Deforestation is carried out in many parts of the world. Explain how deforestation affects the carbon cycle and contributes to climate change.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (5 marks)
1. Trees and plants absorb CO₂ from the atmosphere during photosynthesis, storing it as biomass.
2. When forests are cut down, the number of trees that can take up CO₂ falls, so less CO₂ is removed from the air.
3. The felled trees are either burned or decompose, processes that release the stored CO₂ back into the atmosphere.
4. The net result is an increase in atmospheric CO₂, a key greenhouse gas.
5. Higher CO₂ concentrations trap more infrared radiation, enhancing the greenhouse effect and contributing to global warming and climate change.
2. When forests are cut down, the number of trees that can take up CO₂ falls, so less CO₂ is removed from the air.
3. The felled trees are either burned or decompose, processes that release the stored CO₂ back into the atmosphere.
4. The net result is an increase in atmospheric CO₂, a key greenhouse gas.
5. Higher CO₂ concentrations trap more infrared radiation, enhancing the greenhouse effect and contributing to global warming and climate change.
Examiner tips
- Use the exact terms ‘photosynthesis’, ‘CO₂’, ‘greenhouse gas’, and ‘global warming’.
- Show the causal chain: deforestation → less uptake + more release → higher CO₂ → more heat trapped.
- Keep the answer concise and structured with numbered points.
Common mistakes
- Confusing CO₂ with O₂ or other gases.
- Failing to mention both reduced uptake and increased release.
- Using vague language like ‘more trees’ instead of ‘less CO₂ removal’.
Mark scheme (5 marks)
- Trees/plants absorb/remove carbon dioxide from the atmosphere during photosynthesis
- Fewer trees means less carbon dioxide is removed/absorbed from the atmosphere
- Burning/decomposition of felled trees releases carbon dioxide into the atmosphere
- This increases the concentration of carbon dioxide (a greenhouse gas) in the atmosphere
- Increased carbon dioxide traps more heat/infrared radiation, leading to global warming/enhanced greenhouse effect/climate change
Key terms in this question
Related
- All WJEC A-Level Biology (Wales) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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