Modelling the impact of the Nordic Bioeconomy Pathways and climate change on water quantity and quality in a Danish River Basin

Abstract

A societal transformation towards bio-economy will have extensive implications for land use in Nordic countries. These expected changes in land use combined with a changing climate, will have unknown consequences for water quality and quantity. To address this issue, we used the Nordic Bio-economic Pathways (NBPs), which describe five possible future scenarios (NBP1-5) for the Nordic bio-economy in 2050. The NBPs were quantified by experts using local knowledge and translated into modelling scenarios. The SWAT model was applied to simulate the effect of NBP scenarios for changes in farming intensity (varying chemical fertilizer and manure application rates), land cover change (agriculture vs forest) and nutrient loss mitigation (buffer strips and wetlands) in the River Odense catchment. Subsequently, the NBPs were combined with medium (RCP4.5) and strong (RCP8.5) climate change scenarios for the period 2041–2070 utilising the median of an ensemble of 20 and 57 climate models, respectively. Our study clearly showed that only one of the pathways, namely NBP1 (sustainability first), would enable catchment managers to fulfil the Water Framework Directive reduction target set for the total nitrogen loads in the River Odense catchment by reducing total nitrogen loads by 66%. One of the pathways (NBP5; growth first) caused an increase in the average annual total nitrogen loads by 12%, while the NBP3 scenario (self-sufficiency) reduced the total nitrogen loads with 18% compared to 2% in the case of NBP2 (business as usual) and 29 % for NBP4 (cities first). Surprisingly, climate change had only limited added impacts on the total nitrogen loads due to increased nitrogen uptake of crops. Our study provides policy makers with information on the influence of the different choices and directions taken towards transforming societies into bio-economies in the future.