Tapanuli Orangutan Habitat Under Pressure

Critically endangered Tapanuli orangutans in North Sumatra face mining expansion, landslides, and fire risks, with no coordinated recovery strategy in place.

Nearly a year after extreme rainfall associated with Cyclone Senyar impacted North Sumatra’s Batang Toru ecosystem, home to the largest known population of Tapanuli orangutans, a coordinated recovery strategy for the critically endangered ape remains absent. The species continues to face multiple threats, including ongoing mining operations, landslides, and warnings of a severe fire season.

In late 2025, Cyclone Senyar triggered widespread landslides across the Batang Toru landscape. A scientific study estimated this disaster may have killed around 58 Tapanuli orangutans and damaged more than 8,300 hectares of intact forest in the ecosystem’s western block. Conservation biologists state that the species' long-term survival does not allow for an annual mortality rate higher than 1%, making the estimated loss significant.

Recent satellite footage from June 2026 shows new ground disturbances within the concession for Indonesia’s Martabe gold mine, which overlaps with the orangutan habitat. Mighty Earth, a U.S.-based environmental organization, describes these features as landslides linked to mine development. Agincourt Resources, the mine operator, disputes this, stating the June disturbance resulted from planned material movement following blasting within its operational area. The company maintains its blasting considered topography, geotechnical conditions, and slope stability.

These June disturbances are located near an access road developed for the proposed 50-hectare Tor Ulu Ala (TUA) pit, north of Martabe’s existing mining footprint. While the company says no construction took place on this access road in 2026, Mighty Earth’s analysis indicates portions of the June disturbance fall outside areas planned for disturbance through 2030. Phil Aikman, Mighty Earth campaign director, suggested that earlier earthworks on steep hillsides could have contributed to subsequent instability.

Researchers estimate approximately 716 Tapanuli orangutans remain in Batang Toru, split across three increasingly fragmented subpopulations. This leaves the species with little demographic margin for additional losses. The western block of the Batang Toru ecosystem was considered the epicenter of this population.

Agincourt Resources disputes the study’s estimate of orangutan mortality from the 2025 cyclone, stating its post-disaster monitoring found no evidence of orangutan deaths in the areas it surveyed. The company confirmed the survival of previously identified individuals and recorded three previously undocumented individuals. However, Agincourt also noted its teams surveyed only about 63% of its Martabe Preservation Area due to inaccessible terrain and safety risks, meaning some monitored orangutans have not been reconfirmed. The company did not provide baseline numbers for individuals monitored before the disaster.

Regarding the June disturbances, Agincourt stated its monitoring found no significant effect on Tapanuli orangutans or their habitat, and no orangutans were found in the disturbed area. Aikman questioned what could be inferred from this finding, noting that the absence of orangutans after a disturbance does not establish whether the animals had previously used the area or if the disturbance affected their habitat.

Conservation scientists emphasize that the broader concern is the viability of the orangutan habitat after cumulative impacts from the 2025 disaster, ongoing development, and future disturbances. Erik Meijaard, a conservation biologist and co-author of the study on the cyclone’s impact, suspects the June disturbances may be secondary landslides from slopes destabilized in November 2025. He cautioned that no quantitative analysis has confirmed this. High tree mortality around existing landslides could further destabilize slopes over time, increasing habitat degradation risks.

Indonesia also faces an unusually severe fire season, according to meteorologists, introducing another threat to the already compromised ecosystem.

For travelers and hosts considering jungle stays, understanding the specific environmental pressures on local wildlife populations like the Tapanuli orangutan is essential for supporting conservation efforts.