Orangutan Numbers Plummeting Worldwide; Species May Vanish In Ten Years, Study Says

The study, which appears in the current issue of the journal Oryx, documents the tremendous decline in orangutans throughout their range. The Leuser Ecosystem in northern Sumatra, Indonesia, which supported 12,000 orangutans in 1993 -- the largest population in the world -- lost nearly half its animals over a seven year period. In 1998 and 1999, losses occurred at around 1,000 animals per year.

"The alarming decline in Leuser's orangutan numbers implies that the world's largest natural orangutan population will be extinct in a decade or so, unless the current trend is stopped," said the study's lead author, Dr. Carel van Schaik, a WCS research associate from Duke University who has studied wild orangutans for more than 20 years.

Ironically, the Leuser Ecosystem includes Sumatra's largest protected area, Leuser National Park, where rampant logging is backed by the Indonesian military and police. "All remaining forests that are accessible by road or river are subject to a seemingly unstoppable pandemic of illegal logging, regardless of their protection status," van Schaik said.

Van Schaik found that orangutan densities decreased more than 60 percent in areas that have been selectively logged, due mostly to a decline in trees that produce fruit - a critical food source for orangutans - as well as the loss of canopy trees they use for travel. The rampant illegal logging that inevitably follows selective cutting in Leuser and other areas, has caused densities to drop as much as 90 percent. Many areas are subsequently turned into massive agricultural estates, and therefore do not regenerate into forest.

"Unfortunately, selective logging is rarely followed by the 30-to-40 year rest period prescribed by law. Instead, timber removal continues, illegally now, until just about all of the timber-sized trees of commercially valuable species are gone," van Schaik said. The situation in Borneo, the only other island where orangutans are found, is no better. Up to one third of Borneo's orangutans died during the wave of forest fires that swept through the area in 1997-98. And a similar rash of illegal logging continues to affect the region -- all fueled by the state of political instability throughout Indonesia.

To alleviate this desperate situation, WCS is calling for a moratorium on logging in old-growth forests until the political situation has stabilized, as well as renewed commitment to national parks. Conservation groups have pledged their support of government initiatives to improve protection, and work with local communities and governments to stop illegal logging.

"The documented, long-term decline in orangutan numbers is both depressing and a call to action. We applaud the U.S. Government for its leadership in providing 1.5 million dollars in emergency aid for orangutan conservation in the coming fiscal year, and for the establishment of a fund, under the Great Apes Conservation Act of 2000, which will provide financial assistance in years to come. But tough changes in natural resource management, and protection of remaining habitat, are equally as critical to ensuring a future for the orangutan," said Josh Ginsberg, WCS director for Asia Programs.

Leuser orangutans differ from their Bornean counterparts in having higher densities, and a tendency toward more social behavior. Van Schaik has documented routine use of at least two kinds of feeding tools to extract honey from tree holes and seeds from a woody fruit protected by stinging hairs. The geographical distribution of this tool use implies that it is handed down to generations, similar to what occurs among certain chimpanzee populations. Conservation efforts should therefore strive to preserve multiple populations in both Sumatra and Borneo or this culture will be lost.

"The study of wild orangutans provides us with a unique window on the kinds of conditions that favored origins of human culture. Losing the wild orangutan would forever close that window. If we act now, we can still save enough populations from oblivion, but we cannot afford to waste any time," van Schaik said.