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On Exmoor a blanket of peat which is over a metre deep in places covers the central moorland.

This has been formed over the last 3,000-8000 years by peat-accumulating mire habitats such as blanket bogs, valley bogs and fens.

The most common mire type on Exmoor is blanket bog, with over 30km2 present. Globally this is a scarce habitat with a unique association of plants and animals; 20 per cent of the world's total resource occurs within the British Isles.

The central Exmoor blanket bog has been designated a Site of Special Scientific Status due to its importance nationally and internationally on the south west climatic edge of the blanket bog area in the UK.


Restoring peat bogs has benefits for river water quality and for the plants and animals that thrive in a boggy environment.

By blocking drainage ditches more water is stored and released slowly back into the rivers, giving more stable river flows and cleaner water for abstraction at the water treatment works.

By reducing peak stormwater run-off, the amount of peat washed downstream is also reduced as well as alleviating flooding.


Worldwide peatlands are huge carbon stores, but damaged areas release carbon dioxide into the atmosphere through oxidation processes.

Blocking up drainage ditches on the moorland will help to re-wet the peat and promote the bog grasses and mosses once again. There are many benefits to this work.

More water storage in upland catchments

Drained moorlands respond quickly to rainfall and have little storage capacity as all the water runs down the ditches into the rivers. Blocking up the ditches slows down the flow of water and increases the time it takes to get to the river. This is good for water customers as more storage in the uplands means a steady supply and less expensive pumping or reservoir building.

Better water quality

A slower flow results in less sediment and erosion in the water and cleaner water. This is good for water customers as it requires less treatment and good for wildlife in the river such as Salmon.

More carbon storage in the peat

Peat is all carbon and water so mires are huge carbon stores, but dry peat areas release carbon dioxide (CO2) into the atmosphere through oxidation. Re-wetting halts oxidation and promotes active peat growth, thus increasing the absorption of CO2 from the atmosphere.

More wildlife on the moors

Re-wetted mires have more bog plants, insects, frogs and more food for birds and otters.

More to enjoy

Re-wetted moorland does not mean flooded moorland, just a bit wetter in summer and some small bog pools behind the ditch blocks. Moorland visitors can use these to cross the ditches and there is now more to see and enjoy on your visits with lots of dragonflies, cotton grass and brightly coloured mosses.

More for animals to eat and drink

The new bog pools provide longer lasting drinking water supplies in dry periods for sheep, cattle and deer and the wetter ground has a more diverse mix of species in it which can give better grazing in early spring and late summer when the other moor grasses are dried out.

Fewer pests and problems for stock

Recent evidence from mire ditch blocking studies in Wales has found that the re-wetted areas have fewer ticks, no liver flukes and better access for grazing animals across the ditch blocks.

A better future

Keeping the peat wet will help to keep it in place if the climate warms up as expected. This will help to keep the moor as they are today, protecting the landscape and historic past stored in the peat and enabling all to enjoy them in the future.

Threats to Exmoor's blanket bog

Peatland habitats are sensitive to climatic change and hydrological disturbance and the blanket mires on Exmoor are at the forefront of this change due to their south-westerly position.

In addition, centuries of moorland reclamation, agricultural drainage and domestic peat-cutting has modified the habitat and dried out the peat.

As a result it has lost many of the interesting plants, animals and birds associated with wet peatlands and become dominated by moorland grasses.

As future climate change is likely to increase the drying effect on damaged peatlands in the South West of England, positive engagement with all the moorland stakeholders in the restoration planning is essential.

The failure to re-wet these damaged areas could lead to further degradation and loss of SSSI wetland habitat and associated species. Other risks include degradation of the peat and loss of carbon into the atmosphere, drying out of archaeology and palaeo-ecology on the moors, and damage to moorland river hydrology and ecology. This bring associated problems of erosion, drying out in summer, flooding, and loss of key species and diversity.

Historic environment

Exmoors mires are an important repository of archaeological information for a number of reasons.

Firstly, they are generally located in moorland areas; environments in which human activity has historically been light in comparison with the more densely populated and hospitable lowlands.

This means that the remains left behind by those who have lived and worked in these areas in the past are much more extensive and diverse than is the case in many other areas. This is well illustrated by the archaeology of the mire restoration areas on Exmoor which ranges from 8000 year old Mesolithic hunter gatherer sites to preserved Bronze Age farming and settlement landscapes dating to 3500 years ago to the remains of World War II military training activities.

Also, the mires themselves have enhanced archaeological significance due to the waterlogged environments they provide for buried archaeology. These have exceptional preservative qualities, enabling the survival of a range of organic materials including wood, other plant materials and leather for thousands of years. Mires thus provide access to aspects of the lives of long-dead people and societies that we do not normally have from other sources. They become especially important when the special status 'watery places' had in the eyes of prehistoric societies is considered; many important archaeological discoveries have been made as a result of the deliberate deposition in the past of materials ranging from precious metals to sacrificial victims in bogs.

Finally, the peat of which mires are made grants them further archaeological importance as it contains and preserves abundant grains of pollen from the plants that grew in the vicinity during the course of the mire's development. This means that a record of vegetation change through time is preserved which archaeologists can use to answer questions such as whether the landscape was wooded or open at a given time, or whether people were growing crops nearby. Similarly, the remains of the microscopic animals that lived and died in the mire are often preserved. Many of these are of species that are only able to live in very specific environments which means that by recording them, archaeologists can build up a picture of how climate has changed over time.

By returning mires to healthy condition, restoration will maintain the preservative qualities of mires and safeguard them as repositories of archaeological information for future generations. However, the work of undertaking re-wetting, involving as it does the movement of vehicles and the installation of dams, has the potential to damage or destroy fragile archaeological features. The Exmoor Mires Project mitigates this threat through an extensive programme of archaeological monitoring and survey which identifies and characterizes the archaeology of the each mire restoration area and, through the application of a variety of cutting edge techniques, enhances our knowledge of it.


The project has also been asked by water regulators Ofwat and the Environment Agency to undertake research and monitoring on the hydrological and ecological effects of rewetting peatland.
An extensive program of hydrological and greenhouse gas (GHG) monitoring and research has been developed in partnership with Bristol and Exeter Universities and the Environment Agency.

Take a look in the Document library section to view many of the reports outlined below.

The foundation of the hydrological research has been laid out by the Exmoor Mires Project Hydrological and Hydrogeological monitoring plan written by the project partners in the Environment Agency (Arnott, 2010).

This new research programme builds on the ecological and hydrological monitoring work begun in 1998 by the MIRE pilot project. The studies have focused on monitoring for changes in the hydrology and ecology of the sites resulting from the re-wetting work.

The University of Exeter is carrying out extensive monitoring work, examining hydrological functioning (i.e. water table depth, flow and seepage), water quality (i.e. colour, dissolved and particulate organic carbon), gaseous fluxes, vegetation composition and structure, before and after ditch blocking. The work is taking place on two sites (Aclands and Spooners) representative of upland peatland on Exmoor. On each site, three different drains and the exit point of the catchment are closely monitored. This will provide the first detailed evidence base quantifying the value of peatland restoration in terms of water quantity, quality and carbon sequestration.