Megacities and urban problems
AdvancedA megacity holds over ten million people; more than thirty exist, led by Tokyo, Delhi and Shanghai. Explosive growth brings four classic urban ills — congestion, housing shortage, air pollution and slums — rooted in growth outpacing planning.
- Megacity: over ten million people; more than thirty worldwide, Tokyo's 37 million on top
- Four ills: congestion, housing shortage, air pollution, slums
- Key examples: Delhi's PM2.5, Hong Kong's 220,000 in subdivided flats, Dhaka's and Rio's slums
文體小知識：議題探究課：由「巨型城市」的定義出發，逐項檢視交通擠塞、房屋短缺、空氣污染與貧民窟四大城市病，找出共同根源。
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1A megacity is a city of over ten million people. The UN counts more than thirty: the Tokyo region, about 37 million, tops the list, followed by Delhi, Shanghai, São Paulo and Cairo — most lie in Asia, Africa and Latin America. Size brings economic power, for megacities are national engines, but it magnifies urban problems to the extreme.
2Congestion is the first daily scene: vehicles outgrow roads, and peak hours in Bangkok, Jakarta and Manila can stretch into hours of gridlock, costing time and fuel alike. Housing shortage follows: arrivals send prices soaring, and low-income families crowd into illegal structures, rooftops or tiny subdivided flats — about 220,000 people in Hong Kong live in subdivided flats, an extreme case of crowding.
3Air pollution is the health killer: exhaust, factories and power plants push fine particles (PM2.5) beyond safe levels; Delhi's winter air often forces schools to close. Pollution also means fouled rivers and mountains of waste. Slums are the scar of too-fast urbanisation: newcomers who cannot afford housing build shanties on the urban edge — the slums of Dhaka and Brazil's favelas house millions without piped water, sewers or fire safety, where fire and disease loom.
4All four problems share one root: population growing faster than infrastructure and planning. Remedies include mass transit, public housing, emission controls and slum upgrading with water and power — but the cure lies also in rural jobs and services to slow the inflow, or, as the next lesson argues, in making cities themselves sustainable.
1Summary 重點摘要
A megacity holds over ten million people; more than thirty exist, led by Tokyo, Delhi and Shanghai. Explosive growth brings four classic urban ills — congestion, housing shortage, air pollution and slums — rooted in growth outpacing planning.
2Vocabulary cards Vocabulary
A city of over ten million people; more than thirty exist, led by Tokyo's 37 million.
When vehicles exceed road capacity, costing time, fuel and money.
Fine particles under 2.5 micrometres that reach deep into lungs and blood — from traffic, factories and power plants.
Settlements lacking piped water, sewers and safety, often informal — as in Dhaka and Rio de Janeiro.
The self-built hillside slums of Brazil; over a million people live in Rio de Janeiro's.
Flats chopped into tiny rented cubicles; about 220,000 people live in them in Hong Kong.
When homes cannot keep up with population growth, raising prices and crowding.
The outward, unplanned spread of cities over farmland and open land, lengthening commutes.
High-capacity public transport such as metros and buses — the main cure for congestion and pollution.
3Step by step Steps
- Para 1: definition and global spreadA megacity is a city of more than ten million people — the best memory anchor. Tokyo leads with about 37 million, more than the entire population of Canada. More than thirty megacities now exist worldwide, mostly in Asia, Africa and Latin America, reflecting the astonishing speed of urbanisation there and the sharpest urban problems; it is a frequent exam topic worth mastering item by item.
- Para 2: traffic congestionToo many people, too little road: congestion is almost unavoidable in megacities. Bangkok and Jakarta are famous for rush hours that crawl along at a kilometre an hour, wasting time and fuel beyond counting. The comparison says it best — a private car averages just 1 to 2 occupants yet takes up wide road space, while one packed metro train carries about 2,000 people. Mass transit is therefore the core remedy and the key to cutting urban emissions.
- Para 2: housing shortageInflows of people outstrip housing supply, and low-income families suffer first. Hong Kong is a stark case: about 110,000 subdivided flats house some 220,000 people, at per-person space far below international standards; some newcomers and poor families are pushed into illegal structures and rooftop huts with doubtful fire and structural safety. Poor housing feeds poverty — illness and schooling problems follow — making it the heart of urban social problems.
- Para 3: air pollutionExhaust, industry and power generation foul megacities' air. Delhi's winter PM2.5 often runs past ten times the WHO guideline, forcing schools to close and cars off the road; Beijing has steadily improved through converting coal to gas and licence quotas, proving pollution is not incurable. Dirty air damages respiratory health, hits children and the elderly hardest, and raises medical burdens and economic losses.
- Para 3: slumsWhere formal housing lags growth, slums spring up. Over a third of Dhaka's people live in slums; Rio de Janeiro's favelas number in the hundreds with more than a million residents combined. The traits repeat everywhere: no land tenure, little water, power or sewerage, shacks of timber and sheet metal, high fire and disease risk, and poor access to formal jobs and public services — so poverty circulates without end.
- Para 4: shared root and remediesThe shared root of urban problems is population growth outpacing infrastructure and housing, and the remedies must match: build mass transit such as metros and buses to move people; expand public housing to add supply; tighten vehicle emission controls to clean the air; and upgrade slums step by step — water, power and legal titles — rather than forced clearance. Bangkok's Skytrain, Hong Kong's public housing programme and Dhaka's upgrading projects are examples worth citing.
4Diagrams Diagrams
5Worked example Example
Example: name two environmental and two social problems of megacities, with examples and one remedy each.
- Environmental one: air pollution — Delhi's winter PM2.5 closes schools; remedy: expand metros, add electric buses, tighten emission standards
- Environmental two: water and waste pollution — Dhaka's reeking rivers and rubbish heaps; remedy: sewage plants plus sorting and waste-to-energy
- Social one: housing shortage — about 220,000 Hongkongers in subdivided flats; remedy: build public housing and regulate subdivisions
- Social two: slums — millions in Dhaka and Rio without utilities; remedy: slum upgrading with water, power and legal titles
- Answer: Environmental: air pollution (Delhi) and water and waste pollution (Dhaka); social: housing shortage (Hong Kong's subdivisions) and slums (Rio de Janeiro). Remedies: transit and emission controls; sewage and waste treatment; public housing; slum upgrading. Tip: sort problems into environmental and social, pairing each with one city and one remedy.
6Common mistakes Mistakes
7Quick check Quick check
Q1Define a megacity and give two examples.
Q2What losses does traffic congestion cause?
Q3What are subdivided flats, and what problem do they reflect?
Q4What are three key features of slums?
Q5Why can't congestion be solved by widening roads alone?
8Recap Recap
- Megacity: over ten million people; more than thirty worldwide, Tokyo's 37 million on top
- Four ills: congestion, housing shortage, air pollution, slums
- Key examples: Delhi's PM2.5, Hong Kong's 220,000 in subdivided flats, Dhaka's and Rio's slums
- Shared root: population growth outpacing infrastructure and planning
- Remedies: mass transit, public housing, emission controls, slum upgrading