What makes a city a “mega-city” and what are the environmental implications?

What makes a city a “mega-city” and what are the environmental implications?

—Eva Locke, Seattle, WA

Demographers define “mega-cities” as sprawling, crowded urban centers with populations topping 10 million. In 1995, 14 cities qualified as mega-cities; analysts predict that by 2015 there will be 21. The world’s first mega-cities were in Latin America: Mexico City, Rio de Janeiro, São Paulo and Buenos Aires. But in recent years Asian countries—Japan, South Korea, China and India—have grown the fastest. Today the five largest cities are Tokyo, Mexico City, São Paulo, Mumbai (Bombay) and New York City.

The rapid population growth of these cities is due primarily to intra-country migrations as the rural poor move from the countryside to urban areas in search of better lives. The result, unfortunately, is often the proliferation of urban slums, increased crime, high rates of unemployment—and profound environmental degradation accompanied by serious health challenges for the majority of residents.

“By 2050, two-thirds of the world’s population will live in urban areas, imposing even more pressure on the space infrastructure and resources of cities, leading to social disintegration and horrific urban poverty,” says Werner Fornos, president of the Washington-based Population Institute. The rise of mega-cities, agrees The Washington Post, “poses formidable challenges in health care and the environment
the urban poor in developing countries live in squalor unlike anything they left behind.”

According to the World Resources Institute, “Millions of children living in the world’s largest cities are exposed to life-threatening air pollution two to eight times above the maximum tolerable level [as established by World Health Organization guidelines]. Indeed, more than 80 percent of all deaths in developing countries attributable to air pollution-induced lung infections are among children under five.”

Worldwide, over a billion people live without regular access to clean water. Mega-city residents, crowded into unsanitary slums, also fall victim to serious diseases. Lima, Peru (with population estimated at 9.4 million by 2015) suffered a cholera outbreak in the early 1990s partly because, as The New York Times reported, “Rural people new to Lima
live in houses without running water and use the outhouses that dot the hillsides above.” Consumption of unsafe food and water subjects these people to regular and life-threatening diarrhea and dehydration. “All the demographic data point to the 21st century emerging as the urban century,” says Deane Neubauer of the Yale Center for the Study of Globalization. “But evidence also indicates that a vast portion of the new “megacities” will be infested by 19th-century-style poverty.”

One organization addressing the issue is the non-profit Mega-Cities Project, based at Trinity College in Hartford, Connecticut. The organization has brought together a diverse international group of community, government and business leaders to share ideas on ways to make mega-cities more ecologically sustainable and economically vital. Indeed, the fate of many of the world’s poor rests with such efforts to smooth the transition to a planet where 60 percent of all people crowd into a few dozen sprawling metropolises.


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