ROCKY MOUNTAIN ARSENAL NATIONAL WILDLIFE REFUGE — African elephants could go extinct within 12 years, the latest survey shows — an accelerating decline reflected in a grim trend here at the U.S. government’s warehouse for confiscated animal parts: the size of tusks is shrinking. Key anti-trafficking officials from a dozen hard-hit African nations confirmed the bleak prospects for survival of elephants, rhinos and other imperiled wildlife this past week at an unprecedented workshop in Denver and Washington, D.C.