Lessons from a failed experiment mark new way forward.
Some invasive species targeted for total eradication bounce back with a vengeance, especially in aquatic systems, finds a study led by the University of California, Davis.

The study, published in the journal PNAS, chronicles the effort — and failure — to eradicate invasive European green crabs from a California estuary. The crabs increased 30-fold after about 90 percent had been removed. The study is the first experimental demonstration in a coastal ecosystem of a dramatic population increase in response to full eradication.

“A failure in science often leads to unexpected direction

s,” said lead author Edwin (Ted) Grosholz, a professor and ecologist with the UC Davis Department of Environmental Science and Policy. “We slapped our foreheads at the time, but with thought and understanding, it’s told us a lot about what we shouldn’t be doing and provided a way forward for us. The world should get less focused on total eradication and work toward functional eradication.” //

The scientists did not observe such population explosions of green crab at any of the four other nearby bays they were monitoring, suggesting the increase was the result of eradication efforts and not atmospheric or oceanographic changes.

The study found the population explosion was due in part to the fact that adult decapod crustacea — such as shrimp, lobster, and crab — typically cannibalize younger individuals. When most adults were removed, juveniles grew unchecked and overcompensated for the loss of adults. //

As described in the Frontiers in Ecology study, the authors advise a “Goldilocks level” approach, where the population is low enough to protect native species and ecosystem functions without risking a population explosion of the invasive species.