Causes & Impacts of Deforestation (Cambridge (CIE) IGCSE Environmental Management): Revision Note

Causes of deforestation

• Deforestation means removing trees and clearing forested land

• It often happens quickly and on a large scale

• Forests are often seen as 'empty land', but removing them disrupts entire ecosystems

• The main causes of deforestation are:

Logging and timber extraction

• Logging is often the first step that opens up forests to other activities, such as farming or mining

  • Commercial logging removes trees for wood products

  • Trees are cut for furniture, construction, paper and fuel

  • Selective logging can damage nearby trees as machines move through the forest

  • Illegal logging removes protected species and weakens ecosystem structure

Subsistence farming

• This method is sustainable at a small scale but becomes destructive when populations grow

  • Local people clear small forest areas to grow food for their families

  • Common methods include slash-and-burn farming

  • Burning trees temporarily increases soil fertility, but nutrients quickly run out

  • Farmers move on and clear new forest areas, leading to gradual forest loss

Commercial agriculture

• Forests are cleared to make space for large-scale farms growing crops such as:

  • palm oil

  • soya beans

  • sugar cane

  • coffee

  • cattle ranching

• Commercial farming causes large areas of deforestation because:

  • Land is kept clear permanently

  • Large machinery destroys vegetation

  • Repeated cropping damages soil structure

• This is one of the main drivers of global deforestation today

Roads and settlements

• Road building often triggers a chain reaction of forest loss

  • New roads cut through forests to link cities, farms and mines

  • Roads open remote forests to logging, hunting and land clearing

  • Settlements expand as populations grow, removing more forest for housing

  • Urbanisation increases demand for wood, food and land

Rock, ore and mineral extraction

• Mining transforms forest landscapes permanently

  • Mining removes vegetation to access minerals such as gold, copper and bauxite

  • Open-pit mines destroy large areas of land

  • Toxic waste and pollution damage ecosystems beyond the mining area

  • Mining camps and roads cause further woodland loss

Hydro-electric power (HEP) stations

• HEP provides renewable energy, but it can cause major local deforestation

  • Building dams floods forests and valleys

  • Huge areas of woodland are submerged under reservoirs

  • Dam construction requires clearing land for roads, workers and power lines

  • Altered water flow can damage forests downstream

Climate change

• Climate change makes forests more vulnerable, even without human clearing

  • Rising temperatures increase the risk of wildfires

  • Droughts weaken trees and make them more likely to die

  • Storms become more intense, knocking over large areas of forest

  • Pests and diseases spread more quickly in warmer conditions

Impacts of deforestation

• Deforestation has environmental, social and economic consequences

• Forests are valuable, but unsustainable use destroys future opportunities

• You should think of these in terms of cause and effect

Environmental impacts

Habitat loss

• Habitat loss is the main cause of species extinction worldwide

  • Removing trees destroys the homes of many species

  • Animals lose shelter, nesting sites and food sources

  • Specialist species cannot adapt and may become endangered

  • Reduces biodiversity across the entire ecosystem

Loss of biodiversity

• Biodiversity loss weakens ecosystem stability and reduces future resources

  • Forests contain many different species of plants, animals and microorganisms

  • Clearing trees removes entire communities

  • Food webs collapse as species disappear

  • Genetic diversity is lost, making ecosystems less resilient

Soil erosion and desertification

• Without trees:

  • Roots no longer hold soil in place

  • Rain washes topsoil away

  • Soil becomes dry, dusty and infertile

  • Land may turn into desert in extreme cases

• Soil erosion forces farmers to clear more forest, creating a destructive cycle

Silting and flooding

• Flooding damages homes, farmland and infrastructure

  • Eroded soil washes into rivers

  • This causes silting, which reduces river depth

  • Rivers overflow more easily during heavy rain

  • Blocked channels increase the risk of downstream flooding

Contribution to global warming

• Forests store huge amounts of carbon

• When they are cut or burnt:

  • Carbon dioxide is released instantly

  • Fewer trees are left to absorb carbon

  • The enhanced greenhouse effect becomes stronger

• Deforestation is a major contributor to climate change

Changes to rainfall patterns

• Forests influence local climate by:

  • Releasing water vapour through transpiration

  • Helping clouds to form

  • Stabilising rainfall in the region

• Without forests:

  • Rainfall decreases

  • Dry seasons become longer

  • Droughts become more frequent

• This can collapse agricultural systems in tropical countries

Genetic depletion

• Genetic loss is permanent — once a species is gone, its traits cannot be recovered

  • Many species with unique genetic traits may be lost

  • Genetic resources are essential for new medicines and future crops

  • Losing genetic variation makes species less able to adapt to habitat changes

Social impacts

• Loss of resources for indigenous forest communities

• Reduced food and clean water supplies

• Increased risk of landslides and flooding

• Loss of cultural or spiritual sites

Economic impacts

• Short-term income from selling timber

• Long-term loss of valuable resources

• Reduces the potential for tourism or sustainable harvesting