Nearly half of the world’s 1,200 migratory species — including birds, sea turtles, and whales — are declining in population, and more than a fifth face the risk of extinction, according to a new United Nations report. Migratory sharks, rays, and sturgeons are especially at risk: Their populations have already fallen by 90% since the 1970s. Since migratory species pass through multiple environments, humans need to rethink their impact on key flight and swim paths, as well as land infrastructure, experts said. “We have to look at rail, road, and fences,” the head of the U.N. migratory conservation agency argued. The report named climate change, overexploitation, and habitat loss as the top causes for the declines. |