Megacity

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A megacity is a very large city metropolitan area, typically with a population of more than 10 million people.^[1][2] Precise definitions vary: the United Nations Department of Economic and Social Affairs in its 2014 "World Urbanization Prospects" report counted urban agglomerations having over 10 million inhabitants.^[3] A University of Bonn report held that they are "usually defined as metropolitan areas with a total population of 10 million or more people".^[4] Others list cities satisfying criteria of either 5 or 8 million and also have a population density of 2,000 per square kilometre.^[5] A megacity can be a single metropolitan area or two or more metropolitan areas that converge due to close proximity.^{[citation needed]} The terms conurbation, metropolis, and metroplex are also applied to the latter.^[5]

As of 2017, there are 47 megacities in existence. Most of these urban agglomerations are in China and other countries of Asia. The largest are the metropolitan areas of Tokyo, Shanghai, and Jakarta, each having over 30 million inhabitants. China alone has 15 megacities, and India has five. Other countries with multiple megacities include the United States, Brazil and Pakistan, each with two. African megacities are also present in Nigeria, Egypt and the DRC.

Largest cities[edit]

This is the list of the world's largest metropolitan areas by population as of 2016.

Rank	Megacity	Image	Country	Continent	Population
1	Tokyo		Japan	Asia	38,140,000[6]
2	Shanghai		China	Asia	34,000,000[7]
3	Jakarta		Indonesia	Asia	31,500,000[8]
4	Delhi		India	Asia	27,200,000[9]
5	Seoul		South Korea	Asia	25,600,000[10]
6	Guangzhou		China	Asia	25,000,000[7]
7	Beijing		China	Asia	24,900,000[7]
8	Manila		Philippines	Asia	24,100,000[9]
9	Mumbai		India	Asia	23,900,000[9]
10	New York		United States	North America	23,876,155[11]
11	Shenzhen		China	Asia	23,300,000[7]
12	São Paulo		Brazil	South America	21,242,939[12]
13	Mexico City		Mexico	North America	21,157,000[6]
14	Lagos		Nigeria	Africa	21,000,000[13]
15	Kyoto-Osaka-Kobe (Keihanshin)		Japan	Asia	20,337,000[6]
16	Cairo		Egypt	Africa	19,128,000[6]
17	Wuhan		China	Asia	19,000,000[7]
18	Los Angeles		United States	North America	18,788,800[11]
19	Dhaka		Bangladesh	Asia	18,237,000[6]
20	Chengdu		China	Asia	18,100,000[7]
21	Moscow		Russia	Europe	17,100,000[9]
22	Chongqing		China	Asia	17,000,000[7]
23	Karachi		Pakistan	Asia	16,900,000[9]
24	Bangkok		Thailand	Asia	15,931,300[14]
25	Tianjin		China	Asia	15,400,000[7]
26	Istanbul		Turkey	Asia & Europe	15,033,000[9]
27	Kolkata		India	Asia	14,423,000[15]
28	Tehran		Iran	Asia	14,000,000[9]
29	London		United Kingdom	Europe	13,842,667[16]
30	Buenos Aires		Argentina	South America	13,834,000[17]
31	Hangzhou		China	Asia	13,400,000[7]
32	Rio de Janeiro		Brazil	South America	12,981,000[6]
33	Xi'an		China	Asia	12,900,000[7]
34	Paris		France	Europe	12,405,426[18]
35	Changzhou		China	Asia	12,400,000[7]
36	Kinshasa		Democratic Republic of the Congo	Africa	12,350,000[19]
37	Lahore		Pakistan	Asia	12,200,000[9]
38	Rhine-Ruhr		Germany	Europe	12,190,000[20]
39	Shantou		China	Asia	12,000,000[7]
40	Nanjing		China	Asia	11,700,000[7]
41	Bangalore		India	Asia	11,800,000[9]
42	Jinan		China	Asia	11,000,000[7]
43	Chennai		India	Asia	11,000,000[9]
44	Harbin		China	Asia	10,500,000[7]
45	Bogotá		Colombia	South America	10,350,000[21]
46	Nagoya		Japan	Asia	10,105,000[19]
47	Lima		Peru	South America	10,072,000[6]

History[edit]

The term "megacity" entered common use in the late 19th or early 20th centuries; one of the earliest documented uses of the term was by the University of Texas in 1904.^[22] Initially the United Nations used the term to describe cities of 8 million or more inhabitants, but now uses the threshold of 10 million.^[23]

In 1800, only 3% of the world's population lived in cities, a figure that rose to 47% by the end of the twentieth century. In 1950, there were 83 cities with populations exceeding one million; by 2007, this number had risen to 468.^[24] The UN forecasts that today's urban population of 3.2 billion will rise to nearly 5 billion by 2030, when three out of five people will live in cities.^[25] This increase will be most dramatic on the least-urbanized continents, Asia and Africa. Surveys and projections indicate that all urban growth over the next 25 years will be in developing countries.^[26] One billion people, almost one-seventh of the world's population, now live in shanty towns.^[27] In many poor countries overpopulated slums exhibit high rates of disease due to unsanitary conditions, malnutrition, and lack of basic health care.^[28] By 2030, over 2 billion people in the world will be living in slums.^[29] Over 90% of the urban population of Ethiopia, Malawi and Uganda, three of the world's most rural countries, already live in slums.

