Modelling blanket peat erosion under environmental change

Many peatlands across the world are suffering from degradation and erosion exacerbated by human influences. Blanket peat erosion has adverse impacts on terrestrial and aquatic habitats, reservoir capacity and water quality. It also leads to accelerated carbon release. Bioclimatic modelling suggests that some areas, which are suitable for active peat growth currently, may be no longer under a climate supporting the accumulation of peat by the end of the century. Erosion in these marginal regions is thus more likely. However, there have been no attempts to date, to model blanket peat erosion mechanisms and rates and how they might respond to different climate scenarios and land management drivers. The PESERA-GRID model was chosen as a basis for modelling blanket peat erosion as it had a number of suitable properties such as its applicability in various spatial scales, and hydrological module is theoretically suitable for blanket peatlands. The model was modified to incorporate freeze-thaw and desiccation processes and typical land management practices (artificial drainage and burning) in blanket peatlands. This resulted in a modified model called PESERA-PEAT. In PESERA-PEAT, blanket peat erosion is determined by both sediment supply through weathering and the transport capacity of overland flow. A novel sediment supply index was defined and employed to parameterize the sediment supply from blanket peatlands. Land management practices were parameterized for their influence on vegetation cover and biomass and soil moisture condition. Potential wildfire severity was estimated with a previously developed ignition model. The PESERA-PEAT model was calibrated and validated with field data from previous publications and data from three blanket peat-covered catchments. Model testing suggested that PESERA-PEAT was robust for modelling blanket peat vegetation, runoff and erosion. Climate change scenarios were established and climate data were compiled to 2100. The PESERA-PEAT model was applied at a regional scale for the blanket peatlands of the North Pennines and at a smaller scale for ten sites across Great Britain to examine the response of blanket peat erosion to possible changes in climate and land management practices. Modelling results suggested that the response of blanket peat erosion to climate change was highly variable across space both within regions and across Great Britain with some sites experiencing reduced erosion under some climate scenarios with most experiencing increased erosion. The model suggested that peat erosion change would be generally higher in southern and eastern areas than in western and northern parts of Great Britain. Predicted erosion change was particularly high in the North York Moors where lower rainfall and higher temperatures suppressed the water table, and led the predicted future erosion to be usually transport limited. It was suggested that summer desiccation may become a more important sediment source for British blanket peat erosion in the future, leading to more sediment erosion released from blanket peatlands during subsequent rainstorms. Erosion change with climate change to 2100 was predicted to be smaller in wetter and colder locations. As climate changes, rainfall was shown to be more important than temperature in shaping long-term changes in runoff production while temperature was generally more dominant than rainfall in controlling long-term erosion change. However, in the North York Moors rainfall appeared to be more dominant in long-term erosion change. Overall, the modelling work suggested that land management may have a greater impact on blanket peat erosion than on runoff, while climate plays a more important role in runoff production rather than in blanket peat erosion. It was suggested that adjusting land management practices may be appropriate in order to buffer the impacts of future climate change on blanket peat erosion. However, when blanket peatlands were managed to protect them from soil erosion through ensuring a thriving vegetation biomass cover, then wildfire-awareness and precautionary fire measures would be required as the wildfire risk increased substantially with climate change and may also increase with such land management strategies