Sumatran Orangutan Population Declines by Nearly 20 Percent, IPB University Expert: An Urgent Conservation Priority
The Sumatran orangutan population continues to decline and is now in an alarming state. Dr Dede Aulia Rahman, a researcher at IPB University’s Department of Forest Resource Conservation and Ecotourism, Faculty of Forestry and Environment, stated that this situation must be treated as a conservation emergency.
Based on the results of the latest survey conducted from 2021 to 2023, it is estimated that there are approximately 11.694 Sumatran orangutans (Pongo abelii). This number is down from approximately 13.846 individuals in 2011. Using comparable survey methods and areas, the population decline amounts to about 19,5 percent over a 12 year period, an average of 1,8 percent per year.
The largest population center remains in the Leuser Ecosystem Area (KEL), which supports about 84 percent of the Sumatran orangutan population. This indicates that the sustainability of the KEL is crucial to the future of the species.
Meanwhile, the Tapanuli orangutan (Pongo tapanuliensis) is estimated to number only about 716 individuals. This population is distributed across three metapopulations within the Batang Toru Ecosystem.
“This figure is extremely concerning because orangutans are not animals capable of rapidly recovering their populations,” emphasized Dr Dede.
From Habitat Loss to Illegal Trade
According to him, habitat loss remains the primary threat to the orangutan’s survival. Research shows that approximately 76 percent of the variation in population changes across metapopulations is influenced by forest loss.
During the 2011–2023 period, approximately 94.399 hectares of forest within the orangutan’s range were lost due to plantation expansion, infrastructure development, mining, and illegal encroachment.
However, Dr Dede emphasized that habitat loss is not the sole cause of population decline. Killing resulting from human-orangutan conflict, poaching, illegal trade, and habitat fragmentation also exert immense pressure.
“Therefore, in my view, it is inaccurate to pit habitat loss against killing or conflict as if they were separate threats. The two reinforce each other. Habitat loss and fragmentation drive orangutans into plantations and settlements, which in turn increases conflicts, captures, and killings,” he explained.
On the other hand, Dr Dede explained that orangutans have a very slow reproductive rate. Females generally give birth to only one offspring, with an interval of about seven to nine years between births. These conditions make it difficult for the orangutan population to recover when individual deaths or habitat loss occur.
He cautioned that if habitat loss, forest fragmentation, and deaths caused by human activities continue, the risk of local extinction will increase, particularly for small metapopulations and the Tapanuli orangutan.
Therefore, he argued, conservation efforts must be carried out in an integrated manner by halting the loss of critical habitat, maintaining and restoring ecological corridors, reducing orangutan deaths caused by human activities, and strengthening collaboration among the government, the private sector, academia, local communities, and conservation organizations.
“With these measures, the chance of sustaining the Sumatran orangutan population remains viable,” concluded Dr Dede. (Fj) (IAAS/LAN)
