The bush meat trade and the Ebola virus are devastating great ape populations in west Africa 鈥� their last major refuge
The first major survey for 20 years shows commercial hunters are decimating gorilla and chimpanzee populations near urban centres and logging camps, while Ebola is wiping out large gorilla groups living in remote forests.
The combination could push our closest animal relatives to the brink of extinction in the wild in just a decade, warns Peter Walsh of Princeton University, New Jersey, who led the study.
Advertisement
Gabon and the Republic of the Congo are home to most of the world鈥檚 remaining gorillas and common chimps (Pan troglodytes). The last survey of ape sleeping nests in 1981 to 1983 showed dense ape populations across Gabon.
But new surveys conducted between 1998 and 2002 show the average population density has dropped by 56 percent. And that estimate is deliberately conservative, Walsh warns.
Hidden problem
Satellite photos of Gabon show only modest deforestation, which had been thought the worst threat to the great apes. But big problems were found hiding under the trees.
Selective logging preserves tree cover, but the roads built to remove the wood give hunters easy access to ape populations. Losses were alarmingly heavy in areas where ape populations had been highest. They reached up to 99 percent in the Minkebe forest area in northeast Gabon.
Walsh urges 鈥渞adical intervention鈥� to stop hunting. 鈥淚f we don鈥檛 do something, in 10 to 20 years there will be just isolated pockets of gorillas left,鈥� Walsh told New 杏吧原创.
However, he thinks hunting could be easier to stop than Ebola. The disease can cause catastrophic drops. For example, a group of 143 gorillas in the Lossi area of Congo was reduced to seven in a matter of months by the virus.
Yet what causes the outbreaks remains unknown. Many suspect ecological changes that increase human contact with an as-yet-unidentified animal that harbours the virus.
But Walsh thinks it may instead be an epidemic disease that emerges when gorillas exceed a threshold population density. The difference is critical because the models suggest different ways to stop Ebola鈥檚 spread, so Walsh says tests of the theories should be a top priority.
Critically endangered
The average annual decline of 4.7 per cent is bad enough to move both gorillas and chimpanzees from 鈥渆ndangered鈥� to 鈥渃ritically endangered鈥�, Walsh says. The latter designation requires a projected loss of 80 per cent of the population in three generations.
The current trend will hit that number in 33 years 鈥� 1.5 generations for chimps and about two for gorillas. And Walsh thinks the loss has accelerated in the past decade, making matters even worse.
Apes are important, says Sandy Harcourt of the University of California at Davis. 鈥淚f they go, then we鈥檝e lost a very, very direct connection to the rest of the animal world.鈥�
He agrees that the problem is grave, but says he is 鈥渁 little less worried鈥� about prospects for recovery if the animals can be protected effectively. Mountain gorillas have survived several wars. 鈥淭he situation is way worse than we ever thought, but very far from hopeless,鈥� Harcourt says.
Journal reference: Nature (DOI:10.1038/nature01566)