Megacities of the developing world: WACE Year 12 Geography
“Analyse the growth, characteristics and challenges of megacities in the developing world”
A megacity is an urban area of more than ten million people, and most megacities are now in the developing world; they grow through rapid rural-urban migration and natural increase that outpace the provision of housing, jobs and services, producing large informal settlements, strained infrastructure and serious liveability challenges alongside dynamic economies.
What this dot point is asking
SCSA wants you to define megacities, explain why they cluster in developing countries, describe their characteristics, and analyse the challenges they pose for liveability and planning. A strong answer uses a named megacity in depth.
What is a megacity
A megacity is an urban agglomeration with a population exceeding ten million people. The number of megacities has grown rapidly since the late twentieth century, and the majority are now located in Asia, Africa and Latin America rather than in the developed world.
Megacities such as Tokyo, Delhi, Shanghai, Dhaka, Lagos, Mumbai and Sao Paulo concentrate enormous populations, economic activity and political power.
Why megacities cluster in the developing world
Earlier waves of urbanisation produced large cities in the developed world, but growth there has slowed. Today the fastest growth is in developing countries, driven by high rural-urban migration combined with high natural increase. Because these cities grow far faster than industry and infrastructure, populations swell before the jobs, housing and services to support them exist.
Many developing megacities are also primate cities that dominate their national economy, which concentrates migration even further into a single centre.
The defining challenge of developing-world megacities is the speed of growth rather than size alone. When a city adds millions of residents within a generation, housing, water, sanitation, transport and jobs cannot be built fast enough, so informal solutions fill the gap. Developed megacities like Tokyo are large but grew slowly enough to build the systems that keep them liveable.
Characteristics and challenges
- Informal settlements
- Because formal housing cannot keep pace, large shares of residents live in informal settlements, sometimes called slums, often lacking secure tenure, clean water and sanitation.
- Infrastructure strain
- Water, electricity, waste and transport systems are overwhelmed, producing congestion, pollution and disease risk.
- Employment
- Many work in the informal economy, in insecure, low-paid jobs without protection.
- Environmental hazard
- Rapid, unplanned growth often pushes settlement onto floodplains and unstable slopes, raising disaster risk, which climate change intensifies.
Dhaka has grown into one of the world's largest and densest cities, swelled by migrants from rural areas and from regions hit by flooding. A large share of residents live in informal settlements with limited sanitation; traffic congestion is severe; and much of the city sits on low-lying, flood-prone land. Yet Dhaka also drives the national garment-export economy. It captures the developing-world megacity in full: economic dynamism alongside acute liveability and environmental challenges.
Opportunities as well as problems
Megacities are not only problems. They generate the bulk of national economic output, offer migrants real gains over rural poverty, and concentrate the talent and density that drive innovation. Informal settlements often contain vibrant economies and strong communities. A balanced answer recognises megacities as engines of opportunity that nonetheless face severe and urgent planning challenges.
This dot point sets up the management strategies examined elsewhere in Unit 4, where responses such as upgrading informal settlements, investing in mass transit and decentralising growth are evaluated.
The informal city
A defining feature of developing-world megacities is the scale of the informal sector, in both housing and work. Large shares of residents live in self-built settlements without secure tenure, and many earn a living through informal trade, recycling, transport and services that never appear in official statistics. This informality is not simply a problem to be cleared away: it houses and employs people the formal economy cannot, and informal settlements often contain dense networks of small businesses and strong community organisation. Recognising the informal city explains why modern responses favour upgrading, providing secure tenure, water, sanitation and access to existing settlements, over demolition. A strong answer treats informality as the rational response of poor migrants to a shortage of formal housing and jobs, which is why it persists and why managing it, rather than erasing it, is the realistic planning task.
- Defining a megacity by area or importance
- It is a population threshold of ten million; state it.
- Treating megacities as only negative
- Acknowledge their economic dynamism and opportunity.
- Blaming size rather than speed
- Tokyo is huge yet liveable; the issue is the pace and resources of growth.
- Staying general
- Use a named megacity with specific detail for top marks.
Exam-style questions
Questions in the style of SCSA exam questions on this dot point, each with a worked answer. They are written by ExamExplained unless tagged "Past paper"; the year shows the paper a question is modelled on.
WACE 2022-style10 marksAnalyse the growth and challenges of a developing-world megacity. Use a specific example.Show worked answer →
A 10 mark response needs the growth drivers and the challenges, anchored in a named city.
Growth. Explain that megacities (over ten million people) cluster in the developing world because high rural-urban migration combines with high natural increase, so cities grow faster than industry and infrastructure can support. Primacy concentrates migration further.
Challenges. Cover informal settlements lacking tenure and sanitation, infrastructure strain producing congestion and disease risk, informal-economy employment, and environmental hazard as settlement spreads onto floodplains, intensified by climate change.
Example. Develop Dhaka: swelled by rural and flood-displaced migrants, large informal-settlement share, severe congestion, low-lying flood-prone land, yet driving the national garment-export economy.
Markers reward the speed-of-growth point, specific challenges and a named city used in depth rather than generalities.
WACE 2024-style6 marksExplain why the speed of growth, rather than size alone, is the defining challenge of developing-world megacities.Show worked answer →
A 6 mark response needs the speed argument and a contrast.
Speed argument. When a city adds millions of residents within a generation, housing, water, sanitation, transport and jobs cannot be built fast enough, so informal settlements and overstretched services fill the gap.
Contrast. A large developed megacity such as Tokyo grew slowly enough to build the systems that keep it liveable, so it is huge yet functions well, whereas a fast-growing developing megacity faces acute service deficits at a smaller size.
Conclude that pace and resources, not absolute population, determine the severity of the challenge. Markers reward the speed mechanism and the Tokyo-style contrast.