Locking up carbon in the Somerset Levels · 2019. 4. 5. · 1. Minimise variation in soil moisture...

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Richard Archer Thursday 1 December 2016

Locking up carbon in the Somerset Levels

• 2nd largest area lowland organic soil in UK

• 2,500 ha moss peat, 12,500 ha sedge peat

• Total c. 10.9 M tonnes?

SL&M C store

• Peat wastage 4-8 mm pa? (>12 mm pa?) 6 mm = 20,000 t C pa

• Peat extraction - 1,400 t peat extraction + Baltic peat

• C sequestration – zero?

• Net loss 0.2% pa

SL&M C peat balance sheet

LIDAR – GLK & WSR

4-6 cm difference between SSSI pasture and former arable

Traditional floodplain pasture & hay meadow: 6,000 ha – largest remaining area in UK

• Summer pen: 1 Apr water at field level

• MG8 – water table down to 20 cm

• Snipe/curlew like MG8 hay meadow

• Lapwing/redshank splash

• Aug onwards – maintenance

• Winter pen: mid Dec mean field levels

• No DWR on MG8 wader fields

• No dry ditches

RWLA water management 1

RWLA management favourable for peat soils:

1. Minimise variation in soil moisture content to minimise peat degradation

2. Key factor: don’t allow summer water table to fall below 50 cm.

3. Spring & summer – water table max 30 cm below mean field level

4. High ditch levels don’t guarantee high field groundwater levels

5. Ditch / foot drain / gutter spacing critical – 20 m?

6. Big hydro blocks to minimise mgt & costs

7. Also protects buried archaeology

RWLA water management 2

• RWLAs c.2,000 ha

• SSSIs c.6,000 ha - CO’s adequate?

• 7,500 ha poor peat mgt?

Scale of peat wastage

• Declining output• 1,400 t C per annum. Much smaller than agriculture• Not destroying good habitat• Milled with Baltic peat• Last big new permission Cradlebridge• NPPF – no extensions, except where clear

environmental gain• Habs Regs Review

Peat extraction

1. Short-term – protect what we have:• SPA/Ramsar/RWLAs• Improve SSSI mgt• Create new lowland mire?

2. Medium-term:• C offset market, alternative LWG revenues e.g. biomass• Non-peat alternatives

3. Long-term – climate-proof:• Drought – upper catchment storage?• Bigger hydro units• ?

The Future – a few thoughts

Thank you

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