Key facts
- Extreme rainfall and landslides in Indonesia killed 58 Tapanuli orangutans in November 2025.
- This loss represents 7% of the critically endangered species' total population of 800.
- The event destroyed 11.7% of the orangutans' primary forest habitat.
- Human-induced climate change is estimated to have increased rainfall intensity by up to 50%.
- Scientists are calling for a moratorium on habitat-degrading activities and expansion of protected areas.
Extreme rainfall and landslides, exacerbated by climate change, have resulted in the deaths of 58 Tapanuli orangutans, representing 7% of the world's rarest great ape population. The event, which occurred in Indonesia's North Sumatra province in November 2025 following over 1,000mm of rain in four days, has raised significant concerns for the species' survival.
The study, published in Current Biology, found that the loss of 58 orangutans, an 11% reduction in the local population, is a devastating demographic shock. Scientists attribute the increased rainfall intensity, up to 50%, to human-induced climate change from burning fossil fuels. The event also destroyed approximately 8,300 hectares, or 11.7%, of the orangutans' critical forest habitat in the Batang Toru ecosystem.
Researchers are urging an immediate moratorium on activities that degrade the remaining habitat and the expansion of protected areas. They emphasize that preventing the first modern extinction of a great ape species requires Indonesia to permanently protect the Batang Toru ecosystem and for international partners to provide biodiversity-recovery financing. Previous research indicates that an annual loss of just 1% of the Tapanuli orangutan population could lead to extinction.
In response, the Indonesian government has temporarily halted major industrial activities in the Batang Toru area to allow for investigations into securing the long-term survival of the Tapanuli orangutan while also assessing risks to human lives.