Urban growth: processes, causes, consequences, hierarchy, primate and world cities

Urban Areas and Management – Cambridge AS & A‑Level Geography (9696)

1. Key Concepts

• Scale: processes operate at neighbourhood, city‑region and megacity levels.
• Change over time: historic urbanisation (1950‑2020) and future projections (to 2050).
• Systems approach: cities are interacting physical‑human systems (population, capital, land‑use, services, waste).
• Cause‑and‑effect & evaluation: drivers of growth, their impacts and the management responses required (cost‑effectiveness, equity, sustainability, feasibility, adaptability).

2. Urban Growth – Processes

Urban growth is the increase in a city’s size, population and economic activity. It can be described as a system with inputs, processes and outputs.

Timeline – Change Over Time (1950‑2020)

Year	Global Urban Population	Key Process Dominating Growth
1950	750 million (≈ 55 % of world pop.)	Industrial‑era migration to manufacturing cities (Europe, North America).
1980	1.5 billion (≈ 60 %)	Rise of service‑sector jobs; early vertical development in East Asia.
2000	2.9 billion (≈ 65 %)	Rapid horizontal expansion in Africa & South‑Asia; megacity formation.
2020	4.5 billion (≈ 55 % of world pop.)	Combined horizontal‑vertical growth; dominance of knowledge‑based economies.

3. Causes of Urban Growth – Push & Pull Factors

Push (Rural)	Pull (Urban)
Poverty & limited non‑farm jobs Agricultural mechanisation & land consolidation Environmental degradation (desertification, floods) Conflict or political instability	Higher wages & diverse employment (industry, services) Better education, health and social amenities Improved transport & digital connectivity Perceived higher standard of living & cultural opportunities

4. Consequences of Urban Growth – Evaluation

Each consequence is examined using the AO3 evaluation criteria: cost‑effectiveness, equity, environmental outcome, feasibility and long‑term adaptability. Contrasting examples from a high‑income country (HIC) and a low‑income country (LIC) illustrate the range of outcomes.

Consequence	HIC Example	LIC Example	Evaluation (Pros / Cons)
Economic impacts	London – growth in finance and tech creates high tax revenue.	Lagos – oil‑related boom generates revenue but is volatile.	Pros: Increased productivity, innovation, fiscal capacity. Cons: Dependence on single sectors (oil, finance) → vulnerability; benefits may accrue to elite (equity issue). AO3: High economic gains (cost‑effective) but low equity and resilience.
Social impacts	London – universal health & education, but rising house‑price segregation.	Nairobi – rapid population rise outpaces services, leading to informal settlements (e.g., Kibera).	Pros: Improved access to services where provision is strong. Cons: Social segregation in HIC; severe deprivation and health risks in LIC. AO3: Equity low in both cases; feasibility of service expansion higher in HIC.
Environmental pressures	Paris – air‑quality monitoring, low‑emission zones reduce pollution.	Dhaka – unregulated waste, severe air‑pollution, loss of peri‑urban wetlands.	Pros: Advanced mitigation measures (costly but effective) in HIC. Cons: Limited regulatory capacity in LIC; high environmental damage. AO3: High cost‑effectiveness in HIC, low feasibility in LIC; equity concerns over exposure to pollutants.
Infrastructure challenges	Tokyo – extensive rail network, high‑capacity utilities.	Karachi – overloaded water supply, frequent power cuts.	Pros: Efficient public‑transport reduces congestion (HIC). Cons: Inadequate provision leads to informal solutions (e.g., illegal connections) in LIC. AO3: Investment is cost‑effective long‑term in HIC; low feasibility and equity in LIC.

5. Urban Structure & Change

5.1 Classic Horizontal Zones

• Central Business District (CBD): high‑rise offices, finance, major retail, primary transport hub.
• Inner‑city residential: older mixed‑income housing, often undergoing gentrification.
• Suburban zones: low‑rise detached housing, shopping centres, light industry.
• Peri‑urban fringe: new estates, industrial parks, greenfield development.

5.2 Vertical Development

• High‑rise residential towers (e.g., Hong Kong, Dubai) – increase floor‑area ratio without expanding footprint.
• Mixed‑use skyscrapers (office + residential + retail) – promote “live‑work‑play” environments.

5.3 Residential Zonation

Zone	Typical Characteristics	Influencing Factors (Planning / Market)
High‑income / elite	Gated estates, luxury high‑rise apartments, waterfront or CBD proximity.	Land‑value tax incentives, private developers, security concerns.
Middle‑income	Suburban terraces, semi‑detached houses, good public‑transport links.	Planning zones (e.g., “medium‑density residential”), mortgage availability.
Low‑income / informal	Self‑built housing, limited services, often on marginal land.	Lack of affordable formal housing, rapid rural‑to‑urban migration, insecure tenure.
Ethnic / cultural enclaves	Concentrations of specific migrant groups (e.g., Chinatown, Little India).	Social networks, cultural institutions, targeted commercial services.

5.4 Change Over Time

• 1950‑2020: World urban population rose from 750 million to > 4.5 billion (≈ 55 % of total).
• Projected 2050: ~ 68 % of the global population will live in urban areas, with > 90 % of the increase in Africa and Asia.
• Shift from low‑rise, car‑dependent suburbs to high‑density, transit‑oriented development in many mature cities (e.g., London’s “Garden City” extensions, Shanghai’s vertical densification).

6. Urban Hierarchy – Functional Perspective

The hierarchy is based on the range and scale of functions a city performs, not on fixed population thresholds. Population figures are illustrative only.

