A rare and critically endangered primate species has suffered a devastating blow after a single cyclone wiped out nearly 7% of its global population, scientists warned on Thursday.
Research published on 18 June 2026 reveals that Cyclone Senyar, which struck Sumatra in November 2025, killed at least 58 of the world’s rarest great apes—the Tapanuli orangutan—leaving fewer than 800 individuals remaining. The figure, described as conservative by the study’s authors, excludes deaths from delayed effects such as starvation, injury, or habitat collapse in the weeks that followed.
Erik Meijaard, chief scientist at Borneo Futures and lead author of the report in *Current Biology*, told the BBC that initial estimates of 35 deaths had been revised sharply upward after satellite imagery and population density models revealed the true scale of destruction. “The forest itself became a killing field,” Meijaard said. “When hectares of hillside slide away in seconds, even the strongest orangutans have no chance.”
The disaster unfolded across the Batang Toru ecosystem in northern Sumatra, where the Tapanuli orangutan survives in three isolated forest blocks. Cyclone Senyar dumped between 103 mm and 1,030 mm of rain in just four days, triggering more than 50,000 landslides and stripping 8,300 hectares of forest—nearly 12% of the western block’s canopy. The deluge also killed more than 1,000 people across Indonesia, Malaysia, and Thailand, making it the deadliest natural disaster in Southeast Asia last year.
Scientists directly linked the cyclone’s intensity to human-driven climate change. Douglas Sheil of Wageningen University & Research, a co-author, said the warming atmosphere had increased rainfall associated with Senyar by between 9% and 50%, amplifying the impact on terrain already weakened by deforestation and mining. “We can no longer treat extreme weather and biodiversity loss as separate crises,” Sheil warned.
Indonesia’s government has temporarily halted major development projects in Batang Toru, including mining, palm oil expansion, and new hydroelectric dams. The pause offers a rare opportunity to reassess ecological risks and habitat capacity before resuming activity, the study argues. Meijaard stressed that sustained international funding and climate-adapted planning are now essential to prevent the first modern extinction of a great ape species.
Sergei Vich, a primatologist at Liverpool John Moores University, noted that the Tapanuli orangutan could withstand a loss of no more than 1% of its population annually. “The losses from Senyar are far beyond what this species can tolerate,” Vich said. Jatna Supriatna, a biologist at Universitas Indonesia, called the deaths a demographic catastrophe for the world’s rarest great ape.