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ENVIRONMENTAL CHANGE IN HEADWATER PEAT WETLANDS, UK

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Around 13% of the UK is peat wetland。 The perceived value of this land has been low and much has been invested in converting these lands to agriculture and forestry。 Perhaps a fifth of the British peaty uplands have been drained and， since 1945， about a fifteenth forested。 The traditional view is peat lands adsorb and store rainwater but undisturbed peat wetlands are poor aquifers and act mainly as surface flow systems that do little to moderate floods。 By contrast， after drainage， peat land may do more to moderate flood flow because of increased soil storage。 However， drainage ditches increase the speed of runoff and encourage erosion。 Overgrazing， trampling and burning also encourage accelerated runoff and erosion。 Hill farming fosters pollution through the release of organophosphate sheep dip， fertiliser and pesticides， including the Asulam used to control bracken。 Peat headwaters produce storm runoff that is acidic but drainage increases the chemical loading of most ions and reduces the pH。 Burning moderates pH but forestation encourages acidification。 Peat bogs are net sinks for CO_2， N and many other environmental chemicals but environmental change may reverse this effect。 By contrast， disturbed soils are sinks for methane while undrained peat lands are sources。 Better environmental management understanding is required to maximise the benefits to stakeholders of the UKs upland wetlands and to minimise potential negative impacts due to climatic emissions of greenhouse gases， hydrological changes especially flooding， water chemistry， and sediment release。 There remains a need to assess their continuing role in current and future land use systems， especially hill farming， forestry， water resource management， forestry， tourism， and nature conservation。 Current research evidence is ambiguous but the present presumption favours preserving Britain's peat wetlands and some investment in the restoration of the most degraded areas， especially those used for tourism or nature conservation。

uplandspeat lands: hydrological rolehydrochemistryover-grazingburningdrainageforestationpollutionreclamation

M. HAIGH

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Department of Geography, Oxford Brookes University, Oxford OX3 0BP, UK

Environmental Role of Wetlands in Headwaters; NATO Science Series IV: Earth and Environmental Sciences; vol.63

Marienbad(CZ)

NATO Advanced Research Workshop on the Environmental Role of Wetlands in Headwaters; 20031123-28; Marienbad(CZ)

P.237-255

2003