Population trends are essential indicators for identifying conservation needs. However, collecting and analysing long-term data remains challenging due to decentralized sources, limited accessibility, and lack of standardization. We present BATLAS ( https://batlas.info ), a system for integrating dispersed biodiversity monitoring data, using bats as a model. BATLAS consolidates data from citizen scientists and professional monitoring programmes into a centralized database with an integrated tool for automated trend analysis. The platform provides public access to species-specific trend estimates through an interactive web interface, while the raw data remain with the contributors through data-sharing agreements. This approach has successfully encouraged people to share data on a large scale, resulting in the integration of approximately 150.000 bat records from hundreds of contributors across Germany, enabling population trend estimates for 16 bat species. BATLAS offers openly accessible information on population trends, while incentivizing data sharing through contributor visibility, authorship credit, and control over data use. As a transferable concept, BATLAS illustrates how citizen science and institutional analysis can be combined to improve long-term biodiversity monitoring and support Red List assessments and EU Habitats Directive reporting. • Scalable framework for integrating decentralized biodiversity monitoring data. • Combines citizen science data, data from institutions, and published sources. • Offers automated population trend analysis at variable spatial scales through a web-based platform. • Currently consists of 148,014 bat count records from 16 species of cave-dwelling bats, • Promotes data sharing while maintaining contributor control and credit. • Transferable concept for other taxa and monitoring schemes. • Enhances standardization and supports evidence-based conservation.
Fritze et al. (2026) studied this question.