Carbon - EQ3 - 6.9 - Feedback Mechanisms

Question 1

When does feedback occur

Answer 1

• when an output change is redirected back to an input
• a positive feedback cycle increases change while a negative one decreases change

Question 2

Describe the impilcations of the feeback mechanism from carbon from peatlands & permafrost

Answer 2

• Boreal and tundra biome and climate areas will shift northwards as temperatures increase
• Peatlands and permafrost within these will release methane with drying or melting, which traps more heat, causing further drying/melting
• These organic layers are a large carbon store, with faster decomposition in a warmer climate that releases more CO, to the atmosphere.
• More soil carbon is also released into rivers

Question 3

Describe the impilcations of the feeback mechanism from Forest Dieback

Answer 3

• Tropical rainforest areas could become drier and change to less productive grasslands, so absorb less CO, from the atmosphere - warming will increase, causing more dieback
• Drought stress in boreal forests, with more disease, pests and wildfires, could change it to grassland and shrubs

Question 4

Describe the impilcations of the feeback mechanism from Thermohaline Circulation Changes

Answer 4

• More freshwater (for example, from melting of the Greenland ice sheet), changes seawater density, which changes ocean currents
• For example, in the North Atlantic this may cause the Gulf Stream not to flow as far north
• Such circulation changes could change how the oceans and atmosphere transfer heat energy, causing greater warming and more ice melt

Question 5

What are peatlands

Answer 5

• Peatlands are carbon-rich wetlands which occupy 3% of the global land surface and 12% of UK land area

Question 6

Consequences of climate change for the peatlands

why are peatlands important

Answer 6

• peatlands have a net cooling effect on climate, reduce flood risk, and support biodiversity
• healthy peatlands can reduce flood risk by slowing the flow of water from the uplands, and by providing floodplain storage in the lowlands
• they also provide important nesting and feeding grounds for many wading birds, as well as important habitats for rare insects and plants

Question 7

Consequences of climate change for the peatlands

Are peatlands a carbon store or sink

Answer 7

• Peatlands store vast quantities of carbon - ‘locking in’ an estimated 3.2 billion tonnes in the UK alone,
• However, overall, peatlands in the UK and around the world are estimated to be a net source of greenhouse gas emissions to the atmosphere, as opposed to a net sink,
• due to the way they have been managed now and in the past

Question 8

Consequences of climate change for the peatlands

What is the impact of peatland degredation

Answer 8

• Draining the soil so it is not waterlogged, in order to make it suitable for crop and tree growth —> decomposition of plant material and soil shrinkage —> source of COz emissions into the atmosphere.
• drainage means the land surface reduces an average of 1cm to 2 cm per year through subsidence due to peat oxidation

Question 9

Consequences of climate change for the peatlands

How many greenhouse gas emissions are UK peatlands producing

Answer 9

• emissions from peatlands could exceed the equivalent of around 20 million tonnes of COz each year
• globally, scientists estimate peatlands are emitting the equivalent of 1-2 billion tonnes of COz, which is around 2-4% of all human greenhouse gas emissions
• a large proportion of these emissions are being produced by the tropical peatlands of Southeast Asia.

Question 10

Uncertainties about peatlands

Why is peatland exploited by humans

Answer 10

• farmers and foresters have drained large areas of upland and lowland peat throughout the UK
• Large areas of upland bog have also been drained for conifer forestry and livestock grazing,
• while other areas are rotationally burned as part of grouse shooting estates
• growing medium by the horticulture industry and by gardeners

Question 11

Uncertainties about peatlands

With climate change, how would peatlands change from extreme weather

Answer 11

• Drying out the peat soil allows shrubby vegetation to grow, and makes the land more vulnerable to severe wildfires
• Fire (caused by managed burning, accidental spread or arson) also produces CO2

Question 12

Uncertainties about peatlands

how is semi-natural peatland peatlands expected to be change by climate change

Answer 12

• 41% of the UK peat area remains under semi-natural peatland vegetation,
• but has been affected by human activities including drainage, burn-management, livestock grazing and the cutting of peat for fuel

Question 13

Uncertainties about peatlands

would restoring the UK’s degraded peatlands be economically viable

Answer 13

• restoring the UK’s degraded peatlands could cost between £8bn-£22bn over the next 100 years,
• but would save £109bn in terms of reduced carbon emissions

Question 14

Uncertainties about peatlands

how will degrading peatlands affect farming in the long term

Answer 14

• affects the long-term viability of agriculture in those areas:
• peat subsidence due to drainage also increases the need for expensive pumping to maintain conditions suitable for crop growth —> increases flood risk

Question 15

Consequences of climate change for the peatlands

Why is there a particular problem with peatland emissions in Southeast Asia

Answer 15

• Fire is often used as a tool to clear land for cultivation, and these fires often run out of control into adjacent forests
• These fires produce toxic smog across Indonesia, Malaysia and Singapore’, contributing to dangerous levels of particulate matter harmful to human health
• The degradation of peatlands through drainage and burning, plus the fires themselves, produce significant COz emissions every year
• The IPCC estimates tropical peatland cultivation generates the equivalent of 440 million tonnes of COz per year, with peat fires generating on average a further 200 million tonnes