Airborne DNA can turn the air in a forest into an inventory of its wildlife, according to two studies led by researchers at the University of Copenhagen. Using small devices that draw air through ordinary filters, the scientists detected genetic traces from dozens of vertebrate species in three protected natural areas across Denmark, without needing to see, hear or capture the animals.
The research could support future monitoring of endangered and invasive species, although scientists still need to establish how far animal DNA travels through the air and how long it remains detectable.
How the airborne DNA vacuum works
Animals constantly release microscopic biological material into their surroundings. Hair, feathers, skin cells and other particles contain genetic information that can remain suspended in the air.
Researchers at the University of Copenhagen’s Globe Institute collected this material using a device described as a DNA vacuum. A computer fan placed inside a plastic box draws air through a filter similar to those used in vacuum cleaner bags. The filter is later analysed in a laboratory.
The captured DNA is sequenced and compared with genetic reference databases, allowing researchers to identify the animals that left the traces.
According to the University of Copenhagen, the devices were attached to trees in three areas: Kalvebod Fælled on the island of Amager, Æbelø north of Funen and Lille Vildmose in North Jutland.
Each location represents a different habitat. Kalvebod Fælled includes wetlands and open vegetation, Æbelø is largely forested, while Lille Vildmose contains forests, wetlands and grassland.
The DNA signals reflected local wildlife
The genetic traces collected in each area generally corresponded with the animals expected to live there.
At Kalvebod Fælled, the researchers detected birds including the Eurasian teal, common snipe, bearded reedling and northern lapwing. Samples from Lille Vildmose contained traces from the tawny owl, great spotted woodpecker, Eurasian bullfinch and European bison.
On Æbelø, the filters detected species including the white-tailed eagle, long-eared owl and fallow deer.
“In our studies, we do not see DNA from animals that should only be found many kilometres away,” Kasun Bodawatta, a postdoctoral researcher at the Globe Institute and one of the studies’ lead authors, said. “This indicates that the signals reflect the local wildlife and that the method has become more precise.”
In one of the studies, researchers recorded 52 bird species, 19 mammals and one amphibian across the three areas. In the other, which focused on Lille Vildmose, the filters detected 54 bird species, 18 mammals and one amphibian.
The findings suggest that airborne environmental DNA, commonly known as eDNA, can provide a recognisable profile of the vertebrate community living around a sampling site.
Better filters do not always capture more species
One of the studies, published in Communications Biology, examined how the design and handling of the sampler affected the results.
The researchers compared different filter types, filter sizes, airflow rates and storage methods. They found that coarser filters, larger filtering surfaces and stronger airflow generally produced a higher number of detections.
This may appear counterintuitive, as finer filters are designed to trap smaller particles. However, they can also restrict airflow. A coarser filter allows the device to process a larger volume of air, increasing the overall amount of biological material collected.
The study also found that keeping filters dry at minus 20 degrees Celsius preserved a greater diversity of detectable vertebrate DNA than storing them in a liquid buffer at room temperature.
A second study, published in Methods in Ecology and Evolution, compared airborne filtration with DNA collected by swabbing leaves in Lille Vildmose. Air filtration detected more terrestrial vertebrates, while longer sampling periods produced the best results.
A possible new tool for biodiversity monitoring
Traditional wildlife surveys often depend on direct observation, cameras, sound recordings, footprints or the physical collection of samples. These methods can require extensive fieldwork and may fail to identify animals that are rare, nocturnal, hidden or only briefly present.
Airborne DNA sampling could provide an additional, non-invasive way to establish whether a species is present. Researchers believe it could eventually help conservation authorities assess the effects of habitat restoration, locate threatened animals or identify invasive species before they become widespread.
“We hope that DNA vacuuming can become an additional tool for mapping species presence,” said Kristine Bohmann, associate professor at the Globe Institute and senior author of both studies.
The technology is not yet ready to replace conventional biodiversity surveys. Researchers still need to understand how DNA particles move through different environments, how weather affects their dispersal and how recently an animal must have visited an area to be detected.
The team also plans to test the method outside Denmark, including in tropical climates. If the technique proves reliable across habitats and weather conditions, sampling the air could become a relatively inexpensive way to monitor changes in biodiversity without disturbing the animals being studied.
