Climate change impact on nutrient loss in regions with pronounced winter seasons

Eutrophication manifested by massive algal blooms is the most acute problem in many coastal waters and lakes around the world. The main source of phosphorus and nitrogen transport in the region studied, the Baltic Sea basin, is agriculture. Several studies have predicted adverse climate change impact on eutrophication problems. Here we show that in regions with a climate characterized by pronounced winter seasons and snow-melt flow peaks, this may not be the case. Regional Climate Model results were used to drive hydrological and nutrient modelling. Substantial reductions of phosphorus losses and small reductions for nitrogen were predicted. The main factors behind these results were fewer and less pronounced snow-melt occasions, elevated plant uptake of nutrients and increased growth and crop yield. Based on IPCC scenarios, one ‘market driven’ (A2) and one ‘Local Sustainability’ (B2), the impact on nutrient loss of societal development and future policy lines were assessed. Agricultural adaptation to a future climate, market demand and remedial action policies, e.g. more autumn crops and bio-fuel production, gave further reductions in nutrient loss. The results should not be taken as a motive to reduce efforts to minimize eutrophication in these areas, since severe eutrophication may cause irreversible effects in the decades to come.