Human Geography

Population Change

Demographic Transition Model (DTM)

The DTM describes the historical shift from high birth rates and high death rates to low birth rates and low death rates as a country develops economically. It comprises five stages:

Stage 1 (High stationary): High birth rates ($\approx 40$ per $1000$) and high death rates ($\approx 40$ per $1000$). Population growth is minimal. Characteristic of pre-industrial societies where limited food supply, poor sanitation, and disease keep death rates high.

Stage 2 (Early expanding): Death rates fall rapidly due to improvements in agriculture (food supply), medicine (vaccination, antibiotics), sanitation, and public health. Birth rates remain high. Natural increase accelerates. Examples: many sub-Saharan African countries.

Stage 3 (Late expanding): Birth rates begin to decline due to increased access to contraception, female education and employment, urbanisation (children become an economic cost rather than an asset), and declining infant mortality (fewer births needed to achieve desired family size). Death rates continue to fall but at a slower rate.

Stage 4 (Low stationary): Low birth rates ($\approx 12$ per $1000$) and low death rates ($\approx 10$ per $1000$). Population growth is slow or stabilises. Characteristic of developed economies (e.g., the UK, Japan).

Stage 5 (Decline): Death rates exceed birth rates, leading to natural decrease. Total fertility rate falls below the replacement level of approximately $2.1$. Caused by delayed childbearing, high costs of raising children, and changing social attitudes. Examples: Japan, Germany, Italy.

Population Pyramids

Population pyramids (age-sex structure diagrams) illustrate the demographic characteristics of a country:

• Wide base, narrow top: high birth rates, high death rates (Stage 1 or 2)
• Expanding middle, narrowing base: falling birth rates (Stage 3)
• Columnar shape: low birth and death rates, ageing population (Stage 4)
• Narrowing base, bulging middle/top: very low birth rates, significant elderly population (Stage 5)

A youthful population (wide base) creates dependency pressures, strains education and healthcare systems, and can lead to unemployment if job creation does not keep pace with labour force growth. An ageing population (bulging top) creates pressures on pensions, healthcare, and social care, and reduces the working-age population supporting dependents.

Demographic Dividend

The demographic dividend (or demographic bonus) occurs when the proportion of the working-age population (typically $15$--$64$) is large relative to the dependent population (youth under $15$ and elderly over $65$). If the economy creates sufficient productive employment, this bulge in the working-age population can drive rapid economic growth (as in East Asia from the 1960s to 1990s).

Migration

Types of Migration

• Internal migration: movement within a country (e.g., rural-to-urban, inter-regional)
• International migration: movement across national borders
• Voluntary migration: migrants choose to move, typically for economic, social, or environmental reasons
• Forced migration: migrants are compelled to move by conflict, persecution, natural disasters, or environmental change
• Temporary migration: migrants move for a limited period (e.g., seasonal work, study abroad)
• Permanent migration: migrants intend to settle indefinitely in the destination

Lee's Push-Pull Model

Everett Lee (1966) proposed that migration results from push factors at the origin, pull factors at the destination, and intervening obstacles.

Push factors: unemployment, low wages, political instability, conflict, persecution, environmental degradation, natural disasters, poor public services.

Pull factors: employment opportunities, higher wages, political stability, safety, better healthcare and education, family networks, environmental amenity.

Intervening obstacles: distance, cost of migration, immigration policies and visa restrictions, language barriers, lack of information, physical barriers.

Migration Impacts

On the origin country:

• Positive: remittances (a major source of foreign exchange for many developing countries), reduced population pressure, return migrants bring skills and investment, reduced unemployment
• Negative: brain drain (loss of educated and skilled workers), ageing population if young adults emigrate, family disruption, dependency on remittances

On the destination country:

• Positive: fills labour shortages (particularly in low-skilled sectors and healthcare), cultural diversity, economic dynamism, younger population structure, fiscal contribution from migrant workers
• Negative: pressure on housing, public services, and infrastructure; social tension; wage depression in low-skilled sectors (debated); cultural conflict

Theories of Migration

• Ravenstein's Laws of Migration (1885): migrants move short distances; migration occurs in steps (rural to small town to city); urban areas attract migrants; each migration flow produces a counter-flow
• Todaro migration model: migration is driven by expected income differentials, not actual wage differences. A migrant moves to the city even if urban unemployment is high, because the expected urban wage (probability of employment multiplied by the urban wage) exceeds the rural wage
• Stouffer's intervening opportunities model: the number of migrants from one area to another is proportional to the number of opportunities at the destination and inversely proportional to the number of intervening opportunities

Urbanisation

Definitions and Trends

Urbanisation is the increasing proportion of a population living in urban areas. It results from rural-to-urban migration, natural increase within cities, and the reclassification of rural areas as urban.

In $1950$, $30\%$ of the global population lived in urban areas. By $2018$, this exceeded $55\%$, and it is projected to reach $68\%$ by $2050$. The most rapid urbanisation is occurring in developing countries, particularly in sub-Saharan Africa and South Asia.

