Editing Megacity (section)

==History==
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 at Austin|University of Texas]] in 1904.<ref>{{cite journal |date=1994 |title=Perspectives on Political and Economic Trends in the Americas |url=https://books.google.com/books?id=-1ALAAAAYAAJ&q=megacity |journal=Hemisfile |publisher=Institute of the Americas |volume=5-8 |page=12 |access-date=16 July 2015}}</ref> Initially the [[United Nations]] used the term to describe cities of 8 million or more inhabitants, but now uses the threshold of 10 million.<ref>{{cite journal |date=1981 |title=Special topics |url=https://books.google.com/books?id=pVxQAQAAIAAJ&q=Megacity+%228+million%22 |journal=Population Reports |location=Baltimore |publisher=Johns Hopkins University |issue=15–19 |page=38}}</ref> In the mid 1970s the term was coined by urbanist Janice Perlman referring to the phenomenon of very large urban agglomerations.<ref>{{Cite book|title=Encyclopedia of the City|last=Caves|first=R. W.|publisher=Routledge|year=2004|isbn=9780415252256|pages=454}}</ref> 
[[File:2020 1million cities.jpg|thumb|260px|right|Map showing urban areas with at least one million inhabitants in 2020]]
In 1800, only 3% of the [[world population|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,<ref>{{cite web|url=http://www.citypopulation.de/World.html |title=Principal Agglomerations of the World |publisher=Citypopulation.de |access-date=2010-09-01}}</ref> with 153 of them located in Asia. Among the 27 megacities with populations over 10 million globally, 15 were situated in Asia.<ref name=":0">{{Cite journal |last1=Li |first1=Deren |last2=Ma |first2=Jun |last3=Cheng |first3=Tao |last4=van Genderen |first4=J. L. |last5=Shao |first5=Zhenfeng |date=2019-12-02 |title=Challenges and opportunities for the development of megacities |url=https://www.tandfonline.com/doi/full/10.1080/17538947.2018.1512662 |journal=[[International Journal of Digital Earth]] |volume=12 |issue=12 |pages=1382–1395 |doi=10.1080/17538947.2018.1512662 |bibcode=2019IJDE...12.1382L |issn=1753-8947}}</ref>

In 2010, UN forecasted that urban population of 3.2 billion would rise to nearly 5 billion by 2030, when three out of five, or 60%, of people would live in cities.<ref>{{cite magazine|url=https://www.forbes.com/2007/06/11/megacities-population-urbanization-biz-cx_21cities_ml_0611megacities.html|title=Megacities Of The Future|magazine=Forbes.com|date=2007-06-11|access-date=2010-09-01}}</ref> 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]].<ref>{{cite web|url=http://www.energypublisher.com/article.asp?id=5307 |title=Nigeria: Lagos, the mega-city of slums and plums |publisher=Energypublisher.com |access-date=2010-09-01 |url-status=dead |archive-url=https://web.archive.org/web/20110218170316/http://www.energypublisher.com/article.asp?id=5307 |archive-date=February 18, 2011 }}</ref> One billion people, almost one-seventh of the world's population, now live in [[shanty towns]].<ref>{{cite news|last=Whitehouse |first=David |url=http://news.bbc.co.uk/2/hi/science/nature/4561183.stm |title=Half of humanity set to go urban |work=BBC News |date=2005-05-19 |access-date=2010-09-01}}</ref> In many poor countries, [[overcrowding|overcrowded]] slums exhibit high rates of [[tropical diseases|disease]] due to unsanitary conditions, malnutrition, and lack of basic health care.<ref>{{cite web|url=http://www.blackcommentator.com/88/88_reprint_planet_slums.html |title=Planet of Slums – The Third World's Megacities |publisher=Blackcommentator.com |access-date=2010-09-01}}</ref> By 2030, over 2 billion people in the world will be living in [[slum]]s.<ref>{{cite web|url=http://www.unfpa.org/swp/2007/english/chapter_2/slums.html |title=State of World Population 2007 |publisher=Unfpa.org |access-date=2010-09-01 |url-status=dead |archive-url=https://web.archive.org/web/20090122105358/http://www.unfpa.org/swp/2007/english/chapter_2/slums.html |archive-date=2009-01-22 |df=ymd-all}}</ref> 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). The top eight provincial capital cities in China with urban areas exceeding 400 km²—Beijing, Shanghai, Tianjin, Guangzhou, Chongqing, Hangzhou, Wuhan, and Xi'an—accounted for 54.8% of the total urban area of all provincial capital cities in the country in 2015.<ref name=":0" />

In Africa, [[Lagos]], Nigeria has grown from 300,000 in 1950 to an estimated 21 million today.

