Spatially differentiated regulation measures – can it save the Baltic Sea from excessive nutrient loads, and is it possible?

Jens Christian Refsgaard1, Anne L. Hansen1, Anker L. Højberg1, Jørgen E. Olesen2, Fatemeh Hashemi2, Przemyslaw Wachniew3, Anders Wörman4, Alena Bartosova5, Nico Stelljes6, Hubert De Jonge7, Boris Chubarenko8

 

1 Geological Survey of Denmark and Greenland, Copenhagen, Denmark

2 Aarhus University, Foulum, Denmark

3 AGH University of Science and Technology, Krakow, Poland

4 KTH Royal Institute of Technology, Stockholm, Sweden

5 Swedish Meteorological and Hydrological Institute, Norrköping, Sweden

6 Ecologic Institute, Berlin, Germany

7 Eurofins Environment, Galten, Denmark

8 Atlantic Branch of the P.P. Shirshov Institute of Oceanology of the Russian Academy of Sciences, Kaliningrad, Russia

 

The Baltic Sea Action Plan and the EU Water Framework Directive both require substantial additional reductions of nutrient loads (N and P) to the marine environment. The remediation measures can be grouped into two main classes i) measures at the field surface affecting the leaching out of the root zone from the crops in individual fields (e.g. catch crops, fertilisation norms, set-aside); and ii) measures restructuring the flow pathway affecting the reduction/retention (e.g. wetlands, river restoration). Focussing on nitrate, we present a widely applicable concept for differentiated regulation, where the remediation measures are differentiated spatially between geographical locations and between root zone, groundwater, wetlands and streams. Hereby we can exploit the fact that the removal of nitrate in groundwater and surface water systems shows large spatial variations. Hereby we can exploit the fact that the removal of nitrate in groundwater and surface water systems shows large spatial variations. By targeting measures towards areas where the local capacity for removal is low, spatially differentiated regulation can be much more cost-effective than the traditional uniform regulation.

Differentiated locations of measures will affect stakeholders differently. Hence, it requires reasonably accurate predictions of capacity for natural removal of nitrate, not only in average for large areas, but specifically for local areas down to field scale. This requires substantially more data and knowledge on flow and transport processes at local scale than is usually available today. In order to assess the impacts of local scale measures for the entire Baltic Sea Basin, local data and modelling results have been upscaled from the three study catchments to the HYPE model that is operationally run for the whole Europe, including the Baltic Sea Basin.

The presentation will discuss the key challenges related to implementation of spatially differentiated regulation measures, including the need for better scientific knowledge, handling of uncertainties and practical constraints related to agricultural practise. Finally, a quantitative assessment is given of the potential effects of spatially differentiated measures as well as a discussion of how much can be achieved in practice and to which extent this could matter for the Baltic Sea environment.