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O Levels Biology (5090)•5090/11/M/J/21
Question 32 from 5090/11/M/J/21

Explanation

Deforestation and livestock emissions drive global warming

Steps:

  • Identify greenhouse gases like CO2 and methane as main causes of global warming.
  • Evaluate each option's impact on these gases: CO2 from land use changes, methane from agriculture.
  • Compare contributions: Deforestation releases stored carbon; cattle farming adds methane from digestion and manure.
  • Select the option with the highest combined emissions based on environmental science data.

Why B is correct:

  • Cutting down trees for cattle ranching releases massive CO2 from biomass (deforestation accounts for ~12% of global emissions) and generates methane from enteric fermentation (livestock contributes ~14.5% of emissions per IPCC reports).

Why the others are wrong:

  • A: Replanting offsets some CO2, reducing net emissions compared to permanent loss.
  • C: Reducing diesel lowers CO2 from fossil fuels, mitigating rather than contributing to warming.
  • D: Fewer chemicals has minimal direct impact on greenhouse gases, focusing on pollution instead.

Final answer: B

Topic: Effects of humans on ecosystems

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