Car-Mounted Airborne eDNA Sampling Detects Landscape Scale Biodiversity Turnover Along Environmental Gradients.

Documenting accelerating global biodiversity decline requires monitoring tools that can operate across large spatial scales and repeated timeframes. Analysis of airborne environmental DNA (eDNA) is an emerging method used to track species distributions, but it is unknown whether airborne eDNA retains coherent ecological signals across terrestrial landscapes, or whether atmospheric mixing and DNA transport make it too spatially diffuse to resolve meaningful macroecological patterns. To address this question, we conducted a biodiversity survey using car-mounted airborne eDNA sampling along a repeated 1155 km route across south-western Western Australia, spanning the Southwest Australian biodiversity hotspot and adjacent inland regions. This extensive and environmentally heterogeneous region faces ongoing pressures from habitat loss, invasive species and climate change, highlighting the need for scalable biodiversity monitoring approaches. Samples were collected at ~26 km intervals and analysed using metabarcoding assays targeting plants, vertebrates and arthropods, with generalised dissimilarity modelling used to assess environmental drivers of community turnover. We detected a broad range of plants and animals, including species of ecological and biosecurity importance. Different taxonomic groups showed distinct spatial scales of airborne eDNA community similarity and beta diversity was structured primarily by habitat and environmental gradients rather than geographic distance alone. This indicates that airborne eDNA did not simply reflect spatially homogenised biological material but retained ecological structure informative of macroecological patterns. Together, these findings demonstrate that car-mounted airborne eDNA can recover ecologically meaningful patterns of community turnover across heterogeneous terrestrial landscapes and support landscape-scale biodiversity assessment.