This map shows the world's 20 most populous urban agglomerations in 2004. With 21,503,000 inhabitants, Mexico City ranks third. Click on image for full size (147) Data courtesy of the World Gazetteer; illustration courtesy of Mike Shibao, UCAR.

The 21st century is shaping up to be the Urban Century. Fifty years ago, 30% of the world's population lived in urban settings. Now, for the first time in human history, more people live in cities than do not. In 10 years, this number will reach about 60%. At the recent millennium, the world supported 411 cities that each contained more than one million inhabitants. While the majority of the world's urban population used to live in Europe and North America, today the most explosive growth is occurring in developing nations, particularly in Asia.

Migration within countries is the primary force remaking settlement patterns around the world. In the developing world especially, urban economic opportunities are drawing workers in large numbers from the countryside. During the last decade, for example, an estimated 150 million rural Chinese migrated to the nation's urban areas, filling megacities like Shanghai, Beijing, and Ghangzhou.

As globalization continues to impact economies around the world, these patterns of urbanization will continue. Demographers project that the number of megacities will reach 26 by 2015. Cities that lack the infrastructure and services to support the influx of migrants will be strained to the breaking point, resulting in unsustainable growth and the pollution that so often accompanies it.

This map shows the world's 20 most populous urban areas in 2004. With 21,503,000 people, Mexico City ranks third. Click on image for full size (147) Data courtesy of the World Gazetteer; illustration courtesy of Mike Shibao, UCAR.

The 21st century is definitely shaping up to be the Urban Century. For the first time in human history, more people live in urban areas than do not. (An "urban" area is a city; the opposite is a "rural" area, which means in the countryside.) In 2000, the world supported 411 cities that each had more than one million inhabitants. While the majority of the world's urban population used to live in Europe and North America, today the biggest growth is happening in developing nations, especially in Asia.

People are moving from the countryside into cities in search of more economic opportunities. That is, they expect to make a better living while working in the city. During the last decade, for example, an estimated 150 million rural Chinese moved to the nation's urban areas, filling megacities like Shanghai and Beijing.

In the future, more and more megacities will form. It is estimated that the number of megacities will reach 26 by 2015. Most cities lack the services to support so many new people coming into them, resulting in unsustainable growth and the pollution that so often accompanies it.

This map shows the world's 20 biggest city areas in 2004. With 21,503,000 people, Mexico City is 3rd biggest. Click on image for full size (147) Data courtesy of the World Gazetteer; illustration courtesy of Mike Shibao, UCAR.

Mexico City, where MILAGRO takes place, is a "megacity." A megacity is a BIG city! More exactly, a megacity has over 10 million people living in it.

When someone lives in an urban setting, he or she lives in a city. When someone lives in a rural setting, he or she lives out in the countryside. Do you live in an urban setting? Around the world, more people live in cities than do not. In 2000, the world had 411 cities that each had more than one million people.

People are moving from the countryside into cities in hopes of making more money in the cities. Sometimes cities can’t handle so many more people living there, resulting in too much growth and more pollution, too.