Carbon Cycle Pack E Flashcards
(20 cards)
What is peat?
A thick layer of dark brown/black wet soil
How much global land surface do peatlands cover?
3%
How much carbon is stored in global peatlands?
- 550 billion tonnes
- As much as is contained in all terrestrial biomass
How deep can peatlands be?
- 40cm to 4m in the UK
- Up to 10m globally
Where are peatlands found?
- N Canada
- N and E Europe
- Along Amazon River
- S Chile
- UK
- Finland
- N Russia/Siberia
- DRC
- SE Asia
What vegetation is found in peatlands?
- Sphagnum moss
- Rushes
- Sedges
- Bracken
How does peat form?
- Plant remains are slowly compressed as more matreial is added each year
- Layers of dead matter accumulate
- Decomposition is prevented by a waterlogged environment, creating anaerobic conditions
- This limits microbial decomposition of organic matter
- Despite carbon loss by the water cycle, there is a net accumulation of carbon in undisturbed areas
- Rate at which atmospheric carbon is fixed by photosynthesis in new peat/plants greatly exceeds the loss of carbon through decomposition of leaf litter
Why is decomposition even more limited in upland peatlands?
- Temperatures are cooler
- Vegetation is more acidic, deterring soil organisms
How do peatlands exist in the tropics?
- Humid conditions
- Composed of the remains of rainforest trees
- Peatlands of Indonesia have low relief, impermeable rock and high rainfall
- They store 60 billion tonnes of carbon and can reach 15m deep
What percentage of peatlands in the UK are not degraded?
20%
Why are peatlands being degraded?
- Cutting or extracting peat to burn as a fuel for industrial use
- Extracted for the horticultural industry and sold as a nutrient rich soil and compost (until recently)
- Burnt as part of the whiskey making process in Scotland
How is peat used as a fuel?
- Once dried, it can be burnt
- It is a non-renewable resource due to the long time it takes to form
- Being harvested for fuel on an industrial scale for power stations in Ireland and Scotland
How much carbon is released from the drainage, burning, cultivation and extraction of peatlands?
- 2 billion tonnes of CO2 every year
- 10% of global carbon emissions from all human activities
- Emissions are especially high from Indonesia
Why are peatlands being degraded in the UK?
Drainage for agriculture:
- 1/4 of English peatland is under cultivation
- Drained for agricultural land
- Peat shrank, decomposed and became eroded by wind
Air pollution:
- Yorkshire peatlands subject to pollution from Manchester and Sheffield
- Led to widespread reduction in peat-forming plants, so they are more vulnerable to erosion
Moorland burning:
- Done to manage game
- Encourages the growth of young heather for grouse to feed on
- Damages sphagnum moss
- Too much burning exposes below as vegetation is removed, leading to erosion during heavy rainfall
Invasive species:
- 1/3 of English peatlands support invasive vegetation species
Drained for forest:
- Forestry Commission drained peatlands
- Will emit CO2 and lose soil carbon via leaching and erosion
- May be offset by growing trees
What does the restoration of peatlands usually include?
- Re-establishment of plant cover dominated by peat and species
- Re-wetting of drained peatlands by raising and stabilising local water table
How are peatlands restored?
- Blocking drainage channels to increase infiltration and raise water table
- Creates anaerobic and waterlogged conditions
- Raised banks or berms to prevent drainage
- Wetland plants re-established
- Adopt the peatland code, encourage investment into restoration in the UK
How long does peat restoration take?
20 years
What is the peat degradation in Indonesia?
- Have peat swamp forests formed by dead bits of trees that have fallen to the ground and accumulated in waterlogged conditions
- Caused by logging for timber
- Waterlogged soil is drained by creating trenches to carry logs
- As sunlight enters, peat dries out and O2 enters so decomposition starts
- Large scale damage can cause peat fires as there is no tree cover
- Ground heats up and driers out, in a positive feedback cycle
What is the peat restoration scheme in Ireland?
- A good fuel material because it is easily combustible and stores lots of C
- 80% of peatland lost for domestic use
- Bord Na Mona is restoring peat lands and building wind turbines
- Restoration involves blocking previous drainage channels to create pools of water and adding sphagnum moss
- Takes 50 to 100 years
- Conflict as locals have lost their fuel source, peat cutter have lost their jobs and tradition has been lost
What is the peat restoration scheme in Canada?
- In St Henry peatland, Quebec
- Use moss layer transfer technique
- Area is flattened and berms are built to keep water in
- Donor site provides plants from the top layer
- Taken to restoration site and covered with straw for protection from sun
- Area allowed to slow