Urbanisation in Developed vs. Developing Countries

Developed countries urbanised early (18th--19th centuries), driven by the Industrial Revolution. Urbanisation rates have stabilised or slowed (suburbanisation, counter-urbanisation). Urban areas have mature infrastructure and formal economies.

Developing countries are urbanising rapidly and at lower income levels. Urbanisation is driven by rural poverty and perceived urban opportunity rather than industrial growth. This produces mega-cities (population exceeding $10$ million) with significant informal economies, inadequate infrastructure, and sprawling slums.

Urban Models

Burgess concentric zone model (1925): the city grows outward from the CBD in concentric rings: CBD, transition zone (industry, low-income housing), working-class zone, middle-class zone, commuter zone. Assumes a single centre and uniform terrain.

Hoyt sector model (1939): the city develops in sectors (wedges) radiating from the CBD along transport corridors, with industrial zones and working-class housing extending along transport routes and high-income housing in desirable areas (e.g., along coastlines or elevated ground).

Harris and Ullman multiple nuclei model (1945): the city develops around multiple centres of activity rather than a single CBD, reflecting the complexity of modern urban land use (e.g., separate business districts, industrial parks, university campuses).

These models are simplifications based primarily on North American cities. They do not fully apply to cities in developing countries, where informal settlements, colonial planning legacies, and rapid peripheral growth create different patterns.

Settlement Patterns

Factors Influencing Settlement Location

• Physical factors: water supply (rivers, springs), shelter (natural harbours, valleys), fertile soil for agriculture, defensive sites (hilltops, river bends), aspect and altitude
• Economic factors: proximity to resources, trade routes, and markets
• Social factors: political decisions, religious significance, ethnic or cultural factors

Settlement Hierarchy

Settlements are classified by size and the range of services they provide. Larger settlements offer a greater range and higher-order services, have larger catchment areas (threshold populations), and are spaced further apart (Christaller's Central Place Theory).

Settlement type	Population (approximate)	Services
Hamlet	< 200	Very few: perhaps a village hall or post box
Village	200--2,500	Low-order: primary school, shop, pub, church
Small town	2,500--20,000	Mid-order: secondary school, bank, supermarket, GP
Large town	20,000--100,000	Higher-order: hospital, college, shopping centre
City	> 100,000	Full range: university, specialist services

Central Place Theory

Walter Christaller (1933) proposed that settlements are arranged in a regular hexagonal pattern to maximise the efficiency of service provision. Each settlement serves a hinterland (market area) and is spaced to minimise the distance consumers travel.

The theory assumes: a uniform plain, uniform population density, isotropic (equal in all directions) transport costs, and rational consumers minimising travel distance. These assumptions are rarely met in reality, but the model provides a useful baseline for understanding the spatial distribution of settlements.

Urban Regeneration

Causes of Urban Decline

• Deindustrialisation: the closure of manufacturing industries in developed countries since the 1970s, leading to job losses, population decline, and derelict land
• Suburbanisation: the movement of businesses and affluent residents to the suburbs, hollowing out the urban core
• Social deprivation: concentrated poverty, crime, poor health, and educational underachievement
• Physical deterioration: ageing housing stock, abandoned industrial sites (brownfield land), and decaying infrastructure

Regeneration Strategies

Property-led regeneration: private sector investment in commercial and residential development, often supported by public infrastructure. Example: London Docklands (1980s), Canary Wharf. Can be criticised for gentrification, displacement of existing communities, and insufficient benefit to local residents.

Partnership schemes: collaboration between public, private, and voluntary sectors. Example: Manchester's city centre regeneration after the 1996 IRA bombing. Benefits from combined resources and expertise but can be slow and complex.

Government-funded regeneration: direct public investment in housing, transport, education, and social infrastructure. Example: New Deal for Communities (UK). Targets deprivation directly but is expensive and may be unsustainable without continued funding.

Community-led regeneration: local residents drive the process, ensuring that regeneration addresses community needs. Example: community land trusts, cooperative housing. Empowers communities but may lack resources for large-scale change.

Gentrification

Gentrification is the process by which affluent individuals and businesses move into deteriorating urban neighbourhoods, displacing lower-income residents through rising property values and rents. While it can improve the physical environment and attract investment, it often exacerbates social inequality and cultural displacement.

Indicators: rising property prices and rents, influx of higher-income residents, new cafes, restaurants, and boutique shops, renovation of historic buildings, loss of social housing and local businesses.

Common Pitfalls

• Confusing urbanisation with urban growth. Urbanisation is the increasing proportion of the population in urban areas; urban growth is the absolute increase in the urban population.
• Assuming the DTM applies uniformly to all countries. Some countries skip stages, move backwards (e.g., due to conflict or economic collapse), or exhibit unique patterns.
• Describing migration impacts without specifying whether they apply to the origin or destination country.
• Applying Burgess, Hoyt, or Harris-Ullman models uncritically to cities in the developing world. These models were developed for North American cities and have significant limitations elsewhere.
• Confusing regeneration with gentrification. Regeneration is a planned process that can benefit existing communities; gentrification is a market-driven process that often displaces them (though the two can overlap).

