Around the world, small machines mounted on buildings, utility poles or small metal towers are constantly sniffing the air for pollution. It turns out they might be able to do double duty monitoring biodiversity.
These air quality monitors weren’t built with hedgehogs, songbirds or fungi in mind. Rather, air pollution regulators such as the United Kingdom’s Environment Agency use them to track levels of hazardous pollutants such toxic metals and soot.
But as the machines suck air through filters to capture little specks of pollution, they are also pulling in other things floating through the air. That includes bits of skin, pollen and other biological material that living things are continuously shedding into the surrounding environment.
Scientists in recent years have begun exploring what information can be extracted from the DNA in these incidental excretions, much as detectives scour a crime scene for DNA clues. First in the water and increasingly on land, they have shown the ability to detect the presence of dozens of nearby species. Last year, scientists announced they had used airborne environmental DNA, or eDNA, to pick out 25 different species at the Hamerton Zoological Park near Cambridge in the UK.
The zoo work didn’t automatically translate into a tool for monitoring which species lived in a more natural area. But it piqued the interest of James Allerton, an air quality scientist at the UK’s National Physical Laboratory in Teddington. He and colleagues at the lab approached the scientists involved in the zoo study about the possibility that air quality monitors could be acting as accidental eDNA vacuums.
It turns out they are. When the scientists combed through filters from two monitoring stations – one in Scotland and one on the outskirts of London – they found eDNA from more than 180 species. The catalog included badgers, little owls, newts, hedgehogs, songbirds, wheat and soybean crops, and a forest’s worth of different trees and flowers, the scientists reported this week in Current Biology.
The discovery means air monitors could be a goldmine for ecologists trying to track shifts in what kinds of species are living in different habitats. The loss of biodiversity is one of the central ecological problems of our time, but it’s often tricky to figure out where it’s happening and which species are affected. Scientists today rely on a combination of cameras, traps, field observations and computer models. But it’s labor-intensive to track even a handful of species, much less the hundreds or thousands that fill an ecosystem.
The potential benefits of the air monitors “cannot be overstated,” said Joanne Littlefair, an ecologist at London’s Queen Mary University who took part in the study. “It could be an absolute gamechanger for tracking and monitoring biodiversity. Almost every country has some kind of air pollution monitoring system or network, either government owned or private, and in many cases both.”
It’s also possible the monitors could provide a backwards look at how ecosystems have already changed. In some cases, the used filters have been kept for decades as an archive of air pollution. Depending on how well the DNA holds up over time, these filters might hold a trove of insights.
“The most important finding, to my mind, is the demonstration that aerosol samplers typically used in national networks for ambient air quality monitoring can also collect eDNA,” said Allerton. “One can infer that such networks—for all their years of operation and in other countries around the world—must have been inadvertently picking up eDNA from the very air we breathe.”
While detecting these species is an important first step, it’s still a leap to get from there to discerning meaningful ecological patterns. For instance, will scientists only be able to tell whether or not a species is present or extinct from a local area? Or will there be ways to gauge changes in population numbers based on the amount of eDNA from a particular species that shows up in the filters?
Regardless, the next time you walk past a neighborhood air monitoring station, consider this thought: It might just be detecting you.
Littlefair, et. al. “Air-quality networks collect environmental DNA with the potential to measure biodiversity at continental scales.” Current Biology. June 5, 2023.
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