Mega-cities - An urban area with a total population in excess of ten million people.
Migration - When people move from one area to another. In many LICS people move from rural to urban areas (rural-urban migration).
Natural increase – when birth rates are above death rates and the population increases
Urbanisation levels are affected by 2 things – Migration and Natural increase
FACTOR 1 - MIGRATION
Migration is the movement of population from one area to another. Some migrations are forced, voluntary, permanent and temporary, International and regional. The type of migration that we are principally interested in is Rural to urban migration, which is the movement of people from countryside to city areas.
This type of migration happened in HICs from the 18th Century onwards on a large scale, and has gradually slowed down. In fact in many HICs the movement of people has reversed, and people are moving from urban areas back into the countryside as they search for the quiet life (this is known as counter-urbanisation).
However, many LICs are experiencing massive rural to urban migration, mainly of young males, into the major cities. The major reasons for this movement can be classified into push and pull factors.
A Push factor is something that can force or encourage people to move away from an area. Push factors can include famine (as in Ethiopia in the 1980s), drought, flooding (as in Bangladesh, were people are becoming climate change refugees and having to move to Dhaka), a lack of employment opportunities, population growth and over population, and civil war (as in Darfur at the moment).
A Pull factor is one in which encourages people to move to an area. Pull factors include the chance of a better job, better access to education and services, and a higher standard of living.
These factors have contributed to millions of people in LICs moving to cities, creating mass URBANISATION.
FACTOR 2 – NATURAL INCREASE
Natural Increase also has a major effect on rates of urbanisation. During the initial urbanisation phase natural increase in poorer parts of the world can increase as Death Rates fall in cities as people have;
• Better access to medical care
• Improved water supplies
• Improved sanitary conditions
• Improved wealth so improved food supply
Whilst Birth rates take longer to fall and indeed more babies survive as infant mortality falls in cities. Also, young people move to towns and cities, which also boost the birth rate. These combined factors can fuel the rate of urbanisation.
These 2 factors have pushed world urbanisation above 50% and have led to the emergence of hundreds of Megacities. Megacities are those cities that have a population above 10 million.
These cities have sprung up around the globe but it is clear that in recent history most of them can be found in ASIA, whereas the biggest cities used to be in Europe and North America. These cities have their own unique set of environmental, social and economic challenges, due to their sheer size and scale, and the RAPIDITY of the GROWTH. Mumbai is an example of a megacity.