- A megacity is usually defined as a metropolitan area with more than 10 million inhabitants.
- Some definitions also require it to have a minimum population density of 2000 people/km².
- It can be formed by one, two or more metropolitan areas that have been physically joined together.
- The terms conurbation and metroplex also apply to cases of several united urban areas.
The terms megapolis and megalopolis are sometimes used as a synonym for megacity. Projections suggest that by 2030 there will be 2 billion new urban dwellers, mainly in Asia and emerging countries, hence the use of the category “meta-city” for cities with more than 20 million inhabitants.
This increase is related to the generalization of the urbanization process, which in many countries has exceeded 75-85%. Until 2017 the largest megacity in the world is the area of Guangzhou-Shenzhen, whose population is estimated at more than 48 million inhabitants, depending on the areas that are considered included.
Other lists define megacities as urban agglomerations rather than metropolitan areas.
Until 2017, we find more than 100 cities with this definition.
United Nations projections indicate that the emergence of new mega-cities is declining since 2005.
Another list also defines megacities as agglomerations.
In Canada, the 1990s saw the provinces of Ontario and Quebec forcibly merged into new, larger municipalities.
The process was baptized as a mega-city by the press.
Toronto: the municipalities that make up the Greater Toronto Area were merged into the new Toronto in 1998.
Lagos Kawartha, Ontario: the primarily rural County of Victoria had its towns, villages, and small cities that were merged into one ‘Megacity’ in 2000.
The area has a population of only 70,000 and, although it has an area of 3,059.22 km², it only has a population density of just 22.6 per km².
Ottawa: The municipalities that made up the Ottawa-Carleton Metropolitan Area were merged into the new Ottawa in 2001.
Gatineau: Five municipalities in Southwestern Quebec were merged into the new Gatineau in 2002.
Montreal: All municipalities on the island of Montreal were merged into a new City of Montreal, a merger that lasted a short time until January 1, 2006 when a partial division took place.
The megacities face social and ecological obstacles.
Other concerns include spending responsibilities and resource mobilization.
In Asia and Latin America, mega-cities manage the functions and responsibilities of a province as well as political and economic powers beyond those of municipalities.
This facilitates social policies and public investments.
However, not everything has been the same: there have been partial transfers granting fiscal responsibilities and expenditures, as well as limited transfers that still do not assume partially or totally these responsibilities being covered by the central government.
Another problem is the clarification and separation of functions in advanced and developing countries.
In many countries, especially in Latin America, there are duplicated functions that in other parts of the world would be attributed to a local government.
One of the shortcomings of large cities is the lack of adequate urban planning to provide space, housing, and services to the growing migrant population: thus, many cities become slums, as little attention or priority is given to the needs of the poor.
Another problem cities face is the lack of infrastructure or lack of maintenance – a modern sewage system, a reliable electricity network, well-maintained roads and bridges: these will eventually become obstacles to economic growth.
Finally, another challenge is whether institutions can address all their functions and be close to citizens in providing services.
These must be provided with democratic approaches, otherwise models will be created from the top down.
The urban area
In 1950, only New York exceeded the ten million inhabitants mark, before being joined by Tokyo in 1960.
The megapolitan phenomenon has accelerated since then: 5 megacities in 1975, 7 in 1980, 24 in 20034.
In 2014, the planet will have 28 cities with more than 10 million inhabitants.
With more than 42 million inhabitants in 2014, Greater Tokyo will be the most populated urban area in the world.
What are the challenges faced by big cities?
The high population concentration in megacities and mega urban areas leads to a variety of problems.
These begin with the fact that all inhabitants must be supplied with basic goods and drinking water, which often leads to a massive burden on the surrounding area.
The rural exodus causes the population of cities to grow.
Usually there is not enough living space available for this newly arrived population, so informal settlements are often created.
In the event of a disaster, it is extremely difficult to evacuate the city or provide emergency supplies to the population, since transport infrastructure is usually already overloaded in its normal state and, moreover, accurate figures on demand are often not even available.
The population located in an area can usually only be roughly estimated, since in many countries there is no obligation to communicate.
The current problems of megacities are greater, due to their size and growth rate, than the problems of European and North American cities during the industrialization of the 19th century.