Managing climate change and conservationEdexcel A-Level Biology A: Subtopic test

1. 1
   A council plans to convert 200 hectares of intensively farmed land in the English Midlands into native broadleaf woodland, planting oak, ash and hazel. The scheme is intended to help meet a national target to reduce atmospheric carbon dioxide while providing a habitat for wildlife and a place for recreation. The farmer who currently grows crops on the land will lose income.

   (a)

   Why is planting native broadleaf trees more beneficial for conservation than planting a single non-native, fast-growing conifer?

   [1 mark]

   • ANative trees take up more carbon dioxide per hectare than any other trees.
   • BNative trees do not respire, so they store more carbon.
   • CNative trees can photosynthesise during the winter, unlike conifers.
   • DThey support a greater diversity of native insects, birds and other species that have evolved with them.

   (b)

   After about 80 years the woodland is mature and the total amount of carbon stored in it has almost stopped increasing. What is the best explanation?

   [1 mark]

   • AMature trees stop photosynthesising.
   • BCarbon dioxide taken in by photosynthesis is balanced by carbon dioxide released by respiration and decay.
   • CMature trees convert all of the carbon they absorb into methane.
   • DLeaf litter cannot be decomposed in mature woodland.

   (c)

   Explain how planting the woodland can reduce the concentration of carbon dioxide in the atmosphere.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A South American country produces bioethanol from sugar cane, grown on land that was previously cattle pasture, and biodiesel from oil palm, some of which is grown on land cleared from tropical rainforest. Supporters say that biofuels are carbon neutral and are a sustainable alternative to petrol and diesel. Critics point out that biofuel crops compete with food crops and wildlife for land.

   (a)

   Biofuels are described as carbon neutral. Why is this not completely true in practice?

   [1 mark]

   • APlants release more carbon dioxide by respiration than they absorb.
   • BBurning a biofuel releases methane instead of carbon dioxide.
   • CFossil fuels are used to make fertilisers, run machinery and transport the crop and the fuel.
   • DBiofuels contain no carbon.

   (b)

   Which statement best describes the conflict between human needs and conservation when rainforest is cleared for oil palm?

   [1 mark]

   • AHabitat, biodiversity and stored carbon are lost, while people gain fuel and income.
   • BThe oil palm plants absorb less carbon dioxide than the forest because they do not photosynthesise.
   • CBiodiesel cannot be burned in vehicle engines.
   • DClearing the forest increases the number of rainforest species.

   (c)

   Suggest two ways in which biofuel production could be made more sustainable.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   Two reports on climate change were published in the same month. Report X, written by a group of university climate scientists, appeared in a peer-reviewed journal and concluded that human activity is the main cause of recent warming. Report Y, produced by a trade association funded by coal and oil companies, argued that human activity has only a small effect and that no action is needed. A government minister must decide which report to use as the basis for a new policy to cut net carbon dioxide emissions.

   (a)

   Explain why the source of each report should be considered when deciding how far to trust its conclusions.

   [3 marks]

   (b)

   Using your knowledge of the carbon cycle, suggest four measures that the government could take to reduce the concentration of carbon dioxide in the atmosphere.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A tropical island nation has lost 40% of its forest in 50 years to logging, subsistence farming and oil palm plantations grown for biodiesel. The government proposes a programme to replant native tree species on degraded land, to manage the remaining forest as a sustainable timber resource with felled trees replaced, and to grow biofuel crops only on land that is already cleared. Local farmers worry about loss of income, whereas conservation groups worry about the loss of biodiversity.

   (a)

   Explain how the programme could help to reduce atmospheric carbon dioxide and to conserve biodiversity.

   [6 marks]

   (b)

   Evaluate the extent to which the programme resolves the conflict between human needs and conservation.

   [6 marks]

   Total for question 4: 12 marks

End of questions