COST Office - European Cooperation in Science and Technology
Abstract
This background paper summarizes established and new science on the effects of nitrogen (N)
deposition on ecosystems and considers the potential for improved assessment of N deposition
impacts on Natura 2000 sites. The key aspects covered are N deposition effects on biodiversity and
on biogeochemistry, links to ecosystem services, the importance of N form, N deposition indicators,
management practices and ecosystem reversibility following decreased N input.
The paper shows that:
• Evidence of N impacts on different vegetation types in Europe exists, but that it is important
that it is translated meaningfully to the target habitats listed under the Habitats Directive.
Evidence for N deposition effects to important ecosystem services, such as carbon
sequestration, also exists but the cause and effect relationships underlying them are often
complex and not sufficiently understood.
• Chemical N form can influence both the rate of ecosystem change, and the extent of impacts
on the short and long-term. Evidence is presented for ammonia causing detrimental plant
physiological effects, probably on the majority of species, whilst ammonium and nitrate
effects will depend on plant species present.
• Plant species composition as well as plant biochemical parameters may be useful
bioindicators for assessment of N deposition effects in Natura 2000 sites, however
“baseline” data are mostly not available for rare species. Ecosystem specific indicators,
that are predictive of further damage, rather than a consequence of already existing adverse
effects (i.e., early warning indicators) are needed.
• Site level management practices can be useful to reduce the impact if N deposition but they
will certainly not be able to mitigate all the impacts of enhanced N deposition and enhances N concentration on Natura 2000 habitats. More knowledge is needed to better understand
where and if management intervention is appropriate to mitigate N effects.
• Studies on the reversibility of N impacts show that some ecosystem parameters may revert
quickly, while other components may show strong inertia. In some cases reversion to the
original state may however be impossible.
• Climatic factors interfere with ecosystem effects of N deposition. It is clear that climate
both can emphasize and mitigate effects of N deposition. Current climate and expected
climatic changes must be included in assessments and predictions of N deposition effects
on ecosystems.
The aim is to provide a broad picture of scientific advancement within the field of N deposition
research, and to provide a starting point for workshop discussions. Workshop discussions addressed
the relevance of new science in assessing N deposition impacts on Natura 2000 sites, and identified
when there is potential to make management adjustments to mitigate such effects
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