Introduction to Sustainable Cities

Key Inquiry Question

How can cities be developed sustainably?

This is the guiding question for this entire topic. As you work through these notes, keep asking: What problems do cities face, and how do we solve them without making things worse for future generations?

1. What Is a City?

A city is a large, densely settled area where people live and work, with well-developed infrastructure, a wide range of services, and significant economic and political functions.

Cities are defined by several key characteristics:

1. 1 High Population Density

Population density measures how many people live per square kilometre (km²). Cities have far higher densities than rural areas.

Area	Approximate Population Density
Singapore (overall)	~8,000 people/km²
Central Singapore	~20,000+ people/km²
Rural Malaysia	~30–100 people/km²

High density means more people sharing the same land — this creates both opportunities (more services, jobs) and challenges (congestion, housing pressure).

2. 2 Economic Activity

Cities are economic hubs. They concentrate:

Primary industries at their fringes (some farming, quarrying)
Secondary industries: manufacturing and construction
Tertiary industries: retail, finance, healthcare, education — these dominate in modern cities
Quaternary industries: research, information technology, media

Cities attract businesses because of agglomeration effects: firms benefit from being near suppliers, skilled workers, and customers all in one place.

3. 3 Services and Infrastructure

Cities offer services that rural areas cannot:

Hospitals and specialist medical centres
Universities and tertiary education
Public transport networks (MRT, buses, expressways)
Utilities: piped water, sewage systems, electricity grids
Financial services: banks, insurance companies
Entertainment and cultural facilities: museums, theatres, shopping malls

This concentration of services makes cities attractive destinations for migrants.

4. 4 Political Functions

Many cities serve as seats of government:

Capital cities house national governments (e.g. Jakarta is Indonesia’s capital; Kuala Lumpur is Malaysia’s capital)
Administrative centres host regional/state government offices
Singapore is both a city and a nation-state, meaning its city government and national government are the same body

Political functions concentrate power, decision-making, and public investment in cities.

2. Global Urbanisation

5. 1 What Is Urbanisation?

Urbanisation is the process by which an increasing proportion of a country’s population comes to live in urban areas (towns and cities).

It is measured as the percentage of the total population living in urban areas.

Key global fact: More than 55% of the world’s population now lives in cities (as of the early 2020s). The United Nations projects this will rise to nearly 70% by 2050.

6. 2 Regional Trends

Urbanisation is not happening at the same rate everywhere. Different regions are at different stages:

Region	Level of Urbanisation	Trend
Europe	~75% urban	Already highly urbanised; slow growth
North America	~82% urban	Already highly urbanised; slow growth
Asia	~52% urban	Rapidly urbanising; fastest growth in absolute numbers
Africa	~44% urban	Lower urbanisation but fastest growth rate

Asia: Countries like China, India, Vietnam, and Indonesia are experiencing rapid urbanisation as economies industrialise. Megacities such as Tokyo, Shanghai, Mumbai, and Jakarta dominate the region.

Africa: African cities are growing very quickly — some of the fastest-growing cities in the world are in Nigeria, Ethiopia, and the Democratic Republic of Congo. However, rapid growth often outpaces infrastructure development, leading to large informal settlements.

Europe: European cities are already mature and urbanised. Growth is slow and the focus is on improving liveability and sustainability rather than expanding city size.

7. 3 Push and Pull Factors for Urban Migration

People move from rural to urban areas because of a combination of push factors (reasons to leave the countryside) and pull factors (reasons to move to the city).

Push Factors (leaving rural areas):

Limited job opportunities in agriculture
Low and unpredictable farm income
Natural disasters: droughts, floods, crop failures
Lack of schools and hospitals
Social factors: limited opportunities for women and young people
Land shortages as rural populations grow

Pull Factors (moving to cities):

More job opportunities in factories, services, and commerce
Higher wages
Better schools, universities, and healthcare
Better infrastructure: electricity, clean water, internet
Social opportunities: more people to meet, more cultural activities
Access to markets to sell goods or buy products

Exam tip: Always give specific examples when listing push and pull factors. For example: “A farmer in rural Indonesia may be pushed out by drought destroying crops, and pulled to Jakarta by the availability of factory jobs.”

