DeforestationSpec 20.2.4
In short
Deforestation is the removal of forests on a large scale, for timber, farmland, housing, roads and mining. It reduces biodiversity and can cause extinction, because species lose their habitat and food. Without tree roots, soil is washed away and flooding increases. Carbon dioxide in the atmosphere rises because fewer trees photosynthesise and felled trees are burned or decay.
Deforestation is the removal of forests on a large scale. Forests are cleared for timber, for farmland (crops and cattle), for housing and for roads and mining.
| Effect | Explanation |
|---|---|
| Reduced biodiversity | Trees provide food and shelter, so many species lose their habitat and food source |
| Extinction | If a species lives only in that forest and cannot move elsewhere, the whole species can die out |
| Loss of soil | Tree roots hold soil together; without them rain washes the soil away (soil erosion) |
| Flooding | Tree roots absorb water and leaves intercept rain; without trees more water runs straight into rivers |
| Increase of carbon dioxide in the atmosphere | Fewer trees take in CO₂ for photosynthesis, and burning or decay of the felled trees releases CO₂ |
Do not say trees 'make' oxygen as the main problem. The mark is for fewer trees removing less CO₂ from the air by photosynthesis, plus CO₂ released when wood is burned or decays.
Quick check
Define biodiversity.
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The number of different species that live in an area.
Give three reasons for habitat destruction.
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Housing, crop and livestock production; extraction of natural resources; freshwater and marine pollution.
How does deforestation lead to flooding?
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Fewer roots and leaves to absorb water, so more water runs into rivers.
How does deforestation increase carbon dioxide in the air?
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Fewer trees photosynthesise, and burning or decay of trees releases CO₂.
Written and checked against the Cambridge IGCSE Biology (0610) specification · Updated October 2026