Dartmoor Mires Project – Restoration of damaged blanket bog at South Tavy Head
25 July 2013
During August 2013 the Dartmoor Mires Project will begin a new stage of experimental restoration work on damaged blanket bog high on Dartmoor's north moor. This restoration work is part of a 5 year pilot project which the Dartmoor Mires Project is undertaking to test the feasibility of restoring degraded blanket bog on Dartmoor.
The project aims to restore just over 100 ha of bog which are threatened by encroaching erosion in the form of gullies. These gullies are likely to have been initiated by past burning, adjacent peat cutting, and WWII military activities, and once formed, wind and rain has acted to increase their extent. By blocking these erosion gullies, the project aims to prevent further erosion and create the conditions required for the recovery of the blanket bog.
The blanket bogs of Dartmoor are designated as a Special Area of Conservation (SAC) and Special Site of Scientific Interest (SSSI) due to their unique plant and animal communities. In good condition these blanket bogs can act as a carbon store locking up carbon dioxide (CO2) from the atmosphere as they form layers of peat, helping to mitigate against climate change. They also store large volumes of water which they release slowly as clean clear water into the headwaters of our rivers, so serving an important role in our water supply.
However, where erosion gullies form, the water table is lowered, damaging the unique plant communities and their ability to create peat and store carbon. Further to this, as the bog dries out, the once water logged peat will start to oxidise, releasing the CO2 it had stored back into the atmosphere. As the gullies continue to erode, peat and carbon are washed into the headwaters of our streams, discolouring the water and requiring expensive treatment at extraction, which ultimately impacts on customer's bills.
During restoration works peat turves (small squares of peat with a covering of vegetation) will be used to create a number of small blocks along the length of the gullies. This will slow down the flow of water creating small pools behind the blocks. These pools provide ideal conditions for re-colonisation by blanket bog vegetation. The peat turves are sourced from within the immediate vicinity of the gully. Works are carried out using a specially modified ultra low ground pressure excavator with specialised tracks which do not break the vegetation surface.
To date the project has undertaken restoration work at two sites on Winney's Down (see image of Winney's Down site after restoration works above), which if successful will have restored 35ha of blanket bog. Restoration works at South Tavy Head, if successful, will restore a further 11ha of blanket bog.
To assess the condition of Dartmoor's blanket bogs and the success of the restoration work, the Dartmoor Mires Project is also undertaking an extensive programme of research and monitoring. This includes; vegetation, breeding bird, and invertebrate surveys, photo monitoring, and hydrological monitoring including greenhouse gas emissions. Early indications from our hydrological monitoring suggest high levels of erosion are occurring on the blanket bogs of Dartmoor, with levels of erosion comparable with the much more damaged peatlands in the north of England. Although further data is needed to create a clear view, this early data suggests that without intervention these internationally important habitats will become further degraded, having a serious impact on their ecology, and potentially releasing more carbon into the water and atmosphere.
With 45% of the water South West Water supply to customers across Devon, Cornwall, and part of Dorset being extracted from rivers that source on Dartmoor, and up to 8,500ha of blanket bog on Dartmoor, a lack of intervention could have serious consequences for our water supply.
The Dartmoor Mires Project is led by Dartmoor National Park Authority in partnership with Natural England, the Duchy of Cornwall, Dartmoor Commoners' Council, the Environment Agency, and South West Water, which has provided significant funding as part of its Upstream Thinking initiative. For further information about the project please visit www.dartmoormiresproject.org.uk.
For Further information
Scott Hardy, Assistant Project Officer, Dartmoor Mires Project
Mike Nendick, Communications Officer, Dartmoor National Park Authority.
Tel: (01626) 832093
Notes for Editors
During August the Dartmoor Mires Project will undertake restoration works on damaged blanket bog at South Tavy Head, an area of blanket bog within the Merrivale firing range, on high plateau, just north of Cowsic Head.
The Dartmoor Mires Project is a partnership initiative to investigate the feasibility and effects of the restoration of blanket bog in order to conserve and enhance this special habitat and the species its supports; improve water quality and maintain or increase carbon storage. It is a 5-year pilot project (2010-2015) which has just entered its fourth year.
The Dartmoor Mires Project is led by Dartmoor National Park Authority in partnership with Natural England, the Duchy of Cornwall, Dartmoor Commoners' Council, the Environment Agency, and South West Water, which has provided significant funding as part of its Upstream Thinking initiative.
The UK has about 13% of the world's blanket bog – one of the world's rarest habitats.
Blanket bog forms on plateaux and gentle slopes of moorland above 400 metres allowing peat to develop and specialist plants to thrive. Healthy blanket bogs support unique plants and are a crucial habitat for some rare nesting birds. The saturated peat stores a large volume of water releasing it slowly. However, when blanket bog is damaged, water loss speeds up. This causes erosion and drying out of the peat, which then leads to loss of both carbon and biodiversity.
The pilot work is focused on four sites and if successful will protect over 100 hectares of blanket bog. The sites chosen for this work are areas of high quality blanket bog that are eroding at the edges through erosion gullies.
There is a close working relationship with the commoners and landowner over site selection. No sites go forward for practical restoration without the prior approval of commoners and the landowner.
A central focus for the project is the development of a better understanding of how blanket bogs operate and how we can restore and conserve these internationally important habitats. This includes: vegetation, breeding bird, and invertebrate surveys, photo monitoring, and hydrological monitoring, including greenhouse gas emissions.
Early results from our hydrological monitoring at Flat Tor Pan, which is managed by the University of Exeter, indicate high levels of erosion are occurring on the blanket bogs of Dartmoor, with levels of erosion comparable with the much more damaged peatlands in the north of England.
Professor Richard Brazier (Exeter University) who is leading the hydrological research being undertaken said, "Levels of loss of dissolved organic carbon recorded in water from the Dartmoor monitoring site at Flat Tor Pan are significantly higher than expected. Peak concentrations observed are comparable to those from damaged peat bogs in the north of England which are being restored, and are twice those of damaged bogs on Exmoor. This emphasises the importance of undertaking restoration on Dartmoor."
45% of the water South West Water supply to customers across Devon, Cornwall, and part of Dorset is extracted from rivers that source on Dartmoor. Blanket bog is on the high moor of Dartmoor at the heads of these rivers.
The Dartmoor Mires project is developing our understanding of the internationally important blanket bog. These bogs are a huge asset for society and the project will help us determine how to conserve these areas effectively for multiple benefits.