Air signals

Page Last modified 08 Dec 2022
5 min read
This section of the zero pollution monitoring assessment presents a series of short case studies that highlight additional sources of information on the impacts of air pollution on ecosystems.

Air Signal 1: The significance of airborne nitrogen deposition to the Baltic Sea

Despite significant reductions in nitrogen emissions in Europe over the last three decades, eutrophication remains an environmental concern in the Baltic Sea basin. The waterborne input of nitrogen (mainly through river inflow) generally outweighs its airborne deposition; however, the latter occurs at the surface, where phytoplankton activity is greatest, and therefore particularly encourages plankton growth. Atmospheric nitrogen deposition remains a significant issue in the Baltic Sea.

Reducing atmospheric nitrogen deposition will be key to bringing the Baltic Sea’s total nitrogen levels under the maximum allowable input, a threshold set by the Baltic Marine Environment Protection Commission (Helcom).


Trends and main sectors contributing to airborne nitrogen deposition

Between 2000 and 2020, ammonia and nitrogen oxide emissions in the EU-27 decreased by 13% and 52%, respectively (EEA, 2022). Airborne nitrogen deposition to the Baltic Sea also decreased during the same general period, by around 25% (Gauss et al., 2021).

In 2020, agriculture accounted for 94% of ammonia emissions, while the main sources of nitrogen oxide emissions were transport (43%), agriculture (19%) and the energy sector (14%) (EEA, 2022).

Figure 1 presents the top five countries contributing to oxidised nitrogen deposition in 2017, with inputs presented as absolute values and shares of total deposition to each individual sub-basin. As expected, there are large differences between sub-basins, mainly caused by their different areas and locations relative to the major emission sources.


Figure 1. Top five countries contributing to nitrogen deposition to the Baltic Sea in 2017

Note: The absolute values of oxidised nitrogen deposition are in tonnes(N) yr−1. Each country’s percentage of total deposition of oxidised nitrogen to the respective sub-basin is also provided.

SourceGauss et al. (2021).

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Overall, three Member States (Germany, Poland and Denmark) are the main contributors to nitrogen deposition to the Baltic Sea, with agriculture and transport being the main sources. Agriculture in Germany was the single most important contributor, accounting for about 15% of the total (Gauss et al., 2021).


Impacts of eutrophication

Intensive algal blooms have become increasingly frequent in recent years as a result of a combination of excess nutrients and the increase in temperature in Baltic and Finnish coastal waters. In the Baltic Sea, there are two annual blooms: the spring bloom and the cyanobacterial bloom in late summer. In the southern Baltic Sea, autumnal blooms occur regularly. Additionally, exceptional blooms can occur locally (European Space Agency, 2022).

Massive algal and cyanobacterial blooms, caused by excess nutrients, can lead to ‘dead zones’ — areas where oxygen levels are too low for marine organisms to live. To combat this, Helcom recommends total maximum input limits for nitrogen. These limits clarify the maximum nitrogen level that the Baltic Sea sub-basins specifically can absorb; the target is 792,000 tonnes of nitrogen per year (Helcom, 2013).

Algal blooms along the Baltic coast also result in significant losses for the aquaculture industry. Summer cyanobacterial blooms in the Baltic Sea create foul bathing water and poor-quality beaches. This has an impact on tourism and raises health concerns, as some cyanobacteria produce toxins (Karlson et al., 2021).



EEA, 2022, ‘Air pollutant emissions data viewer (Gothenburg Protocol, LRTAP Convention) 1990-2020’, European Environment Agency ( accessed 11 October 2022.

European Space Agency, 2022, ‘Algal bloom in the Baltic Sea’ (,occur%20in%20freshwater%20as%20well%20as%20marine%20environments) accessed 11 October 2022.

Gauss, M., et al., 2021, ‘Airborne nitrogen deposition to the Baltic Sea: past trends, source allocation and future projections’, Atmospheric Environment253, 118377 (

Helcom, 2013, HELCOM Copenhagen Ministerial Declaration: taking further action to implement the Baltic Sea Action Plan — reaching good environmental status for a healthy Baltic Sea (,of%20the%20Helsinki%20Commission%2C%20on%203%20October%202013) accessed 18 October 2022.

Karlson, B., et al., 2021, ’Harmful algal blooms and their effects in coastal seas of Northern Europe’, Harmful Algae 102, 101989 (

Air Signal 2: Wheat production losses due to ground-level ozone pollution in Europe

Ground-level ozone is formed in the atmosphere when the air pollutants nitrogen oxides, methane and non-methane volatile organic compounds combine with sunlight. While the levels of these air pollutants have decreased over the last few decades, ozone is still one of the most prominent air pollution problems in Europe because of its effects on crops and natural ecosystems (EEA, 2022).

Ground-level ozone polluting the air damages vegetation. Ozone enters the plant leaf and reduces photosynthesis, slowing the plant’s growth and increasing its vulnerability to pests and disease. At the ecosystem level, high levels of ground-level ozone can drive species diversity loss and lead to changes to ecosystem structure and habitat quality.

Ground-level ozone also damages agricultural crops and timber, affecting the quality and yield of production and entailing significant economic losses for the sector. For example, in 2019, losses in wheat yields due to exposure to ozone were 9% in Greece, with losses of between 8% and 9% seen in Albania, Cyprus, Czechia and Portugal. In 17 European countries, the wheat yield loss due to ground-level ozone exposure exceeded 5%.

The countries most affected by economic losses from ground-level ozone’s impact on wheat yields are those with high overall wheat production (see Figure 1). Losses in wheat yields were highest in France, reaching €350 million, followed by €280 million in Germany and €140 million in Poland. Most countries faced losses worth several millions of euros (ETC/ATNI, 2021).


Figure 1. Economic cost of wheat yields lost due to ground-level ozone exposure in some European countries in 2019

Note: The figure ranks the countries in terms of the 2019 economic value of lost wheat production. Data sources include Eurostat data on wheat production by NUTS2 region. When not available, regional data were estimated from national production, using the number of holdings by area category (ha) and by region as a proxy. Wheat price data were obtained by dividing gross production value for wheat by wheat production data (both from Faostat).

SourceETC/ATNI, 2021

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EEA, 2022, ‘Exposure of Europe's ecosystems to ozone’, European Environment Agency ( accessed 24 November 2022.

ETC/ATNI, 2021, Wheat yield loss in 2019 in Europe due to ozone exposure, ETC Report ETC/ATNI 2021/17 ( accessed 3 November 2022.

Cover image source: © Panagiotis Dalagiorgos, Well with Nature /EEA


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Filed under: ecosystems, air
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