A megacity is a very large city, typically with a population in excess of 10 million people. 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. A University of Bonn report held that they are "usually defined as metropolitan areas with a total population of 10 million or more people". Others list cities satisfying criteria of either 5 or 8 million and also have a population density of 2,000 per square kilometre. A megacity can be a single metropolitan area or two or more metropolitan areas that converge. The terms conurbation, metropolis, and metroplex are also applied to the latter. The term metacity has been used to describe metropolitan conurbations containing over 20 million people.
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 six. Other countries with megacities include the United States, Brazil and Pakistan, each with two.
This is the list of the world's largest cities and metropolitan areas by population as of 2016.
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. Initially the United Nations used the term to describe cities of 8 million or more inhabitants, but now uses the threshold of 10 million.
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. 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. 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. One billion people, almost one-seventh of the world's population, now live in shanty towns. In many poor countries overpopulated slums exhibit high rates of disease due to unsanitary conditions, malnutrition, and lack of basic health care. By 2030, over 2 billion people in the world will be living in slums. 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.
For almost five hundred years, Rome was the largest, wealthiest, and most politically important city in Europe. Its population passed one million people by the end of the 1st century BC. 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. 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. 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.
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. Geographers had identified 25 such areas as of October 2005, 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. 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. As of 2010, there are 25 megacities by this definition, like Tokyo.[needs update] Other sources list Nagoya and the Rhein-Ruhr as megacities.
This section may require cleanup to meet Wikipedia's quality standards. The specific problem is: A lot of vague statements without up-to-date / worldwide-applicable supporting examples or data. Can also be further expanded. (May 2014) (Learn how and when to remove this template message)
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. 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. These issues raise problems in the political, social, and economic arenas. People who live in slums or informal settlements often have minimal or no access to education, healthcare, or the urban economy.
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, Mumbai, Cairo, Rio de Janeiro, and Lagos.
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.
In 2002, research showed that children and families were the largest growing segment of the homeless population in the United States, 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.
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. Traffic congestion is increasing in major cities and delays are becoming more frequent in smaller cities and rural areas.
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. 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.
Gentrification and urban gentrification denote the socio-cultural changes in an area resulting from wealthier people buying housing property in a less prosperous community. 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 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 and is expected to increase 48% to 9.98 billion short tons by 2030. 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.
Energy and material resourcesEdit
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.
Megacities are a common backdrop in dystopian science fiction, with examples such as the Sprawl in William Gibson's Neuromancer, 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. 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. 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.
- Consolidated city-county
- Economies of agglomeration
- Financial centre
- Global city
- List of largest cities throughout history
- List of metropolitan areas by population
- List of metropolitan areas in Europe
- List of million-plus urban agglomerations in India
- List of urban areas by population
- Merger (politics)
- Primate city
- Principles of intelligent urbanism
- Urban sprawl
- "Definition of megacity in English". Oxford Dictionaries. Retrieved 27 March 2018.
- "megacity Meaning in the Cambridge English Dictionary". dictionary.cambridge.org. Retrieved 27 March 2018.
- "World Urbanization Prospects, The 2014 Revision" (PDF). UN DESA. 1 July 2015. p. 16.
- Kötter, Theo; Friesecke, Frank (1 March 2009). "Developing urban Indicators for Managing Mega Cities". World Bank. University of Bonn.
- "Land Use and Land Use Change". seos-project.eu. Retrieved March 26, 2018.
- "The World's Cities in 2016" (PDF). United Nations. 2016. p. 11.
- OECD Urban Policy Reviews: China 2015, OECD READ edition. OECD iLibrary. OECD Urban Policy Reviews. OECD. 18 April 2015. p. 37. doi:10.1787/9789264230040-en. ISBN 9789264230033. ISSN 2306-9341.Linked from the OECD here
- "Jakarta Population 2014". World Population Review. Retrieved January 13, 2015.
- "The Principal Agglomerations of the World". citypopulation.de. Retrieved 8 December 2017.[better source needed]
- "Annual Estimates of the Resident Population: April 1, 2010 to July 1, 2017 – United States – Combined Statistical Area; and for Puerto Rico - 2017 Population Estimates". United States Census Bureau. Retrieved April 27, 2018.
- "Região Metropolitana de São Paulo". Empresa Paulista de Planejamento Metropolitano S.A (EMPLASA). 2017. Archived from the original on 25 September 2017. Retrieved 9 August 2017.
- "What Makes Lagos a Model City". New York Times. 7 January 2014. Retrieved 16 March 2015.
- "Thailand: Division (Planning Regions and Provinces) - Population Statistics, Charts and Map". citypopulation.de. Retrieved 8 December 2017.
- "Population Division Data Query (2015)". United Nations. Retrieved 1 July 2015.
- "Eurostat – Data Explorer". Eurostat. Retrieved 2 July 2015.
- "Encuesta Permanente de Hogares" (PDF). Indec. 23 August 2015. p. 3.
