Growth in population and area: globally and at city level

Urban Growth – Overview

Urban growth consists of two inter‑linked processes that the syllabus treats separately:

• Population growth – increase in the number of people living in urban areas (natural increase + net migration).
• Spatial (area) growth – expansion of the built‑up footprint of a city (horizontal spread, vertical densification or a combination of both).

Both processes influence economic development, infrastructure demand, environmental pressure and social equity.

6.1 Urban Growth – Processes & Causes

6.1.1 Types of Urban Growth

Growth type	Definition (syllabus focus)	Typical example
Urbanisation	Shift of population from rural to urban areas, raising the proportion of people living in cities.	China (1990‑2020)
Suburbanisation	Movement of households and jobs from the city centre to surrounding suburbs, creating low‑density residential zones.	Chicago, USA
Urban sprawl	Unplanned, low‑density outward expansion of the built‑up area, usually car‑dependent. Scale note: sprawl can be examined at local (city fringe) and regional (metropolitan) scales.	Melbourne, Australia
Counter‑urbanisation	Migration from cities to smaller towns or rural areas, generally by higher‑income households seeking a better quality of life.	South‑west England
Re‑urbanisation (urban regeneration)	Renewal of inner‑city areas through demolition of derelict housing, mixed‑use development and attraction of new residents.	London Docklands
Urban renewal	Targeted improvement of specific districts (e.g., slum upgrading, brownfield redevelopment) to raise living standards and stimulate investment.	Johannesburg’s Maboneng Precinct

6.1.2 Drivers of Urban Growth

The syllabus groups drivers into four categories. Each can act alone or in combination.

• Social drivers – changing household size, aspirations for city life, education and health services, demographic transition.
• Economic drivers – industrialisation, service‑sector expansion, employment opportunities, higher wages, global trade links.
• Political drivers – government policies (housing programmes, decentralisation), planning regulations, land‑use incentives, migration controls.
• Historical drivers – colonial legacies, transport revolutions (railways, motorways), past settlement patterns that continue to shape growth.

6.1.3 Urban Hierarchy – Primate & World Cities

Global Trends in Urban Growth

Population Growth in Urban Areas

Year	World urban population (million)	Urbanisation rate (% of total population)
1950	751	29.6
1975	1 210	38.0
2000	2 200	48.5
2025 (proj.)	3 300	55.0
2050 (proj.)	5 000	68.0

Average annual urban‑population growth rate (AO2 skill):

\[ r = \frac{\Delta P}{P_{0}\times t} \]

• Interpretation cue: A higher r indicates faster demand for housing, services, transport and employment in urban areas.

Spatial Expansion of Urban Areas

Region	Average annual area growth (%)	Key drivers (link to drivers above)
North America	2.1	Automobile dependence, low‑density housing, suburbanisation
Europe	1.3	Suburbanisation, planning policies, counter‑urbanisation
Asia (incl. China, India)	3.4	Rapid industrialisation, rural‑to‑urban migration, land‑reclamation
Africa	3.8	Population pressure, informal‑settlement growth, limited planning capacity

City‑Level Growth

Population Change in Cities

City growth is measured by natural increase and net migration:

\[ \Delta P_{\text{city}} = (B - D) + (I - E) \]

• Interpretation cue: In fast‑growing megacities, the migration component (I‑E) often exceeds natural increase.

Fast‑growing megacities (population > 10 million)

• Tokyo, Japan – stable, slight decline (≈ ‑0.2 % yr⁻¹)
• Delhi, India – ≈ 3.5 % yr⁻¹ (rural‑to‑urban migration, high natural increase)
• Shanghai, China – ≈ 2.8 % yr⁻¹ (government‑led expansion, industrial jobs)
• Lagos, Nigeria – ≈ 4.1 % yr⁻¹ (informal settlement growth, high fertility)

Mid‑size cities often show higher proportional growth because of a lower base population (e.g., Nairobi, Kenya; Monterrey, Mexico).

Area Expansion in Cities

Urban sprawl is quantified by the change in built‑up area relative to population. Change in density:

\[ \Delta D = \frac{P_{t}}{A_{t}} - \frac{P_{t-1}}{A_{t-1}} \]

• Interpretation cue: A negative ΔD indicates that area is growing faster than population – a hallmark of sprawl.

City	Built‑up area 2000 (km²)	Built‑up area 2020 (km²)	Average annual area growth (%)
Beijing, China	1 200	2 400	3.5
Johannesburg, South Africa	1 050	1 450	1.7
Mexico City, Mexico	1 500	2 050	1.6
Chicago, USA	780	820	0.3

Case Study Requirement (AO3)

For the exam you must develop a detailed specific example from one urban area. The case study should:

1. Describe the pattern of population and/or spatial growth.
2. Identify the main drivers (social, economic, political, historical).
3. Analyse the impacts (e.g., housing, transport, environment).
4. Evaluate at least one management strategy, using the evaluation framework below.

