A single season of landslides in Indonesia may have killed nearly 60 of the world's rarest great apes. A new study estimates that 58 Tapanuli orangutans died when heavy rain triggered massive earth movements in North Sumatra.
A deadly season in the Batang Toru forest
The deaths happened in late 2024 across the Batang Toru ecosystem, the only place on Earth where Tapanuli orangutans live. Researchers used field surveys, satellite imagery, and population models to calculate the toll. They found that landslides destroyed large patches of forest where the orangutans lived and fed.
Why local people and scientists are alarmed
Tapanuli orangutans were only identified as a distinct species in 2017. Fewer than 800 remain in the wild. Losing 58 individuals in a few months represents a major blow to the species' survival. Local communities depend on the same forest for water and livelihoods. The landslides also damaged farmland and roads.
Scientists linked the disaster to climate change. Warmer temperatures and shifting rainfall patterns made extreme downpours more likely in the region. Deforestation for roads, mining, and agriculture weakened the slopes, making them more prone to collapse.
What the study found on the ground
Researchers walked transects through the landslide zones and counted orangutan nests. They also analyzed satellite data to map the full extent of the damage. The 58 deaths are an estimate, not a precise count. Some orangutans may have escaped or died later from injuries. The true number could be higher or lower.
The study's authors stressed that the landslides did not happen in isolation. They occurred in a landscape already fragmented by human activity. The combination of a changing climate and broken forests created conditions for a single extreme event to kill a significant share of an entire species.
A fragile future for a newly discovered ape
The Tapanuli orangutan now faces a more uncertain future than before. The landslides removed not just individual animals but also parts of the habitat they need to recover. With the species confined to one small area, any large disturbance can have outsized consequences.
