5.10 Impacts of Urbanization

Urban sprawl and habitat loss

Urbanization converts natural land into cities and suburbs, causing habitat fragmentation and biodiversity loss. Urban sprawl (low-density outward expansion) increases car dependence, energy use, and infrastructure costs while paving over farmland and wetlands that once absorbed water and supported wildlife.

Impervious surfaces and runoff

Cities are covered with impervious surfaces (roads, roofs, parking lots) that prevent water infiltration. This increases stormwater runoff volume and speed, causing flooding, erosion, and pollution as runoff carries oil, trash, and chemicals into waterways, degrading water quality downstream.

Urban heat and air quality

The urban heat island effect occurs when dark pavement and buildings absorb and re-radiate heat, making cities warmer than surrounding rural areas. This raises energy demand for cooling and worsens air pollution, including smog formation, since heat speeds up photochemical reactions.

Key terms

Urbanization

The growth and expansion of cities as populations shift from rural to urban areas.

Urban sprawl

Low-density outward expansion of cities into surrounding natural or agricultural land.

Impervious surface

A hard surface (road, roof, parking lot) that prevents water infiltration, increasing runoff.

Urban heat island effect

Cities being warmer than surrounding rural areas due to heat-absorbing pavement and buildings.

Habitat fragmentation

Breaking up of continuous habitat into smaller, isolated patches, often due to urban development.

Try an AP-style question

What is the urban heat island effect?

1. Heat moves from cities to oceans
2. Islands have hotter climates
3. Cities are colder than rural areas
4. Cities are warmer than surrounding rural areas