The widespread contamination of ecosystems with plant protection products (pesticides in this text) around the world is evident (Hoferkamp et al., 2010; Shunthirasingham et al., 2011; Stehle and Schulz, 2015a; Ferrario et al., 2017; Hvězdová et al., 2018; Silva et al., 2019). Pesticide effects on the physiology, activity and diversity of various aquatic and terrestrial non-target organisms is addressed by numerous studies, and many new aspects are also described in a recent Frontiers Research Topic.
We currently observe a deterioration of biodiversity in agricultural landscapes, and the dramatic losses are increasingly discussed by the public (European Commission, 2018a). Declines of insect biomass of more than 70% in the last few decades in Germany, the halving of farmland bird populations in Europe and effects on pollinators are widely known (Donald et al., 2001; Potts et al., 2010; Hallmann et al., 2017). Out of a set of recorded parameters of agricultural intensification (such as field size, fertilizer application, landscape heterogeneity) a unique, pan-European study identified pesticide application as the responsible factor for lower biodiversity of plants, ground beetles, and birds in wheat fields (Geiger et al., 2010). Recently, a review recognized chemical pollution including pesticides as the second most important driver for the worldwide decline in insect populations (Sánchez-Bayo and Wyckhuys, 2019). Other drivers were habitat loss and conversion to intensive agriculture, fertilizer inputs, introduced species, and climate change.
There is agreement in the scientific community that pesticides are a central responsible factor for the observed terrestrial biodiversity declines. However, pesticides are perceived also as the chemicals with the strictest regulation, requiring an in-depth Environmental Risk Assessment (ERA) for registration in the European Union (European Parliament, 2009). This procedure includes the performance of a set of toxicity studies and calculations using predicted exposure values to calculate a risk. If the risk is deemed acceptable pesticides can be placed on the market (for an overview see.g. Storck et al., 2017). Interestingly during this step of the authorization process the “acceptable risk” is leading to pesticides considered “safe” for the environment (EFSA, 2019). Farmers, assuming they are using “safe” pesticides, are currently confronted with the public, blaming them for the observed declines of biodiversity. It seems that the ERA for pesticide regulation as currently carried out is inappropriate since it cannot prevent that registered and commonly used pesticides have detrimental effects on our environment.
In the last decade we have seen an increasing complexity in ERA of pesticides. The European Food Safety Authority (EFSA), as the responsible authority for pesticide registration in Europe, published guidance documents describing the required studies for different groups of aquatic and terrestrial organisms and their implementation in risk calculations (EFSA, 2010, 2013a). For the terrestrial environment there are also specific documents for birds and mammals as well as for bees (EFSA, 2009, 2013b). Furthermore, EFSA also recently published scientific opinions on in-soil organisms, non-target arthropods, amphibians, and reptiles as well as non-target terrestrial plants calling for improvement of ERA for the respective groups (EFSA, 2014, 2015, 2017, 2018). In some instances, such as for the currently neglected amphibians and reptiles, standard toxicity studies to produce reliable endpoints are lacking and the entire ERA is not even outlined yet. Scientific opinions are documents that highlight steps in ERA that need to be improved. However, the ERA is still performed as before until a guidance document is issued.
The current scheme for ERA of pesticides was also recently addressed by the group of chief scientific advisors, recommending among others the setting of unambiguous and quantifiable protection goals and structural changes of the registration process in the EU (European Commission, 2018b). The majority of the members of the European parliament agreed on a motion for a resolution on the authorization procedure for pesticides that mentions concern regarding the widespread use of pesticides and a lack of public knowledge about hazard and risk of pesticide use (European Parliament, 2018). A few scientific assessments of the European ERA scheme and its shortcomings exist (e.g. Newman et al., 2006; Schäfer et al., 2011; Stehle and Schulz, 2015b; Storck et al., 2017). Main points that are often raised are the inclusion of new test or surrogate species, the extension of studies to more realistic scenarios, the validity of the used uncertainty (assessment) factors, the lack of including sublethal endpoints in risk assessments and the need to address ignored groups of organisms (e.g. Jänsch et al., 2006; Desneux et al., 2007; Stahlschmidt and Brühl, 2012; Brühl et al., 2013). The consideration of interactions of pesticide effects with additional stressors such as nutrients or climate change was also pointed out (Köhler and Triebskorn, 2013; Baier et al., 2016).
But instead of highlighting all the open questions on various stages of a complex ERA scheme we consider it necessary to step back and address its entire structure. The observed biodiversity declines in European agricultural landscapes are mostly discussed for terrestrial organisms and not for aquatic systems. We will therefore specifically focus on the terrestrial part of ERA.