Upland Peat Bogs
by Jane Firth
What are peat bogs and how do they form?
Upland peat bog, or blanket bog, began forming after the last ice age as the climate became warmer and wetter. It is found on hilltops that have acid bedrock and high rainfall (more than 2 metres a year) so the ground is almost always saturated.
20% of the world’s blanket bog is found in Britain and Ireland.
Blanket bogs are found on many of the fell tops around Ullswater, such as High Street, Place Fell and Little Mell Fell.
These acidic conditions promote the growth of sphagnum moss, heathers, cottongrass and a variety of carnivorous plants.
In the anaerobic conditions of the peat bog, these plants break down very slowly to form peat. Peat accumulates at a rate of just 1mm a year. Carbon from the decomposing plants is locked away in the peat, with every hectare of peat bog locking away about 1000 tonnes of carbon.
Peat bogs and climate change
“Peat is the largest and most efficient land-based store of carbon, and the world’s second largest carbon store after the oceans. Peat bogs store on average 10 times more carbon per hectare than any other ecosystem, including forests".(1)
However, when peat comes into contact with air, its carbon combines with the atmospheric oxygen and carbon dioxide is released.
“Burning, draining, and degrading peat bogs emits carbon dioxide equivalent to more than one tenth of the global emissions released from burning fossil fuels.” (1)
Peat bogs and flood mitigation
Peat bog moss holds about twenty times its own weight in water so in extreme rainfall it helps to store water and moderate the effects of flooding downstream. It absorbs the water slowing the runoff and reducing erosion.
Less erosion means less acidic peat is washed into streams and lakes where it may have a negative impact on aquatic life. It also means less discolouration of the water supply, which is expensive for water companies to rectify.
Peat bogs under threat
About 8% of the UK is covered by peat moorland, but in the last century much of it has become degraded.
In many areas of the UK the surface of the upland peat bogs is burned to promote fresh growth for livestock or grouse. Burning causes loss of the peat-forming mosses that protect the surface of the peat, causing it to dry out, shrink and erode.
Peat bogs are also under threat from drainage and afforestation "About 200,000 hectares of peat bog in Great Britain have been afforested. Establishing forests on peatlands requires drainage, deep ploughing and fertiliser application. This exposes peat to the atmosphere, promotes peat decomposition and can lead to erosion. The growth of trees themselves also dries out bogs and results in the loss of peatland vegetation”. (2)
In the Lake District damage to upland peat bogs is caused by feet, mountain bicycles, quad bikes, off-road scramble motorbikes and overgrazing.
Peat bogs are also threatened by climate change because increased warming, more extreme droughts and more extreme floods result in the drying out and erosion of the peat.