New and revised critical loads for nitrogen for Flemish habitat types and vegetation types of regional importance
The deposition of nitrogen on the natural environment has stirred quite some controversy in Flanders over recent years. Excess nitrogen deposition can harm the biodiversity of several habitats. Soils become more acidic and ubiquitous, nitrophilous plants expand at the expense of critical species. An important scientific concept to assess the impact of atmospheric deposition on habitats is the critical load (CL). This is the maximum amount of nitrogen deposition a habitat type can tolerate without - according to present knowledge - significant harmful effects to its quality. In this approach empirical critical loads (CLemp) have been applied. For the majority of European ecosystems, ranges of CLemp are set and reviewed every 10 years according to new empirical evidence. The most recent review was published in 2022.
At the request of the Flemish Department for Environment, INBO assessed the consequences of the recent revision for the CLs that are currently in use in Flemish policy, within the framework of the Nitrogen Decree. An adjustment of the Flemish CLs is needed for 44 of the 75 Annex I habitat types and subtypes that are present in Flanders. For 42 types, the CL is now lower (i.e. habitat types and subtypes are more nitrogen sensitive than previously assumed). In two others, the CL is higher (less nitrogen-sensitive). At the request of the Agency for Nature and Forests, INBO also determined a suitable CL for nitrogen deposition on vegetation types of regional importance. These are vegetation types that are protected by Flemish legislation, but not by European legislation. For 15 vegetation types of regional importance, we proposed a CL for use in policy.
Jeroen Vanden Borre, Johan Neirynck, Luc De Keersmaeker
Image above: purple moor-grass dominates grassy heathland (photo Lars Soerink - Vildaphoto)
Read more:
- Vanden Borre J., Neirynck J. & De Keersmaeker L. (2024). Advies over de herziening van de kritische depositiewaarden voor stikstof voor de Vlaamse habitattypes. Adviezen van het Instituut voor Natuur- en Bosonderzoek; nr. INBO.A.4770. Instituut voor Natuur- en Bosonderzoek, Brussel
- Vanden Borre J., De Keersmaeker L. & Neirynck J. (2024). Advies over kritische depositiewaarden voor stikstof voor regionaal belangrijke biotopen. Adviezen van het Instituut voor Natuur- en Bosonderzoek; nr. INBO.A.4532. Instituut voor Natuur- en Bosonderzoek, Brussel