World Resources 1996-97
(A joint publication by The World Resource Institute, The United
 Nations Environment Programme, The United Nations Development
 Programme, and the World Bank)
 (Edited by Dr. Róbinson Rojas)

1. Cities and the Environment

URBAN GROWTH PATTERNS

Between 1990 and 2025, the number of people who live in urban areas is expected to double to more than 5 billion people (11). Almost all of this growth--a staggering 90 percent--will occur in the countries of the developing world (12). (See Figure 1.1.)

In the developed world, the most rapid urban growth took place over a century ago. By 1995, more than 70 percent of the population in both Europe and North America was living in urban areas (13). Urban growth continues, although at a much slower rate on average than in previous decades. Much of the population shift now under way involves movement away from concentrated urban centers to vast, sprawling metropolitan regions or to small- and intermediate-size cities. Some of the most rapidly growing cities are in the southwestern United States--but because this growth is fueled largely by urban-to-urban migration, it does not affect the overall level of urbanization.

In the developing world, Latin America and the Caribbean constitute the most urbanized region--with more than 70 percent of its population living in urban areas in 1995 (14). Rapid urban growth is continuing especially in small- and intermediate-size cities (15). By contrast, Africa and Asia are now only about 30 to 35 percent urban (16). It is in these regions that the most explosive growth is under way, at roughly 4 percent per year. This trend is projected to continue for several decades. Both Asia and Africa are expected to be about 54 percent urban by 2025 (17). (See Figure 1.2.)

In some respects, the patterns of urban growth in developing countries today are not much different from what occurred a century ago in Europe and North America. Many of the forces driving urbanization today are the same--chief among them the shift of jobs from agriculture to industry and services and the concentration of economic opportunities in urban areas. And although cities of the developing world are growing at least twice as fast today as those of the developed world, these rates are not unprecedented. A number of European and U.S. cities sustained very rapid growth in the early 20th Century, as fast as that now under way in the developing countries (18).

What is unprecedented now, however, is the absolute scale of the change, in terms of the number of countries undergoing rapid urbanization, the number of cities worldwide that are growing rapidly, and the sheer number of people involved (19). Roughly 150,000 people are added to the urban population of developing countries every day (20). Because of the huge population base in developing countries, even a relatively slow rate of urban growth can mean an enormous increase in absolute numbers. Given the huge size of the world's population, even at these somewhat reduced rates of growth the urban population will continue to increase dramatically, slowing down significantly only well into the 21st Century (21).

Although rates of growth vary dramatically from region to region and city to city, growth is generally most pronounced in two contexts: in the poorest regions and in those regions that are undergoing rapid economic growth. Each has vastly different implications for the urban environment and quality of life. In the least developed countries, urban growth rates are among the highest in the world, at nearly 5 percent per year (22). Between 1990 and 1995, some of these countries--Burkina Faso, Mozambique, Nepal, and Afghanistan, to cite a few--were experiencing even higher urban growth rates--more than 7 percent per year (23). Local governments are often strapped for cash and do not have the resources to provide even the most basic environmental services for their residents. In 1994, some 30 percent of African urban residents were not served by municipal water services in any form (24). (See Box 1.1.)

Growth rates are also extremely high in the rapidly industrializing cities, located mostly in Southeast Asia and Latin America. Cities in these regions offer several advantages over rural villages, having both more numerous job opportunities and superior infrastructure and living conditions. Even so, infrastructure facilities, such as road networks and wastewater treatment plants, lag far behind what is needed. The result is congested city streets, mounting air and water pollution, and other citywide problems. In addition, although many urban dwellers in these wealthier cities live in comfortable dwellings with piped water and weekly garbage pickups, vast numbers of poor people still live in illegal settlements with conditions nearly as dismal as those in the poorest cities. Thus, residents of these cities face the "worst of both worlds" : the environmental problems associated with economic growth and the yet unsolved problems of sanitation (25). (See Box 1.2.)

The rapid growth rates of many cities in developing countries, combined with their huge population bases, are pushing cities to unprecedented sizes. In contrast to earlier in the century, most of the world's giant urban agglomerations are now and will continue to be in the developing world.

One commonly used metric for measuring urban growth is the "megacity," defined as a city with a population exceeding 8 million. In 1950, just two such megacities existed: New York, with a population of 12.3 million, and London, with 8.7 million (26). By 1990, there were 21 megacities, 16 of them in the developing world (27). In 2015, there will be 33 megacities, 27 in the developing world (28).

Any such rankings and comparisons, however, must be approached with caution, because the population of a given city depends on how its boundaries are chosen--for instance, whether the historic city boundary or the boundaries of the extended metropolitan region are used (29). (See Box 1.3.)

Table 1.1 shows the world's 25 largest cities and their recent growth rates. With a few notable exceptions, such as Dhaka, Bangladesh, and Lagos, Nigeria, the annual growth rates of many of these were relatively modest during the early 1990s, although it is unclear how much of this apparent slowdown is due to the dispersion of the population to areas right outside official boundaries (30).

Many intermediate-size cities may actually be growing faster on average than the largest cities, at rates well over 5 percent per year. As a result, there is a proliferation of what have been called "million cities" (with populations of between 1 million and 10 million)(31). (See Table 1.2.) By 2015, there will be 516 of these cities, compared with only 270 in 1990. Small cities, home to more than half of the world's urban dwellers in 1990, are also experiencing extremely rapid population growth (32). These cities are often especially affected by inadequate investment in environmental infrastructure or services, because many countries direct their resources to the larger urban centers.

Some of the most rapid urban growth is occurring in distinct parts of cities--either within the official urban area or on the periphery. The urban fringe of Jakarta, Indonesia, for instance, is growing much faster than the city itself--in some areas at nearly 18 percent per year (33). Spontaneous, or squatter, settlements in particular tend to grow much faster than the rest of the city. These settlements can swell to huge proportions--becoming cities unto themselves. These "unintended" cities, as they have been called, may be technically within the boundaries of a metropolitan area but are beyond the service domain or taxation reach of the local government (34).

Along with population growth have come changes in the physical dimensions of cities as they sprawl into wider regions. Sometimes called "extended metropolitan regions" or "functional urban regions," these include smaller urban centers and even rural areas outside of the urban core whose populations and activities are clearly part of the functioning of the city (35).

This phenomenon of urban sprawl has been especially manifest in the United States. The traditional downtown has been replaced by urban regions such as Silicon Valley in California, where enterprises are concentrated along major roads and highways, transforming the urban landscape into a string of "100-mile cities." In the developing world, many cities remain compact because infrastructure and labor are still concentrated in city centers and transportation and communications systems are less developed (36). Yet cities such as Sao Paulo, Mexico City, Jakarta, and Bombay are all experiencing increasing decentralization. While some expansion results from the suburbanization of high-income groups, a large share can be attributed to attempts by low-income groups to escape the high land prices in the city's core. The speed of this decentralization and its spatial configuration vary greatly from city to city (37).

Sprawl is not concomitant with rapid population growth, however, although it may seem that way in North America. Whereas Bangkok, Thailand, Manila, Philippines, and Jakarta have spread like cities in North America, Shanghai, China, and Seoul, Republic of Korea, remain much more compact. The densities in parts of Shanghai and Calcutta, India, range between 800 and 1,000 people per hectare, and in Bangkok and Seoul between 300 and 400, as compared with 70 or even fewer in most North American cities (38). As is discussed in Chapter 3, "Urban Impacts on Natural Resources," urban form has important environmental implications.

References and Notes

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