Suspended sediment response to Nordic bioeconomy and climate change scenarios in a first-order agricultural catchment

Abstract

Soil loss by erosion threatens food security and reduces the environmental quality of water bodies. Prolonged and extreme rainfalls are recognized as main drivers of soil erosion, and climate change predictions for large parts of the world foresee such increases in precipitation. Erosion rates are additionally affected by land use, which may change as a result of the shift from a fossil fuel-based economy to an economy relying on using renewable biomass, a “Bioeconomy”. In this study we aimed at investigating, through modelling, i) if future changes in land use, due to a bioeconomy, would increase the risk for soil loss and enhance suspended sediment yields in streams and ii) if these changes, when combined with climate change effects, would further aggravate suspended sediment conditions in a catchment. We used hydrological and bias adjusted climate models to compare the effect of seven land use pathways on discharge and sediment transport relative to a baseline scenario under present and future climate conditions. The study was carried out based on data from a small headwater stream, representative for cereal production areas of S-E Norway. By modelling our scenarios with the PERSiST and INCA-P models, we found that land use change had a greater influence on both future water discharge and sediment losses than a future climate. Changes from climate showed strongest differences on a seasonal basis. Out of the modelled land use pathways, a sustainable pathway manifested the least occurrence of extreme flood and sediment loss events under future climate; whereas a pathway geared towards self-sufficiency indicated the highest occurrence of such extreme events. Our findings show that careful attention must be placed on the land use and soil management in the region. To maintain freshwater quality, it will be increasingly important to implement environmental mitigation measures.