8 - changing carbon stores in peatlands over time ✅

Question 1

what is peat

Answer 1

Peat is a thick layer of black or dark brown sticky and wet soil material

Question 2

where are peatlands

Answer 2

Large areas of peatlands exist in upland UK areas and some lowland areas such as the poorly drained fenlands of East Anglia

Question 3

what colour is peat and why

Answer 3

dark brown colour derives from very high levels of only partially decomposed vegetable matter (sphagnum mosses, rushes, sedges + bracken).

The plant remains are slowly compressed as more material is added each year.

Question 4

how deep are peat soils

Answer 4

can reach 2-4m in depth

Question 5

what are the conditions of peatlands and what are the effects

Answer 5

Decomposition is prevented by a waterlogged environment which creates oxygen-deficient anaerobic conditions.

This limits microbial decomposition of organic matter, especially in cooler, wetter upland areas.

Question 6

how long have peatlands existed

Answer 6

peat has been accumulating for much of the Holocene + most peatlands began to form 7000 years ago

Question 7

what can be found in peat

Answer 7

Occasionally, recognisable animal remains are found in peat from thousands of years ago due to the anaerobic conditions.

In 1984 a 2000 year old well-preserved human body was found buried in Wilmslow, Cheshire (“Pete Marsh”)

Question 8

what are different variations of peat (3)

Answer 8

• Poorly drained anaerobic peat soils are known as marsh, swamp + bog.
• Fen peatlands form where groundwater meets the surface (springs, hollows, edge of open water)
• Blanket peatlands occur on hilltops receiving over 1500mm of rain annually. They are fed entirely by rain or snowfall. 1.5 million hectares, most in Scotland.

Question 9

how do raised bogs occur

Answer 9

they occur in valley bottoms where soils are saturated because of the frequent arrival of throughflow and overland flow from the slopes above.
over time the accumulation of peat naturally forms a dome-shaped raised area of land.

Question 10

how does peat affect carbon storage

Answer 10

• Water removes some carbon from peat (often being black or brown colour).
• However, undisturbed peat is a net accumulator of carbon, with the organic matter in peat being over 50% carbon.
• This is because the fixing of carbon by photosynthesis greatly exceeds the loss through decomposition of plant litter.

Question 11

where is carbon stored in the UK and how much is stored (2)

Answer 11

• Over half of all UK soil carbon is stored in peatlands, up to 90% being in Scotland - this is equivalent to 3 years total UK carbon emissions.
• Only 5% of Wales is covered in peat, but peatland soils represent 30% of the country’s total soil carbon storage.

Question 12

how much carbon do peatlands store

Answer 12

Globally, peatlands store about double the amount of carbon stored in all forests, an estimated 550 billion tonnes

Question 13

how much peat is there in the world

Answer 13

3% (4 million square km) of the Earth’s surface is covered in peat.
It is found on all continents and
more than 250 Gigatonnes of carbon is stored in peat globally.

Question 14

where is the peat in the world found (4)

Answer 14

• 20% of global soil carbon is stored in peatlands in Siberia + Canada.
• Peat soils form in some tropical areas as the remains of rainforest trees decompose.
• Indonesian peatlands store 60 billion tonnes of carbon.
• Raised deposits of woody peat can reach depths of 15m + store up to 3000 tonnes of carbon per hectare.

Question 15

how does peat extraction affect the wider environment (3)

Answer 15

• The drainage, burning, cultivation + cutting (extraction) of peatlands releases approx 2 billion tonnes of CO2 into the atmosphere every year.
• This represents 10% of total carbon emissions from human activity.
• Emissions from Indonesia are particularly high.

Question 16

how have peatlands been affected (4)

Answer 16

• In the UK, only 20% of peatlands are not degraded and remain in pristine state.
• According to Natural England this figure is just 1% in England.
• Rates of carbon sequestration in degraded peatlands are reduced; they may potentially become sources of carbon emissions themselves.
• Some areas have been directly affected by cutting peat to burn as a fuel.

