Jörg Römbke, ECT Oekotoxikologie; Kees van Gestel, Vrije Universiteit Amsterdam; Liesje Mommer, Wageningen University; Silvia Pieper, Federal Environment Agency Germany; Mike Coulson, ERM; Luca Montanarella, European Commission Joint Research Centre – SETAC Special Science Symposium Steering Committee

The SETAC Europe 14th Special Science Symposium (SESSS) titled “Soil Biodiversity” was held from 19–20 November 2019 at the Marivaux Hotel in Brussels, Belgium.

Protecting the structure and functioning of soil ecosystems is one of the central aims of current regulations on chemicals in soil. This is, for instance, shown by the emphasis on the protection of key drivers and ecosystem services as proposed in the protection goal options by the European Food Safety Authority (EFSA). Safeguarding soil biodiversity is key to protecting ecosystem services. This requires insight into soil biodiversity, its role in the functioning of ecosystems, and the way it responds to stress. It also requires appropriate tools and methodologies for properly assessing biodiversity.

The central aim of the SESSS was to provide a state-of-the-art overview on soil biodiversity and soil functions with respect to the protection goal options, as well as the effects of chemicals and other stressors on soil biodiversity. The symposium was attended by 62 participants from various backgrounds and consisted of presentations by experts in soil ecology and ecotoxicology on novel scientific developments in this area. Presentations included both experimental and modeling approaches, as well as case studies. It was a main aim to discuss how these different approaches contributed to informing future risk assessment of chemicals in the regulatory context of protecting soil ecosystems. In addition, 22 posters were presented that provided more case studies and approaches to the participants of the meeting.

Jan Frouz (Charles University, Czech Republic), Katarina Hedlund (Lund University, Sweden) and Stefan Scheu (Göttingen University, Germany) gave an update on the wealth of scientific data that has been gathered recently on soil biodiversity and the composition of soil ecosystems. Specifically, the presentations highlighted the importance of interactions between different organisms in the soil food web and their role in ecological processes. In addition, the interactions between above- and below-ground, as presented by plants living in both compartments, were highlighted. For example, these interactions may lead to below-ground effects cascading into effects on above-ground interactions. Frouz, Hedlund and Scheu also discussed the influence of time on these interactions between organisms in the soil and their effect on soil functioning may change. Food-web analysis and modeling appeared essential to assess changes in soil biodiversity.

Silvo Knäbe (Eurofins, Germany), Paul Henning Krogh (Aarhus University, Denmark) and Rachel Creamer (Wageningen University, The Netherlands) described existing and novel methods for assessing soil ecosystem responses to chemical and non-chemical stressors. The measurement and the assessment of soil invertebrate biodiversity is often hindered by large spatial variation in the abundance of soil invertebrates, making it challenging to see differences between treatments. Also, the lack of experienced taxonomists continues as an ongoing problem. However, novel DNA-based species determination (barcoding, eDNA, metagenomics, etc.) may provide a solution, albeit requiring specific expertise with regard to the interpretation of topsoil structure and functioning. Recent European inventories of soil biodiversity in agriculture have highlighted a number of soil functions, including biodiversity, that collectively determine soil quality. There are rather large regional and land-use differences that affect soil quality. This insight showed that in addition to chemical stressors, other factors like land use and climate change can greatly impact soil biodiversity.

Jörg Römbke (ECT Oekotoxikologie GmbH, Germany) discussed soil biodiversity in relation to three different categories of stressors, including chemical, contaminated land and general environmental monitoring. Pernille Thorbeck (BASF, Germany) presented available modeling approaches and emphasized the importance of properly estimating exposure by accounting for organism behavior in a heterogeneous medium like soil to allow the prediction of effects. Two case studies were presented, one by Andreas Toschki (gaiac Research Institute, Germany) describing the effect of pesticides in Terrestrial Model Ecosystems, the other by Michiel Rutgers (RIVM, The Netherlands) outlining how useful the application of the TRIAD approach is to assess the risk of soil contamination using three lines of evidence including chemical analysis, bioassays and an assessment of soil biodiversity effects. The role and position of soil biodiversity in regulatory frameworks was discussed by Maria Arena (EFSA. Italy). It became clear from her talk that soil biodiversity is going to be more prominent in the current developments in defining specific protection goal options for plant protection products. Silvia Pieper (German Federal Environment Agency, Germany) and Mike Coulson (ERM, UK), representing government and industry, respectively, gave their views on the effective assessment and management of soil biodiversity.

Based on the presentations and discussions, it was concluded there is value in the current single-species testing for chemical compounds, but also that there should be more emphasis on multi-species interactions in the soil ecosystem, both in testing and modeling. Widespread interest was noted in going beyond testing of single chemicals, and environment realism should be realized by accounting for multiple stressors. Testing should also acknowledge the effect of time in ecological processes, long-term exposures, development of exposure levels, multiple generation effects, delayed effects, etc. Assessing biodiversity should account for regional differences in climatic factors, soil properties or land management practices. Recent developments in modeling could help with all the above aspects and should be included early in the process of risk assessment. Finally, post-registration monitoring was felt necessary to help inform on the impact of chemical (and non-chemical) stressors in the field, something that cannot easily be incorporated in pre-registration.

To further explore the details of these issues, activities are being planned, including a workshop in the near future.

Authors’ contact information: j-roembke@ect.de and kees.van.gestel@vu.nl

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