- "Les 60 premières aires urbaines en 2013". INSEE. 1 January 2015. Archived from the original on 25 March 2016.
- Urban agglomeration only: "Demographia World Urban Areas, 14th Annual Edition" (PDF). April 2018. Archived from the original (PDF) on 3 May 2018.
- Regionales Monitoring 2008 - Daten und Karten zu den Europäischen Metropolregionen (EMR) in Deutschland (PDF) Retrieved 22 June 2009.
- "Bogota Population 2018 (Demographics, Maps, Graphs)". worldpopulationreview.com. Retrieved 2018-02-11.
- "Hemisfile: perspectives on political and economic trends in the Americas". 5–8. Institute of the Americas. 1904: 12. Retrieved 16 July 2015.
- "Population Reports: Special topics" (15–19). Baltimore: Johns Hopkins University. 1981: 38.
- "Principal Agglomerations of the World". Citypopulation.de. Retrieved 2010-09-01.
- "Megacities Of The Future". Forbes.com. 2007-06-11. Retrieved 2010-09-01.
- "Nigeria: Lagos, the mega-city of slums and plums". Energypublisher.com. Archived from the original on February 18, 2011. Retrieved 2010-09-01.
- Whitehouse, David (2005-05-19). "Half of humanity set to go urban". BBC News. Retrieved 2010-09-01.
- "Planet of Slums – The Third World's Megacities". Blackcommentator.com. Retrieved 2010-09-01.
- "State of World Population 2007". Unfpa.org. Retrieved 2010-09-01.
- "Roman Empire Population". Unrv.com. Retrieved 2010-09-01.
- "Population crises and cycles in history". Home.vicnet.net.au. Archived from the original on April 5, 2011. Retrieved 2010-09-01.
- "Largest Cities Through History". Geography.about.com. 2010-06-16. Retrieved 2010-09-01.
- New Book of Tang, vol. 41 (Zhi vol. 27) Geography 1.
- Metropolis: Angkor, the world's first mega-city, The Independent, August 15, 2007
- Tertius Chandler, 1987, St. David's University Press. "Top 10 Cities of the Year 1950". Four Thousand Years of Urban Growth: An Historical Census. Retrieved 2007-03-24.CS1 maint: Multiple names: authors list (link)
- "Population statistics". Citypopulation.de. Retrieved 2010-09-01.
- "Greater Tokyo population statistics". Stat.go.jp. 2008-10-01. Archived from the original on March 4, 2008. Retrieved 2010-09-01.
- "Tokyo metropolitan area population statistics". Citypopulation.de. Retrieved 2010-09-01.
- "Archived copy" (PDF). Archived from the original (PDF) on 2015-09-24. Retrieved 2013-08-07.CS1 maint: Archived copy as title (link)
- "p. 26" (PDF). Retrieved 2010-09-01.
- P. H. Liotta; James F. Miskel (2012-02-01). The Real Population Bomb: Megacities, Global Security & the Map of the Future. Potomac Books. ISBN 9781597975513. Retrieved 2014-05-03.
- "Glossary defining homelessness". Homeless.org.au. Retrieved 2010-09-01.
- FACS, "Homeless Children, Poverty, Faith and Community: Understanding and Reporting the Local Story", March 26, 2002 Akron, Ohio. "Archived copy". Archived from the original on 2007-09-28. Retrieved 2006-10-24.CS1 maint: Archived copy as title (link)
- National Coalition for the Homeless, "Homeless Youth" 2005 "Homeless Youth" (PDF). (164 KB)
- Abel, David, "For the homeless, keys to a home: Large-scale effort to keep many off street faces hurdles", Boston Globe, February 24, 2008.
- PBS, "Home at Last? – A radical new approach to helping the homeless", NOW TV program, December 21, 2007.
- What is Sprawl? Archived 2010-01-05 at the Wayback Machine. SprawlCity.org. Retrieved on 2008-02-07.
- Benjamin Grant (June 17, 2003). "PBS Documentaries with a point of view: What is Gentrification?". Public Broadcasting Service.
- World coal consumption 1980-2006 Archived 2008-09-22 at the Wayback Machine October 2008 EIA statistics
- EIA, World Energy Projections Plus (2009)
- "U.S. Coal Supply and Demand". Eia.doe.gov. Retrieved 2010-09-01.
- Sharp, Michael D. (2005). Popular Contemporary Writers. Marshall Cavendish. ISBN 978-0-7614-7601-6.
- Powell, Vincent (2005). The Legal Companion. Robson. p. 54. ISBN 978-1-86105-838-6.
- Namu, Adilifu (2008). Black space: imagining race in science fiction film. University of Texas Press. ISBN 978-0-292-71745-9.
- Westfahl, Gary (2005). The Greenwood encyclopedia of science fiction and fantasy: themes, works, and wonders, Volume 2. Greenwood Publishing Group. ISBN 978-0-313-32952-4.