History of Megacities 

For almost five hundred years, Rome was the largest, wealthiest, and most politically important city in Europe with a population that surpassed one million people by the end of the 1st. century BC. Baghdad most likely became 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 The Chinese capital cities Chang’an and Kaifeng also experienced huge population booms during prosperous empires with the 742 AD census recording 362,921 families with 1,960,188 persons

A megacity is defined by the United Nations

A megacity is pegged as any city with more than 10 million residents. Another term often used to describe this is cornubation, a somewhat more comprehensive label that incorporates agglomeration areas such as the Rhine-Ruhr region in Germany’s west which has 11.9 million inhabitants (2010).

Of the 30 biggest megacities worldwide, 20 of them are in Asia and South America alone, including Baghdad, Bangkok, Buenos Aires, Delhi, Dhaka, Istanbul, Jakarta, Karachi, Kolkata, Manila, Mexico City, Mumbai, Osaka-Kobe-Kyoto, Rip de Janeiro, Sao Paulo, Seoul, Shanghai, Teheran and Tokyo-Yokohama. European megacities include London and Paris and the UN estimates that the number of megacities worldwide will only increase.

As a city which has a population of 10 million or more people. Currently, there are 37 megacities in the world. The 2017 UN statistics indicate that the cities with the largest populations worldwide are Tokyo and Shanghai with 38.8 million and 35.5 million people respectively. Recently, the UN has predicted that the number of megacities will rise to 41 by the year 2030.

According to a UN Habitat forecast, two thirds of the world's population will live in cities by 2030. Not least because of their population density, cities have become a huge focal point when it comes to sustainable development.

According to a UN Habitat forecast, two thirds of the world’s population will live in cities by 2030. Not least because of their population density, cities have become a huge focal point when it comes to sustainable development.

Megacities aren’t getting any smaller themselves and new members are joining this elite club on a regular basis

Cities the UN Classifies As Megacities

Rank Megacity Population (Millions)
1 Tokyo 38.1
2 Delhi 26.4
3 Shanghai 24.5
4 Mumbai 21.4
5 Sao Paulo 21.3
6 Beijing 21.2
7 Mexico City 21.2
8 Osaka 20.3
9 Cairo 19.1
10 New York 18.6
11 Dhaka 18.2
12 Karachi 17.1
13 Buenos Aires 15.3
14 Kolkata 15
15 Istanbul 14.4
16 Chongqing 13.7
17 Lagos 13.7
18 Manila 13.1
19 Guangzhou 13
20 Rio de Janeiro 13
21 Los Angeles 12.3
22 Moscow 12.3
23 Kinshasa 12
24 Tianjin 11.6
25 Paris 10.9
26 Shenzhen 10.8
27 Jakarta 10.5
28 Bangalore 10.5
29 London 10.4
30 Chennai 10.1
31 Lima 10

The faster a city develops, the more critical these issues become.

Due to their rapid growth, megacities in developing countries and in the southern hemisphere have to battle in order to provide for their inhabitants. Between 1950 and 2000, cities in the north have grown an average of 2.4 times.

In the south they’ve grown more than 7 fold over the same period. (Bronger 2004). Lack of financial resources and sparse coordination between stakeholders at different levels intensify the problems. Megacities usually do not represent one political-administrative unit, instead dividing the city into parts such as with Mexico City, which is made up of one primary core district (Distrito Federal) and more than 20 outlying municipalities (municípios conurbados) where differing planning, construction, tax and environmental laws are carried out than in the core district. For the most part, urban planning is based on the needs of the consumer and culture-oriented upper classes and economic growth sectors with the result being that the gap between rich and poor continues to grow. Such fragmented cities are a fragile entity in which conflicts are inevitable.

As cities grow, so too do the unplanned and underserved areas, the so-called slums. In some regions of the world, more than 50 percent of urban populations live in slums. In parts of Africa south of the Sahara, that number jumps to around 70 percent. In 2007, a reported one billion people lived in slums and by 2020, that figure could grow to 1.4 billion, according to the UN.

On an international level, there are countless efforts currently being undertaken to support sustainable urban development. A number of large UN projects, such as the UN-HABITAT- Programe Sustainable Urban Development Network (SUD-Net) or the Urban Management Programm (UMP), are endeavouring to improve and strengthen governmental and planning abilities. One of the goals of the UMP is to also implement the Millennium Development Goals at the city level.