By 2025, Asia alone will have at least 30 megacities, including Mumbai, India (2015 population of 20.75 million people), Shanghai, China (2015 population of 35.5 million people), Delhi, India (2015 population of 21.8 million people), Tokyo, Japan (2015 population of 38.8 million people) and Seoul, South Korea (2015 population of 25.6 million people). In Africa, Lagos, Nigeria has grown from 300,000 in 1950 to an estimated 21 million today.

Growth[edit]

For almost five hundred years, Rome was the largest, wealthiest, and most politically important city in Europe.^[30] Its population passed one million people by the end of the 1st century BC.^[31] Rome's population started declining in 402 AD when Flavius Honorius, Western Roman Emperor from 395 to 423, moved the government to Ravenna and Rome's population declined to a mere 20,000 during the Early Middle Ages, reducing the sprawling city to groups of inhabited buildings interspersed among large areas of ruins and vegetation.

Baghdad was likely the largest city in the world from shortly after its foundation in 762 AD until the 930s, with some estimates putting its population at over one million.^[32] Chinese capital cities Chang'an and Kaifeng also experienced huge population booms during prosperous empires. According to the census in the year 742 recorded in the New Book of Tang, 362,921 families with 1,960,188 persons were counted in Jingzhao Fu (京兆府), the metropolitan area including small cities in the vicinity of Chang'an.^[33] The medieval settlement surrounding Angkor, the one-time capital of the Khmer Empire which flourished between the 9th and 15th centuries, could have supported a population of up to one million people.^[34]

Map showing urban areas with at least one million inhabitants in 2006

From around 1825 to 1918 London was the largest city in the world, with the population growing rapidly; it was the first city to reach a population of over 5 million in 1900. In 1950, New York City was the only urban area with a population of over 10 million.^[35] Geographers had identified 25 such areas as of October 2005,^[36] as compared with 19 megacities in 2004 and only nine in 1985. This increase has happened as the world's population moves towards the high (75–85%) urbanization levels of North America and Western Europe.

Since the 2000s, the largest megacity has been the Greater Tokyo Area. The population of this urban agglomeration includes areas such as Yokohama and Kawasaki, and is estimated to be between 37 and 38 million. This variation in estimates can be accounted for by different definitions of what the area encompasses. While the prefectures of Tokyo, Chiba, Kanagawa, and Saitama are commonly included in statistical information, the Japan Statistics Bureau only includes the area within 50 kilometers of the Tokyo Metropolitan Government Offices in Shinjuku, thus arriving at a smaller population estimate.^[37][38] A characteristic issue of megacities is the difficulty in defining their outer limits and accurately estimating the populations.

Another list defines megacities as urban agglomerations instead of metropolitan areas.^[39] As of 2010, there are 25 megacities by this definition, like Tokyo.^{[citation needed][needs update]} Other sources list Nagoya^[9] and the Rhein-Ruhr^[40] as megacities.

Challenges[edit]

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Slums[edit]

According to the United Nations, the proportion of urban dwellers living in slums or informal settlements decreased from 47 percent to 37 percent in the developing world between 1990 and 2005.^[41] However, due to rising population, the absolute number of slum dwellers is rising. The majority of these are located in informal settlements which often lack sufficient quality housing, sanitation, drainage, water access, and officially recognized addresses. The increase in informal settlement population has been caused by massive migration, both internal and transnational, into cities, which has caused growth rates of urban populations and spatial concentrations not seen before in history.^{[citation needed]} These issues raise problems in the political, social, and economic arenas.^{[citation needed]} People who live in slums or informal settlements often have minimal or no access to education, healthcare, or the urban economy.

