Multiple threats endanger the world's rarest great ape, a new study on the Tapanuli orangutan reveals

The Tapanuli orangutan, the world's rarest great ape, is facing a multitude of threats according to a recent study published in Biological Conservation. Existing in the Batang Toru ecosystem of North Sumatra, Indonesia, fewer than 800 individuals remain in this region that is also home to other rare species like Sumatran tigers and helmeted hornbills. While discussions about the future of this area have primarily centered around major development projects, the research suggests a more complex situation.

Utilizing satellite data, community interviews, and an impact evaluation method called the synthetic control method, the study tracked forest loss and the human activities driving it. Between 2000 and 2023, Batang Toru lost 7,659 hectares of forest (18,900 acres), about 5% of its total forest cover. This loss accelerated sharply after 2012, coinciding with the start of three major extractive projects in the region.

The synthetic control method indicated that Batang Toru lost around 3,472 hectares more forest (8,600 acres) than would have been expected without these projects.

However, the study also found that small-scale agriculture and logging accounted for around 70% of the total forest loss. While extractive industries caused an initial surge in forest loss, these agricultural and logging activities have continued and even intensified over time. This indicates that different drivers of forest loss operate on varying timescales, with large infrastructure projects causing abrupt changes and agricultural expansion and logging contributing to a slower but continuous habitat fragmentation.

The researchers emphasize the need to integrate social and ecological perspectives in conservation efforts. Local communities and Tapanuli orangutans have coexisted in the same habitat for generations, making conservation problems ultimately human as much as environmental. The study highlights that preventing the extinction of the Tapanuli orangutan requires addressing multiple pressures, including extractive industries, agricultural expansion, logging, governance challenges, market forces, and climate change.

Effective conservation strategies will need to focus on strengthening land tenure security, improving logging monitoring, supporting sustainable livelihoods, and rewarding communities for preserving forests. Private-sector involvement through restoration, biodiversity offsets, and long-term stewardship is also crucial. Ultimately, protecting the Tapanuli orangutan is about preserving the resilience of an entire biodiverse and imperiled landscape.