Community-Driven IUCN Red List Assessments for European Crayfish: A Call to Action

Abstract Accurate IUCN Red List assessments for European crayfish remain hindered by fragmented distribution data, scarce documentation of extinctions, and unresolved taxonomy within several species complexes. Although robust analytical tools now exist to quantify occurrences, range metrics, temporal dynamics, and fragmentation patterns, these alone cannot compensate for the primary limitation: the astacological community has not yet assembled the harmonized evidence base required for high-confidence conservation evaluations. Using contrasting case studies, I show that assessment quality depends directly on data completeness, integration, and taxonomic clarity. I outline the technical infrastructure now available to support transparent and reproducible analyses and argue for a coordinated effort to consolidate the evidence underpinning Red List assessments. Without such contributions, IUCN evaluations—regardless of how urgently updates are needed—will continue to reflect evidence gaps rather than biological reality, limiting their policy relevance. Although focused on Europe, the principles presented here offer a scalable model for crayfish conservation worldwide.