Restoring Dartmoor’s blanket bogs

The Background
Peatlands across the UK have experienced historic human impacts such drainage, peat cutting, unsustainable grazing and burning pressures along with acidification and damage from atmospheric pollution. These pressures are well known to limit the capacity of peatlands to carry out their natural regulatory functions. These include their ability to sequester and store carbon, store and deliver potable drinking water and support animal and plant communities which are of European importance.

The Dartmoor Mires project which ran from 2010 to 2015 piloted peat restoration works on the north moor to assess their feasibility, desirability and potential for success. Work was carried out at three sites: Winneys Down, South Tavy Heads and Flat Tor Pan. Interventions, which have included blocking gulleys, were carried out which aimed to raise the water tables in the pilot areas. The project involved extensive pre- and post-project hydrological monitoring carried out by the University of Exeter. This work demonstrated that prior to the restoration works the water table was dropping to an average of 30cm below the surface. Once the works had been carried out the water table had risen by an average of 9cm.

Pre-works monitoring also showed that high levels of dissolved organic carbon (i.e. peat) was being lost in water flowing from the blanket bog as a result of exposed and unvegetated peat erosion. Monitoring work is currently being carried out by the University of Exeter to determine whether the restoration works have reduced this.

In the areas where the wetting occurred breeding dunlin numbers increased by 38% and vegetation surveys showed that bog plants such as Sphagnum mosses returned to areas where they had previously been absent.

South West Water have funded the bulk of this work as 40% of their (our) water comes from Dartmoor and if peatlands are degraded the dissolved organic carbon has to be expensively removed at a Water Treatment Works.

The Dartmoor Peatland Investigation and Mapping Project
In November 2016 the Dartmoor National Park Authority commissioned the University of Exeter’s Mire Research Team to produce a GIS resource of peatlands on Dartmoor to include bare peat areas, gullies and erosion features, areas of peat cutting and previously unmapped archaeological features. These impacted areas were included as they are known to affect ecological and hydrological processes operating in peatlands.

Various datasets were used in the analysis including LIDAR, infrared analysis and soil maps. In May 2017 two outputs were delivered to the DNPA: a technical report ‘Dartmoor Peatland Investigation and Mapping Project Report’ and an on-line summary of the features mapped. This can be viewed at https://maps.dartmoor.gov.uk/peatland.html.

The table below summaries the extent of the peatland resource and the extent of damaged areas.

The on-line GIS map produces outputs such as this.

This shows the extent of peat less than 40cm deep and more than 40cm deep based around the National Trust land in the Plym Valley with an OS map base.

This is the same area and features but with an aerial photo base.

This map is of the same area but shows areas of bare peat, drains, peat cutting along with gulley areas where erosion is possible.

The same area and features but with an aerial base – this interpretation highlights the gulley erosion areas more clearly (yellow and red markings).

This on-line resource is very flexible and can be manipulated and zoomed to highlight specific features in specific locations.

 DPIM Supplementary Report
Following on from this report the DNPA asked the University of Exeter team to undertake a further piece of work to

  • Estimate the extent of eco-hydrologically damaged areas of peatland within Dartmoor National Park.
  • Estimate and map the area/s of functionally intact bog.
  • Identify the best candidate sites for future restoration based on ecohydrological analysis.

This work was completed during 2017  and can be summarised as follows.

The report also includes a map displaying these features across Dartmoor.

I was very surprised at the low area of intact bog (3.6km2) – perhaps I shouldn’t have been surprised as Dartmoor has clearly had a great deal of human manipulation since the Mesolithic.

Defra Fund to restore peatlands
The DNPA used this new information to make a bid to Defra’s new peatland restoration fund which was launched in July 2017 (see here). This DNPA bid (submitted along with projects on Bodmin and Exmoor) includes completion of works started during the pilot re-wetting project at Flat Tor Pan along with new restoration schemes at Red Lake, Hangingstone Hill and Amicombe / Rattlebrook. The Dartmoor element is costed at £1.68m. Members of the DNPA approved the project on the 1st December 2017 and Defra will announce who has been successful on the 22nd December 2017.

The dominant narrative is that peatlands need to be restored (as they have been damaged by anthropogenic activities over the millennia) in order to ensure they effectively deliver their ‘ecosystem services’ e.g. carbon capture and storage, drinking water provision, biodiversity conservation and flood prevention. The need and benefits of such an approach are set out in the British Ecological Society’s Review volume ‘Peatland Restoration and Ecosystem Services’ see here.

However there are some that disagree and later in the week I will set out the position held by the Dartmoor Society who believe that such an approach unduly favours nature at the expense of the cultural landscape.

 

 

 

 

2 thoughts on “Restoring Dartmoor’s blanket bogs

  1. This is an excellent summary of the work. I think – to give them their due – South West Water should get a mention for funding the bulk of the research. They are doing this because 40% of our drinking water comes from Dartmoor and at present the DOC must be removed during water treatment. But as you identify, it has many other benefits too.

    • Thanks Lorna – you are quite write I should have mentioned SWW, I have done in other pieces I have written but forgot this time as I was focusing on the U of E work …. Will update accordingly. A

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