Marine ecologists have been grappling with a puzzler. They had expected that, as climate change warms the oceans, most species would migrate toward the poles, fleeing the ever hotter waters near the equator and tracking the zone of their preferred water temperature as it shifts. But some studies revealed that some species seemed to migrate in the “wrong” direction. Now, however, researchers have apparently solved the riddle: For the past 4 decades, marine species found along North America’s coasts mostly have followed cooler water, but that doesn’t always mean moving poleward.
“This is really quite a neat study,” says Trevor Branch, a fisheries scientist at the University of Washington, Seattle, who was not involved in the work. “It is likely to be the highest profile fisheries paper this year and an instant classic.”
Scientists had long assumed warming oceans would generally drive species’ geographical ranges toward higher latitudes. But some studies have found just the opposite, says Malin Pinsky, a marine ecologist at Rutgers University, New Brunswick, in New Jersey. Off the shores of California, he notes, some species have been moving south, not north. Other researchers have seen the same trend in the Gulf of Mexico. “Scientists were asking themselves, ‘Why aren’t certain species doing what we expect?’ ” Pinsky notes.