Megacities & Urban Growth
The world's largest cities are growing at extraordinary speed. This lesson examines the rise of megacities, explores where they are located, and investigates the factors driving their rapid growth. For AQA GCSE Geography, understanding the concept and distribution of megacities is essential.
What Is a Megacity?
A megacity is defined as an urban area with a population of more than 10 million people.
- In 1970, there were only 3 megacities worldwide (New York, Tokyo, and Osaka).
- By 2000, there were 18 megacities.
- By 2020, there were over 30 megacities.
- By 2030, there are projected to be 43 megacities.
Exam Tip: You will be expected to know the definition of a megacity (10 million+). Some exam boards also use the term millionaire city (1 million+), so make sure you know the difference.
The World's Largest Megacities
| Rank | City | Country | Population (approx.) | Income Classification |
|---|
| 1 | Tokyo | Japan | 37 million | HIC |
| 2 | Delhi | India | 32 million | NEE |
| 3 | Shanghai | China | 29 million | NEE |
| 4 | Sao Paulo | Brazil | 22 million | NEE |
| 5 | Mumbai | India | 21 million | NEE |
| 6 | Cairo | Egypt | 21 million | NEE |
| 7 | Mexico City | Mexico | 22 million | NEE |
| 8 | Beijing | China | 21 million | NEE |
| 9 | Dhaka | Bangladesh | 22 million | LIC |
| 10 | Osaka | Japan | 19 million | HIC |
Distribution of Megacities
Key pattern:
- The majority of megacities are now in LICs and NEEs, particularly in Asia, Africa, and South America.
- In 1970, most of the world's largest cities were in HICs (New York, London, Tokyo).
- The shift reflects the rapid urbanisation occurring in the developing world.
Regional breakdown:
- Asia: Home to the most megacities — China, India, Japan, Bangladesh, Pakistan, Indonesia
- South America: Sao Paulo, Buenos Aires, Rio de Janeiro, Bogota, Lima
- Africa: Lagos, Cairo, Kinshasa, Johannesburg — the fastest-growing continent
- Europe: London, Paris, Istanbul, Moscow — growth is relatively slow
- North America: New York, Los Angeles, Mexico City
Exam Tip: If asked about the distribution of megacities, describe the pattern (most are in Asia and the developing world), give examples, and then explain why (rapid industrialisation, rural-to-urban migration, high natural increase).
Factors Driving Megacity Growth
Economic factors
- Industrialisation — factories and industries concentrate in cities, creating jobs
- Globalisation — megacities act as hubs for international trade and finance
- Foreign investment — transnational corporations (TNCs) locate in major cities
- Informal economy — cities offer opportunities for self-employment even without formal jobs
Social factors
- Education and healthcare — cities have more schools, universities, and hospitals
- Cultural opportunities — entertainment, social networks, diverse communities
- Perception of opportunity — the "bright lights" effect, even if reality is different
Political factors
- Government investment — infrastructure, transport, and services concentrated in capital/primate cities
- Conflict — refugees and displaced people move to cities for safety
- Land reform — changes in land ownership can push people off rural land
Demographic factors
- High natural increase — young urban populations have high birth rates
- Rural-to-urban migration — the dominant driver of growth in LICs and NEEs
Urban Growth: Planned vs. Unplanned
The nature of urban growth differs significantly between HICs and LICs/NEEs:
| Feature | HICs | LICs / NEEs |
|---|
| Rate of growth | Slow | Rapid |
| Planning | Mostly planned | Often unplanned |
| Infrastructure | Keeps pace with growth | Cannot keep up |
| Housing | Formal housing dominates | Informal settlements common |
| Services | Well-provided | Patchy or absent in new areas |
| Transport | Integrated systems | Congestion, limited public transport |
Problems Associated with Rapid Urban Growth
When cities grow faster than their infrastructure, services, and governance can cope, serious problems arise:
Housing
- Squatter settlements (slums, favelas, shanty towns) — self-built, often illegal housing
- Overcrowding and poor building quality
- Lack of legal tenure — residents can be evicted at any time
Services
- Inadequate water supply and sanitation
- Unreliable electricity
- Poor waste management — open dumping, pollution
Health
- Waterborne diseases (cholera, typhoid)
- Air pollution from vehicles, industry, and cooking fires
- Mental health pressures — stress, isolation
Employment
- High unemployment and underemployment
- Reliance on the informal economy — street selling, waste picking, domestic work
- Exploitation and poor working conditions
Environment
- Loss of green space and farmland
- Water and air pollution
- Urban heat island effect
- Flood risk from building on floodplains
The Informal Economy
In many LIC and NEE cities, a large proportion of the workforce operates in the informal economy:
- Jobs are not regulated, taxed, or officially recorded
- Examples: street vendors, waste pickers, rickshaw drivers, domestic servants
- In Lagos, up to 70% of the workforce is in the informal sector
- Provides essential income but offers no job security, health insurance, or pension
Exam Tip: The AQA specification expects you to understand both the opportunities and challenges created by rapid urban growth. Always present a balanced view — cities create problems, but they also offer significant opportunities for employment, education, and social mobility.
Key Vocabulary
| Term | Definition |
|---|
| Megacity | A city with a population exceeding 10 million |
| Millionaire city | A city with a population exceeding 1 million |
| Primate city | A city more than twice the size of the second-largest city in a country |
| Informal economy | Unregulated and untaxed economic activity |
| Squatter settlement | An area of self-built, often illegal housing, lacking basic services |
| Urban sprawl | The uncontrolled expansion of urban areas into surrounding countryside |
Summary
- Megacities are cities with over 10 million people; their number is growing rapidly.
- Most megacities are now in LICs and NEEs, especially in Asia and Africa.
- Growth is driven by economic, social, political, and demographic factors.
- Rapid, unplanned growth creates major challenges: housing, services, health, employment, and the environment.
- Understanding these patterns prepares you for the Lagos and London case studies.
Exam Tip: You may be asked to compare the causes and effects of urban growth in LICs/NEEs and HICs. Prepare a clear table in your revision notes summarising the key differences.
Case Study Spotlight: Rio de Janeiro (NEE) and London (HIC)