Large-scale illegal logging is to blame for the catastrophic floods and landslides, which saw more than 1,100 people die and more than a million others displaced. That is according to new research from Earthsight and Auriga Nusantara, which revealed that hundreds of hectares of natural forest were illegally cleared inside the concession of pulp and timber company PT Toba Pulp Lestari (TPL), located in the Batang Toru watershed — one of the areas worst affected by the disaster.
According to the ENGOs, much of the clearing occurred on steep upland terrain officially designated as protected forest and recognised by the Indonesian government as highly prone to landslides.
Armed with satellite imagery, the investigation shows extensive deforestation in the Aek Raja block of TPL’s concession between 2021 and December 2025, with clearing accelerating in the months leading up to the floods. The researchers documented that landslides occurred in areas adjacent to recently cleared land immediately after Cyclone Senyar made landfall on 26 November.
“This was not just a natural disaster,” said Timer Manurung, Chair of Auriga Nusantara, at the launch of the report on Monday. “Many experts have said this was also an environmental disaster. What we are seeing is how deforestation in upland areas worsens the impacts of extreme weather,” he said, adding that the findings were intended to support “fact-based discussion and policy debate.”
Manurung said Auriga’s analysis combined satellite data with field investigations in flood‑affected watersheds across North Sumatra. “We documented logging roads, heavy machinery, and piles of tropical logs in areas that should have been protected. This happened on a very large scale over several years,” he said. “It is hard to believe activity of this magnitude could occur without the knowledge of both the company and local authorities.”
According to the report, at least 758 hectares of natural forest were cleared within TPL’s concession, with a further 125 hectares cleared beyond its boundaries. Field surveys also identified logs lacking the markings required under Indonesia’s timber legality system, suggesting potential illegal sourcing.
TPL has rejected the allegations, saying there is “no credible evidence” linking its operations to the floods and landslides in Batang Toru. In a written response dated 23 December, the company said its activities comply with Indonesian laws and sustainability standards, and that it does not log natural forests.
“Based on spatial, hydrological, topographical, and operational data, these events cannot be attributed to TPL’s activities,” the company said, arguing that the deforestation identified by Earthsight and Auriga was caused by “unauthorised third-party activities” beyond its control. TPL added that some of the affected areas were part of community‑managed land under a forestry partnership scheme, and that any planting carried out by the company constituted rehabilitation required under its permits.
The researchers dispute this explanation, noting that some of the illegally cleared areas have since been planted with monoculture eucalyptus — a pattern they say is inconsistent with third‑party encroachment. “Why would illegal loggers replant eucalyptus?” Manurung asked during the press conference. “This looks like a gradual expansion of plantation operations.”
Indonesia’s Forestry Ministry has sealed five locations in the Tapanuli area, including two inside TPL’s concession, as part of an ongoing investigation. President Prabowo Subianto has ordered an audit of the company, while the Environment Ministry has said the disaster “cannot be attributed solely to natural causes.”
Auriga and Earthsight have urged the government to trace the destination of illegally logged timber, prosecute those responsible, and strengthen regulations to protect remaining natural forests. They also called on international buyers of pulp and rayon products to scrutinise their supply chains for links to deforestation in Sumatra. “This tragedy should be a turning point,” Manurung said. “If we do not stop deforestation in vulnerable areas, disasters like this will keep happening.”
Government Crackdown Intensifies After Cyclone Senyar
Last month, Indonesian authorities cancelled more than 1.5 million hectares of forestry permits and launched a sweeping criminal probe after new research linked large‑scale illegal logging in North Sumatra to the catastrophic floods and landslides triggered by Cyclone Senyar — one of Southeast Asia’s deadliest natural disasters in 2025.
In late November, relentless rain hammered northern Sumatra for three straight days, with one district in Aceh Province recording 16 inches in a single day. Four villages were destroyed, and farther south, the storm unleashed another hazard: torrents of timber smashing into homes.
When Cyclone Senyar made landfall, it sent logs and debris into residential areas of North Sumatra Province. “Everywhere you look — left and right along the road — there are piles of timber,” said Sarma Hutajulu, a volunteer helping clear wreckage in Tukka District who spoke to the New York Times. “Those are what smashed into people’s homes.”
