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Status Report 2010

Progress in the Modelling of Critical Thresholds and Dynamic Modelling, including Impacts on Vegetation in Europe



This report describes the status of the impact assessment of nitrogen, sulphur and heavy metal depositions in Europe and the progress made regarding the relation between nitrogen deposition and loss of biodiversity.

Part 1 Progress CCE

The Centre for Integrated Assessment Modelling (CIAM) prepared Baseline (BL) and Maximum Feasible Reduction (MFR) scenarios with resulting nitrogen and sulphur depositions. Chapter 1 reports the impacts regarding exceedances of acidification and nitrogen critical loads, including results of the so-called “ex-post analysis”. In addition, results from dynamic modelling were used to analyse the delays in responses of soil chemistry to changes in depositions. Conclusions include that ‘environmental improvements’ achieved under MFR in comparison to BL are considerable for all indicators. However, it should also be noted that MFR does not lead to non-exceedance of critical loads and requirements for sustainable soil chemistry (i.e. non-violation of the chemical criterion) for all ecosystem areas in Europe. Knowledge on nitrogen impacts has been further extended within the effects community by assessing the interaction between N and carbon (C). This is also reflected in an extension of the widely-used VSD model to include interactions between N- and C-pools and -fluxes, in a new model version, named VSD+. VSD+ has been applied by National Focal Centres (NFCs) of the International Collaborative Programme Modelling and Mapping (ICP M&M) on sites for which measurements are available. Another step forward in the assessment of impacts is the use of models that predict the abundance of species, based on abiotic conditions. NFCs were urged to familiarize themselves with one of them, the VEG model. Also data on species abundance in combination with abiotic data to feed vegetation models has been requested from NFCs for assimilation into a European database. These issues have been bundled into the 2009-2010 call for data of the CCE, of which the results are discussed in Chapter 2. In total 14 NFCs have responded to (part of) the call. A workshop on the review and revision of empirical critical loads and dose-response relationships was held under the Convention on Long-range Transboundary Air Pollution, in Noordwijkerhout, from 23-25 June 2010. The newly agreed critical loads and recommendations on their use are summarized in Chapter 3.

Part 2 Indicators and Assessment of Change of Plant

Species Diversity This part elaborates the progress in the model development to link soil chemistry to vegetation effects. This is in line with the long-term strategy of the Convention which includes the encouragement of the assessment of air pollution effects with respect to the change of biodiversity. For this the VSD+ model has been linked to the VEG model. Results of this model combination have been evaluated and compared to results of the ForSAFE-VEG model combination. An important aspect for vegetation modelling that was missing in VSD+ is the modelling of the light that plants receive below the forest canopy. How this and the model coupling have been implemented together with results of the comparison can be found in Chapter 4. In recent years, discussions took place on selecting an appropriate effect indicator to quantify changes in biodiversity with respect to (nitrogen) deposition. The arguments and proposed approaches are brought together in a framework which can help to focus this discussion. The reader can find this rationale and the framework in Chapter 5.

Part 3 Heavy Metals

The Protocol on Heavy Metals (HM) was signed in 1998 and entered into force in 2003. Currently the process for the revision of the Heavy Metals Protocol is underway. To support additional information to the negotiations on the proposed amendments on the HM Protocol, a research project has been commissioned by the Netherlands to TNO, EMEP MSC-E and the CCE. In this project four scenarios were compared for which emissions, costs of emission reductions, depositions and exceedances of critical loads have been calculated. The description of the emission scenarios, including the potential measures and their costs can be found in Chapter 6. The depositions that result from the emissions are reported and discussed in Chapter 7, including the estimation of re-suspension of metals from soils into the air. Chapter 8 gives the exceedances of the critical loads for the given scenarios and discusses the implications of re-suspension on the critical load concept. In chapter 9 the toxicological effects of metal concentrations in the soil solution on soil microorganisms, plants and invertebrates are tentatively addressed using the CCE background database of a European ecosystem.
Conclusions of Part 3 include that the costs of revision of the HM protocol for UNECE Europe are estimated to be 1.3 and 11.6 billion €for Option 2 and Option 1, respectively.

The reduction of emissions is not only beneficial regarding heavy metal pollution, the measures taken in Option 2 and Option 1 may also bring about considerable reductions of PM2.5 emissions in Europe. For the additional Hg emission reduction measures another 2.6 billion € should be added for both options. Depositions of heavy metals are reduced, but not to the same extend as the reductions in emissions, due to the process of re-suspension. While the emission reductions are reflected in the lowering of critical load exceedances everywhere, still large parts of Europe’s nature remain at risk. Uncertainty analysis requires further assessment of the state of implementation of the current protocol and of the origins of re-suspended deposition.

Part 4

Finally, consists of the national reports sent by the NFCs describing their submissions to the 2009-2010 call for data, which was adopted by the Working Group on Effects at its 28th session (Geneva, 23-25 September 2009).

Key words

Acidification, air pollution effects, biodiversity, critical loads, dose−esponse relationships, dynamic modelling, ecosystem services, eutrophication, exceedance, LRTAP Convention, heavy metals


Progress in the Modelling of Critical Thresholds and Dynamic Modelling, including Impacts on Vegetation in Europe (pdf, 16 mb)

Author(s) Slootweg J, Posch M, Hettelingh J-P (eds)
Report no.


Publication date February 2011
ISBN 978-90-6960-249-3
Pages 182


last update 21 Jan 2014


(pdf, 16 mb)