Climate change was meant to mean big trouble for Bicknell’s thrush. One of North America’s rarest songbirds, the species was already struggling with mercury poisoning and habitat loss. As the bird’s mountainous home warmed, ecologists worried that a new threat would move in: the American red squirrel, a mammal that will supplement its seed-rich diet with songbird eggs and nestlings. The squirrels are found downslope of the thrushes and were expected to move up the mountainside as temperatures rose.
But that didn’t happen. Toni Lyn Morelli, an ecologist at the University of Massachusetts Amherst, discovered that the squirrels have actually begun moving downhill. It is good news for songbird conservationists, but puzzling news for ecologists more generally. The squirrels seem to be heading the wrong way.
They aren’t alone. In some locations, as many as half the species studied are defying the prediction that they would shift to cooler places. The discovery is making it difficult for conservationists and land managers to protect vulnerable species. Working on the assumption that the species would move away from the heat, they have been conserving or buying up cooler areas they assumed would become climate refuges. But what if they are protecting land in the wrong places?
“I am left with more questions than answers about what is the best pathway to safeguard things in the face of climate change,” says Inna Osmolovsky, an ecologist at the University of New South Wales in Australia.