Scientific American: The baiji dolphin is functionally extinct, orangutans are disappearing and even some species of bats–the most numerous of mammals–are dying out. A new survey of the world’s 5,487 mammal species–from rodents to humans–reveals that one in four are facing imminent extinction. “Mammal species that are just declining, not necessarily near extinction, that’s 50 percent,” says conservation biologist Jan Schipper of the International Union for Conservation of Nature (IUCN), which keeps …