3. Relationship Between Cities and Rural Areas

Cities and rural areas are interdependent — they depend on each other and cannot function in isolation.

8. 1 How Cities Depend on Rural Areas

What Cities Need	What Rural Areas Provide
Food	Farms grow rice, vegetables, fruit, and raise livestock
Raw materials	Forests provide timber; mines provide metals; quarries provide stone
Water	Reservoirs and catchment areas are often in rural zones
Labour	Rural-to-urban migrants fill factories, construction sites, and service industries
Land for expansion	Cities expand into surrounding rural land for new housing and industry

Example: Singapore imports over 90% of its food from Malaysia, Indonesia, and other countries — because Singapore’s own rural land is extremely limited.

9. 2 How Rural Areas Depend on Cities

What Rural Areas Need	What Cities Provide
Markets	Cities are the main buyers of farm produce and raw materials
Services	Hospitals, specialist schools, government offices are mainly in cities
Manufactured goods	Tractors, fertilisers, tools, electronics, clothing
Investment	Government spending on roads and irrigation in rural areas comes from taxes collected in cities
Information and technology	New farming methods, seeds, and techniques are developed in universities and research centres in cities

This mutual dependence means that neglecting rural areas can hurt cities too. If farmers cannot earn a living, food prices in cities rise.

4. What Makes a City Sustainable?

10. 1 Defining Sustainable Development

Sustainable development means development that meets the needs of the present without compromising the ability of future generations to meet their own needs. (Brundtland Commission, 1987)

Applied to cities: a sustainable city can grow and provide for its residents today while preserving resources, protecting the environment, and maintaining social cohesion for the future.

11. 2 The Three Pillars of Sustainability

Sustainability rests on three pillars that must all be addressed together:

         SUSTAINABLE
             CITY
           /       \
    Social         Economic
 Sustainability   Sustainability
           \       /
        Environmental
        Sustainability

If any one pillar is neglected, the city is not truly sustainable.

Pillar 1: Environmental Sustainability

The city manages natural resources carefully and minimises environmental damage.

What it involves:

Reducing pollution (air, water, soil, noise)
Managing waste (reducing, reusing, recycling)
Protecting green spaces, parks, and biodiversity
Using renewable energy (solar, wind) instead of fossil fuels
Building energy-efficient buildings
Managing water resources responsibly

Examples:

Singapore’s ABC Waters Programme cleans rivers and reservoirs and turns them into recreational spaces
Singapore recycles NEWater (treated wastewater) to reduce dependence on imported water
Copenhagen (Denmark) runs largely on wind energy and aims to be carbon-neutral
Singapore targets 80% green buildings under the Green Mark scheme

All residents have access to basic needs, services, and opportunities; communities are cohesive and safe.

What it involves:

Affordable, adequate housing for all income groups
Access to quality healthcare and education
Safe public spaces that promote interaction
Social inclusion: no group is left behind (elderly, disabled, low-income)
Cultural opportunities: libraries, community centres, parks
Low crime rates

Examples:

Singapore’s HDB (Housing & Development Board) provides affordable public housing to over 80% of Singaporeans — one of the highest rates in the world
Singapore’s ethnic integration policy ensures HDB estates are racially mixed, preventing the formation of ethnic enclaves
Curitiba, Brazil built community centres in low-income areas and subsidised bus tickets for workers

Pillar 3: Economic Sustainability

The city has a diverse, resilient economy that provides jobs and income for residents at all skill levels.

What it involves:

Diverse industries so the economy does not depend on a single sector
Job creation for all skill levels, not just highly educated workers
Fair wages and reasonable working conditions
Investment in education and skills training
Attracting new industries and innovation
Economic inclusion: opportunities for people of all backgrounds

Examples:

Singapore continually upgrades its workforce through SkillsFuture to adapt to new industries like AI and biomedical research
Medellín, Colombia transformed from one of the world’s most dangerous cities to an economic success story by investing in education and connecting poor hillside communities with cable cars and escalators to the economic centre
Singapore’s Jurong Lake District is being developed as a new business district to spread economic activity beyond the CBD

5. The Key Question for Sec 2 Geography

How can cities be developed sustainably?

