Deforestation poses a serious threat to Sumatra’s orangutans

Study finds that Sumatran orangutan numbers have been underestimated, but warns of decreases.

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Scientists have found that the number of orangutans living on Sumatra is more than double the previous estimate – but insist that their findings are not good news.

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That’s because the study also determined that deforestation rates are so high that many of these ‘new’ orangutans will be lost within the next 15 years.

The population is now assessed at 14,613, compared with 6,600.

The higher number is based on orangutans being found at a higher altitude than previously anticipated – up to 1,500m, as opposed to only 900m – and because they can live in partially logged forests.

The current known range of the Sumatran orangutan – a separate species to those found on Borneo – now covers 17,797km2, more than two-and-a-half times the area it did before.

“These results should not be interpreted as indicating that Sumatran orangutan numbers have increased, nor that their range has expanded,” the scientists conclude. “Since 2004, their numbers have declined, and they continue to do so because of deforestation and poaching and persecution.”

Indeed, the study – led by Dr Serge Wich of Liverpool John Moores University – found that the population is likely to decrease by 4,500 by 2030.

Helen Buckland, director of the Sumatran Orangutan Society, said there were particular concerns about the loss of habitat in the Leuser Ecosystem in Aceh Province, the species’ main stronghold.

Companies, she argued, should be careful about their practices in the light of development plans being made for the region.

“Purchasing palm oil and other commodities from plantations [there] carries extreme risks, so we urge companies sourcing from northern Sumatra to engage with landscape-level efforts to protect Leuser,” she said.

Orangutans in Borneo are also at risk from the ongoing spread of oil palm plantations, though their population is thought to be somewhere between 45,000 and 69,000 individuals.

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