Spatially explicit boundaries for agricultural nitrogen inputs in the European Union to meet air and water quality targets

Wim de Vries; Lena Schulte-Uebbing; Hans Kros; Jan Cees Voogd; Geertrui Louwagie

doi:10.1016/j.scitotenv.2021.147283

Spatially explicit boundaries for agricultural nitrogen inputs in the European Union to meet air and water quality targets

Sci Total Environ. 2021 Sep 10:786:147283. doi: 10.1016/j.scitotenv.2021.147283. Epub 2021 Apr 23.

Authors

Wim de Vries¹, Lena Schulte-Uebbing², Hans Kros³, Jan Cees Voogd³, Geertrui Louwagie⁴

Affiliations

¹ Wageningen University and Research, Environmental Research, PO Box 47, 6700 AA Wageningen, the Netherlands; Wageningen University and Research, Environmental Systems Analysis Group, PO Box 47, 6700 AA Wageningen, the Netherlands. Electronic address: wim.devries@wur.nl.
² Wageningen University and Research, Environmental Systems Analysis Group, PO Box 47, 6700 AA Wageningen, the Netherlands.
³ Wageningen University and Research, Environmental Research, PO Box 47, 6700 AA Wageningen, the Netherlands.
⁴ (formerly) European Environment Agency, Kongens Nytorv 6, 1050 Copenhagen, Denmark.

PMID: 33958210
DOI: 10.1016/j.scitotenv.2021.147283

Abstract

Agricultural production in the EU has increased strongly since the 1940s, partly driven by increased nitrogen (N) fertiliser and manure inputs. Increased N inputs and associated losses, however, adversely affect air and water quality, with widespread impacts on terrestrial and aquatic ecosystems and human health. Managing these impacts requires knowledge on 'safe boundaries' for N inputs, i.e., N flows that do not exceed environmental thresholds. We used a spatially explicit N balance model for the EU to derive boundaries for N losses and associated N inputs for three environmental thresholds: (i) N deposition onto natural areas to protect terrestrial biodiversity (critical N loads), (ii) N concentration in runoff to surface water (2.5 mg N l^-1) to protect aquatic ecosystems and (iii) nitrate (NO₃^-) concentration in leachate to groundwater (50 mg NO l^-1) to meet the EU drinking water standard. Critical N losses and inputs were calculated for ~40,000 unique soil-slope-climate combinations and then aggregated at country- and EU-level. To respect thresholds for N deposition, N inputs in the EU need to be reduced by 31% on average, ranging from 0% in several countries to 59% in Ireland and Denmark. The strongest reductions are required in intensive livestock regions, such as Benelux, Brittany and the Po valley. To respect thresholds for N concentration in runoff to surface water, N inputs need to be reduced by 43% on average, ranging from 2% in Estonia to 74% in the Netherlands. Average critical N inputs in view of the threshold for NO₃^- concentration in leachate to groundwater are close to actual (year 2010) inputs, even though leaching thresholds are exceeded in 18% of agricultural land. Critical N inputs and their exceedances presented in this paper can inform more targeted mitigation policies than flat-rate targets for N loss reductions currently mentioned in EU policies.

Keywords: Ammonia emission; Biodiversity; Critical limits; Eutrophication; Nitrate leaching; Nitrogen runoff.