At least one in five reptile species are threatened with extinction, including more than half of turtles and crocodiles, according to the first major global assessment of the world’s so-called cold-blooded creatures. Catastrophic declines in biodiversity across the world are increasingly seen as a threat to life on Earth — and as important as the interrelated menace of climate change. Threats to other creatures have been well documented. More than 40 percent of amphibians, 25 percent of mammals and 13 percent of birds could face extinction. But until now, researchers did not have a comprehens…