The commitment of the EU Biodiversity Strategy for 2030 is unfeasible for marine threatened species affected by invasive alien species

The paper examines the feasibility of achieving the ambitious quantitative commitment stated in the EU Biodiversity Strategy for 2030 "a 50 % reduction in the number of Red List species threatened by invasive alien species" concerning marine species. The limited knowledge base and poor confidence in the evidence concerning impacts of IAS in the marine realm, and the complexity of multiple stressors affecting marine biota, pose major challenges to achieving the management goal. Specifically, i) assessments of IAS impacts in European seas were available only for 73 % of the investigated Red List species (RLS; Critically Endangered, Endangered, Near Threatened, and Vulnerable), ii) for 40 % of the assessed RLS (in Europe or globally) the threat/severity impact posed by IAS remains to be fully assessed, and iii) threat/harm-posing IAS were identified at the species level only in 64 % cases. Overall, the i) relative IAS impact compared to other threats, ii) certainty of IAS impact evidence, iii) IAS control potential, and iv) potential for reducing threat category of RLS following IAS management remain low. Given the generally poor knowledge base on IAS impacts on the RLS inhabiting European seas (irrespective of the EU boundaries), we advocate a re-examination of the available data augmented with targeted studies to support management actions. While the 50 % reduction of RLS threatened by IAS, as laid out by the EU Biodiversity Strategy for 2030, via direct management of these IAS is unfeasible, addressing other evidence-based threats to reduce the pressure on RLS should be considered.