This question asks you to connect urban challenges with solutions, and to evaluate whether those solutions truly address all three pillars of sustainability.

Framework for answering this question:

Identify the urban challenge (e.g. housing shortage, traffic congestion)
Explain why it is a problem for sustainability (which pillar does it threaten?)
Describe a solution with a specific case study example
Evaluate: Does the solution work? Does it address all three pillars? Are there trade-offs?

6. Urban Challenges Overview

12. 1 Housing

The challenge: As cities grow rapidly, there is often not enough affordable formal housing. Two types of housing exist:

Formal Housing	Informal Settlements (Slums)
Built with planning permission	Built without planning permission on unused/illegal land
Has connections to water, electricity, sewage	Often lacks clean water, electricity, sewage
Safe building materials and structures	Unsafe structures; fire and flood risk
Residents have legal ownership	Residents have no legal tenure
Examples: HDB flats in Singapore	Examples: Tondo district in Manila; Dharavi in Mumbai

Why it matters for sustainability:

Poor housing threatens social sustainability (health, safety, dignity)
Informal settlements often harm environmental sustainability (pollution, waste)
Slum residents are trapped in poverty, undermining economic sustainability

13. 2 Transport

The challenge: As cities grow, more vehicles use roads → traffic congestion.

Problems caused by congestion:

Lost productivity (time wasted in jams)
Air pollution from vehicle emissions → respiratory diseases
Carbon dioxide emissions contributing to climate change
Road accidents

Solutions:

Public transport (MRT, bus rapid transit) reduces the number of private vehicles
Congestion charging: charging motorists to enter busy areas (e.g. Singapore’s ERP — Electronic Road Pricing)
Car-free zones in city centres
Cycling infrastructure and pedestrian-friendly streets
Transit-oriented development (TOD): building homes and offices near MRT stations

14. 3 Waste Management

The challenge: Cities produce enormous amounts of solid waste. Without proper management, waste causes:

Soil and water pollution
Disease (rats, mosquitoes breed in garbage)
Blockage of drains → flooding
Greenhouse gas emissions from landfill

Solutions:

The 3Rs: Reduce, Reuse, Recycle
Waste-to-energy incineration (Singapore incinerates much of its waste at its waste-to-energy plants before landfilling the ash)
Semakau Landfill (Singapore’s only landfill, offshore): used for ash from incineration
Zero Waste Masterplan: Singapore aims to reduce waste sent to Semakau by 30% by 2030

15. 4 Inequality

The challenge: In many cities, the gap between rich and poor is wide and growing. This is called social inequality or income inequality.

Consequences:

Rich and poor live in completely different neighbourhoods with very different quality of life
Poor residents cannot afford healthcare, good schools, or housing near job centres
Social unrest and crime can increase

Gentrification is a related process: when wealthier residents move into a previously low-income neighbourhood, property prices rise and the original residents are priced out.

Gentrification: The process by which a low-income urban area is renovated and upgraded, attracting wealthier residents and businesses, often displacing the original lower-income community.

16. 5 Green Space

The challenge: As cities expand and densify, natural land is replaced by buildings and roads. This causes:

Urban heat island effect: cities are hotter than surrounding areas because concrete and tarmac absorb and retain heat
Loss of biodiversity
Reduced mental health and well-being of residents
Increased surface runoff and flooding (less soil to absorb rain)

Solutions:

Parks and nature reserves (e.g. Singapore’s Central Catchment Nature Reserve)
Green roofs and vertical gardens (e.g. Jewel Changi Airport’s indoor waterfall and gardens)
Park Connector Network in Singapore: 300+ km of green corridors linking parks
Urban biodiversity programmes: planting native species, creating wildlife corridors

The challenge: Cities bring together people of different ethnicities, religions, languages, and socioeconomic backgrounds. Without deliberate policies, communities can become segregated (separated), leading to:

Distrust and tension between groups
Discrimination
Difficulties in national identity formation

Solutions:

Singapore’s Ethnic Integration Policy (EIP) for HDB flats: ensures each block and neighbourhood has a racial mix that reflects national proportions
Community centres and residents’ committees: spaces for neighbours to meet and interact
Common national school curriculum and national service: shared experiences that cross ethnic and class lines

7. Singapore as a Model Sustainable City

Singapore is often cited as one of the world’s most successful examples of sustainable urban development. Here is why:

18. 1 Compact City Form

Singapore is a small island (733 km²) with a population of ~6 million. Rather than spreading out (urban sprawl), Singapore has grown upward with high-rise buildings and has carefully planned land use to keep a compact footprint.

