific Asia—the coastal region from Japan to Southeast Asia—has undergone a remarkable economic transformation over the past generation, and China is now the site of 16 of the world’s 20 most polluted cities.14 In western China, South Asia, and interior Asia, urbanization is also rapid, but economic growth has been slower, and poverty burdens nearly a third of India’s urban population.15

Since 1975, more than 200 urban agglomerations in the developing world have grown past 1 million inhabitants, so local governments are facing greater sanitation, housing, transportation, water, energy, and health care needs.16 By 2005, 15 of these were megacities (see Figure 3), although these areas account for only about 9 percent of the total urban population.17 Just over half of the world’s city dwellers live in settlements with fewer than 500,000 inhabitants.18

More than half of the rise in urban population is caused by natural increase.19 But migration is also a leading factor, as economic opportunities and improvements in sanitation and clean water have made city life more desirable. Yet the benefits of urban prosperity are shared unequally, and the poor public health conditions of slums still sicken and kill on a large scale.20

The environmental challenges that cities face vary with the level of economic activity.21 The poorest cities and their slums typically have the worst local hazards, such as diseases spread by dirty water and lack of toilets.22 As a city industrializes, problems at the metropolitan scale, such as air pollution from industry and traffic, tend to worsen first and then improve as economic growth allows for cleaner technologies.23 But a city’s burden on the global environment often increases with economic growth as residents buy more cars, bigger houses, and other consumer goods.24

Yet the economies of scale possible with high-density settlement provide a crucial opportunity to create living patterns in harmony with nature’s rhythms. Urban planners are beginning to embrace the concept of “circular metabolism,” in which much of the waste from the water, food, fuels, and materials that course through cities is reused or recycled.25 Architects are beginning to apply this idea to buildings: the 15-story IBM headquarters in Kuala Lumpur, Malaysia, for example, uses plantings on its exterior to capture water that would otherwise be wasted.26

Includes the following charts and graphs
World Urban Population, 1950-2005
Urban Population by Region, 1950, 1990, and 2005
Population of 14 Largest Cities, 1950, 1990, and 2005

Notes
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