Peter Andrey Smith in Undark:
eDNA serves as a surveillance tool, offering researchers a means of detecting the seemingly undetectable. By sampling eDNA, or mixtures of genetic material — that is, fragments of DNA, the blueprint of life — in water, soil, ice cores, cotton swabs, or practically any environment imaginable, even thin air, it is now possible to search for a specific organism or assemble a snapshot of all the organisms in a given place. Instead of setting up a camera to see who crosses the beach at night, eDNA pulls that information out of footprints in the sand. “We’re all flaky, right?” said Robert Hanner, a biologist at the University of Guelph in Canada. “There’s bits of cellular debris sloughing off all the time.”
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