Benefits of compact form:

Land is used efficiently
Public transport is viable because people live close to MRT/bus routes
Green spaces can be preserved at the city’s edges and within neighbourhoods

19. 2 Integrated Planning: The URA

The Urban Redevelopment Authority (URA) is Singapore’s national land use planning authority. It produces the Concept Plan (long-term, 40–50 year vision) and the Master Plan (detailed land use map, updated every 5 years).

Why this matters:

All development must follow the Master Plan — no ad hoc sprawl
Housing, transport, industry, green space, and utilities are planned together, not separately
Long-term planning means infrastructure is built before problems become crises

20. 3 Green Buildings

Singapore’s Green Mark Scheme (run by Building and Construction Authority, BCA) rates buildings on energy efficiency, water efficiency, and use of green features.

Target: 80% of all buildings to be Green Mark certified by 2030
New public buildings must achieve Green Mark Platinum (highest rating)
Green buildings reduce energy consumption, lowering carbon emissions and utility bills

Example: The CapitaGreen building in the CBD features a sky garden, a wind scoop to channel cool air, and high-efficiency air conditioning.

21. 4 Public Housing: HDB

Over 80% of Singaporeans live in HDB flats (much higher than most countries)
HDB flats are affordable because the government subsidises them and sells them on 99-year leases
Each HDB town is a self-contained community with schools, clinics, markets, and MRT stations within walking distance — this reduces the need to travel far for daily needs
The ethnic integration policy prevents racial segregation

22. 5 Public Transport

Singapore’s Land Transport Master Plan prioritises public transport over private cars:

Extensive MRT network (over 130 stations across 6 lines as of the mid-2020s)
Integrated bus network feeds into MRT stations
ERP (Electronic Road Pricing): gantries charge motorists entering congested areas, reducing car use
Certificate of Entitlement (COE): limits the total number of private cars by requiring buyers to bid for permission to own a vehicle — this keeps car numbers in check

23. 6 Water Management: Four National Taps

Singapore has achieved water sustainability through its Four National Taps strategy:

Local catchment water from reservoirs (e.g. Marina Reservoir covers 1/6 of Singapore’s land area)
Imported water from Johor, Malaysia (agreements run until 2061)
NEWater (reclaimed and ultra-purified wastewater — meets WHO drinking water standards)
Desalinated water (seawater purified by removing salt — energy-intensive but drought-proof)

This diversification ensures Singapore is never fully dependent on any single source.

8. Case Study: Jakarta, Indonesia — Urban Challenges in a Developing Asian City

24. 1 Background

Location: Northwestern coast of Java, Indonesia
Population: ~10.6 million in the city proper; ~34 million in the Greater Jakarta metropolitan area (Jabodetabek) — one of the world’s largest urban agglomerations
Status: Former capital of Indonesia (the capital is being relocated to Nusantara on Borneo)
Context: Rapid industrialisation and rural-urban migration since the 1970s

25. 2 Urban Challenges Facing Jakarta

1. Flooding Jakarta is built on swampy, low-lying coastal land. It experiences severe annual flooding due to:

Heavy monsoon rains (up to 300mm in a single day)
Rivers carrying runoff from surrounding hills through the city
Land subsidence (sinking): Jakarta is sinking by 1–25 cm per year in some areas because residents illegally pump groundwater from beneath the city, causing the ground to collapse. Some parts of North Jakarta are already below sea level.

Consequences: Homes and businesses destroyed; disease outbreaks (dengue fever, cholera); disruption to transport and economy.

