Atmospheric nitrogen deposition is related to plant biodiversity loss at multiple spatial scales

van der Plas, Fons and Hautier, Yann and Ceulemans, Tobias and Alard, Didier and Bobbink, Roland and Diekmann, Martin and Dise, Nancy B. and Dorland, Edu and Dupré, Cecilia and Gowing, David and Stevens, Carly (2024) Atmospheric nitrogen deposition is related to plant biodiversity loss at multiple spatial scales. Global Change Biology, 30 (8): e17445. ISSN 1354-1013

Abstract

Due to various human activities, including intensive agriculture, traffic, and the burning of fossil fuels, in many parts of the world, current levels of reactive nitrogen emissions strongly exceed pre‐industrial levels. Previous studies have shown that the atmospheric deposition of these excess nitrogen compounds onto semi‐natural terrestrial environments has negative consequences for plant diversity. However, these previous studies mostly investigated biodiversity loss at local spatial scales, that is, at the scales of plots of typically a few square meters. Whether increased atmospheric nitrogen deposition also affects plant diversity at larger spatial scales remains unknown. Here, using grassland plant community data collected in 765 plots, across 153 different sites and 9 countries in northwestern Europe, we investigate whether relationships between atmospheric nitrogen deposition and plant biodiversity are scale‐dependent. We found that high levels of atmospheric nitrogen deposition were associated with low levels of plant species richness at the plot scale but also at the scale of sites and regions. The presence of 39% of plant species was negatively associated with increasing levels of nitrogen deposition at large (site) scales, while only 1.5% of the species became more common with increasing nitrogen deposition, indicating that large‐scale biodiversity changes were mostly driven by “loser” species, while “winner” species profiting from high N deposition were rare. Some of the “loser” species whose site presence was negatively associated with atmospheric nitrogen deposition are listed as “threatened” in at least some EU member states, suggesting that nitrogen deposition may be a key contributor to their threat status. Hence, reductions in reactive nitrogen emissions will likely benefit plant diversity not only at local but also at larger spatial scales.