megacity

megacity, a major city whose total metropolitan area contains a population of more than 10 million inhabitants. They are characterized by their large geographic footprint and are found on all continents except Australia and Antarctica, extending across a broad range of environmental, cultural, political, and economic conditions (see also urban sprawl). Megacities in developing countries tend to have a faster growth rate than in developed ones, although in developing countries and developed countries alike, the cause of rapid population growth in megacities is largely attributed to increasing immigration and birth rates. A 2018 United Nations report stated that there were 33 cities whose metropolitan areas fell into this category worldwide and that megacities were home to approximately one-eighth of the world’s urban population. The same report predicted that the planet could have 43 megacities by 2030. The largest megacities—that is, areas with populations over 20 million—are also known as metacities or hypercities.

Distribution

Delineating the extent of a given metropolitan area varies between countries and is, in many cases, open to some degree of interpretation. As a result, the list of megacities and their associated populations can differ from source to source (see also list of the world’s largest cities by population). Despite these challenges, researchers agree that most of the world’s largest megacities are located in Asia, with most sources listing Tokyo; Shanghai; Delhi; Guangzhou, China; and Jakarta as the largest examples. As of the 2020s, China and India had the most megacities.

History

Sources differ with respect to the location and timing of the emergence of the world’s first megacity. Some researchers note that the population of New York City’s metropolitan area surpassed 10 million inhabitants as early as 1930. Tokyo followed in the 1950s after population growth brought on by postwar industrialization attracted millions of workers to the city. Tokyo later became the world’s first metacity when its population doubled to more than 20 million in the 1960s. Such urban population growth continued around the world during this period. Urban populations of Northern Hemisphere cities grew by 2.4 times, and those of the Southern Hemisphere expanded by 7 times between 1950 and 2000, which helped propel Moscow, Los Angeles, Mexico City, São Paulo, Kolkata, Buenos Aires, and Seoul into the ranks of megacities.

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Environmental resource issues

Megacities are attractive places to settle and live because they are often centers of economic opportunity. Rapid population growth and intensive urban development in such relatively small areas—which occur more frequently in the developing world—require an ever-increasing supply of resources, including food and water, energy, sewage and waste disposal, transportation, and housing. In the developing world, the population growth rate in megacities ranges from 2.3 to 4.1 percent. A megacity whose population grows at a manageable rate (that is, approximately 1 percent per year or less) is typically able to provide adequate resources and infrastructure for its people. However, at higher rates of growth, the pool of available resources and infrastructure will not be enough to serve all of the city’s inhabitants, which leads to the creation of overcrowded, unplanned, resource-poor areas (slums).

Regardless of whether or not megacities can be managed to provide for their growing populations, on the whole megacities tend to have drastically greater environmental demands and resource requirements than smaller urban areas. They have significantly higher food, water, and energy demands, and they have higher rates of water scarcity and waste issues—all of which often results in higher rates of water pollution and air pollution, the latter of which is often demonstrated by higher emission rates of carbon dioxide and other greenhouse gases. Megacities made up 12 percent of Earth’s carbon dioxide emissions in 2005, releasing 1.1 petagrams (or 1.1 gigatons) of carbon annually, which some studies expect will increase to 2.2 petagrams (2.2 gigatons) by 2050. Still, if megacities prioritize the environment (such as by emphasizing green architecture, renewable energy, and sustainability) as they grow and develop, and they add infrastructure that favors rapid transit, bicycle use, and walking over automobile use, megacities can be more energy and resource efficient than smaller cities on a per capita basis.