Suggested case studies (choose one for full AO3 development):

• Delhi, India – rapid migration, informal peri‑urban settlements.
• Shanghai, China – government‑led land reclamation and vertical expansion.
• Lagos, Nigeria – explosive slum growth and flood risk.
• Portland, USA – Urban Growth Boundary and managed sprawl.

6.2 Urban Structure & Change

Factors Influencing Urban Structure (syllabus list)

• Physical factors – topography, climate, water bodies, natural hazards.
• Social factors – household size, cultural preferences, income distribution, ethnicity.
• Economic factors – location of jobs, transport costs, land values, industrial location.
• Political & planning factors – zoning legislation, planning policies, land‑use incentives, decentralisation.
• Historical factors – legacy of colonial settlement, historic transport routes, previous land‑use patterns.

Horizontal vs. Vertical Structure

• Horizontal (low‑rise) structure – typical of many North‑American and African cities; spreads outward, low densities, car‑dependent.
• Vertical (high‑rise) structure – common in Asian megacities (e.g., Hong Kong, Shanghai); maximises land use, high densities, mixed‑use towers.

Typical Land‑Use Zones (simplified concentric model)

• Central Business District (CBD) – high‑value commercial land, headquarters, major transport hub.
• Transition zone – mixed commercial‑residential, often the focus of regeneration.
• Low‑rise residential – suburban houses, usually middle‑income.
• High‑rise residential – apartments, high‑density inner‑city or vertical growth areas.
• Industrial / logistics – located on city edges or near major transport corridors.
• Green belt / open space – protects agricultural land, reduces sprawl, provides recreation.

Place‑Identity

Sense of belonging and distinctiveness attached to a part of the city, shaped by:

• Historical architecture (e.g., Old Town of Edinburgh)
• Cultural institutions (museums, theatres)
• Community activities and festivals
• Physical landmarks (riverfronts, parks)

Changing Location of Activities

Key factors that move activities away from the traditional CBD:

• Rising land values and rents → retail shifts to out‑of‑town shopping centres.
• Transport improvements (motorways, rail) → easier access for logistics, prompting industrial parks on the periphery.
• Desire for larger floor‑space and lower costs → manufacturing relocates to suburban/edge zones.
• Policy incentives (tax breaks, enterprise zones) → targeted relocation of specific sectors.

Residential Zonation

• Income‑based zoning – high‑income suburbs (e.g., Beverly Hills, USA) vs. low‑income inner‑city estates or informal settlements (e.g., Kibera, Kenya).
• Ethnic / cultural zoning – Chinatowns, Little Italy, ethnic townships in South Africa.
• Planning‑driven zoning – council‑mandated residential densities, mixed‑use developments, green‑space requirements.
• Cultural preferences – extended‑family housing in South Asia vs. nuclear‑family homes in Europe.

6.3 Sustainable Urban Development

Key Challenges (AO2)

• Housing shortage → unaffordable rents, growth of informal settlements.
• Transport congestion → air pollution, carbon emissions.
• Solid‑waste management → landfill pressure, illegal dumping.
• Water supply & sanitation → over‑extraction, contamination.
• Loss of green space → urban heat‑island effect, reduced biodiversity.
• Social inequality → spatial segregation, unequal service provision.

Management Strategies (evaluation focus)

Strategy	Purpose	Potential Benefits	Possible Limitations
Urban Growth Boundaries (UGBs)	Contain sprawl by legally defining the limit of urban expansion.	Preserves farmland, promotes higher densities, reduces infrastructure costs.	May increase housing prices; requires strong enforcement.
Mixed‑Use Development	Combine residential, commercial and leisure uses in the same area.	Reduces travel distances, supports public transport, creates vibrant neighbourhoods.	Complex planning approvals; may clash with existing land‑use patterns.
Public‑Transport‑Oriented Development (TOD)	Focus growth around high‑capacity transit nodes.	Lower car dependence, lower emissions, encourages compact form.	High upfront investment; success depends on reliable service.
Green Infrastructure	Integrate parks, river corridors, green roofs and permeable surfaces.	Mitigates flood risk, improves air quality, enhances well‑being.	Requires land availability and ongoing maintenance.
Slum Upgrading & Informal‑Settlement Regularisation	Improve housing, sanitation and services in existing informal areas.	Rapid improvement of living standards, avoids displacement.	Funding constraints; politically sensitive.

Evaluation Framework (AO3)

1. Effectiveness – Does the strategy achieve the intended environmental, social and economic outcomes?
2. Equity – Are benefits shared across income groups and communities?
3. Feasibility – Are financial, technical and political resources available?
4. Flexibility – Can the approach adapt to future demographic or climate changes?
5. Unintended consequences – e.g., gentrification, traffic displacement, loss of cultural heritage.

Implications of Urban Growth – Summary Diagram (Suggested)