title: Impact of nitrogen deposition at the species level.
abstract: In Europe and, increasingly, the rest of the world, the key policy tool for the control of air pollution is the critical load, a level of pollution below which there are no known significant harmful effects on the environment. Critical loads are used to map sensitive regions and habitats, permit individual polluting activities, and frame international negotiations on transboundary air pollution. Despite their fundamental importance in environmental science and policy, there has been no systematic attempt to verify a critical load with field survey data. Here, we use a large dataset of European grasslands along a gradient of nitrogen (N) deposition to show statistically significant declines in the abundance of species from the lowest level of N deposition at which it is possible to identify a change. Approximately 60% of species change points occur at or below the range of the currently established critical load. If this result is found more widely, the underlying principle of no harm in pollution policy may need to be modified to one of informed decisions on how much harm is acceptable. Our results highlight the importance of protecting currently unpolluted areas from new pollution sources, because we cannot rule out ecological impacts from even relatively small increases in reactive N deposition.
authors.affiliation: School of Science and the Environment,  Manchester Metropolitan University, Manchester M1 5GD,  United Kingdom.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Payne
authors.forename: Nancy B
authors.initials: NB
authors.lastname: Dise
authors.forename: Carly J
authors.initials: CJ
authors.lastname: Stevens
authors.forename: David J
authors.initials: DJ
authors.lastname: Gowing
mesh_terms: D000393:Air Pollutants / Q000633:toxicity; D000397:Air Pollution / Q000517:prevention & control*; D016208:Databases, Factual; D017753:Ecosystem; D005060:Europe; D019055:No-Observed-Adverse-Effect Level; D006109:Poaceae / Q000187:drug effects / Q000378:metabolism; D026361:Reactive Nitrogen Species / Q000633:toxicity*; D013045:Species Specificity
chemical_list: D000393:Air Pollutants; D026361:Reactive Nitrogen Species