Change in nutrient loads to the Baltic Sea Basin with changing climate, socioeconomic impacts, and land management practices

Alena Bartosova1, Johan Strömqvist1, René Capell1, Jørgen E. Olesen2, Mohamed Jabloun2,3, Berit Arheimer1, Chantal Donnelly1, Kari Hyytiäinen4, Søren M. Pedersen5, Andis Zilans6, Karin Tonderski7, and Marianne Zandersen2


1 Swedish Meteorological and Hydrological Institute, Norrköping, Sweden

2 Aarhus University, Tjele and Roskilde, Denmark

3 University of Nottingham, Nottingham, U.K.

4 University of Helsinki, Helsinki, Finland

5 University of Copenhagen, Copenhagen, Denmark

6 University of Latvia, Riga, Latvia

7 Linköping University, Linköping, Sweden


An integrated dynamic model E-HYPE v.3.1.4 developed by SMHI allows us to investigate impacts of changing climate, socioeconomic development, and implementation of mitigation measures on nutrient loading to the Baltic Sea Basin on a large scale. The new scenarios framework developed by the climate change research community over the recent years consists of two sets of pathways: Representative Concentration Pathways (RCPs) that describe the extent of climate change and Shared Socioeconomic Pathways (SSPs) that depict plausible socioeconomic conditions during the 21st century.

We have investigated the following for the Baltic Sea Basin:

  • What nutrient loads can we expect to be delivered to the Baltic Sea by 2050s given the potential future socioeconomic development and climate changes?
  • How do combinations of changes in climatic conditions with targeted changes in land use and land management affect nutrient loading to the Baltic Sea in different basins?
  • How effective are spatially differentiated, single-objective, and multi-objective measures at reducing nutrient loads to the Baltic Sea under the current and future conditions?

We selected RCP 8.5 together with three SSPs: SSP1 (Sustainability), SSP2 (Middle of the road), and SSP5 (Fossil-fueled development). SSPs were interpreted within the context of the RCP 8.5 to project land use and agriculture practices as well as changes in waste water discharges to 2050s. Four climate models were selected for simulation. Compared to the current situation, the nutrient loads are expected to increase by 8% (between 2% and 13%) for N and by 14% (between 6% and 20%) for P as a response to climate change. However, when socioeconomic changes are considered together with changing climate the nutrient load to Baltic Sea is affected even more significantly. The load can decrease by 13% and 6% (SSP1) or increase by 11% and 10% (SSP5) for nitrogen and phosphorus, respectively, compared to the current situation.

Spatially differentiated measures take advantage of the fact that the retention (removal by biogeochemical processes or sedimentation) of nutrients in groundwater and surface water systems shows a significant spatial variation. The strategic placement of anthropogenic activities can be used to help achieve the goals for nutrient load reduction set out in the Baltic Sea Action Plan. The traditional uniform regulations can be much less cost-effective than spatially differentiated regulations with measures targeted towards areas where the natural retention is low. The effect of multi-objective measures on nutrient load is not as pronounced but the efficiency needs to be weighted also with respect to providing other benefits such as reduction in flooding or increase in biodiversity.