2. Informal Settlements (Kampungs) Rapid migration from rural Java has outpaced formal housing supply. Around 60% of Jakarta’s population lives in informal settlements called kampungs:

Often built along riverbanks (flood-prone areas)
Limited access to clean water and sanitation
Fire risk from densely packed, makeshift structures
Residents have insecure land tenure

3. Traffic Congestion Jakarta is notorious for some of the worst traffic in the world:

Over 20 million motor vehicles registered in greater Jakarta
Road network has not kept pace with vehicle growth
Commuters often spend 3–5 hours per day in traffic
Air pollution from vehicles causes serious respiratory health problems

4. Air and Water Pollution

Vehicle emissions + industrial activity = severe air pollution. Jakarta has regularly ranked among the world’s most polluted cities
Rivers (e.g. Ciliwung River) are heavily polluted with domestic waste, industrial effluent, and plastic — many residents have no access to piped sewage disposal

5. Inequality

Jakarta contains some of the wealthiest neighbourhoods in Southeast Asia (e.g. Menteng, Kebayoran Baru) alongside vast slum areas
Access to quality schools, healthcare, and clean water is very unequal

26. 3 How Jakarta Is Trying to Address These Challenges

Challenge	Response
Flooding	Sea wall (National Capital Integrated Coastal Development); river normalisation; retention ponds
Congestion	MRT Jakarta (opened 2019); TransJakarta BRT (bus rapid transit, the world’s longest BRT corridor); restrictions on private cars during peak hours
Informal settlements	Some kampungs have been upgraded with piped water and improved sanitation; however, some residents have been evicted to build infrastructure (controversial)
Air pollution	Emission testing programmes; push for electric buses
Sinking	Restrictions on groundwater extraction; piped water expansion to reduce illegal pumping

27. 4 Evaluation

Jakarta illustrates the tension between rapid economic growth and sustainability. Economic growth has brought jobs and lifted millions out of poverty, but the pace of urbanisation has overwhelmed infrastructure. The city’s challenges are deeply interconnected: sinking land worsens flooding; flooding destroys homes in kampungs; kampung residents lack resources to move; inequality limits political will to invest in poor areas.

The relocation of Indonesia’s capital to Nusantara (Borneo) is partly intended to relieve pressure on Jakarta — but critics argue this is expensive and does not solve Jakarta’s existing problems.

Contrast with Singapore: Singapore’s success is partly the result of being a city-state with complete government control over a small territory, high income, and no rural hinterland demanding government attention. Jakarta, as one city within a huge archipelago nation, faces far more complex political and financial constraints.

9. Geographical Skills

28. 1 Reading Urban Land Use Maps

Urban land use maps show how land is used across a city. Common land use categories and their map colours (may vary by map):

Land Use	Typical Colour	Key Features to Look For
Residential	Yellow / Orange	HDB estates, private housing, apartment blocks
Commercial / CBD	Red	Shops, offices, financial district, high-rise buildings
Industrial	Purple / Grey	Factories, warehouses, port areas
Green / Open Space	Green	Parks, nature reserves, golf courses, cemeteries
Transport	Grey / White	Roads, MRT lines, airports, ports
Institutional	Blue	Schools, hospitals, government buildings
Water Bodies	Blue	Rivers, reservoirs, sea

Tips for reading land use maps:

Always read the legend/key first
Note the scale — how large is each land use zone in real life?
Look for patterns: Is commercial land concentrated in one area (CBD)? Is industrial land near the port or away from residential areas?
Describe location using compass directions and landmarks: “Industrial land is found mainly in the western part of the city, near the port”
Look for transitions: how do land uses change from the city centre outward?

The Concentric Zone Model (Burgess Model) describes a typical pattern:

Zone 1 (Centre): CBD — most accessible, highest land values
Zone 2: Transition zone — old factories, warehouses, inner-city housing
Zone 3: Working-class housing
Zone 4: Middle-class housing
Zone 5: Outer suburbs / commuter zone

Note: Singapore does not fit this model perfectly because of its planned, compact form.

29. 2 Interpreting Population Density Maps

Population density maps show how many people live per unit area. They come in two main types:

Choropleth Maps:

Areas are shaded in different colours or intensities to show density
Darker shade = higher density (usually)
Read the legend carefully — what does each shade represent?
Look for spatial patterns: Where is density highest? Lowest? Why?

