Abstract
The Baltic Sea is considered the marine water body most severely affected by eutrophication within Europe. Due to its limited water exchange nutrients have a particularly long residence time in the sea. While several studies have analysed the costs of reducing current nutrient emissions, the costs for remediating legacy nutrient loads of past emissions remain unknown. Although the Baltic Sea is a comparatively well-monitored region, current data and knowledge is insufficient to provide a sound quantification of legacy nutrient loads and much less their abatement costs. A first rough estimation of agricultural legacy nutrient loads yields an accumulation of 0.5–4.0 Mt N and 0.3–1.2 Mt P in the Baltic Sea and 0.4–0.5 Mt P in agricultural soils within the catchment. The costs for removing or immobilising this amount of nutrients via deep water oxygenation, mussel farming and soil gypsum amendment are in the range of few tens to over 100 billion €. These preliminary results are meant as a basis for future studies and show that while requiring serious commitment to funding and implementation, remediating agricultural legacy loads is not infeasible and may even provide economic benefits to local communities in the long run.
Highlights
Urbanisation and agricultural intensification since the 1950s have caused an increase in emissions of excessive nutrients (mainly compounds of nitrogen (N) and phosphorus (P))
More than a century of N and P emissions from municipal and industrial wastewater, as well as agricultural runoff have led to a situation, were 97% of the Baltic Sea are impaired by elevated nutrient levels, reoccurring cyanobacterial blooms, high oxygen debt and other eutrophication impacts [3]
In the Baltic Sea region several studies have analysed the costs of reducing nutrient loads to the sea [13,14,15,16,17], sometimes juxtaposing them to the value people assign to a healthy sea [13] or comparing economic effects of an intact and an environmentally degraded marine environment [16]
Summary
Urbanisation and agricultural intensification since the 1950s have caused an increase in emissions of excessive nutrients (mainly compounds of nitrogen (N) and phosphorus (P)). N and >50% for P since their peak in the 1980s), the 2021-targets of the BSAP are missed and eutrophication continues to be one of the most pressing issues in the region [3] Both aspects, the severity of the problem as well as the good documentation of emissions, their impacts, and the effects of different mitigating measures, could enable the Baltic Sea region to become a forerunner for a successful large-scale transition towards a circular, green economy and society. In the Baltic Sea region several studies have analysed the costs of reducing nutrient loads to the sea [13,14,15,16,17], sometimes juxtaposing them to the value people assign to a healthy sea [13] or comparing economic effects (employment, property values, etc.) of an intact and an environmentally degraded marine environment [16]. The costs of extracting P from the water or permanently binding it in bottom sediments and on land are quantified
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