Urban Sustainability and Megacities

GeographyAQAGCSEUnit: Urban Issues and Challenges
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The basics

300,000 New Arrivals Every Year

🏙️ 300,000 New Arrivals Every Year

It is 6am in Dhaka, Bangladesh. The city is already moving. Rickshaws weave between trucks. A garment worker catches the bus that will take her to one of the thousands of factories producing clothes for high-street brands across Europe and North America. She left her village three years ago — the floods had taken the harvest twice in a row, and her family needed a wage that farming could no longer provide.

She is one of approximately 300,000 people who move to Dhaka every single year. That is the equivalent of a city the size of Coventry arriving in Dhaka in twelve months. Add them year after year, decade after decade, and you have one of the most extraordinary human stories of our time: the rise of the megacity.

In 1950, there were just two cities on Earth with more than 10 million inhabitants — New York and Tokyo. By 2024 there were 37 of them, home to more than half a billion people. Almost all of that growth happened not in the wealthy countries of Europe and North America, but in the rapidly urbanising nations of Africa and Asia. Understanding why megacities grow, what problems they create, and how those problems can be managed is one of the central challenges of 21st-century geography — and one of the most reliably examined topics in your GCSE.

What does urban sustainability mean?: Improving city life without creating bigger future social, economic or environmental problems.
Key terms

Geography glossary

What does urban sustainability mean?
Improving city life without creating bigger future social, economic or environmental problems.
Spotlight
What is a Megacity?

A megacity is a city with a population of more than 10 million people. The term was first widely used in the 1970s, when planners began to recognise that cities of this scale created challenges that smaller urban areas simply did not face. A city of 500,000 needs a bus network and a water supply. A city of 22 million n

Exam tip

Earn the mark scheme marks

🧠 Memory Aid: TRAFFIC

Use the acronym TRAFFIC to remember the key challenges facing megacities. Each letter gives you a topic to write about in an exam answer:

  • T — Traffic congestion (Mumbai: 10 km/h; Dhaka: 7 km/h — costs Bangladesh 3% of GDP annually)
  • R — Resources under strain (water, electricity, food systems overwhelmed by rapid growth)
  • A — Air pollution (Mumbai PM2.5 levels 5× WHO limit; 7 million deaths/year globally from urban air pollution)
  • F — Flooding and environmental risk (Dhaka: 70% below 6m sea level; Mumbai 2005: 944mm in 24 hours)
  • F — Finances and informal economy (60% of LIC urban workers in informal economy without legal protections)
  • I — Informal settlements / Infrastructure gap (1 billion people in informal settlements globally; infrastructure always lags population)
  • C — Congestion of services (schools, hospitals, waste collection overwhelmed — Dhaka generates 35,000 tonnes waste/day)
  • For case study data, use this quick memory frame:

  • Mumbai numbers to know: 21.4m population | 6.6% of India's GDP | Dharavi: 1m people in 2.4km² | £1bn Dharavi economy | 15,000 factories | 10 km/h traffic | 944mm rain July 2005 | Metro Line 3: 33.5km
  • Dhaka numbers to know: 22.5m population | 300,000 new arrivals/year | 40% in bastis | 7 km/h traffic | 35,000 tonnes waste/day | Rana Plaza 2013: 1,134 dead | BRAC: 100m people reached
  • Global facts: 37 megacities in 2024 | 90% of growth in LICs/NEEs | 1 billion in informal settlements | 2050: Africa's urban population triples
  • Now try it yourself

    Quiz · Question 1 of 17

    What is the minimum population required for a city to be classified as a megacity?

    Tap an answer to check it

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