Eutrophication caused by atmospheric nitrogen deposition in Europe

One of the targets of the European Commission’s zero pollution action plan is to reduce the area of ecosystems in the EU at risk of eutrophication caused by atmospheric nitrogen deposition by 25% by 2030, compared with 2005. Between 2005 and 2021, the total area where nitrogen deposition exceeded the so called critical loads for eutrophication - the scientific parameter that measures such a risk - fell by 10%. Initiatives such as the national emission reduction commitments directive, farm to fork strategy and biodiversity strategy for 2030 are key frameworks to further reduce the risk of eutrophication in ecosystems.

Risk of eutrophication measured as exceedance of critical loads of nitrogen deposition in Europe, in 2021

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 zero pollution action plan (ZPAP) aims to reduce pollution in the EU to levels not harmful to human health or ecosystems . ZPAP’s target 3 sets a clear objective to reduce the area of ecosystems where nitrogen deposition exceeds critical loads by 25% by the year 2030, compared to the levels in 2005. This indicator monitors progress towards meeting this target and is also relevant for the follow-up to the Air Convention review of the Gothenburg Protocol (2019-2022), 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 target of reducing 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 would then still represent 983,500 km². Furthermore, the analyses highlight the importance of focusing on specific actions to address ammonia emissions from agriculture, particularly through more efficient management and application of manure from cattle, pigs, and poultry, as well as mineral fertilisers to reduce ammonia emissions. The analyses also suggest that future stricter air quality standards would enable the EU to meet the ecosystem target by the 2030 deadline (see the underpinning study for the Third Clean Air Outlook ).

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 can also contribute to reducing atmospheric nitrogen deposition.

Country	2005 Area	2021 Area	2005 average accumulated exceedance (AAE)	2021 AAE
EU-27	84	73	541.2	346.3
Luxembourg	100	100	1349.7	966
Cyprus	100	100	347	280.4
Greece	100	100	552.4	322.5
Denmark	100	100	1054.6	699.2
Malta	99	99	772	570.6
Lithuania	99	99	432.5	391.6
Slovakia	98	95	527.1	382.7
Spain	96	93	426.3	353.4
Romania	96	91	475	298.1
Czechia	98	87	639.5	321.2
Latvia	94	85	245.2	172.1
Portugal	85	82	228.2	188.7
Hungary	96	81	638.6	438.2
Netherlands	88	80	1313.5	787.1
Bulgaria	94	79	389.4	193.5
Croatia	95	79	571	275.4
Germany	85	73	920.9	562.3
Slovenia	92	73	529.4	306.9
Poland	79	71	429.5	301.9
France	85	67	496.6	269.4
Belgium	82	61	1161.2	674.4
Italy	80	55	453.9	212
Austria	75	54	352.9	172.1
Ireland	51	52	134.7	117.7
Estonia	57	39	92.9	51.1
Sweden	17	14	71	41.7
Finland	9	2	6.8	0.9

Liechtenstein	100	98	965.8	607.2
Albania	94	91	386.3	315.3
Serbia	94	90	718	414.7
Kosovo*	82	79	342.8	237.5
Bosnia and Herzegovina	78	73	347.5	202.8
North Macedonia	84	69	332.7	166.6
Montenegro	72	62	191	130.1
Switzerland	66	51	470.1	263.4
Norway	19	7	47.4	12.8

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 2021, emissions of oxidised nitrogen (NO₂, nitric acid and nitrate-containing particles) was highest in Belgium, northern Germany, northern Italy, the Netherlands and Poland (see 2023 EMEP Report).

The agriculture sector accounted for 94% of all reduced nitrogen deposition in EU-27 Member States, from which about 72% of emissions came from livestock in 2021. 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 (see 2023 EMEP Report).

In 2021, the highest exceedances of nitrogen critical loads were found in the Po Valley in Italy, on the border areas between the Netherlands and Germany, along the border between Denmark and Germany and in north-eastern Spain. However, exceedances hot spots can also be found in the Netherlands and its border areas with Belgium.

Supporting information

DefinitionMethodology

Areas where critical loads for eutrophication are exceeded are given as percentages of the total ecosystem area in each grid cell. ‘Total ecosystem area’ is defined as the area of ecosystem types classified according to the European Nature Information System (EUNIS) habitats classification. European background information from around 2001, when the national emission ceilings directive (2001/81/EC) was adopted, covered only forest ecosystems (EUNIS class G) and freshwater ecosystems. Now, semi-natural vegetation ecosystems (EUNIS classes D, E and F) are also included. For details on changes in the scientific knowledge base since 2001, please see Hettelingh et al. (2017).

