Logging, mining, oil palm, paper, and linked deforestation have been blamed for the the diminishing numbers.
However, researchers also found many orangutans have vanished from more intact, forested regions, suggesting that hunting and other direct conflict between orangutans and humans continues to be a chief threat to the species.
The report published in the Current Biology Journal found more than 100,000 of the island’s orangutans vanished in the period of 1999 to 2015.
“Orangutans are disappearing at an alarming rate,” said Emma Keller, agricultural commodities manager at the Worldwide Fund for Nature (WWF).
“Their forests homes have been lost and degraded, and hunting threatens the existence of this magnificent great ape.
“Immediate action is needed to reform industries that have pushed orangutans to the brink of extinction. UK consumers can make a difference through only supporting brands and retailers that buy sustainable palm oil.”
Around half of the orangutans living on the island of Borneo, the largest island in Asia, were lost as a result of changes in land cover.
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Researchers said the Bornean orangutan’s survival is dependent on forging successful alliances with logging companies and other industries and raising public awareness of the issue.
Looking at predicted future losses of forest cover and the presumption orangutans are ultimately not able to stay alive outside forest areas, the researchers predict that over 45,000 more orangutans will be lost in the space of the next 35 years.
The report comes after an orangutan was shot at least 130 times with an air gun before it died earlier in the month, according to police in Borneo.