Evaluating Genetic Diversity Indicators for European Bird Species in the Context of Biodiversity Policy

Genetic diversity is a fundamental component of biodiversity and underpins the adaptive potential of species and ecosystems. Despite its recognized importance, explicit protection of genetic diversity of all species has only recently been incorporated into global conservation commitments through the Convention on Biological Diversity’s Kunming-Montreal Global Biodiversity Framework (CBD KMGBF), notably in Goal A and Target 4. The recently accepted genetic indicators by the CBD KMGBF, such as effective population size (Ne500) and the proportion of populations maintained over a specific time period (PM), offer ways to quantify genetic variation at large scales and inform policy. This study provides the first continental-scale assessment of genetic indicators for European birds. Our study lies within an important policy context: together with the Habitats Directive, the EU Birds Directive forms the foundation of EU nature conservation policy, protecting all wild bird species and their habitats, with Annex I listing those that require special conservation measures.

Using abundance data and census data from the European Breeding Bird Atlas (EBBA) and the European Environment Information and Observation Network (EIONET), we delimited populations for species listed within Annex I and calculated both indicators. We then tested for correlations between the indicators and migratory strategy, habitat type, range size, and IUCN Red List status. We found that, while a default Ne/Nc ratio of 0,1 is often used, empirical data suggest higher but uncertain values, with clear habitat-related patterns. Species-specific differences emphasize the need for broader genetic studies to refine taxon-specific Ne/Nc estimates.

Finally, we concluded that data availability was sufficient for both indicators, though population delimitation and temporal alignment of datasets posed challenges and often required expert knowledge. The results highlight both the feasibility and current limitations of implementing genetic indicators for large, well-monitored taxa such as birds. This work provides guidelines for integrating genetic indicators into continental monitoring and for extending similar approaches to other taxonomic groups and regions.