(a)
Bithynia feeds on plant material in the wetland ecosystem.
[ 2 ]
(i)
Describe its role in the carbon cycle of the system.
[ 2 ]
[Maximum number: 2]
Figure 1 shows the process of carbon capture and storage (CCS) that can be used to manage climate change. Carbon dioxide ( ) is pumped into three different underground locations, where it is stored.
Flow 1 pumps into an underground saline reservoir.
Flow 2 pumps into an oil reservoir; replaces oil; oil is produced.
Flow 3 pumps into a coal seam; replaces methane ; methane is produced.
Figure 1: Carbon capture and storage flow chart
(a)
Outline how Flows 1 and 2 shown in Figure 1 may contribute to the capture and storage of atmospheric carbon.
[ 2 ]
(a)
Figure 8(a): River before and after beaver dam construction
Figure 8(b): Graphs to show nutrient and oxygen content in beaver pond and stream
With reference to Figures 8(a) and 8(b), describe the changes in nutrient and oxygen content that occur after beaver dams are constructed. Include quantities in your response.
[ 2 ]
[Maximum number: 2]
With reference to Figure 6, outline the effectiveness of mangroves and tropical rainforests in the mitigation of climate change.
| Ecosystem | Soil carbon | Living biomass | Total carbon |
|---|---|---|---|
| Boreal forest | 150 | 94 | 244 |
| Tropical forest | 83 | 167 | 250 |
| Mangroves | 1030 | 464 | 1494 |
| Tidal marsh | 920 | 31 | 951 |
| Seagrass meadows | 608 | 10 | 618 |
Figure 6: Carbon storage in different ecosystems
(a)
| Year | Percentage of forest cover |
|---|---|
| 1940 | |
| 1962 | 54\% |
| 1987 | 22\% |
| 1998 | 43\% |
| 2010 | 53\% |
Figure 7(a): Variation in forest cover in Costa Rica between 1940 and 2010
Resource booklet context: forest policy
- PES pays landowners to plant trees in deforested areas and manage land sustainably.
- In 1996, deforestation of mature forest was banned.
- The goal is to achieve 60% forest coverage.
Outline how the change in the area of forest cover since 1987 may contribute to the mitigation of climate change.
[ 1 ]
(a)
Resource booklet context: Siberian taiga
- Taiga forest provides habitat, stores carbon, helps regulate climate and supplies timber.
- Deforestation can affect biodiversity, carbon storage and downstream/global systems.
Figure 7(b): Total exports of timber (in units of thousand cubic metres) from Russia between 2012 and 2014
Explain how deforestation in the taiga may impact the world's oceans.
[ 3 ]
(a)
Discuss how human activities impact the flows and stores in the nitrogen cycle.
[ 9 ]
(a)
Explain human effects on the nitrogen cycle and predict the impact of these changes on an ecosystem.
[ 6 ]
(a)
Describe how carbon dioxide is added to the atmosphere through natural and human processes.
[ 5 ]
[Maximum number: 5]
Figure 3 shows an incomplete model for the nitrogen cycle.
Figure 3
(a)
Label the diagram above to complete the processes and flows in the nitrogen cycle.
[ 3 ]
(b)
Describe two ways in which humans may impact the nitrogen cycle.
[ 2 ]