If a tree falls in the forest and no one is around to hear it, does it make a sound? This philosophical musing on perception and reality is often vaguely attributed to Irish philosopher George Berkeley, the San Francisco, California, Bay Area city’s namesake, whose own philosophy boiled down to, “To be is to be perceived.”
For much of the discipline’s history, ecological researchers studying the presence of endangered species in underwater habitats were forced to operate under a similar axiom.
If, for instance, after a day of trudging through ponds and combing the water with dip nets, Brian Woodward, an ecological researcher at the Santa Lucia Conservancy in Carmel Valley, was unable to perceive with his own eyes the presence of a California tiger salamander or its larvae, he would have no physical evidence of its existence. The rules of detective work 101.
Earlier this spring, with the help of a grant and a partnership with the Elkhorn Slough National Estuarine Research Reserve, Woodward and a team of researchers set out to monitor the presence of the tiger salamander and the similarly endangered California red-legged frog on the Santa Lucia Preserve. Instead of sweeping the ponds with a net and manually counting the adults and larvae they found, the team bagged up samples of pond water and shipped them to Caren Goldberg’s laboratory at Washington State University for analysis. The results, which Woodward expects to receive by September, will tell which ponds are hosting the endangered species.
The use of eDNA does for ecology what forensic labs did for crime scene investigators.