Protecting the peatlands at Malham Tarn
We have been pushing ahead to complete the restoration of the impressive and important raised bog that lies within the Malham Tarn National Nature Reserve. Find out how we've been getting on.
Tarn Moss is a particularly valuable and unusual example of a bog because of its position within a natural mosaic of wetland habitats, notably with a very species rich area of ‘lagg fen’ to its western edge. This marginal area of fen is fed by lime-rich ground water from the surrounding catchment and has a very different flora and fauna to the dome-shaped raised bog which has grown up above the fen, over the centuries, to become rain-water fed.
How it's suffered
Although Tarn Moss is considered a high quality raised bog, it has suffered from man’s attention over the years. Drainage ditches have been dug; sections have been cut for peat turves; the surface has been impacted by periods of burning and heavy sheep grazing; and most bizarrely a sizeable area of the eastern part of the bog has been eroded away since a past landowner raised the level of Malham Tarn in the 1790s.
The damaging grazing and burning impacts were stopped when the Trust acquired the land and the drainage ditches have also been dammed for a long time now. However, the remaining impacts of erosion into the tarn and of the old peat cuttings have been more complex problems.
After much scientific investigation and advice we concluded that the best environmental solution to the wave erosion from the tarn was not to drop the water level back to its original position (as this would now damage the fen and tarn itself) but to pursue a novel ‘soft engineering’ solution. This has involved inserting larch logs to create a solid revetment along the peat edge with an offshore wave-break to hopefully halt further erosion. Natural England has been working with us on this large restoration project and we are grateful for their resourcing of the major cost of the works.
Work was also undertaken in summer 2014 to restore the areas that were affected by past peat cutting. Peat bunding has been shown to be a very effective way of speeding the recovery of such areas by stimulating active growth of the bog mosses that lay down the peat – and bunds have now been built across all the old peat cuttings.