Dot Maps:

Each dot represents a certain number of people
Clusters of dots = high density; scattered dots = low density

Questions to ask when interpreting population density maps:

Where is the highest density? Why? (near CBD, transport hubs, employment centres)
Where is the lowest density? Why? (industrial zones, green spaces, airports)
How does density change from the centre to the edge?
Are there any unexpected patterns? (e.g. a low-density pocket in the city centre might be a park or military base)
How has density changed over time? (if you have maps from different years)

For Singapore specifically:

Highest densities in central and northeastern HDB towns (Toa Payoh, Tampines, Jurong West)
Lower densities in western industrial zones (Jurong Island, Tuas) and nature reserves (Central Catchment)
Density is generally more even than in unplanned cities because HDB new towns distribute population across the island

10. Key Vocabulary with Definitions

Term	Definition
Urbanisation	The process by which an increasing proportion of a population comes to live in urban areas (towns and cities). It is measured as the percentage of a country’s population living in urban areas.
Urban sprawl	The uncontrolled, low-density outward expansion of urban areas into surrounding rural or natural land, typically characterised by car-dependent suburbs, scattered development, and inefficient land use.
Megacity	A city with a population of 10 million or more people. Examples: Tokyo (~37 million), Jakarta (~34 million in the metro area), Mumbai (~21 million).
Sustainable development	Development that meets the needs of the present without compromising the ability of future generations to meet their own needs. (Brundtland Commission definition, 1987.)
Liveability	The degree to which a city provides a pleasant, comfortable, and fulfilling environment for its residents. It encompasses safety, affordability, access to services, green space, and social cohesion.
Gentrification	The process by which a low-income urban neighbourhood is renovated and upgraded, attracting wealthier residents and businesses, and often displacing the original lower-income community through rising rents and property prices.
Informal settlement / Slum	A residential area that has developed without official planning permission, typically lacking access to clean water, sanitation, electricity, and secure land tenure. Also called squatter settlements or kampungs.
Population density	The number of people living per unit area, usually expressed as people per square kilometre (people/km²).
Urban heat island	The phenomenon whereby urban areas are significantly warmer than surrounding rural areas, due to the absorption of heat by concrete, tarmac, and buildings, and the loss of vegetation.
Agglomeration	The clustering of economic activities (businesses, industries) in a city or specific location, creating mutual benefits such as shared infrastructure, labour pools, and customer access.
Transit-oriented development (TOD)	An urban planning approach that concentrates housing, businesses, and services around public transport nodes (e.g. MRT stations), reducing car dependency and encouraging walkability.
Congestion	The state of being overcrowded or overfull, particularly referring to traffic — when roads carry more vehicles than they can handle efficiently, causing slow movement and delays.
Resilience	The ability of a city or community to withstand, adapt to, and recover from shocks and stresses (e.g. floods, economic crises, pandemics) while maintaining essential functions.
Land subsidence	The gradual sinking or settling of the ground surface, often caused by excessive extraction of groundwater, oil, or gas, or by the natural compaction of soft sediment. Particularly severe in Jakarta.

11. Model PEEL Answers

PEEL structure: Point → Evidence → Explanation → Link

Question 1: Explain why cities attract rural migrants. [4 marks]

Model Answer:

Cities attract rural migrants primarily because of the greater economic opportunities they offer compared to the countryside. For example, in Indonesia, many rural Javanese migrate to Jakarta to work in factories, construction, and the service sector, where wages are significantly higher than in subsistence agriculture. This is because urban areas concentrate businesses and industries that create far more paid employment than rural areas, where income is often seasonal and dependent on unpredictable harvests. As a result, rural migrants see the city as a path to a higher and more stable standard of living, which is why Jakarta’s population has grown to over 34 million in its metropolitan area. Therefore, economic pull factors are a primary driver of rural-to-urban migration.

Question 2: Explain how Singapore has achieved environmental sustainability. [4 marks]

Model Answer:

Singapore has achieved environmental sustainability by carefully managing its water resources through its Four National Taps strategy. Specifically, Singapore has developed NEWater — reclaimed and ultra-purified wastewater — and desalination plants, supplementing traditional sources such as reservoirs and imported water from Malaysia. This is because Singapore recognised that relying on a single water source, particularly imported water, was environmentally and strategically risky, and that water security was fundamental to sustaining its population and economy long-term. As a result, Singapore is now able to meet over 40% of its water needs from NEWater alone, drastically reducing its vulnerability to water shortages. This demonstrates that environmental sustainability can be achieved through technological innovation and long-term planning, even in a land-scarce city-state like Singapore.

