Tomás Santiago Duque Acosta

• Biodiversity has declined by approximately 70% in the last 50 years for vertebrate and invertebrate species. This loss in biodiversity is strongly connected with anthropogenic activities, such as agricultural intensification and pollution. Currently, pesticides are needed to secure the growing global food demand, although they are recognized as one of the main drivers of biodiversity loss, mainly in agricultural areas. In the European Union, pesticides are regulated within the risk assessment framework, which aims to protect both the environment and human health from undesirable effects. The effects on non-target organisms are mostly assessed following a “one-size-fits-all” approach, focused on sensitive species tests. However, it has been recognized that the current methodology can be improved in order to minimize undesirable effects. Aiming to provide valuable data to inform future risk assessment, this thesis focused on two terrestrial organism groups that play beneficial roles, especially in agroecosystems: earthworms and spiders. Although the earthworm Eisenia fetida is included in pesticide regulation, its use as the only earthworm representative may lead to uncertainties for the risk assessment. Therefore, we collected ecotoxicological data on field-captured earthworm species via acute exposure to imidacloprid and copper. In addition, we investigated the relationships between earthworm chemical sensitivity, biological traits and habitat preferences, and potential links with their ecosystem services (Chapter 2). We found that earthworms sampled from extremely acidic soils were less sensitive to copper than earthworms from neutral soils. Moreover, anecic and endogeic earthworms were more sensitive to imidacloprid than epigeic earthworms. Spiders have, thus far, been understudied in regulatory risk assessment in comparison to other non-target arthropods. Thus, we aimed to collect ecotoxicological data of spider species sampled in different European climates via acute exposure to lambda-cyhalothrin. Moreover, we explored relationships between spider chemical sensitivity, phylogeny, biological traits and habitat preferences, as well as potential links with their ecosystem services (Chapter 3). Spiders showed a high sensitivity to lambda-cyhalothrin. Furthermore, our results showed that spider sensitivity varies depending on climate. We confirmed this relationship by incorporating different rearing and test temperatures into the toxicity testing protocol (Chapter 4). The outcomes of this thesis contribute to informing pesticide regulatory practices, allowing for an improved protection and conservation of terrestrial organism groups and the ecosystem services they provide. The consideration of ecological traits, habitat variability and related plasticity, key species, and ecological network structure could improve the risk assessment framework and minimize the effects of pesticides and other stressors on an ecosystem-level.