Improving the cost-effectiveness of water quality improvements through spatial scale changes to target-setting

Czajkowski Mikołaj1, Andersen Hans E2., Blicher-Mathiasen Gitte2, Elofsson K3., Hagemejer Jan1, Hasler Berit2, Humborg C.5,4 Smart Jim5, Smedberg Erik4, Stålnacke Per6 Thodsen Hans2, Wąs Adam7, Wilamowski Maciej1, Żylicz Tomasz1, Hanley Nick8


1 University of Warsaw, Poland

2 Aarhus University, Denmark.

3 Swedish Agricultural University. Sweden

4 Stockholm University, Sweden

5 Griffith University, Brisbane, Australia

6 Norwegian University of Life Sciences, Norway

7 Warsaw University of Life Sciences, Poland

8 University of Glasgow, Scotland


In this paper, we investigate the potential gains in cost-effectiveness from changing the spatial targeting of nutrient reduction targets in the Baltic Sea, focusing on nutrient loadings associated with agriculture. A new, fully disaggregated model, which represents losses in agricultural profits, changes in root zone N concentrations and transport to the Baltic Sea is proposed, and is then used to estimate the gains in cost-effectiveness from changing the spatial scale of nutrient reduction targets.  The model includes 14 Baltic Sea marine basins, 14 countries, 117 watersheds and 19,023 10×10 km grid cells. Costs of achieving loadings reductions are compared across five levels of spatial scale, namely the entire Baltic Sea; at the marine basin level; at the country level; at the watershed level; and at the grid square level. Cost-effectiveness turns out to be highest when targets are set at the largest area of spatial aggregation and lowest when targets are set at the smallest level. We argue that our results have important implications for both domestic and international policy over achieving water quality improvements where non-point pollution is a key stressor of water quality, and discuss the range of policy options, which are available to get close to the cost-effective reductions in N loadings identified by the constrained optimization model.