Eutrophication caused by atmospheric nitrogen deposition in Europe

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The quantitative assessment of nitrogen deposition on terrestrial and aquatic ecosystems is estimated as critical loads. When the deposition of nitrogen exceeds such critical loads, it can lead to eutrophication and biodiversity loss. Nitrogen deposition is mainly caused by ammonia (NH₃) from agricultural activities and nitrogen oxides (NO_x) from combustion processes.

The European Commission zero pollution action plan (ZPAP) aims to reduce pollution in the EU to levels not harmful to human health or ecosystems. Target 3 of the plan sets a clear objective to reduce the area of ecosystems where nitrogen deposition exceeds critical loads by 25% by the year 2030, compared levels in 2005. This indicator monitors progress towards meeting this target. It is also relevant for the Air Convention review of the Gothenburg Protocol (2019-2022) follow-up, indicating a coordinated effort to address air pollution.

The European Commission's Third Clean Air Outlook provides valuable analyses of the progress and prospects of achieving the reduction of ecosystems at threat of eutrophication by 25% and identifies potential policy adjustments to meet the goal by 2030. It emphasises the importance of continuous efforts to effectively combat air pollution and its impacts on ecosystems. The baseline scenario, which assumes no additional measures beyond current efforts, predicts a reduction of only 20% in affected ecosystems by 2030, compared to 2005.

While this represents progress, it falls short of the 25% reduction goal for all affected areas, which still represents 983,500 km². The analyses highlight the importance of focusing on specific actions to address ammonia emissions from agriculture. This is completed particularly through more efficient management and application of manure from cattle, pigs, and poultry, as well as mineral fertilisers to reduce ammonia emissions. Future stricter air quality standards would enable the EU to meet the ecosystem target by 2030 (see the underpinning study for the Third Clean Air Outlook), as recommended by the analyses.

The implementation of measures intended to achieve the 50% reduction in nutrient losses set out in the Farm to fork strategy and the nature restoration targets of the Biodiversity strategy will also contribute to reducing atmospheric nitrogen deposition.

Since 2005, the critical loads for nitrogen were exceeded in almost all EU Member States. Exceedances are attributed to both reduced nitrogen compounds from agricultural activities and oxidised nitrogen from combustion processes.

In 2022, emissions of oxidised nitrogen (NO₂, nitric acid and nitrate-containing particles) was highest in Belgium, northern Germany, northern Italy, the Netherlands and Poland. The agriculture sector accounted for 93% of all reduced nitrogen deposition in EU-27 Member States, with 71% of emissions stemming from livestock in 2022. Reduced nitrogen is deposited in ecosystems as NH₃ and ammonium (NH₄⁺). Deposition was highest in Belgium, parts of France, northern Germany, northern Italy, the Netherlands and Poland.

The highest exceedances of nitrogen critical loads for 2022 were found in the Po Valley in Italy and the border areas between the Netherlands and Germany. They were also found along the border between Denmark and Germany and in north-eastern Spain. Exceedances hot spots appeared in the Netherlands and its border areas with Belgium.