Tropical forest is cut down and the land is used to grow crops for biofuels.
Why can this increase the carbon dioxide concentration of the atmosphere, even though the biofuel crops photosynthesise?
Biofuel crops cannot photosynthesise in tropical soil, so they remove no carbon dioxide at all
Burning biofuels releases methane rather than carbon dioxide, and methane traps more heat
Biofuel crops absorb more carbon dioxide than trees do, so the soil must release the extra carbon
The crops store far less carbon than the trees removed, and the trees are burned or decayed
49 exam-style questions on AQA GCSE Biology 7.3 Biodiversity and the effect of human interaction on ecosystems, covering 7.3.1 Biodiversity, 7.3.2 Waste management, 7.3.3 Land use, 7.3.4 Deforestation, 7.3.5 Global warming, and 7.3.6 Maintaining biodiversity. Each one has a worked solution and a mark scheme showing where the marks go.