2.1.8 Changing carbon stores in peatlands over time

What are peatlands

Waterlogged ecosystems where partially decomposed plant material accumulates as peat

Why are peatlands important in the carbon cycle

They are highly efficient long term carbon stores

How much of Earth’s land surface do peatlands cover

About 3 percent

How much carbon do peatlands store globally

Around 550 gigatonnes of carbon

Why do peatlands store so much carbon

Waterlogging creates anaerobic conditions that slow decomposition

How does peat form

Dead plant material accumulates under oxygen poor conditions and compresses into peat over time

What conditions are needed for peat formation

High water table cool temperatures low oxygen and slow decomposition

How much carbon can peat accumulate per hectare annually

Around 1 tonne of carbon per hectare per year

Why is peat considered part of the slow carbon cycle

Carbon is stored for thousands to millions of years

How deep can peat deposits become

Over 10 metres in some locations

Why are peat carbon stores climatically significant

They represent carbon removed from the active carbon cycle for millennia

What makes peatlands vulnerable carbon stores

Drainage climate change land use change and peat extraction

What happens when peatlands are drained

Aerobic decomposition increases and CO₂ and methane are released

What is the carbon balance change when peat is drained

Peatlands can shift from carbon sinks to carbon sources

What are bogs mires and fens

Different types of peatland formed under varying water and nutrient conditions

What is an ombrotrophic bog

A rain fed peatland isolated from groundwater and nutrients

Why are ombrotrophic bogs nutrient poor

They receive water only from rainfall

What vegetation dominates ombrotrophic bogs

Sphagnum mosses sedges and cotton grass

What conditions slow decomposition in bogs

High rainfall low temperatures and anaerobic soils

Where has peat formed in the UK uplands

Exmoor and the Peak District

When did peat formation begin on Exmoor

Around 6 000 to 8 000 years ago

How deep is peat on Exmoor in some locations

Over 2.5 metres

How much carbon can Exmoor peat store per hectare

Up to around 400 tonnes of carbon per hectare

What is a fen peatland

A peatland fed by groundwater and surface runoff

Why are fens more nutrient rich than bogs

They receive minerals from groundwater

Where is Wicken Fen located

Cambridgeshire

When did peat formation begin at Wicken Fen

Around 5 000 years ago

How deep did peat reach at Wicken Fen historically

Up to 4 metres

What human activities reduce peat carbon stores

Peat extraction drainage agriculture forestry and development

How does peat extraction reduce carbon storage

It physically removes peat and exposes carbon to oxidation

How much CO₂ can extracted peatlands emit annually

Around 5 to 20 tonnes of CO₂ per hectare per year

How does drainage reduce peat carbon even without extraction

Lower water tables expose peat to oxygen increasing microbial decomposition

What has drainage caused in the East Anglian Fens

Peat shrinkage and carbon loss of over 10 tonnes per hectare per year

Why are drained peatlands more fire prone

Dry peat is highly flammable

What example shows fire related peat carbon loss

The 2018 Saddleworth Moor fire

What proportion of England’s peatlands are degraded

Over 80 percent

Why are degraded peatlands a climate problem

They emit greenhouse gases instead of storing carbon

What management strategy restores peat carbon stores

Re wetting peatlands

How does re wetting restore carbon storage

Raises the water table and restores anaerobic conditions

What actions are used to re wet peatlands

Blocking drainage ditches and restoring natural hydrology

What role do Sphagnum mosses play in restoration

They promote peat formation and carbon sequestration

What is the Exmoor Mires Restoration Project

A project restoring peatlands by blocking drainage grips

How much drainage ditch blocking occurred on Exmoor between 2010 and 2020

Over 1 000 kilometres

How much peatland area was re wetted on Exmoor

Around 2 000 hectares

How has restoration changed water tables on Exmoor

Raised them by around 15 centimetres on average

How have CO₂ emissions changed after restoration

Reduced by around 100 to 150 kilograms of carbon per hectare per year

What was Exmoor’s carbon balance before degradation

A net carbon sink

What is Exmoor’s carbon balance after degradation

A net carbon source releasing 2 to 5 tonnes of CO₂ per hectare per year

How did drainage affect peat depth on Exmoor

Reduced peat depth to less than 1 metre in some areas

What vegetation change occurs after degradation

Loss of Sphagnum replaced by grasses heather or bare peat

How does grazing management support peat restoration

Prevents overgrazing and allows vegetation recovery

Why is stopping peat extraction important

It allows natural peat accumulation to resume

What is the long term outlook for restored peatlands

They can return to being net carbon sinks but recovery takes centuries

Why are peatlands important for climate mitigation

Protecting and restoring them prevents large carbon emissions