Impacts of Climate Change on Erosion, Sediment Transport and Soil Carbon in the UK and Europe

For the government agencies and statutory bodies responsible for management of land and water resources, the past decade has witnessed growing recognition of a series of pressing environmental issues and an awareness that significant uncertainties exist concerning their future trajectories: 1. Erosion by water is the most severe threat to soil in Europe (Kirkby et al., 2004). Furthermore, rates of soil erosion are sensitive to changes in surface runoff, yet spatially-explicit predictions of future erosion rates under changing climatic conditions are not yet available. 2. Redistribution of soil by agricultural tillage is a key influence on the evolving spatial variability of soil properties and productivity (Quine and Zhang, 2002), and consequently exerts a strong control on the emission and sequestration of soil carbon from arable land (Van Oost et al., 2004, 2005). Soils are expected to represent an important control on carbon cycle feedbacks under changing climatic conditions (Cox et al., 2000). However, the role of soil erosion and redistribution in the carbon cycle remains an area of significant controversy, with estimates of the global carbon flux associated with erosion ranging from a 1 Gt/year source to a 1 Gt/year sink (Stallard, 1998; Lal, 2003). 3. Delivery of eroded sediment to river channels causes many environmental problems including diffuse pollution, transport and storage of fine sediment and associated contaminants, degradation of aquatic ecosystems, and changes in flow conveyance capacity and flood frequency due to in-channel and overbank sedimentation (Walling et al., 1999, 2001; Greig et al., 2005). Defra and the Environment Agency currently face the significant challenges posed by implementation of the EC Water Framework Directive (WFD) and the requirement to address the issues highlighted above in order to manage and maintain the ecological status of all surface waters. Furthermore, potential changes in the threats posed by these problems under future climates have yet to be quantified. Tackling these challenges at national and regional scales will necessitate the development of new modelling approaches capable of investigating the feedbacks between climatic, hydrologic, geomorphic and biogeochemical processes, which are poorly understood at present. This project will link CEH and Met. Office expertise in regional climate and hydrological modelling with geomorphological models developed by the universities of Leeds and Exeter to build for CEH a solid, strategic platform from which to address this set of fundamental scientific and environmental questions, which lie at the heart of the EHFI programme, and are central to both CEH and NERC's core missions. This project will build on recent modelling advances to develop new models in the following areas: 1. Hillslope hydrology and soil erosion; 2. Sediment routing within rivers, flood conveyance and floodplain sedimentation; 3. Soil redistribution on hillslopes and soil organic carbon dynamics on slopes and floodplains. All model components will be evaluated and assessed using a wide range of existing data sources. Models will then be implemented within an integrated framework to examine environmental responses to climate change over the next century in the UK and at selected sites in Europe. Key questions that will be addressed using this approach include: 1. What are the effects of projected future changes in climate on soil erosion and sediment delivery into and through river channels? 2. What are the projected effects of climate change and accelerated erosion on river channel morphology, and how might these changes alter future flood risk and sediment storage on floodplains? 3. Can the effects of future changes in climate on the redistribution of soil organic carbon within the landscape be quantified and incorporated as a feedback into future models of terrestrial carbon biogeochemistry? Note: References are in case for support