Crime[edit]

As with any large concentration of people, there is usually crime. High population densities, placing lots of people together, invariably result in higher crime rates, as visibly seen in growing megacities such as Karachi, Delhi, Cairo, Rio de Janeiro, and Lagos.^[42]

Homelessness[edit]

Megacities often have significant numbers of homeless people. The actual legal definition of homelessness varies from country to country, or among different entities or institutions in the same country or region.^[43]

In 2002, research showed that children and families were the largest growing segment of the homeless population in the United States,^[44][45] and this has presented new challenges, especially in services, to agencies. In the USA, the government asked many major cities to come up with a ten-year plan to end homelessness. One of the results of this was a "Housing first" solution, rather than to have a homeless person remain in an emergency homeless shelter it was thought to be better to quickly get the person permanent housing of some sort and the necessary support services to sustain a new home. But there are many complications with this kind of program and these must be dealt with to make such an initiative work successfully in the middle to long term.^[46][47]

Traffic congestion[edit]

Bangkok is notorious for its traffic congestion.

Traffic congestion is a condition on road networks that occurs as use increases, and is characterized by slower speeds, longer trip times, increased pollution, and increased vehicular queueing. The Texas Transportation Institute estimated that, in 2000, the 75 largest metropolitan areas experienced 3.6 billion vehicle-hours of delay, resulting in 5.7 billion U.S. gallons (21.6 billion liters) in wasted fuel and $67.5 billion in lost productivity, or about 0.7% of the nation's GDP. It also estimated that the annual cost of congestion for each driver was approximately $1,000 in very large cities and $200 in small cities.^{[citation needed]} Traffic congestion is increasing in major cities and delays are becoming more frequent in smaller cities and rural areas.

Urban sprawl[edit]

A flat land area in the Greater Los Angeles Area in the U.S. state of California with houses, buildings, roads, and freeways. Areas constructed to capacity contribute to urban expansion.

Urban sprawl, also known as suburban sprawl, is a multifaceted concept, which includes the spreading outwards of a city and its suburbs to its outskirts to low-density, auto-dependent development on rural land, with associated design features that encourage car dependency.^[48] As a result, some critics argue that sprawl has certain disadvantages including longer transport distances to work, high car dependence, inadequate facilities (e.g. health, cultural. etc.) and higher per-person infrastructure costs. Discussions and debates about sprawl are often obfuscated by the ambiguity associated with the phrase. For example, some commentators measure sprawl only with the average number of residential units per acre in a given area. But others associate it with decentralization (spread of population without a well-defined center), discontinuity (leapfrog development), segregation of uses, etc.^{[citation needed]}

Gentrification[edit]

Gentrification and urban gentrification denote the socio-cultural changes in an area resulting from wealthier people buying housing property in a less prosperous community.^[49] Consequent to gentrification, the average income increases and average family size decreases in the community, which may result in the informal economic eviction of the lower-income residents, because of increased rents, house prices, and property taxes. This type of population change reduces industrial land use when it is redeveloped for commerce and housing. In addition, new businesses, catering to a more affluent base of consumers, tend to move into formerly blighted areas, further increasing the appeal to more affluent migrants and decreasing the accessibility to less wealthy natives.

Air pollution[edit]

Air pollution is the introduction into the atmosphere of chemicals, particulate matter, or biological materials that cause harm or discomfort to humans or other living organisms, or damages the natural environment. Many urban areas have significant problems with smog, a type of air pollution derived from vehicle emissions from internal combustion engines and industrial fumes that react in the atmosphere with sunlight to form secondary pollutants that also combine with the primary emissions to form photochemical smog.

Smog is also caused by large amounts of coal burning, which creates a mixture of smoke and sulfur dioxide. World coal consumption was about 6,743,786,000 short tons in 2006^[50] and is expected to increase 48% to 9.98 billion short tons by 2030.^[51] China produced 2.38 billion tons in 2006. India produced about 447.3 million tons in 2006. 68.7% of China's electricity comes from coal. The USA consumes about 14% of the world total, using 90% of it for generation of electricity.^[52]

Energy and material resources[edit]

The sheer size and complexity of megacities gives rise to enormous social and environmental challenges. Whether megacities can develop sustainably depends to a large extent on how they obtain, share, and manage their energy and material resources. There are correlations between electricity consumption, heating and industrial fuel use, ground transportation energy use, water consumption, waste generation, and steel production in terms of level of consumption and how efficiently they use resources.^[53]

In fiction[edit]

Megacities are a common backdrop in dystopian science fiction, with examples such as the Sprawl in William Gibson's Neuromancer,^[54] and Mega-City One, a megalopolis of between 50 and 800 million people (fluctuations due to war and disaster) across the east coast of the United States, in the Judge Dredd comic.^[55] In Demolition Man a megacity called "San Angeles" was formed from the joining of Los Angeles, Santa Barbara, San Diego and the surrounding metropolitan regions following a massive earthquake in 2010.^[56] Fictional planet-wide megacities (ecumenopoleis) include Trantor in Isaac Asimov's Foundation series of books and Coruscant (population 2 trillion) in the Star Wars universe.^[57]

See also[edit]

Notes[edit]

References[edit]