A novel passive airborne eDNA approach for scalable terrestrial biodiversity monitoring

Terrestrial biodiversity’s rapid decline demands expansion of
high-resolution biomonitoring to support science-based policy.
Environmental DNA (eDNA) analysis has proven effective in aquatic systems
but remains underexplored for terrestrial habitats, partly due to
point-source sampling bias and difficulty in upscaling. Air has emerged as
a promising substrate, yet most studies use active samplers which tend to
be expensive, bulky, and require power, potentially hindering broad
deployment. We present a newly developed, inexpensive, reusable, and
easy-to-use passive approach (Nutshell eDNA sampler) to capture eDNA
suspended in air across time (6-96 hours) within Rotterdam Zoo, the
Netherlands. Its performance was compared to two commonly-used active
airborne eDNA samplers for vertebrate diversity detection. In total, 88
species were detected, including 24 zoo residents. The Nutshell eDNA
sampler was the most effective at detecting zoo residents, surpassing
active samplers in species richness within 48 hours and continuing to
accumulate new species beyond 96 hours, including detections of both
patchy and singleton signals. It also detected the furthest species signal
(515m). Zoo airborne eDNA further demonstrated a positive correlation to
species total biomass, suggesting larger vertebrates or populations
release proportionately more DNA into the air. Our findings indicate that
for long, unsupervised biomonitoring, passive airborne eDNA sampling
presents a promising approach for assessing vertebrate communities and
putatively reduces detection noise in stochastic air eDNA signals due to
its signal integration. While deeper investigations into airborne eDNA
sampling strategies are needed, passive methods can offer a much needed
logistically flexible, low-maintenance approach compared to short-burst
collection strategies employed by many active samplers.