How do you study something you can't see? Environmental DNA gives scientists clues about wildlife

The world is teeming with biodiversity: Fungi, plants, insects, animals, and all of the living things. Often, these things exist unknowingly right alongside us. In our woods, in our streams, in our skies, and in our soil. It’s understandable that we don’t see the biodiversity around us. Sometimes, for so many reasons, it remains obscured from our view. But that does not make it any less important. 

Biodiversity brings value to our lives, often referred to as “ecosystem services.” Conservation biologists are frequently tasked with finding and cataloging all of the biodiversity in our world. However, this is not so easy a task, as much of our biodiversity does not want to be found. So, over the years, numerous “gears” such as nets, traps, snares, and other devices have been developed to capture and understand the biodiversity in our world. And while these gears are tried-and-true tools used to detect very specific twigs and branches of the Tree of Life, they are often costly, time-consuming, and difficult to deploy at a large landscape scale. 

So, scientists are increasingly turning to technological and methodological innovations to document the world’s biodiversity, and among the most exciting is environmental DNA, or eDNA.

What is environmental DNA?

All living things, as they do the things they do in the habitats where they live, leave behind their unique genetic signature. From the falling leaves in autumn, to a snake shedding its skin, to a wolf’s saliva on a deer carcass, to a bat sloughing hairs as it navigates the night sky, DNA is everywhere. In the past two decades, scientists have found a way to harness that genetic information to better understand where, when, and how biodiversity is interacting with the world around it. 

So how does it work? It’s simple, really. People travel out to the habitats and collect bulk samples of environmental materials. A liter of water, a kilogram of soil, dust in the air, even a flower (Image 1), can all hold critical genetic information. From these environmental samples, a mix of chemistry, biology, and cutting-edge technology can unlock the biodiversity secrets of that time and place, sight unseen.

Why eDNA is revolutionizing biodiversity monitoring

Environmental DNA biodiversity surveys have shown great promise in being faster, less expensive, easier to scale, and, often, more sensitive than conventional gears and approaches. It also shines in situations where conventional gears simply aren’t an option, like searching for rare Blanding’s Turtles through the winter ice in a western Minnesota prairie stream (Image 2). The flexibility and universality of this tool is providing unprecedented opportunities to ask and answer new and exciting questions about not only where species occur, but how they are interacting with each other and their environment in time and space.

More importantly, where eDNA has shone brightest is in those very rare things that we perhaps care most about. This tool has been effective in detecting new invasive species entering the Great Lakes through ballast water in transatlantic ocean ships. It has been successful in tracking the leading edge of invasive carp in the Mississippi River. It has also shown promise in detecting the rarest snake in North America, the Louisiana Pinesnake (Pituophis ruthveni; Image 3). The success of eDNA to detect the rarest things in our environment has rendered it a remarkable tool in the conservation biologist’s toolbox.