Question 3: “Social sustainability is the most important pillar of sustainability for cities.” Do you agree? [6 marks]

Model Answer:

I partially agree that social sustainability is the most important pillar, as it directly affects the quality of life of residents. Singapore’s Housing & Development Board (HDB) is a strong example: by providing affordable public housing for over 80% of Singaporeans, the government ensures that all residents have safe, adequate shelter regardless of income. The ethnic integration policy embedded in HDB allocation also prevents racial segregation, promoting social cohesion. Without this foundation of social stability, economic and environmental progress would be difficult to achieve, as citizens who lack basic needs or live in fear of violence cannot productively contribute to the city.

However, environmental sustainability is equally critical, as environmental problems can undermine social gains if left unaddressed. Jakarta illustrates this: despite economic growth, severe flooding — worsened by land subsidence from groundwater extraction — destroys the homes of hundreds of thousands of residents annually, many of them living in informal kampungs. This shows that social sustainability cannot be maintained when the physical environment is degraded. Similarly, economic sustainability underpins both other pillars, because without a functioning economy, governments cannot fund the housing, healthcare, and environmental management that sustainability requires.

In conclusion, all three pillars are interdependent and equally important. Prioritising one at the expense of others leads to imbalance: a city that is economically productive but environmentally degraded and socially unequal is not truly sustainable. The most successful sustainable cities, such as Singapore, are those that balance all three pillars simultaneously through integrated long-term planning.

Question 4: Describe and explain the distribution of population density in a city you have studied. [4 marks]

Model Answer:

In Singapore, population density is highest in the central and northeastern parts of the island, such as in HDB new towns like Toa Payoh, Tampines, and Hougang, where density can exceed 20,000 people per km². This is because these areas have been systematically developed by the Housing & Development Board with high-rise residential blocks to accommodate a large population in a compact area close to employment centres and MRT stations. In contrast, population density is much lower in the western parts of Singapore, particularly in industrial zones such as Jurong Industrial Estate and Tuas, as well as in the Central Catchment Nature Reserve. This is because these areas are zoned for industrial use or conserved as natural green space, meaning little residential development is permitted. Therefore, Singapore’s population distribution reflects its highly planned land use zoning, with high-density residential areas deliberately located near transport and employment, and low-density zones reserved for industry and nature.

12. Exam-Style Questions with Model Answers

Short-Answer Questions

Q1: What is a megacity? Give one example. [2 marks]

A megacity is a city with a population of 10 million people or more. An example is Jakarta, Indonesia, which has a metropolitan area population of approximately 34 million.

Q2: State two pull factors that attract people to cities. [2 marks]

(1) Greater job opportunities and higher wages in urban industries and services. (2) Better access to healthcare, education, and other services.

Q3: State two characteristics of informal settlements. [2 marks]

(1) Residents lack legal ownership of the land and live under threat of eviction. (2) The settlement often lacks access to clean piped water, electricity, and proper sewage disposal.

Q4: What is meant by the term “urban heat island”? [2 marks]

The urban heat island refers to the phenomenon whereby urban areas are significantly warmer than the surrounding rural countryside. This occurs because the concrete, tarmac, and buildings in cities absorb and retain heat, while the lack of vegetation reduces the cooling effect of evapotranspiration.

Structured Questions

Q5: Study the information below and answer the questions that follow.

Data: In 2000, 40% of the world’s population lived in cities. By 2024, this had risen to over 55%. The fastest growth is occurring in Asian and African cities.

(a) Describe the trend in global urbanisation shown by the data. [2 marks]

The proportion of the world’s population living in cities has increased significantly, rising from 40% in 2000 to over 55% by 2024. This represents a growth of more than 15 percentage points over approximately 24 years. The fastest urbanisation is occurring in Asia and Africa.

