Describe the effects of deforestation on the carbon cycle and explain how these effects may contribute to global warming.

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

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

Model answer (4 marks)

Deforestation reduces the number of trees and other plants that can absorb CO₂ through photosynthesis.

When trees are cut down and burned, the carbon stored in their biomass is released as CO₂.

Even if the trees are not burned, the dead wood decomposes and decomposers release CO₂.

The extra CO₂ in the atmosphere increases the greenhouse effect, trapping more infrared radiation and raising the Earth’s average temperature, which contributes to global warming.

Examiner tips

Use the word ‘deforestation’ first, then list the four effects in order. Show the link: more CO₂ → stronger greenhouse effect → warming. Use UK spelling (e.g. ‘deforestation’, ‘decomposition’).
Include the phrase ‘trapping more heat/infrared radiation’ to hit the wording of the mark scheme.

Common mistakes

Not mentioning the photosynthetic loss of trees. Failing to state that burning or decomposition releases CO₂. Using ‘global warming’ without explaining the greenhouse‑gas mechanism.

Mark scheme (4 marks)

Deforestation reduces the number of trees / plants available to absorb carbon dioxide through photosynthesis
Burning / combustion of felled trees releases carbon dioxide into the atmosphere
Decomposition of dead / felled trees by decomposers also releases carbon dioxide into the atmosphere
Increased atmospheric carbon dioxide acts as a greenhouse gas, trapping more heat / infrared radiation, causing global warming / rise in average temperature of the Earth

Key terms in this question

deforestation · carbon cycle · global warming