You don’t need to actually see an animal to know if it was present -- you just need to find its DNA.
Environmental DNA, or eDNA, is any genetic material from an organism released into the surrounding environment. It can come from skin cells shed by a fish into the water or from plant cells cast onto the soil. By collecting this DNA and analyzing it in the lab, biologists learn what plants and animals are present in a given area.
U.S. Forest Service scientists at the Rocky Mountain Research Station are leaders in developing eDNA tools to detect aquatic species of high ecological and social interest. These include invasive brook trout in the Intermountain West, as well as bull trout, which are listed as threatened under the Endangered Species Act.
The assessment of species distributions is a crucial first step to restoration and conservation. By tracking fish and wildlife populations over time, we can recognize trends in population size and range shifts. This information informs biologists when efforts to conserve an endangered species or remove invasive species have been successful.
eDNA sampling is used to detect invasive species such as zebra mussels, non-native lake trout, and even feral pigs, as well as mapping the range-wide distribution of rare and threatened species. Early detection of invasive species is often the only way to eliminate them before they become established, and eDNA allows this early detection in a cost-effective manner.
Environmental DNA allows biologists to maximize their conservation dollars because it is more sensitive, accurate, and cost effective than many traditional sampling techniques. For aquatic species, traditional methods could involve snorkeling, trapping, or electrofishing, which can take a crew of two to six people multiple hours to complete a single survey. Comparatively, it takes a single person about 10 minutes to collect an eDNA sample. The samples are sent back to the lab, where results can be available within three days.
In addition to the common approach of detecting a single species at a time, the Forest Service is piloting eDNA use for broad-scale biodiversity monitoring. Scientists are developing technology that allows researchers to learn the suite of species that are present all at once rather than analyzing for one individual species at a time.
Forest Service scientists have also optimized sampling protocols that provide easy instructions for any biologist to collect eDNA samples in the field. Using these tools and protocols, Forest Service scientists collaborate with biologists across the nation, including those employed by states and tribes, to inform management decisions. Aquatic managers and stakeholders use this new and improved tool to inform management related to recreational fishing opportunities, native species protection, and the early detection of aquatic invasive species.