===Growth===
[[File:Détail de la maquette de Rome à lépoque de Constantin (5839479770).jpg|thumb|[[Italo Gismondi|Gismondi]]'s model of Rome in the time of [[Constantine the Great|Constantine]]]]
For almost five hundred years, during the period of the [[Roman Republic|Republic]] and later of the [[Roman Empire|Empire]], [[Rome]] was the [[Historical urban community sizes|largest]], wealthiest, and most politically important city of the ancient world, rulling over Europe, Western Asia and Northern Africa.<ref>{{cite web|url=http://www.unrv.com/empire/roman-population.php |title=Roman Empire Population |publisher=Unrv.com |access-date=2010-09-01}}</ref><ref>{{Cite web |title=Pax Romana: Rome's Golden Age |url=https://www.historyhit.com/pax-romana-romes-golden-age/ |access-date=2024-09-18 |website=History Hit |language=en-GB}}</ref> It is often stated that its population passed one million people by the end of the 1st century BC, however, it is debated about whether the population actually reached such a large size.<ref>{{cite web|url=http://home.vicnet.net.au/~ozideas/poprus.htm |title=Population crises and cycles in history |publisher=Home.vicnet.net.au |access-date=2010-09-01 |url-status=dead |archive-url=https://web.archive.org/web/20110405081151/http://home.vicnet.net.au/~ozideas/poprus.htm |archive-date=April 5, 2011 }}</ref><ref>{{cite journal|last=Storey|first=Glenn R.|year=1997|title=The population of ancient Rome|journal=Antiquity|volume=71|issue=274|pages=966–978|doi=10.1017/S0003598X00085859|url=https://www.cambridge.org/core/services/aop-cambridge-core/content/view/BACD7DF32B0B77609CD6713B8AF88882/S0003598X00085859a.pdf/div-class-title-the-population-of-ancient-rome-div.pdf|access-date=30 May 2024|archive-date=23 July 2018|archive-url=https://web.archive.org/web/20180723072210/https://www.cambridge.org/core/services/aop-cambridge-core/content/view/BACD7DF32B0B77609CD6713B8AF88882/S0003598X00085859a.pdf/div-class-title-the-population-of-ancient-rome-div.pdf|url-status=bot: unknown}}</ref> Rome's population started declining in 402 AD when [[Honorius (emperor)|Flavius Honorius]], [[Western Roman Empire|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.<ref>{{cite web |url=http://geography.about.com/library/weekly/aa011201a.htm |title=Largest Cities Through History |publisher=Geography.about.com |date=2010-06-16 |access-date=2010-09-01 |archive-date=2005-05-27 |archive-url=https://web.archive.org/web/20050527095609/http://geography.about.com/library/weekly/aa011201a.htm |url-status=dead }}</ref> 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.<ref>''New Book of Tang'', vol. 41 (Zhi vol. 27) Geography 1.</ref> 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.<ref>[https://www.independent.co.uk/news/world/asia/metropolis-angkor-the-worlds-first-megacity-461623.html Metropolis: Angkor, the world's first mega-city], The Independent, August 15, 2007</ref>
[[File:Trafalgar Square by James Pollard.jpg|thumb|During the 19th century, [[London]] was transformed into the world's largest city and capital of the [[British Empire]].]]

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.<ref>{{cite web|url=http://geography.about.com/library/weekly/aa011201g.htm|title=Top 10 Cities of the Year 1950|work=Four Thousand Years of Urban Growth: An Historical Census|author=Tertius Chandler, 1987, St. David's University Press|access-date=2007-03-24|archive-date=2016-04-15|archive-url=https://web.archive.org/web/20160415044639/http://geography.about.com/library/weekly/aa011201g.htm|url-status=dead}}</ref> Geographers had identified 25 such areas as of October 2005,<ref>{{cite web|url=http://www.citypopulation.de/World.html |title=Population statistics |publisher=Citypopulation.de |access-date=2010-09-01}}</ref> 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, Kanagawa|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 Prefecture|Chiba]], [[Kanagawa Prefecture|Kanagawa]], and [[Saitama Prefecture|Saitama]] are commonly included in statistical information, the Japan Statistics Bureau only includes the area within 50 kilometers of the [[Tokyo Metropolitan Government Building|Tokyo Metropolitan Government Offices]] in [[Shinjuku, Tokyo|Shinjuku]], thus arriving at a smaller population estimate.<ref>{{cite web|url=http://www.stat.go.jp/english/data/handbook/c02cont.htm |title=Greater Tokyo population statistics |publisher=Stat.go.jp |date=2008-10-01 |access-date=2010-09-01 |url-status=dead |archive-url=https://web.archive.org/web/20080411094023/http://www.stat.go.jp/English/data/handbook/c02cont.htm |archive-date=April 11, 2008 }}</ref><ref>{{cite web|url=http://www.citypopulation.de/World.html |title=Tokyo metropolitan area population statistics |publisher=Citypopulation.de |access-date=2010-09-01}}</ref> A characteristic issue of megacities is the difficulty in defining their outer limits and accurately estimating the populations.

Another list defines megacities as [[urban agglomeration]]s instead of metropolitan areas.<ref>{{Cite web |title=World Megacities - Urban Areas with More than 10,000,000 Population (2015) |url=http://www.demographia.com/db-megacity.pdf |website=Demographia}}</ref> As of 2021, there are 28 megacities by this definition, like Tokyo.<ref>{{Cite web |last=Society |first=National Geographic |date=2018-08-28 |title=The Age of Megacities |url=http://www.nationalgeographic.org/interactive/age-megacities/ |access-date=2022-04-19 |website=National Geographic Society |language=en}}</ref> Other sources list [[Nagoya]]<ref name="citypopulation"/> and the [[Rhein-Ruhr]]<ref>{{cite web |url=http://www.espon.eu/export/sites/default/Documents/Projects/ESPON2006Projects/StudiesScientificSupportProjects/UrbanFunctions/fr-1.4.3_April2007-final.pdf |title=ESPON project 1.4.3 Study on Urban Functions Final Report |access-date=2013-08-07 |url-status=dead |archive-url=https://web.archive.org/web/20150924002318/http://www.espon.eu/export/sites/default/Documents/Projects/ESPON2006Projects/StudiesScientificSupportProjects/UrbanFunctions/fr-1.4.3_April2007-final.pdf |archive-date=2015-09-24 }}</ref> as megacities.