A study published in Current Biology reports that 58 Tapanuli orangutans, representing 7% of the species’ total population, died following extreme rainfall and landslides in Indonesia’s North Sumatra province in November 2025. Researchers attribute the intensity of the event to human-induced climate change, which they state increased rainfall by up to 50% during the four-day period, resulting in the destruction of 8,300 hectares of critical habitat.
Prior research indicates that an annual population loss of just 1% is sufficient to push the Tapanuli orangutan—the world’s rarest great ape—toward extinction. The recent loss of 58 individuals in a single event represents a significant demographic blow to a total population estimated at only 800.
Why the Batang Toru Ecosystem is at Risk
The Tapanuli orangutan (Pongo tapanuliensis) resides primarily in the West Block of the Batang Toru ecosystem, an area already under pressure from mining, palm oil plantations, and a large hydropower project. According to satellite imagery analyzed by researchers from Borneo Futures, World Weather Attribution, and Liverpool John Moores University, the November 2025 rainfall caused landslides that wiped out 11.7% of this essential forest habitat.
Prof. Serge Wich, a primatologist at Liverpool John Moores University, noted that such weather events carry severe consequences for species living in small, fragmented populations. The loss of 11% of the local population in a single event has prompted experts to warn that the species’ survival is increasingly precarious.
The collision of industrial land-use pressures and climate-driven extreme weather creates a “demographic shock” that leaves little room for recovery. While current protection efforts are focused on stabilizing the population, the reliance on international biodiversity-recovery financing suggests that local conservation alone may struggle to offset the impact of rapid environmental degradation.
What Happens Next for the Species
The Indonesian government has implemented a temporary pause on all major industrial activity in the Batang Toru area. This moratorium is intended to allow scientists to assess the risks to human lives while determining the most effective strategies for securing the long-term survival of the orangutans.
Researchers are advocating for a permanent moratorium on land-use activities that degrade the habitat and are calling for an expansion of protected areas. Prof. Jatna Supriatna of Universitas Indonesia emphasized that preventing the first modern extinction of a great ape species requires both local protection and international support to secure the necessary funding for recovery.
Frequently Asked Questions
How many Tapanuli orangutans are left?
The total population is estimated at approximately 800 individuals.
What caused the extreme rainfall in November 2025?
According to researchers, the rainfall intensity was increased by up to 50% due to human-induced climate change resulting from the burning of fossil fuels.
What is the current status of industrial activity in the region?
The Indonesian government has temporarily paused all major industrial activity in the Batang Toru area to facilitate scientific investigation into habitat protection and risk assessment.
How should the international community prioritize biodiversity-recovery funding to prevent the extinction of critically endangered species?
