LandIB Environmental Systems and Societies HL: Topic test

1. 1
   Peatlands in Borneo store carbon because waterlogged conditions slow the decay of dead plant material, so the dead organic matter builds up faster than it is broken down. Large areas have been drained for oil palm plantations. Once drained, air enters the peat, decomposition speeds up and the peat surface sinks. Drained peat also burns easily in dry years.

   (a)

   Peat can act as a carbon sink, store or source. Which statement describes undrained peat?

   [1 mark]

   • AIt is a source, because decomposition is faster than the input of dead organic matter
   • BIt is a sink, because input of dead organic matter exceeds decomposition
   • CIt is a source, because it contains no organic matter
   • DIt has no effect on the carbon cycle

   (b)

   (HL) In which form is carbon mainly released from soils when decomposition happens without oxygen, as in waterlogged peat?

   [1 mark]

   • AOxygen
   • BNitrogen
   • CMethane
   • DLimestone

   (c)

   Explain why draining peatland can change it from a carbon sink to a carbon source.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A patch of tropical rainforest in the Amazon basin grows on an old, deeply weathered soil that contains few nutrients. Fallen leaves and branches decompose within weeks in the warm, damp conditions, and the nutrients they release are taken up again quickly by a dense mat of roots near the surface. Heavy rain falls on the area almost every day.

   (a)

   Which of the following is an input to the soil system in this rainforest?

   [1 mark]

   • ALeaching of minerals in drainage water
   • BUptake of nutrients by roots into the trees
   • CHeat lost to the air
   • DFallen leaves and branches

   (b)

   Which process is a transfer within the soil, rather than an input or output?

   [1 mark]

   • ARainwater washing dissolved nutrients down from the upper layers to the layers below
   • BDecomposers turning leaf litter into humus
   • CSeeds falling on the soil surface
   • DHeat radiated from the soil to the air

   (c)

   Explain why the loss of minerals from the soil is likely to increase if this forest is cleared.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A farmer tested four plots of the same field, each given different amounts of compost over several years. Plot 1 had 1.5% organic matter and a wheat yield of 3.0 tonnes per hectare. Plot 2 had 3.0% organic matter and a yield of 4.2 tonnes per hectare. Plot 3 had 4.5% organic matter and a yield of 5.1 tonnes per hectare. Plot 4 had 6.0% organic matter and a yield of 5.4 tonnes per hectare. The plots had the same sand, silt and clay content and the same rainfall.

   (a)

   Calculate the percentage increase in wheat yield between Plot 1 and Plot 3.

   [3 marks]

   (b)

   Using the data, explain how organic matter affects primary productivity in these plots.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A road cutting through a hillside in the cocoa-growing region of Ghana exposes the soil to a depth of about 3 metres. The top 5 cm is dark, crumbly and full of roots and fallen leaves. Beneath it, to about 40 cm, lies a darker brown layer rich in humus mixed with mineral particles. Below this is a reddish, clay-rich layer to about 1.5 m, then partly weathered rock above solid granite. The climate is hot and wet and the area was once forest.

   (a)

   (HL) Describe the soil horizons that can be seen in the road cutting and explain why the dark upper layers are the most valuable for plant growth but also the most vulnerable.

   [6 marks]

   (b)

   (HL) Explain how the climate, organisms, landscape, parent material and time have influenced the formation of this soil.

   [6 marks]

   Total for question 4: 12 marks

5. 5
   In the Punjab region of India, the introduction of high-yielding wheat and rice varieties in the 1960s, together with canal and tube-well irrigation, synthetic fertilisers and pesticides, caused grain output to rise several times over within a few decades. India stopped relying on food imports. Today farmers in the region report falling water tables, rising fertiliser costs, pesticide residues in the environment and declining soil quality.

   (a)

   Which feature is part of the Green Revolution?

   [1 mark]

   • AMoving herds to follow the rains
   • BBreeding of high-yielding crop varieties
   • CLeaving fields fallow for ten years
   • DBurning forest to release nutrients into the soil

   (b)

   Which is a criticism of the Green Revolution that is supported by the information given?

   [1 mark]

   • AIt reduced the amount of grain produced
   • BIt increased the need to import food
   • CIt has depleted groundwater and increased input costs for farmers
   • DIt made soils more fertile without any inputs

   (c)

   Explain how high-yielding varieties, irrigation and synthetic fertiliser together increased food production.

   [2 marks]

   Total for question 5: 4 marks

6. 6
   The Wodaabe and other pastoral peoples of the Sahel in Niger move their cattle, goats and camels over hundreds of kilometres each year, following the rains and the fresh grass they bring. They graze each area briefly before moving on and return only after the vegetation has regrown. Recently, the human population in the region has risen, more land has been fenced for crops, and the routes the herders use have been blocked or shortened.

   (a)

   Which statement describes nomadic pastoralism?

   [1 mark]

   • AFarmers plough the same field each year using machinery
   • BHerders move their animals between grazing areas, often following the rains
   • CCrops are grown in stacked trays under artificial light
   • DAnimals are kept indoors and fed grain throughout the year

   (b)

   Why can nomadic pastoralism sustain a low-density population without long-term damage?

   [1 mark]

   • AIt uses large amounts of synthetic fertiliser
   • BIt removes all grazing animals from the land
   • CIt increases the number of animals each year without limit
   • DIt allows vegetation to recover because grazing pressure is moved around

   (c)

   Explain why nomadic pastoralism may become unsustainable as shown in the scenario.

   [2 marks]

   Total for question 6: 4 marks

7. 7
   A review of global farm data estimated the approximate land needed to produce 100 grams of protein from different foods: beef 160 square metres, pork 11 square metres, poultry 7 square metres, peas 8 square metres and tofu 2 square metres. The review also noted that some foods are transported long distances by air, that soya for animal feed has caused forest clearance in some regions, and that some grazing land is too steep or dry to grow crops.

   (a)

   Calculate how many times more land beef requires than peas for the same amount of protein, and explain this difference.

   [3 marks]

   (b)

   (HL) Discuss why choosing a diet lower in the food chain does not always make a diet more sustainable.

   [4 marks]

   Total for question 7: 7 marks

8. 8
   Brazilian farmers in the cerrado region grow soybeans and maize on millions of hectares using zero tillage: seed is drilled straight into the stubble of the last crop without ploughing, and the soil is kept covered with plant residue. Yields have stayed high and soil erosion has fallen. Some campaigners argue that farming should instead return to traditional, low-input indigenous systems, while critics reply that these systems alone cannot feed a growing global population.

   (a)

   (HL) Explain how zero tillage and other regenerative farming techniques can improve soil and productivity.

   [6 marks]

   (b)

   (HL) Evaluate the claim that low-productivity, traditional food systems are sustainable and could replace modern farming in feeding the world.

   [6 marks]

   Total for question 8: 12 marks

End of questions