Explain how deforestation can lead to an increase in global warming.

Pearson Edexcel International GCSE Biology (4BI1) — 4.4 Human influences on the environment · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Large areas of tropical forest are cleared each year to provide land for cattle grazing and crop production. Scientists have linked this land-use change to rising levels of carbon dioxide in the atmosphere.

Model answer (4 marks)

Deforestation removes trees that normally absorb CO₂ during photosynthesis, so less CO₂ is taken up from the atmosphere.
When the trees are cut, burned or decompose, the stored carbon is released as CO₂ (and some CH₄ from wet soils).
CO₂ and CH₄ are greenhouse gases that trap heat in the Earth’s atmosphere.
The increased concentration of these gases raises the average temperature of the planet, causing global warming.

Examiner tips

Use the word ‘deforestation’ early. Show the chain: removal → less photosynthesis → more CO₂ released → greenhouse effect → temperature rise. Mention both CO₂ and CH₄ as greenhouse gases.
Use UK spelling (e.g. ‘deforestation’, ‘temperature’).

Common mistakes

Failing to mention the release of CO₂ from burning or decomposition. Confusing photosynthesis with respiration. Using vague terms like ‘more heat’ instead of ‘global warming’.

Mark scheme (4 marks)

Trees/plants removed so less photosynthesis occurs
Carbon dioxide is released into the atmosphere when trees are burned or decay / respired by decomposers
Carbon dioxide (and methane) are greenhouse gases that trap heat in the Earth's atmosphere
This causes the average temperature of the Earth to rise / global warming

Key terms in this question

deforestation · global warming