The Aaverage accumulated exceedance (AAE) can be computed for an ecosystem, a grid cell or any region or country for which multiple critical loads and deposition values are available.

The European database of critical loads for eutrophication used in this indicator is compiled by the Coordination Centre for Effects (CCE) under the Air Convention. The CCE applies methods that are described in detail in CCE status reports, and adopted by the Task Force of the International Cooperative Programme on Modelling and Mapping (ICP M&M) in a mapping manual, for use by national focal centres (NFCs) under the ICP M&M. NFCs compute critical loads and submit data to the CCE at regular intervals after a consensus has been reached by Parties to the Air Convention (including most EEA member countries).

The CCE uses a European background database to compute critical loads for ecosystems in countries that do not submit data.

Input sources for critical load calculations include:

· nitrogen dose-response relationships, provided/updated under the Air Convention’s Working Group on Effects, based on latest scientific knowledge

· ecosystem types defined according to the EUNIS habitats classification (member countries report to the EEA)

· country-specific critical loads of nitrogen for ecosystem types such as nutrient-poor grasslands, forests or freshwater ecosystems (reported by European countries to the CCE)

· for countries that do not submit national data, values from the European background database, maintained by the CCE in collaboration with Wageningen Environmental Research (Alterra)

· gap-filled air pollutant emissions data based on data officially reported under the Gothenburg Protocol (gridded), derived by the Centre on Emission Inventories and Projections (CEIP) at UBA Vienna, Austria

· the European Monitoring and Evaluation Programme (EMEP) atmospheric dispersion model, which simulates how pollutants emitted to the air disperse in the ambient atmosphere (EMEP MSC-West at the Norwegian Meteorological Institute)

· a meteorological driver as an input to the EMEP model (provided by the European Centre for Medium-Range Weather Forecasts (ECMWF))

· modelled ecosystem-specific (gridded) nitrogen deposition rates (nitrate-N plus ammonium-N) for calculating critical load exceedances for single years (EMEP MSC-West at the Norwegian Meteorological Institute)

· monitoring of wet and dry nitrogen deposition, used to calibrate the EMEP model (e.g. monitored by the International Cooperative Programme on Integrated Monitoring, under the Air Convention).

Hindcast (2005) and forecast (2030) emission scenarios, based on the second clean air outlook, were prepared by the International Institute for Applied Systems Analysis (IASA), consultant to the Directorate-General for Environment and the Centre for Integrated Assessment Modelling under the Air Convention.

Policy/environmental relevance

Target 3 of the European Commission’s zero pollution action plan is for the EU to achieve a reduction of 25% in the ecosystem area where nitrogen deposition is above critical loads for eutrophication by 2030, compared with 2005. The basis for achieving this target is the 2016 National Emission Reduction Commitments Directive (NEC Directive).

The NAPCPs (under Article 6 of the NEC Directive) are the main governance instruments of the NEC Directive and set out how EU Member States must ensure that their emission reduction commitments for 2020-2029 and 2030 onwards are met. With respect to nitrogen, the NEC Directive includes binding commitments for NO_x and NH₃ emissions.

Target 3 of the zero pollution action plan is realistically expected to be achieved through:

1. the implementation of measures already announced by Member States in their first NAPCPs (see the third clean air outlook and underpinning study) and of further measures to reach the NEC Directive ammonia emission reduction commitments.

2. the implementation of additional measures needed to achieve the 50% reduction in nutrient losses set out in the Farm to Fork strategy and the nature restoration targets set out in the Biodiversity strategy for 2030.

The indicator is also relevant for the ongoing review (2019-2022) and planned revision of the Gothenburg Protocol of the United Nations Economic Commission for Europe’s Convention on Long-Range Transboundary Air Pollution (Air Convention).

Accuracy and uncertainties

Since the critical loads exceedance approach is a tool used in policy-related analysis, assessment of biases and the robustness of the approach are a major focus when addressing uncertainties. This assessment is also affected by the degrees of uncertainty in the emissions and atmospheric dispersion modelling estimates, and the scenarios used. Sensitivity analyses using, for example, different emission estimates for future years or excluding the correlation in the dispersion of pollutants give information on the uncertainty range.

