Hydrology of peat-forming wetlands in Scotland

Peatlands cover approximately 14% of Scotland, although only part of this area is active (peat-forming) mire. Mires are important for the biodiversity of the specialist plant and animal communities they support. Study of mire ecosystems has revealed intimate relationships between their organic components and water, which mean that it is impossible to understand their ecology without considering hydrology. Whilst ecohydrological studies have concentrated on the internal functioning of mires, the insights gained are relevant to runoff generation in peat-covered river catchments. This paper reviews our knowledge of processes occurring in mires and relates these to wider catchment hydrology, on the basis of published information and recent research in Scotland. The influence of different types of land management is considered, and it emerges that mire is most effective in delaying storm run-off, in preventing soil erosion and in retaining inorganic nutrients when it is undrained; although there can be adverse effects on water quality under certain conditions. In the context of global warming, mire ecosystems are sensitive but at the same time robust to climate change, and thus contain archives of climatic data for the Holocene. Moreover, peatlands store significant quantities of carbon, and influence directly the concentrations of greenhouse gases in the atmosphere. Various issues related to conservation and restoration of peatland biodiversity have been addressed constructively in recent decades, although approaches and objectives are not always consistent between sites. These are reviewed, and some outstanding issues and research needs are identified.