Accidental collection of DNA from air sensors can change how wildlife is tracked

Catching Environmental DNA in the Local Environment: A Light-Bulb Moment for Natural Biological Scientists and the Natural History Museum of the UK

A badger ambling through the grass, an oak growing in the forest, or an eagle soaring overhead are all indicators of a living thing with an invisible signature. Fur, feathers, skin cells, spores, pollen—all of it is loaded with genetic information that floats away into a data-rich atmospheric soup. Scientists call this information environmental DNA, or eDNA, and it is so potent that in January 2022 researchers announced they’d been able to identify the species in two zoos just by sampling eDNA in the surrounding air.

James Allerton, an air quality scientist at the UK’s National Physical Laboratory, read about that experiment and had one of those wait just a minute ideas. The UK has a heavy metals network which the laboratory operates. The air is analyzed at the monitoring stations for levels of toxic metals. We did not think about the fact that there could be DNA material on the filters. Allerton recalls. Yet the idea was too intriguing to ignore. “When you read a report about people who’ve successfully managed to capture animal DNA out of the air—and there we are, working in particulate measurements—then you have the light-bulb moment.”

In the latest research, Clare and her colleagues ran a pilot study in which they got access to existing UK air-quality monitoring stations in London and near Edinburgh, to see whether they could trap airborne eDNA from the local flora and fauna. Both are designed to monitor atmospheric pollutants such as lead in particulate matter that becomes trapped in the devices’ filters. The Edinburgh station is part of a UK-wide network that is run in part by the National Physical Laboratory (NPL) in Teddington.

The air quality scientists haven’t considered it either. “We’ve had a lot of these conversations with scientists the last couple of weeks and people who run these networks,” says Clare. Did you realize it does this too? They all have a look of shock on their face. And then they go, ‘Oh, but of course it must.’ It really seems obvious once you’re told about it, but it isn’t obvious, because the people operating them aren’t biologists.”

Other unknowns include how far eDNA travels in air, which will determine how large an area this method can monitor. The team is still working out what ecological data eDNA can provide beyond identifying species, according to study co-authorJoanne Littlefair. For example, she suggests it is unlikely that the method will be able to measure species abundance. But it could monitor bird migrations and how they are changing in response to climate change.

But before the monitoring method can be rolled out widely, researchers need to work out some details, including the optimal sampling time to ensure broad eDNA collection. The team says its data suggest that a day is too short for sampling, but a week is too long — there is a sweet spot between collecting enough DNA and keeping it for so long that the material degrades.

DNA from samples of an air-monitoring station and its use for assessing biodiversity in the North and South of the world: wrens, Parus major, ash trees, Soleirolia and Septoriella

The advantage of using existing air-monitoring stations is that this infrastructure is already set up in many countries around the world, including across North and Central America, Europe, Asia and the Southern Hemisphere, the researchers say. They want air-quality analysis filters preserved so that ecologists can use them.

The researchers were surprised to find DNA from so many groups of organism on the filters. These included 34 species of bird, such as wrens (Troglodytes troglodytes) and great tits (Parus major), as well as ash trees (of the genus Fraximus), nettles (of the genus Soleirolia) and pathogenic Septoriella fungi (see ‘Keeping tabs on taxa’).

The research team, which included scientists from the NPL, extracted and sequenced eDNA from one-quarter of each filter. The scientists compared the sequences to those available in a database run by the National Institute of Health.

The London station has been set up next to a deer park to allow the researchers to take samples from various times of the day. They also explored how long samples could be preserved by analysing the Edinburgh stations’ filters, which had collected DNA for a week before being stored for eight months.

Estimates suggest that the worldwide population of wildlife has fallen by at least 69% since 1970. Scientists struggle to keep track of changes in ecosystems and rates of species decline because they lack infrastructure to measure biodiversity on large scales. Typically, researchers and volunteers monitor a fewTerrestrial species in small regions using labour- intensive methods such as camera research, in-person observations and examining traces. Only a very general assessment of forest cover is possible over large scales.