(b) Explain why urbanisation is occurring most rapidly in Asia and Africa. [4 marks]

Urbanisation is occurring most rapidly in Asia and Africa because these regions are undergoing rapid industrialisation and economic development, creating large numbers of urban jobs that attract rural migrants. In countries like Indonesia and Nigeria, many people are pushed from rural areas by limited agricultural opportunities, poverty, and natural disasters, and pulled to cities by higher wages and better services. Because these regions still have relatively large rural populations — unlike Europe and North America, which urbanised much earlier — there is a larger pool of potential urban migrants, so the rate of urban growth is faster. As manufacturing industries set up in cities across Asia and Africa, the demand for urban labour increases, accelerating the pace of urbanisation.

Cities and rural areas need each other and cannot function independently. Cities depend on rural areas for essential resources: for example, Singapore imports the majority of its food from rural agricultural areas in Malaysia, Indonesia, and further afield because it lacks the land to grow enough food domestically. Rural areas also supply cities with labour — many factory and construction workers in Singapore and Jakarta come from rural hinterlands. Conversely, rural areas depend on cities for markets to sell their produce: a Malaysian palm oil farmer, for example, sells to processors and exporters based in urban Kuala Lumpur. Rural areas also rely on city-based services such as hospitals and universities, and on manufactured goods (tractors, fertilisers) produced in urban factories. This mutual dependence means that policies affecting one region will always have consequences for the other.

Q6: To what extent is Singapore a model sustainable city? [8 marks]

Singapore is often cited as one of the world’s most successful examples of sustainable urban development, and there is considerable evidence to support this claim across all three pillars of sustainability.

In terms of environmental sustainability, Singapore has made remarkable progress. Its Four National Taps water strategy ensures water security without overexploiting any single source: NEWater (reclaimed wastewater) and desalination together provide over 40% of supply, reducing dependence on imported water. Singapore’s Green Mark Scheme incentivises energy-efficient buildings, and the Park Connector Network preserves biodiversity and provides urban green space. The ABC Waters Programme has transformed polluted drains and canals into clean recreational waterways. These initiatives demonstrate that a dense urban environment can achieve high environmental standards.

Socially, Singapore scores strongly through its HDB public housing programme, which provides affordable, high-quality homes to over 80% of residents — far exceeding rates in most countries. The ethnic integration policy embedded in HDB allocation ensures neighbourhoods are racially mixed, promoting social cohesion in a multi-ethnic society. Universal healthcare through Medishield Life and a comprehensive public education system further underpin social sustainability.

Economically, Singapore has built a diversified, resilient economy by attracting multinationals, developing Jurong Island as a petrochemical cluster, and investing in biomedical and digital industries through SkillsFuture training programmes. Per capita GDP is among the highest in the world, and unemployment remains consistently low.

However, Singapore is not a perfect model. High housing costs in the private market and the cost of living make the city unaffordable for low-income residents and foreign workers, who may live in crowded dormitories with limited amenities. Gentrification in heritage areas like Tiong Bahru has displaced original communities. Singapore also remains heavily dependent on fossil fuels for electricity, though it is transitioning towards solar and regional grids. Its small size and city-state status give it governance advantages — a single government controls all land use — that are not replicable in larger countries.

In conclusion, Singapore is an exceptional model of sustainable urban planning, demonstrating that economic growth, social inclusion, and environmental care can be pursued together. However, it should be studied with awareness of its unique context: its wealth, size, and governance structure make some of its solutions difficult to transfer directly to larger developing cities like Jakarta or Manila.

13. Summary: Key Concepts at a Glance

Concept	One-Line Summary
City	A large, dense settlement with economic, service, and political functions
Urbanisation	Growing % of population living in cities; now >55% globally
Push/pull factors	Push = reasons to leave countryside; pull = reasons to move to city
Urban-rural interdependence	Cities need food/labour from rural; rural needs markets/services from cities
Three pillars	Environmental + Social + Economic sustainability must all be addressed
Singapore strengths	HDB housing; integrated URA planning; NEWater; Green Mark; MRT/ERP
Jakarta challenges	Flooding, land subsidence, informal settlements, congestion, inequality
Megacity	City with 10 million+ people
Gentrification	Upgrading a poor neighbourhood, often displacing original residents
Urban heat island	Cities are hotter than surroundings due to concrete and lack of vegetation

End of Notes — Introduction to Sustainable Cities