Biologists spend a lot of time trying to prove an animals’ presence and abundance, but according to a new study the evidence is often easily obtainable in a place no one thought to look. Thousands of air quality monitoring stations are collecting particulates around the world, and these often come with DNA attached. A study of two UK stations identified more than 180 species of animals, plants and fungi present in the local area. Better still, many of these stations have decades of preserved samples, providing a perfect resource for determining how populations have changed.
Study after study has revealed air pollution is killing us, along with a host of other disastrous effects. Even when governments are slow to act, there’s often enough interest in identifying the problem to establish air quality monitoring stations. When they don’t, sometimes others step in, such as US embassies keeping track of air pollution in capital cities worldwide. Which aspects of pollution are monitored varies, but filters to measure PM10 (particulates 10 micrometers across or less) are usually a feature.
Dr Elizabeth Clare of York University led a team that collected particles stuck to the filters from a sampler in suburban London, opposite a deer park, and compared them with a counterpart in rural southern Scotland. DNA attached to the particles was extracted and analyzed to seek the presence of known species, with the results reported in a recent paper.
The fact that birds, flowering plants, and common mammals are shedding their DNA all over the place, with some landing in filters, may not surprise too much. However, what Clare and co-authors found is much more diverse. How DNA from fish and amphibians ended up in the filters may take some explaining, but it did, allowing the authors to establish their presence nearby.
The detections included “charismatic species such as badgers, dormice, little owls, and smooth newts,” the paper reports. More importantly, the team identified “species of special conservation interest such as hedgehogs, and songbirds, trees including ash, linden, pine, willow and oak, plants like yarrows, mallows, daisy, nettles and grasses, arable crops such as wheat, soybean and cabbage and pathogenic fungi like Septoriella.” For the record we would like it noted that IFLScience regards hedgehogs as very charismatic, and are offended on their behalf they weren’t included.
“One of the single biggest issues facing the planet today is the accelerating loss of biodiversity,” Clare said in a statement.
“The potential of this cannot be overstated. It could be an absolute gamechanger for tracking and monitoring biodiversity,” added co-author Dr Joanne Littlefair of Queen Mary University. “Almost every country has some kind of air pollution monitoring system or network, either government owned or private, and in many cases both. This could solve a global problem of how to measure biodiversity at a massive scale.”
The shorter a country is in resources to investigate its wildlife, the more valuable a low-cost path to monitoring could be. In some cases, DNA we don’t recognize could be found, leading to the discovery of previously unknown species.
The longer period the samples were taken over, the more vertebrates were recorded, probably indicating that some migrate in and out of the monitors’ catchment areas. We might expect that tracking for too long would cause DNA from the start of the period to degrade, but the paper notes, “The viability of the Scottish samples stored in ambient conditions suggests that, once collected, DNA on the filters is surprisingly stable.”
As significant as this could be for biodiversity tracking, there is more work to do before it can reach its potential. “As a priority we must determine the useful range of these samplers, the degradation rate of airborne eDNA […] and the potential value of older stored filters,” the authors write. They also note that “early experiments suggest airborne eDNA signals are local.”
If the monitors are good enough failure to detect a species could prove as significant as finding it, providing a warning of local extinction. However, the paper notes, “It also remains unclear why some taxa are more 'detectable' than others.” The absence of DNA may indicate a species is hard to detect, rather than being absent.
The study is published in Current Biology.