Question 17

how have humans exploited peat

Answer 17

• In rural areas peat has traditionally been used as a fuel source.
• Once dried it can be burnt as a non-renewable fuel.
• In Scotland + Ireland peat is extracted on an industrial scale to use in power stations.
• Peat taken from raised bogs in lowland areas is commercially extracted by the horticultural industry + sold as nutrient rich soil and compost in garden centres.

Question 18

how has peat been used in UK products

Answer 18

• Peat in Islay, Scotland is burned as part of the whisky-making process.
• Lagavulin + Laphroaig distilleries depend on peat smoke for their unique flavouring.
• Peat fuel is also used to produce smoked fish and meat.

Question 19

how has extraction of land impacted peat

Answer 19

• 25% of English peatland is under cultivation. Since 1640 large areas, such as the East Anglian Fens, were drained for farming.
• Land quality improved but peatlands were degraded.
• No longer waterlogged, the peat shrank, decomposed + became eroded by the wind.
• More CO2 was therefore released into the atmosphere.

Question 20

how has pollution affected peatlands

Answer 20

• Pollution from Sheffield + Manchester has affected peatlands in Yorkshire.
• The pollution reduced peat-forming plant species, making the peatlands more vulnerable to erosion.

Question 21

how have spagnum mosses been impacted

Answer 21

• Moorland burning for the management of game, such as grouse, affects peatlands.
• The burning encourages the growth of new heather but damages the wet sphagnum mosses that create peat.
• Too much burning can ruin vegetation, leading to rapid + widespread erosion of topsoil peat during heavy orographic rainfall.

Question 22

how does agriculture affect peat

Answer 22

• Livestock grazing often introduces new invasive species which reduce the rate of peat formation and carbon sequestration.
• Almost 1/3 of all English peatlands now support invasive vegetation species.

Question 23

how does extraction affect carbon storage

Answer 23

• Peatlands drained by the Forestry Commission will begin to emit CO2 and lose some soil carbon via leaching and erosion.
• This may be offset over time by the CO2 captured by the growing trees.

Question 24

do peatlands affect emissions

Answer 24

• Most of England’s peatlands are now sources of carbon emissions due to human damage. Only undamaged areas (20% in total) continue as carbon sinks.
• The peatland areas heavily used for agriculture are now releasing increasing amounts of carbon.

Question 25

what are the levels of carbon release in peatlands

Answer 25

Net carbon flux (tonnes of CO2 per hectare per year)
Cultivated + temporary grass- -22.4
Improved grassland- -8.7
Rotationally burnt- -2.6
Afforested land- -2.5
Bare peat- -0.1
Overgrazed- -0.1
Undamaged- +4.1

Question 26

arguments to restore peatlands

Answer 26

• Biodiversity is maintained.
  Restoration could help countries meet their greenhouse gas emissions targets.
• Restoration is a form of offsetting greenhouse gas emissions.
• If a functioning “global carbon market” operates, restoration is an important restoration practice.

Question 27

how does restoration work

Answer 27

• Re-establishment of plant cover by a peatland species such as sphagnum mosses.
• Re-wetting of drained peatlands by raising + stabilising the local water table.
• As soon as anaerobic conditions have returned new peat formation will start and carbon will be sequestrated.

Question 28

what occurred in the Southern Pennines in Yorkshire

Answer 28

• Erosional gullies have been blocked with stone dams, raising the water table and restoring anaerobic conditions.
• Wetland species are reintroduced, such as re-seeding with cottongrass + sphagnum moss.
• Seed and fertiliser are applied using helicopters.

Question 29

what occurred in scottish peatlands

Answer 29

• In Scotland, large areas of peatland that were drained for forestry are being restored to their natural state.
• Drains have been blocked + trees removed, which appears to be an effective approach in reducing carbon loss from peatlands.