unit six: changing carbon stores in peatlands over time Flashcards
what is peat?
a soil, which over 80% is composed of partially decomposed organic matter
under what conditions does peat form?
- climate where precipitation exceeds evaporation
- waterlogged grounds
- anaerobic conditions
- acidic conditions
where is peat found?
- most in the northern hemisphere (canada, northern europe, russia)
- minimal in north africa/middle east
- higher latitude locations
- more spread out in south america, africa and oceania
how much land, in the uk, does peat cover and how much carbon does it store?
- covers around 3 million hectares or 12% of land
- store over 3.2 billion tonnes
what are the 3 main types of peatlands in the uk?
- fen peatlands: in areas of low lying topography where groundwater meets the surface
- blanket peatlands: on flat hill tops, with impermeable rocks, where drainage is impeded
- raised bogs: on topographical depression/valley bottoms where drainage of water from the surrounding landscapes accumulates
how much carbon do peatlands store globally?
500 gigatons of carbon
how does peat form?
1) end of devensian glaciation - vegetation around the the edge, where they then die and fall in. formed lakes in low-lying areas. ice melted 10,000 years ago as climate became warmer
2) during holocene - plants grow around edges of the lakes, and why they died > sank > accumulated at the bottom of the lake. after hundreds of years, the dead plants, peat had filled the entire lake and transformed into fern
3) present day - new types of plants, like sphagnum mosses, colonised the surface of the fern and as they died, and accumulated, transferred into bog. over the years, the centre of the bog became elevated, like a dome = raised bog
why is sphagnum moss vital?
- can hold 20 times its own weight in water, acting as a sponge and helps waterlogged conditions
- releases hydrogen ions = makes the water acidic
- releases a chemical called sphagnan = has antibacterial properties and reduces decay of organic matter
what is the impact on the carbon and water cycle for cutting peat and burning a fuel?
- carbon: increase carbon dioxide in the atmosphere (combustion)
- water: changing water movements = impact on water table
what is the impact on the carbon and water cycle for cutting peat and use in horticulture?
- carbon: dried out = release carbon
- water: less water = lowers the water table, which increases the risk of flooding
what is the impact on the carbon and water cycle for drainage of peat and use for agriculture or forestry?
- carbon: increases decomposition rate = less carbon stored in peat. storage capacity is less in agriculture, due to crop harvesting
- water: divert water = decrease in water table
what is the impact on the carbon and water cycle for blocking drainage channels?
- carbon: prevents decomposition = increase carbon
- water: restores water table
what is the impact on the carbon and water cycle for removing invasive shrub and tree species?
- carbon: lowers uptake of water = increase waterlogged conditions = more optimum for spaghnum moss to grow
- water: less carbon removed by photosynthesis and decrease in biomass, but increase in peat
what are the peatland targets and how they can reduce climate change?
- increased tree planting by 13-17% by 2050 helps reduce carbon dioxide levels
- encourage low-carbon farming practices = sustainable
- restoring peatlands = carbon sink helps tackle emissions
what is the impact on the carbon and water cycles between a healthy and damaged peatland?
healthy:
- carbon sink = large carbon store
- good water quality
- plant consumer
- sustainable land use
damaged:
- carbon released, but stored
- decrease biodiversity
- not sustainable land use
- not as good of a carbon sink
