Air pollution monitors have been accidentally harvesting wildlife DNA

Air samples collected at pollution monitoring stations could provide a treasure trove of data on plant and animal life thanks to new environmental DNA methods.

Environmental DNA (eDNA) comes from shed cells, waste and blood left in the air, water or soil. Methods to detect it have revolutionised wildlife surveys in recent decades: rather than needing to physically see and capture animals to confirm their presence, we can now simply analyse the DNA they leave behind.

While these methods are remarkable, they are still too intensive to carry out on the extremely wide and regular scales needed to track the rise and decline of species over time. But a new approach could change all that by making use of samples that are already routinely taken, and in some cases stored for decades, in order to track air pollution.

James Allerton at the National Physical Laboratory in Teddington, UK, says he read a report about harvesting eDNA with air filters and realised that it was remarkably similar to his own work monitoring air quality. He contacted the biologists behind the report and an international team has now carried out experiments that prove that air pollution monitoring stations have inadvertently collected and stored DNA samples that can now be analysed.

“It seemed like a no-brainer,” he says. “It’s a really good lesson: read around your subject, and read outside your subjects.”

His collaborator Elizabeth Clare at York University in Toronto, Canada, says the new technique will be able to detect the rise of invasive species as well as the decline of native species, but will also reveal entirely new creatures and plants that are thus far unknown to science.

In tests, the team took filters from air monitors in London and Auchencorth Moss near Edinburgh, UK, and stored them for eight months before analysing them for DNA. They identified DNA from more than 180 different plants, fungi, insects, mammals, birds, fish and amphibians. They included hedgehogs, badgers, smooth newts, songbirds, trees and arable crops.

Clare and her colleagues are now hunting for archives of the standardised 47-millimetre air filters from government and private institutions around the world with the hope of building a global database of biodiversity information, both historic and contemporary.

“I talked to somebody with more than half a million of these in storage,” she says. “There are probably millions of them in existence around the world, archived.”

Douglas Yu at the University of East Anglia, UK, says being able to create new data sets from historical samples will be useful, but perhaps the biggest advantage of the technique will be as a way to easily collect samples in the future. This could help to monitor the success of initiatives aiming to restore biodiversity, he says.