AquaSchild: Evidence-based Management of Non-native Terrapins in Germany

Biological invasions drive biodiversity loss and result in significant economic costs. The pond slider (Trachemys scripta) is classified as an invasive alien species (IAS) in the European Union. Non-native terrapins have become widespread in Germany, and genetic evidence confirms the reproduction of three species and their establishment in the wild (Tietz et al., 2023). However, the ecological impact of these terrapins on freshwater ecosystems remains poorly quantified, leaving authorities without a robust basis for prioritising management. The AquaSchild project brings together scientists, authorities, and society to compile ecological and social evidence on non-native terrapins in water bodies of varying ecological value, assess the risks associated with different habitats, and co-develop prevention-first management strategies. In Baden-Württemberg, we are implementing an evidence sprint that combines standardised terrapin surveys in two contrasting water bodies with DNA metabarcoding of diets, parasites, and pathogens. This will enable us to characterise trophic and pathogen-mediated impacts between two water bodies with differing conservation values, and develop a habitat-risk ranking that highlights habitat types where the establishment of invasive terrapins is of particular concern. In parallel, a survey of stakeholders, including official authorities, planning offices, NGOs, the pet trade and citizen science coordinators, will assess their knowledge and perceived feasibility of management measures, and reveal implementation barriers. Subsequently, we will synthesise the ecological and social findings during co-design workshops. This will result in a practical management decision tree and associated standard operating procedures for the removal and handling of non-native terrapins. Targeted communication tools will be produced for the relevant authorities, the pet trade, and citizen scientists, together with a policy brief on management needs in Germany that will inform the Standing IAS Committee and embed these tools in national governance. Collectively, these outputs will provide a blueprint for the prevention-focused management of non-native terrapins, before they become invasive, which could be extended to other vertebrate species under the EU IAS Regulation. This will contribute to the implementation of the Kunming-Montreal Global Biodiversity Framework (GBF) and other biodiversity strategies.