The rise of megacities revision notes

Edexcel International GCSE Geography (4GE1), chapter 6: Urban environments, specification point 6.1b. Free lesson.

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A megacity is a city with 10 million people or more. Knowing how their number and location have changed, and what causes cities to grow, helps you answer questions about urban growth.

What makes a city a megacity?

A megacity has 10 million people or more. The UN figures used here count the whole built-up area, not just the official city boundary. This matters because the way a city’s edge is drawn can affect its population and ranking. The UN counted Jakarta at about 42 million people in 2025. City rankings can differ between sources because they may use different boundaries. Older books put Tokyo first.

How the number of megacities has changed

The number rose sharply between 1975 and 2025. The UN projects further growth by 2050, but a projection is an estimate of the future, not a confirmed count. 1975: 8 megacities 2000: 20 megacities 2025: 33 megacities 2050: 37 megacities are projected

Where megacities are found

Asia has more megacities than all the other regions put together. The main pattern to remember is that new megacities are mostly in Asia and Africa. Asia: 19 Latin America: 5 Africa: 4 Europe: 3 Northern America: 2

Five factors that make megacities emerge

A factor is a cause. These factors explain why a city’s population grows to 10 million or more. Traffic jams and squatter settlements are problems megacities may have, but they are effects of growth, not causes. Economic growth: factories and offices create jobs. Workers spend their wages, so more businesses open. This is called the multiplier effect. Migration: people move from rural areas for jobs, schools and hospitals. Natural increase: migrants are often young and have children. Births outnumber deaths, so the population grows. Location: ports and capital cities…

How to develop an explanation

For an explain question, give causes and show how they lead to population growth. A definition or a problem does not explain why a city grew. Two different factors, each developed with a link such as “so”, can earn the marks in a four-mark answer. For example, industry creates jobs, so people migrate from rural areas and the city’s population may pass 10 million. Young migrants may have children, so births far outnumber deaths and the city continues to grow through natural increase.

How to describe a change

A describe question asks what changed, not why it changed. State the direction of change and support it with figures. No reason is needed.