Nature Features

A straw bale dam at Codsend Moors

Encouraging biodiversity and preventing global warming and winter flash flooding are some of the reasons why work is being done to re-wet the moorlands on Exmoor.

The £400k project has so far re-wetted 140 hectares and a further 25 sites have been identified by the Exmoor National Parks Authority which could benefit from this work.

Water needs to be put back into the peat bogs as they act as a huge natural carbon store.

When these areas dry out carbon dioxide is released into the atmosphere adding to global warming.

It's being done through the Exmoor Mire Restoration Project which has been running since 2006 funded predominantly by South West Water.

Climate change

Peat cutting has been taking place for centuries on Exmoor and was done by digging out ditches to find natural springs which criss-crossed the moorland.

The natural springwater was channelled away from the land to dry out the peat so it could be cut and used for fuel.

A rare plant: Devil's bit scabious

Using up this natural resource had a far-reaching effect on the area's biodiversity and ecology.

Mire restoration project officer Dr David Smith said:

"What happens with dry peat is that it oxidises the environment and turns into carbon dioxide, and that's loading CO2 into the atmosphere which contributes to climate change which is the last thing we want.

"If you can re-wet these peats that dries the oxygen out you end up with a peat mass which is stable again."

The ditches are blocked by using two different methods, by building wooden dams across them or by using straw bales.

In two years over 20km of drains have been blocked with over 1,000 dams.

The reason why water companies have backed this project is because the peat bogs act as reservoirs trickling water down to the River Exe keeping its water levels stable.

An added benefit is that winter flash floods can be avoided because the amount of time it takes for water to flow into the River Exe is increased.

140 hectares of peatland have been saved

'Natural bonding'

Codsend Moors is a site where the project exclusively used straw bales to build the dams because it was archaeologically sensitive, as it's the site of a Bronze Age settlement.

Straw bales were made using moorland grass, bracken and heather which were sourced from the neighbouring land and used to block the ditches.

"The water is very acidic. It creates an environment where the water doesn't rot the bales, it just turns to peat and the seeds in the bales start to grow.

This moss is 95 percent water

"You get a natural bonding together between the roots of the plants so it holds up very well," said David.

Since the dams have been put in place biodiversity has improved.

Marsh fritillary butterflies have been spotted, and rare mosses like sphagnum and devil's bit scabious are also flourishing.

"The total amount of carbon on these moors would be the equivalent of the output from the South West for a few years, so it's potentially a huge amount of carbon you're saving and not putting into the atmosphere.

"Effectively you are turning the clock back. Instead of losing the carbon, plants start accumulating peat so you take carbon out of the atmosphere and store it here."