IB Environmental systems and societies 8.2B Urbanization and Suburbanization Notes

Urbanization: A Growing Share of Humanity Now Lives in Cities

Characteristics of Urbanization

Urbanization changes land use, making areas more built-up, industrialized, and densely populated.

1. High population density: a large number of people live per square kilometre.
2. Built-up environment: buildings, roads, and industrial zones expand.
3. Economic shift: work moves from agriculture to manufacturing and services.
4. Social and cultural diversity: different ethnicities, languages, and lifestyles mix.
5. Infrastructure growth: transport, healthcare, and communication systems improve.

Causes of Urbanization: Push and Pull Factors

Urbanization is driven by push factors (rural disadvantages) and pull factors (urban opportunities).

Impacts of Urbanization: Real Gains and Real Costs

Positive Impacts

1. Economic growth: cities drive national and global economies.
2. Better living standards: people gain access to education, healthcare, and jobs.
3. Innovation: cities become hubs for new technology and ideas.
4. Efficient services: dense populations make public transport, energy, and waste systems easier to provide.

Negative Impacts

1. Overcrowding: high housing demand pushes people into slums and informal settlements.
2. Traffic congestion: heavy vehicle use raises pollution and lengthens journeys.
3. Social inequality: the wealth gap between rich and poor often widens in cities.
4. Environmental pressure: expansion damages ecosystems, water, and air, covered in the dedicated section below.

Urbanization and Land Use Change

As urbanization progresses, land use shifts from natural or agricultural landscapes to built-up environments.

Rural-Urban Migration: The Main Engine of City Growth

Scale and Direction of the Flow

1. A greater share of the global population now lives in urban areas, and the trend is expected to continue.
2. Most rural-urban migration is internal migration within a single country.

Causes of Rural-Urban Migration: Push and Pull

Migration is shaped by push and pull factors and can be voluntary or forced.

1. Push factors (reasons for leaving rural areas)
   1. Few jobs exist outside agriculture.
   2. Farming and small industries give low, unstable incomes.
   3. Healthcare and schools are limited.
   4. Floods, droughts, and soil degradation force people out.
   5. War, violence, and land disputes displace rural populations.
2. Pull factors (attractions of urban areas)
   1. Industry, services, and tech offer higher wages.
   2. Cities have better transport, electricity, and internet.
   3. Hospitals, universities, and skilled professionals are within reach.
   4. Cities offer entertainment, diversity, and social mobility.

Forced Versus Voluntary Migration

1. Voluntary migration: most rural migrants move by choice for jobs, education, and a better life.
2. Forced migration: some are displaced by conflict, disasters, or policy, such as dam projects that flood communities.

Perceived Versus Real Advantages of City Life

Rural-Urban Migration Trends Within Countries

Migration patterns vary with economic development, government policy, and environmental conditions.

Counter-Urbanization and Deurbanization: The Reverse Flow

In some richer countries people move from cities back to rural areas, a process called counter-urbanization or deurbanization.

1. High cost of living: rising rent and expenses push people out of cities.
2. Remote work and technology: digital jobs let people work from rural areas.
3. Ageing population: retirees prefer quieter, less polluted places.
4. Decentralization policy: governments promote rural development.

Suburbanization: Cities Spread Outward Into Their Edges

Suburbanization as Urban Sprawl

Suburbanization is often called urban sprawl because it spreads development over a larger area of land.

1. It is a key driver of urban expansion, turning rural land into residential, commercial, and industrial zones.

Causes of Suburbanization

1. Housing and space
   1. Suburbs offer larger homes at lower prices than city centres.
   2. Many people want more space, a private garden, and a quieter setting.
2. Transport and infrastructure
   1. Highways, railways, and transit make commuting from suburbs easier.
   2. Rising car ownership lets people live farther from work.
3. Economic and social factors
   1. Businesses relocate to suburbs, creating local jobs.
   2. Suburbs are seen as having better schools, less crime, and more green space.
4. Technology
   1. Working from home, boosted by the COVID-19 pandemic, cut the need to live near city jobs.
   2. Fast internet makes suburban living more workable.

Impacts of Suburbanization

1. Environmental impacts
   1. Expanding suburbs replace natural areas, cutting biodiversity.
   2. Car dependency raises greenhouse gas and air pollutant emissions.
   3. Roads and driveways increase runoff, causing erosion and water pollution.
2. Social and economic impacts
   1. Rising demand pushes up suburban house prices, displacing original residents.
   2. City centres can decay as businesses and residents leave.
   3. Suburbs can become bedroom communities whose residents commute out for work.
3. Infrastructure and resource use
   1. Larger suburban homes use more energy than urban apartments.
   2. Low-density building uses more land, fuelling sprawl.

Environmental Impacts of Urban and Suburban Expansion

As cities and suburbs grow, agricultural land, forests, and other ecosystems are converted into built-up space, with mostly negative environmental effects.

Loss of Agricultural Land and Natural Ecosystems

1. Loss of arable land: farmland is paved over, reducing land for food production.
2. Loss of biodiversity: forests, wetlands, and grasslands are replaced by concrete, harming the species that depend on them.
3. Habitat fragmentation: development splits ecosystems into small, isolated patches that species struggle to cross.
4. Loss of ecosystem services: water filtration, carbon storage, and pollination are all weakened.

Declining Water Quality

Urbanization changes water quality in several ways.

1. Urban runoff: impervious surfaces increase stormwater runoff that carries oil, heavy metals, and chemicals into water bodies.
2. Wastewater discharge: untreated sewage often enters rivers and lakes, degrading water quality.
3. Eutrophication: fertilizer runoff overloads water with nutrients, which depletes oxygen and harms aquatic life.

Altered River Flows

Urban growth reshapes river systems through construction and development.

1. Dams and channelization: dams and weirs built for flood control or water supply change natural river flow and harm downstream ecosystems.
2. Less infiltration, more runoff: impervious surfaces cut groundwater recharge, so rivers swell faster during rainfall.
3. Water table depletion: heavy extraction for urban use lowers local water resources and river flow.

Air Pollution From Urban Expansion

1. More vehicles and industry raise emissions of nitrogen oxides, carbon monoxide, and particulate matter that lower air quality.
2. The detailed chemistry of urban air pollution, including smog and acid rain, belongs to topic 8.3.

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