Nitrogen-containing air pollutants affect biodiversity

Elevated nitrogen inputs have a negative effect on nitrogen-sensitive ecosystems due to over-fertilization. Ammonia emissions from agriculture account for about two-thirds, nitrogen oxide emissions from combustion processes to about one-third of the total nitrogen inputs. With the objective of protecting human health and the environment, the Swiss Federal Council intends to reduce ammonia emissions by about 40% and nitrogen oxides by about 50% compared to 2005.

Air pollutants can travel long distances to end up in sensitive aquatic and terrestrial ecosystems due to dry and wet deposition. Nitrogen and sulfur deposition cause acidification and over-fertilization of sensitive ecosystems. For example, acidification of alpine lakes and streams in higher altitudes and forest soils in all altitudes. Overfertilization also adversely affects a wide range of nitrogen-sensitive ecosystems such as forests, species-rich natural pastures and dry grassland, alpine heathland, raised bogs and fens. Consequences of the nitrogen overload in the forest are nitrogen leaching from the forest floor into the groundwater and changes in biodiversity.

Main sources

About two thirds of the nitrogen deposition in sensitive ecosystems originate from ammonia emissions in agriculture, about one third from nitrogen oxides of combustion processes. 

National and international need for action

Both internationally and in Switzerland it is undisputed that the current situation with respect to the nitrogen input into the environment must be improved. Effect-thresholds in form of Critical Loads and Critical Levels for nitrogen deposition and ammonia concentrations are defined in the framework of the UNECE Convention on Long-range Transboundary Air Pollution (CLRTAP). Both thresholds are exceeded in large parts of Switzerland. The biggest need for action lies in reducing ammonia emissions from agriculture.

Goals of the Swiss Federal Council

In the report «Konzept betreffend lufthygienische Massnahmen des Bundes» (Concept concerning air pollution control measures of the Federal Government) from 11th September 2009 the Swiss Federal Council defined the goal to reduce ammonia emissions by about 40% and nitrogen oxide emissions by about 50% compared to 2005. In this context, further developments in the Agricultural Policy should achieve a substantial reduction of ammonia emissions.

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Last modification 08.02.2019

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