Urban Expansion (DP IB Environmental Systems & Societies (ESS))

Suburbanisation & Urban Sprawl

What is suburbanisation?

• Suburbanisation is the process where people move from the dense central parts of cities (urban areas) to the less dense, peripheral areas (suburbs)

  • It involves the expansion of cities into nearby rural or undeveloped areas, creating lower-density residential areas

  • People often move to the suburbs in search of larger homes, green spaces, and better living conditions away from the congested city centre

What is urban sprawl?

• Urban sprawl refers to the uncontrolled expansion of urban areas into surrounding rural land, creating spread-out developments

  • Urban sprawl is closely related to suburbanisation, as lower-density housing and commercial developments require more land, stretching the boundaries of the city

  • Sprawl often leads to longer commutes, greater car dependency, and increased demand for infrastructure such as roads and services

Causes of suburbanisation

1. Desire for more space:

   • People move to the suburbs for larger homes and gardens

   • Suburban areas often have more green spaces and parks than city centres

2. Improved transport links:

   • Advances in public transport and the widespread use of cars have made commuting from the suburbs to city centres easier

   • Suburban residents can travel to the city for work, shopping, and leisure

3. Perception of better quality of life:

   • Suburbs are often seen as safer, quieter, and better for raising families compared to crowded city centres

   • Suburban areas may offer better schools and lower crime rates

4. Rising urban costs:

   • High costs of housing and living expenses in city centres push people to move to the more affordable suburbs

5. Traffic congestion and overcrowding in city centres:

   • City centres are often very busy with people and congested with traffic, making commuting and living in the urban core more difficult

Environmental Impacts of Urban Expansion

Loss of agricultural land and natural ecosystems

• Loss of farmland:

  • As cities expand, they often take over land previously used for agriculture

  • This reduces the amount of land available for growing food

  • For example, in Beijing, China, rapid urbanisation has consumed large areas of farmland, leading to concerns about food security

• Deforestation:

  • Urban expansion can lead to the clearing of forests to make way for housing, roads, and businesses

  • This destroys natural habitats and reduces biodiversity

    • For example, the growth of São Paulo, Brazil, has resulted in the destruction of parts of the Amazon rainforest

• Loss of wetlands and ecosystems:

  • Expanding urban areas often fill in wetlands, rivers, and lakes, reducing habitats for wildlife and affecting water systems

    • For example, in Florida, USA, urban sprawl has reduced the size of the Everglades, an important wetland ecosystem

Changes to water quality and river flows

• Water pollution:

  • Increased construction and industrial activities near cities can cause pollution to rivers, lakes, and groundwater

  • Chemicals from factories, waste from homes, and run-off from roads can contaminate water supplies

    • For example, the Ganges River in India suffers from severe pollution due to urban growth and industrial waste from several major cities

• Altered river flows:

  • Expanding cities often build dams, divert rivers, or drain wetlands, which changes the natural flow of water

  • This can lead to flooding or drought in nearby areas

    • For example, in Las Vegas, USA, the city’s rapid growth has strained the Colorado River, leading to water shortages and environmental issues

Air pollution

• Increased traffic and industry:

  • As cities grow, they generate more air pollution from cars, trucks, and factories

  • This increases levels of harmful gases like carbon dioxide and nitrogen oxides, contributing to climate change and health problems

    • For example, Mexico City is known for having high levels of smog and poor air quality due to urban expansion and traffic congestion

• Heat islands:

  • Urban expansion often creates urban heat islands

  • This is where cities become significantly warmer than surrounding rural areas

  • This happens because buildings, roads, and other urban surfaces absorb and retain more heat than natural landscapes like forests or grasslands

  • Air conditioners, vehicles, and industrial activities release additional heat into the environment

Loss of biodiversity

• Habitat destruction:

  • Urban expansion can destroy the natural habitats of plants and animals, leading to a reduction in biodiversity

  • This puts species at risk of extinction