Protection of biodiversity as the ultimate goal of environmental safety assessment : how does chemical pollution affect biodiversity?

Biodiversity is unequivocally declining and chemical pollution is a major driver of its loss. Ecotoxicological studies report various effects of chemicals at different levels of biological organization, mostly individual and sub-organismal levels, while biodiversity is typically measured by taxonomic richness and abundance. This misalignment of metrics hampers building a causal link between chemical pollution and its effects on biodiversity. This review addresses the existing evidence (the obvious and the subtle ones) of the impact of chemicals on each sub-class of descriptors proposed by the list of Essential Biodiversity Variables (EBVs). For each biological level of organization, examples of ecotoxicological studies are reported that highlight strengths and weaknesses in describing the effects of chemical pollution on the specific biodiversity identifiers. In the last part, modelling is presented as one of the most powerful approaches to answer such a complex issue. Different modelling approaches are described according to their potential, for instance mechanistic models can simulate the effects of chemicals on organisms and populations while Bayesian network models and Threshold Indicator Taxa Analysis (TITAN) can be used to predict the risk of chemicals to communities and ecosystems. Finally, biodiversity in the regulatory context and future perspectives are discussed, highlighting how crucial the collaboration between ecologists and ecotoxicologists is, as well as the integration of data from field and laboratory studies, and the development of new specific indicators to track progress towards biodiversity conservation.