Hierarchy Level	Illustrative Population	Core Functions (Scale & Influence)	Typical Example(s)
World (Global) City	> 10 million (illustrative)	International finance, HQs of MNCs, global media, major air‑sea hub; generates ~ 60 % of world GDP.	London, New York, Tokyo
Metropolitan City	5–10 million	National capital or regional power centre; diversified service sector; national transport hub; major university.	Paris, Shanghai, São Paulo
Regional City	1–5 million	Regional administration, specialised health/education, secondary transport hub, export‑oriented industry.	Manchester, Medellín, Adelaide
District Town	100 000–1 million	Local market centre, basic secondary services, limited rail/road connections.	Wigan, Pécs, Guntur
Rural Service Centre	< 100 000	Primary schools, small health facilities, local trade; serves surrounding villages.	Village hubs, small market towns

Note: A city may occupy different levels when examined locally, nationally or globally – the hierarchy is therefore scale‑dependent.

7. Primate Cities

• Definition: The single city in a country that is disproportionately larger (often 2–5 times the second‑largest) and dominates politically, economically and culturally.
• Key characteristics:
  • Concentration of national government and major corporate headquarters.
  • Primary international transport hub (airport, seaport, rail).
  • Dominant cultural institutions (universities, museums).
  • Accounts for a large share of national GDP (often > 30 %).
• Examples: Bangkok (Thailand), Mexico City (Mexico), Lagos (Nigeria), Paris (France – though France also has a strong secondary city, Lyon).

Evaluation – Primate City Implications

Aspect	Opportunities (Pros)	Challenges (Cons)
Economic efficiency	Economies of scale in service delivery, concentration of finance and innovation.	Over‑reliance on one city makes the national economy vulnerable to local shocks.
Social & cultural	Strong national identity, vibrant cultural scene.	Regional disparities – peripheral areas lag in services, prompting further migration.
Infrastructure	Justified investment in high‑capacity transport, utilities, and housing.	Extreme pressure on housing, transport and environment; high cost of mitigation.
Governance	Centralised decision‑making can be efficient.	Risk of political centralisation; reduced local autonomy elsewhere.

8. World (Global) Cities – The “Global City” Network

World cities are nodes in the global economic system. The Globalisation and World Cities (GaWC) research classifies them into three tiers based on connectivity and concentration of advanced services.

• Alpha++: London, New York – most integrated, command > 30 % of global finance flows.
• Alpha+: Singapore, Hong Kong, Paris – highly connected, major regional command centres.
• Alpha: Sydney, Dubai, Seoul – strong global links but slightly less extensive than Alpha+.

Key indicators used in the ranking (examples):

• Number of advanced‑service firms (law, accountancy, finance, advertising) with offices in the city.
• Volume of international air‑passenger movements and direct flight connections.
• Foreign direct investment (FDI) inflows and outflows.
• Global corporate headquarters and R&D centres.

9. Sustainable Urban Development – The Four Inter‑linked Challenges

9.1 Solid‑waste Management

• Integrated collection, recycling and energy‑recovery schemes (e.g., Copenhagen’s waste‑to‑energy plant).
• Policy tools: landfill‑tax, extended producer responsibility, pay‑as‑you‑throw.

9.2 Transport & Mobility

• Shift from private car use to public‑transport, cycling and walking (e.g., London’s Ultra‑Low Emission Zone).
• Investment in rapid‑transit (metro, BRT) and smart‑traffic management.

9.3 Housing Density & Affordability

• Infill development and vertical housing to limit sprawl.
• Inclusionary zoning – a set % of new units must be affordable.
• Slum upgrading programmes (e.g., Brazil’s “Favela‑Bairro”).

9.4 Green Space & Water Management

• Urban green belts, pocket parks, green roofs to mitigate heat‑island effect.
• Sustainable drainage systems (SuDS) and water‑recycling for irrigation.
• UN‑Habitat guideline: ≥ 15 % of city area as green space.

10. Management of Urban Growth – Evaluation Framework

Effective management balances development with sustainability, using the following policy tools linked to AO2 evaluation criteria.

• Planning policies: zoning, land‑use plans, urban growth boundaries – control sprawl, protect green belts.
• Infrastructure investment: public‑transport, water treatment, renewable‑energy grids – improve service provision, reduce environmental impacts.
• Housing strategies: affordable‑housing quotas, slum upgrading, densification incentives – address segregation and shortages.
• Environmental regulation: air‑quality standards, mandatory green‑space ratios, waste‑to‑energy mandates – mitigate pollution.
• Economic diversification: support for creative industries, tech hubs, green economies – reduce reliance on a single sector, increase resilience.

Evaluation criteria (AO3): cost‑effectiveness, equity (who benefits), environmental outcome, administrative feasibility, and long‑term adaptability.

11. Temporal Perspective – Historic Trends & Future Projections

• 1950‑1990: Rapid urbanisation in Europe & North America; industrialisation drove migration to manufacturing cities.
• 1990‑2020: Shift of growth to Asia & Africa; emergence of megacities (> 10 million) such as Delhi, Shanghai, Lagos.
• 2020‑2050 (projection): World Bank predicts 2.5 billion additional urban dwellers, with 90 % of this growth in the Global South.
• Implications: Need for scalable infrastructure, climate‑resilient design, and policies that manage both horizontal and vertical expansion.

12. Case‑Study Prompt (Syllabus Requirement)

Choose one city (e.g., Mumbai, Nairobi, São Paulo, or a UK city). In your answer you should:

1. Describe its urban structure – CBD, residential zones, vertical development and any distinctive zoning patterns.
2. Identify the main causes of its recent growth (push‑pull factors, natural increase, migration).
3. Analyse the consequences (economic, social, environmental, infrastructure) using the evaluation criteria in section 4.
4. Discuss the city’s position in the urban hierarchy (regional, metropolitan or world‑city status) and any primate‑city characteristics.
5. Evaluate the management strategies employed (planning, housing, transport, waste) and suggest improvements based on sustainability criteria.