Disappearing Peat-Regenerating Peat? The Impact of Climate Change on British Peatlands

Abstract

On a global scale, over the past 200 years peatlands have become a source rather than a sink of carbon. Drainage for agriculture, forestry and peat extraction have resulted in a 16-37 per cent loss in the carbon sink capacity. The current scenarios for climate change in Britain will exacerbate this loss. A shift in the carbon balance of peatlands is not necessarily the only outcome of climate change. Indirect hydrological changesespecially alteration of the position of the peat water table-will affect the stability of peatland ecosystems. This raises a number of questions concerning the future of British peatlands: the most important of which is how will the water balance change on a regional scale? In Britain the potential response of peatlands to climate change varies spatially. In upland areas, where rainfall is the main source of water, the key question is will erosion increase and if so, how fast? It will also be important to establish the drainage network response in terms of run-off, sediment loading and stream water quality. Increased precipitation may increase the rate of sedimentation in reservoirs thus affecting their water-holding capacity and water quality. Enhanced decomposition at elevated temperatures may also increase the microbial release of humic acids and increase the incidence of colour in upland waters which will in turn increase the cost of water quality treatment. In lowland Britain, the increased flood risk and more or less permanently elevated water table (as a result of both a rising sea level and sinking land surface) may enable peat regeneration through paludification. Key areas that are likely to be affected have spring or floodwater as their main source of water. They include the Norfolk Broads, Suffolk valley peats, Cambridgeshire Fens, Humberhead Levels, Derwent Ings and possibly the Somerset and Gwent Levels. In order to minimize the effects of climate change on peatlands and to preserve their existing carbon sink capacity (however small) they must remain hydrologically intact, and as high a water table as possible must be maintained. This may be possible in low-lying areas if flooding reinstates paludification but the process of peat regeneration is a slow one. In upland areas the effect of climate change is less clear; increased precipitation may encourage peat formation but it may also result in greater erosion.