Environmental quality of terrestrial ecosystems: nitrogen deposition 1994–2022

Assessment of environmental quality of terrestrial ecosystems

This indicator gives information about environmental quality in terms of nitrogen deposition, which is a key factor in the conservation and restoration of species richness in ecosystems. Other indicators of environmental quality include spring groundwater level and soil pH.

• Ecosystem quality and trends in soil pH
• Ecosystem quality and trends in groundwater-dependent ecosystems

The assessment of the environmental quality of terrestrial systems in terms of nitrogen deposition uses three categories of environmental quality: ‘high’, ‘moderate’ and ‘low’. The boundaries between these categories are determined by the critical deposition loads (CDLs) of the EU habitat types present in the ecosystem type under assessment. If the nitrogen deposition exceeds the CDL, there is a greater chance that vulnerable plant and animal species will disappear. Ecosystems that require nutrient-poor conditions are particularly sensitive to nitrogen deposition.

A ‘high’ environmental quality in terms of nitrogen deposition in an area means that the CDL is not exceeded for any of the habitat types present in that area and that the environmental quality in terms of nitrogen deposition is suitable for the long-term persistence of species in ecosystems such as heath and forest. A ‘low’ environmental quality means that the CDL is exceeded for all of the habitat types in that area and that the environmental quality in terms of nitrogen deposition is unsuitable for the long-term persistence of species in those ecosystems. A ‘moderate’ environmental quality means that the deposition in the area lies between the values for high and low and the environmental quality is suitable for the long-term persistence of some of the species present in the ecosystem.

Decrease in the area of terrestrial ecosystems with a low environmental quality
Nitrogen deposition decreased from the beginning of the 1990s until about 2010. This reduction in nitrogen deposition led to a lowering of the environmental pressure on terrestrial ecosystems and the area of natural and semi-natural habitat with a better environmental quality increased. The percentage of the area of terrestrial ecosystems with a low environmental quality in terms of nitrogen deposition decreased from 64% in 1994 to 25% in 2022. This improvement in environmental quality stalled in 2010, but the area with low environmental quality has decreased again over the past four years. The percentage of the area of terrestrial ecosystems with a high environmental quality remains low, and was still just 4% in 2022. To increase the area with a high environmental quality, nitrogen deposition will have to decrease further.

• Nitrogen deposition

Nitrogen deposition has the biggest impact on sandy soils

Eutrophication and acidification of ecosystems via nitrogen deposition is particularly problematic on the nutrient-poor sandy soils in the south and east of the Netherlands. These are areas which support ecosystems that are highly sensitive to nitrogen deposition and which are in close proximity to intensive livestock farms with high levels of nitrogen emissions (ammonia). In nitrogen-sensitive ecosystem types such as forest and heath on sandy soils, the environmental quality in terms of nitrogen deposition of the majority of the area is moderate or low. For open dunes the situation is better; a relatively large part of the area of dunes falls within the category ‘high’, because there are few intensive livestock farms in the vicinity of these areas. Many of the natural and semi-natural grasslands and marshes, particularly those in river and marine clay regions in the north and west of the country, are not sensitive to nitrogen deposition. 

Policy focuses on reducing environmental pressure

To prevent the effects of eutrophication and acidification, Dutch environmental policy focuses on reducing emissions of eutrophying and acidifying substances in the Netherlands. Over the last few decades, both national and international environmental policies have led to cleaner air, resulting in lower acid and nitrogen deposition on ecosystems. However, the achievements of environmental policy are not yet sufficient to create good conditions, such as a high environmental quality in terms of nitrogen deposition, for the sustainable conservation of all ecosystems and species. Since 2010 the reduction in nitrogen deposition has stalled, primarily because ammonia emissions have hardly decreased. Ammonia emissions are responsible for about two-thirds of all nitrogen deposition in the Netherlands. Most of this ammonia is agricultural in origin; the remaining deposition is from nitrogen oxide emissions from transport, industry and other sources. Between 2013 and 2017 ammonia emissions even increased slightly owing to an increase in the number of dairy cattle as a consequence of the lifting of milk quota. Since 2018 ammonia emissions have fallen slightly again, as has the degree of exceedance of CDLs.

The Integrated Approach to Nitrogen (PAS) was introduced in 2015 with the aim of reducing nitrogen deposition and improving ecological quality in natural areas while at the same time making economic development possible. In 2019 the Council of State ruled that the PAS cannot guarantee that the conditions for nature conservation and restoration will be good enough to provide a sufficient basis for permitting new development or activities. The Nitrogen Reduction and Nature Improvement Act was adopted to remedy this situation. The Act sets targets for the area of nitrogen-sensitive habitat in Natura 2000 sites where the nitrogen deposition level is lower than the CDL. The target for 2025 is 40%, for 2030 is 50% and for 2035 is 74%.

The indicator on this page shows the environmental quality in terms of nitrogen deposition of all Dutch terrestrial ecosystems, including those outside Natura 2000 sites. The area of nitrogen-sensitive habitat types in Natura 2000 sites where nitrogen deposition levels are below the CDL, as stated in the targets of the Nitrogen Reduction and Nature Improvement Act, increased from 20% in 2005 to 29% in 2022. The habitat types where nitrogen deposition levels are below the CDL are in ecosystems where the environmental quality is in the categories ‘high’ and ‘moderate’.

Restoration measures to improve environmental quality

Since 1989 nature restoration measures have been taken in natural areas to combat the effects of acidification and eutrophication, first under the ‘subsidy scheme for effect-oriented measures’ (EGM), subsequently under the ‘quality initiative for nature and landscape’ (SKNL) and the Integrated Approach to Nitrogen (PAS), and recently under the Nature Programme (Programma Natuur). The Nature Programme is aimed at restoring and improving the quality of natural and semi-natural habitats in Natura 2000 sites in addition to what had already been agreed in the Nature Pact. In the Nature Pact (EZ, 2013) the national and provincial governments agreed to maintain ecological quality within the national ecological network by providing a sufficient level of standard conservation management, and to raise ecological quality by intensifying efforts for temporary or permanent restoration measures aimed at improving water quality and environmental quality.

Many of the restoration measures are not only geared to removing nutrients such as nitrogen, but also aim to combat acidification and reduced groundwater levels/desiccation. The availability of nutrients depends not only on the current deposition of nitrogen, but also on reduced water levels and the quality of surface water and groundwater. Nitrogen deposition raises the acidity of soils in natural areas, leading to the decline or disappearance of plant and animal species in those areas. Soil acidity can also be influenced by changes in hydrological conditions, such as a loss of base-rich groundwater seepage or the accumulation of organic matter in the humus layer. Acidification, eutrophication and desiccation are environmental factors that can reinforce each other.