A comprehensive uncertainty analysis of the integrated assessment approach, including ecosystem effects (critical loads), was compiled by Suutari et al. (2001).

The critical loads concept has been applied to the air pollution policy context for several decades (Air Convention and EU legislation).

Critical load calculation methods are based on information provided by the scientific community in the Working Group on Effects (UNECE WGE, 2021) under the Air Convention.

Critical loads exceedance modelling requires input from many different sources, all of which are well documented and based on international standards/consensus (please see input sources listed under data sources and providers).

For deriving the indicator, the latest scientific knowledge and modelling approaches, consistent with the ones used under the Air Convention (Gothenburg Protocol), are used by the CCE.

Both critical loads and land cover-specific EMEP deposition data are geo-referenced with a harmonised land cover data set, allowing for spatially consistent critical load exceedance maps.

Data sources and providers

Metadata

DPSIRTopicsTagsTemporal coverageGeographic coverage

TypologyUN SDGsUnit of measureFrequency of disseminationContact

References and footnotes

EC, 2021, Communication from the Commission to the European Parliament, the Council, the European Economic and Social Committee and the Committee of the Regions: Pathway to a healthy planet for all — EU action plan: ‘Towards zero pollution for air, water and soil’, COM(2021) 400 final.

^a^b
UNECE, 2021, 'Air', United Nations Economic Commission for Europe (https://unece.org/environment-policy/air).

^a^b
EC, 2022, 'The Third Clean Air Outlook', (https://environment.ec.europa.eu/publications/third-clean-air-outlook_en).

^a^b^c
Reduced nitrogen comprises mainly gaseous NH3, aerosol NH4+and wet deposited NH4+. Wet deposition of reduced N comprises fine particulate ammonium (NH4+) salts or aerosols of acidic gases.
^↵
EEA, 2021, 'Welcome to EUNIS, the European Nature Information System', European Environment Agency (https://eunis.eea.europa.eu).

^↵
Hettelingh, J.-P., Posch, M. and Slootweg, J., 2017, European critical loads: database, biodiversity and ecosystems at risk, CCE Final Report 2017, Coordination Centre for Effects, Bilthoven, Netherlands.

^↵
CCE, 2020, 'Manual for modelling and mapping critical loads & levels', Coordination Centre for Effects, Umwelt Bundesamt (https://www.umweltbundesamt.de/en/manual-for-modelling-mapping-critical-loads-levels).

^↵
EU, 2016, Directive (EU) 2016/2284 of the European Parliament and of the Council of 14 December 2016 on the reduction of national emissions of certain atmospheric pollutants, amending Directive 2003/35/EC and repealing Directive 2001/81/EC, OJ L 344, 17.12.2016, p. 1–31.

^↵
EC, 2021, 'Farm to fork strategy', European Commission (https://ec.europa.eu/food/horizontal-topics/farm-fork-strategy_en).

^↵
EC, 2021, 'Biodiversity strategy for 2030', European Commission (https://ec.europa.eu/environment/strategy/biodiversity-strategy-2030_en).

^↵
UNECE, 2021, 'Gothenburg Protocol', United Nations Economic Commission for Europe (https://unece.org/gothenburg-protocol).

^↵
Hettelingh, J.-P., Posch, M. and Slootweg, J., 2012, EC4MACS modelling methodology — The CCE-EIA ecosystems impact model, European Consortium for Modelling of Air Pollution and Climate Strategies, Coordination Centre for Effects, Bilthoven, Netherlands.

^↵
Suutari, R., Amann, M., Cofala, J., Klimont, Z. and Schöpp, W., 2001, From economic activities to critical load exceedances in Europe — An uncertainty analysis of two scenarios of the RAINS integrated assessment model, Interim Report, IR-01-020, International Institute for Applied Systems Analysis, Laxenburg, Austria.

^↵
UNECE WGE, 2021, 'The Working Group on Effects (WGE) under the UNECE Air Convention', Working Group on Effects of the Convention on Long-range Transboundary Air Pollution (http://www.unece-wge.org).

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Eutrophication caused by atmospheric nitrogen deposition in Europe

Figure 1. Risk of eutrophication measured as exceedance of critical loads of nitrogen deposition in Europe, in 2021

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Figure 2. Evolution of the risk of eutrophication in European countries, measured as exceedance of critical loads of nitrogen deposition, in 2005 and 2021

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