Practice Problems

Problem 1: Demographic Calculations

Country A has a crude birth rate of $22$ per $1000$, a crude death rate of $8$ per $1000$, and a population of $50$ million. Calculate the natural increase rate and the natural increase per year.

Natural increase rate $= \mathrm{CBR} - \mathrm{CDR} = 22 - 8 = 14$ per $1000$, or $1.4\%$ per year.

Natural increase per year $= 50000000 \times \frac{14}{1000} = 700000$ people.

The population grows by approximately $700000$ per year from natural increase alone (excluding migration).

Problem 2: Dependency Ratio

A country has a population of $10$ million, of which $3$ million are under $15$, $5.5$ million are aged $15$--$64$, and $1.5$ million are over $65$. Calculate the youth dependency ratio, elderly dependency ratio, and total dependency ratio.

Youth dependency ratio $= \frac{3000000}{5500000} \times 100 = 54.5$

Elderly dependency ratio $= \frac{1500000}{5500000} \times 100 = 27.3$

Total dependency ratio $= \frac{3000000 + 1500000}{5500000} \times 100 = 81.8$

For every $100$ working-age people, there are approximately $82$ dependents ($55$ youth and $27$ elderly). A high total dependency ratio places fiscal pressure on the working-age population through taxation and social contributions.

Problem 3: Migration Impact Evaluation

Poland joined the EU in 2004, and approximately $2$ million Polish workers migrated to the UK between 2004 and 2016. Evaluate the impacts on both the origin (Poland) and destination (UK).

On Poland (origin):

Positive:

• Remittances: Polish workers in the UK sent substantial sums home, supporting families and local economies
• Return migrants brought back skills, experience, and investment capital
• Reduced unemployment pressure in the short term
• Some returning migrants started businesses, contributing to entrepreneurship

Negative:

• Brain drain: many migrants were young, educated, and skilled (doctors, engineers, tradespeople)
• Ageing population structure as working-age adults left
• Labour shortages in sectors that lost workers (construction, healthcare)
• Family separation and social disruption in sending communities

On the UK (destination):

Positive:

• Filled labour shortages in construction, agriculture, hospitality, and healthcare
• Migrants were generally young and economically active, contributing to fiscal revenues
• Cultural diversity and enrichment
• Some migrants started businesses, creating employment

Negative:

• Wage depression in low-skilled sectors (though evidence is contested and context-dependent)
• Pressure on local housing markets and public services in areas of high migration
• Social tension and political backlash (contributing to Brexit)
• Integration challenges, particularly for non-English speakers

Problem 4: Urban Model Application

A city in a developing country has a central business district, a ring of informal settlements (slums) surrounding it, and wealthy residential areas on the outskirts along main roads. Explain which urban model best fits this pattern and why.

This pattern is best described by a modified concentric zone model or, more specifically, by features of the Griffin-Ford model for cities in the developing world.

In many developing-world cities:

• The CBD contains commercial and administrative functions but is surrounded by a zone of informal settlements (slums or squatter settlements) rather than the transition zone of light industry found in Burgess's model
• Industry is often located on the urban periphery rather than near the centre
• High-income residential areas are located on the outskirts along major transport routes (reflecting the importance of road access for commuting and the desirability of newer, less congested areas)
• Peripheral commercial development (shopping malls, business parks) may occur alongside high-income residential areas

The Burgess model does not predict slums immediately surrounding the CBD, which is a distinctive feature of rapid, unmanaged urbanisation in the developing world where rural migrants settle as close to employment opportunities as possible.

Problem 5: Regeneration Evaluation

Evaluate the success of property-led regeneration using London Docklands as a case study.

Background: The London Docklands area declined from the 1960s as containerisation rendered its docks obsolete. By 1981, the area had high unemployment ($\approx 18\%$), derelict land, and poor housing. The London Docklands Development Corporation (LDDC) was established in 1981 to regenerate the area through property-led investment.

Successes:

• Created over $120000$ jobs, replacing those lost from dock closures
• Attracted major financial institutions to Canary Wharf, establishing a second financial district
• Triggered private investment estimated at over $\pounds 10$ billion
• Improved transport infrastructure (Docklands Light Railway, Jubilee Line extension)
• Transformed the physical landscape from dereliction to modern commercial and residential development

Limitations and criticisms:

• Gentrification: local residents were priced out by rising property values
• Many new jobs went to incoming professionals rather than local unemployed residents
• Social housing was replaced by luxury apartments, reducing affordable housing stock
• The community felt excluded from decision-making; the LDDC was widely perceived as undemocratic
• Benefits were unevenly distributed; some parts of the Docklands saw little improvement
• The emphasis on financial services created an economy vulnerable to sector-specific downturns