Urbanization

The growth of urban areas has produced concentrations of human population of unprecedented magnitude, and governments are failing to manage the resulting environmental and social service problems.

The interaction between population dynamics and environmental and social problems is important to Americans because population growth and environmental degradation can contribute both to migration pressures and to the potential for civil conflict. The population-environment interaction is a factor in the growing proportion of the world¹s people who live in and around cities Population growth fuels the growth of urban areas in two ways: as "natural increase," stemming from high birth rates within metropolitan areas, and as migration from outlying rural areas, where the labor force tends to grow more rapidly than employment. Urban populations are growing faster than those of surrounding areas. The average growth rate for cities and their environs in developing countries is 3.5 percent a year, compared to 1.9 percent for these countries as a whole.1 Indeed, a recent study of national and urban population growth in developing countries found that on average each 1 percent increase in national population growth yields a 1.78 percent increase in urban population.2

The population increments being added to urban areas in developing countries today have no precedent in history, so there is little guidance to predict the magnitude of the problems they may pose. But it is clear that many cities have reached the point where further population growth jeopardizes the delivery of basic services to all.

People move to cities to improve their economic opportunities and quality of life, and urban migrants have often adapted swiftly to the stresses of city life. As a recent United Nations report on urban areas noted, however, "the situation is rapidly changing. Many options previously available to low-income urban populations, such as that of settling in unused public land and low-density central city neighborhoods, are rapidly disappearing. While the demand for land is growing‹indeed, it has been calculated that rapid urbanization is likely to lead to a doubling in size of built-up urban areas in most developing countries over the next 15 to 20 years‹the supply in most developing country cities is both genuinely and artificially limited."3

The environmental byproducts of large and concentrated urban populations pose direct threats to health and to the quality of city life. In Mexico City, considered home to the world¹s worst air pollution, most children who are tested have elevated lead levels. Ozone pollution, with concentrations that are often three times as high as the World Health Organization¹s safety standard for ozone,4 have led the city¹s government to curtail driving and industrial activity to help clear the air. A recent scientific study suggested that the primary culprit for the city¹s air pollution may be the combustion of liquefied petroleum gas, which is used to heat homes and cook food throughout the city.5 At the same time, the need to provide fresh water to a growing population of about 16 million in an arid mountain valley has forced Mexico City to overdraw its underground supplies of fresh water and pipe water from across the surrounding mountains, at a high and growing cost in electricity. The level of the city¹s aquifer is sinking by more than three feet per year, causing land to subside and structures to buckle in the city¹s center.6

In Cairo, a city of nearly 10 million people, space in public parks is in such demand that many charge admission. Even the grassy median of the road between the city and its airport has become the scenes of family picnics, with cars whizzing by a few yards away.7 The further adaptations that continued population growth will require in many urban areas are hard to imagine.