Overview
- The June 2026 joint study used satellite imagery of landslide scars in the Batang Toru West Block and orangutan density maps to estimate that Cyclone Senyar’s November 2025 rains killed at least 58 Tapanuli orangutans.
- The estimated 58 deaths represent roughly 7% of the species’ about 800 known individuals and researchers called the loss a devastating demographic shock that greatly increases the risk of extinction.
- Authors found about 8,300 hectares of forest—more than 11% of the West Block—were damaged, and the analysis covered only the western block so the true toll across the species’ whole range could be higher.
- Researchers linked the event to human-driven climate change increasing extreme rainfall and said decades of rapid deforestation and local development made slopes and habitat far more vulnerable to fast-moving landslides.
- Conservation groups and scientists are pressing Indonesian authorities and international partners for permanent protection of Batang Toru, a funded species action plan, and emergency biodiversity-recovery financing.