Validating airborne eDNA using observer-based monitoring, acoustic loggers and camera traps to detect birds and mammals
The worldwide loss of biodiversity prioritizes the need for comprehensive and effective biomonitoring methods. Airborne eDNA has shown promise for monitoring terrestrial vertebrates but has not yet been rigorously compared to established biomonitoring methods. This study aims to compare species detection from airborne eDNA with observer-based monitoring (OBM), camera trapping (CT) and passive acoustic monitoring (PAM), focusing on birds and mammals. Monitoring was performed over the course of four weeks within a agroforestry ecosystem in the Netherlands. Bird species were monitored using eDNA, OBM and PAM, while eDNA and CT were used for mammals. Four mammal species were detected by both CT and eDNA, with eDNA identifying an additional 17 species, primarily small-bodied, including two invasive species. A total of 78 bird species was detected, with 28 identified by all three methods. In terms of species uniquely identified per method, eDNA detected the most (19 species), followed by PAM (10) and OBM (2). All but four bird and two mammal species detected were consistent with known diversity near the study site. Rarefaction shows that airborne eDNA has the highest potential species diversity, but OBM is most efficient when limited time is available. Unique species can largely be explained by method characteristics or limitations; PAM detections are limited to species that make sound, while airborne eDNA requires further research on detection range and sensitivity. This is the first study to compare airborne eDNA with OBM and acoustic data, showing that airborne eDNA captures nearly all species detected by other available methods.