Almost half of the world's monkeys, apes and other primates are in danger of going extinct due to man's activities, a new review has warned.

Major threats include habitat destruction and hunting of primates for food and an illegal wildlife trade.

The World Conservation Union (IUCN) study of the 634 kinds of primates found that nearly 50 per cent face extinction, but in Asia 70 per cent of primates are classified as vulnerable, endangered or critically endangered.

In both Vietnam and Cambodia, approximately 90 per cent of primate species are considered at risk of extinction.

Populations of gibbons, leaf monkeys, langurs and other species have fallen due to rampant habitat loss exacerbated by hunting for food and to supply the wildlife trade in traditional Chinese medicine and pets.

In Africa, 11 of the 13 kinds of red colobus monkeys assessed were listed as critically endangered or endangered.

Two may already be extinct: Bouvier's red colobus has not been seen in 25 years, and no living Miss Waldron's red colobus has been seen by a primatologist since 1978, despite occasional reports that some still survive.

"We've raised concerns for years about primates being in peril, but now we have solid data to show the situation is far more severe than we imagined," said Russell Mittermeier, chairman of the IUCN Species Survival Commission's Primate Specialist Group and the president of Conservation International.

"Tropical forest destruction has always been the main cause, but now it appears that hunting is just as serious a threat in some areas, even where the habitat is still quite intact. In many places, primates are quite literally being eaten to extinction."

Some positive findings emerged from the review; in Brazil, the black lion tamarin was downlisted to endangered from critically endangered, as was the golden lion tamarin in 2003, as a result of three decades of conservation efforts.

"If you have forests, you can save primates," said Anthony Rylands, deputy chair of the IUCN Primate Specialist Group.

"The work with lion tamarins shows that conserving forest fragments and reforesting to create corridors that connect them is not only vital for primates, but offers the multiple benefits of maintaining healthy ecosystems and water supplies, while reducing greenhouse gas emissions that cause climate change."

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