LISLE, Ill. (AP) -- The world's great apes are hurtling toward extinction at a rate that is alarming scientists. At an urgent meeting this month of wildlife and zoo researchers from 12 nations, experts said new estimates of the populations of chimpanzees, gorillas and orangutans are far lower than they were even a year or two ago, with some species down to a few thousand, or even a few hundred. Even more alarming, experts reported, is the expansion of hunting and habitat destruction in some of the most politically unstable nations in Africa and Asia. But agreeing how to rapidly and effectively save humans' closest relatives, or even deciding which species might be the most endangered, is proving to be a complicated and contentious task. "We have a crisis of such immense proportions that I don't believe that most people realize how bad it is,'' said primate expert John F. Oates of the Graduate Center of the City University of New York. "We have to stop sitting on our hands. Jane Goodall has said that in 20 years there would be no more chimpanzees. Well, that is being revised to 10 years, or even five.'' The great apes might be the most well-known of the endangered primates, but their plight is not unique. According to Conservation International, a Washington-based non-profit group, 10 percent of the world's 608 primate species and subspecies on three continents are critically imperiled, meaning they could vanish at any time. Another 10 percent are endangered, meaning they would probably go extinct in the next 20 years without intervention. The most urgent threats are logging, hunting, war and the millions of impoverished refugees who rely on the same forests as the primates for food, fuel and shelter.