The death of seven percent of the world’s rarest orangutans from prolonged rainfall may sound like a paradox. Yet for the Tapanuli orangutan, a species already numbering fewer than 800 individuals, the deluge that struck Sumatra’s Batang Toru forest in late 2024 proved catastrophic. Torrential rain, linked to a persistent La Niña pattern intensified by climate change, triggered landslides and floods that wiped out an estimated 50 animals. British zoos, in an unprecedented collaboration, have launched an emergency conservation fund to prevent the species from tipping into extinction.
Dr. Helena Vance, Science & Climate Correspondent.
The Tapanuli orangutan, Pongo tapanuliensis, was only identified as a distinct species in 2017. With its habitat confined to a single upland forest block, it is the most endangered great ape on Earth. The recent weather event killed more individuals in weeks than the average annual poaching toll. Necropsies revealed that most deaths were due to trauma from falling debris, drowning, and hypothermia. The loss represents a demographic blow from which the population may not recover without intervention.
“This is not an anomaly,” says Dr. Vance. “Climate models predict that the Indonesian archipelago will experience more extreme rainfall events as sea surface temperatures rise. For a species already on the precipice, a single weather event can erase decades of conservation gains.”
The response from British zoos has been swift. Twelve institutions, including Chester Zoo, Edinburgh Zoo, and the Zoological Society of London, have pooled resources to create the Tapanuli Emergency Conservation Fund. The fund will finance three critical actions: emergency rescue and rehabilitation of orphaned or injured orangutans, reinforcement of critical hillside habitats to prevent further landslides, and deployment of early-warning weather stations to enable preemptive evacuations.
“This is a military-style operation,” explains Dr. Simon Grove, conservation director at Chester Zoo. “We are coordinating with the Indonesian government and local forestry authorities. The goal is to stabilise the population within two years. If we fail, the Tapanuli orangutan will be functionally extinct within a decade.”
The funding, totalling £2.3 million, will also support research into the species’ immune system and stress responses. “We need to understand how these animals cope with chronic environmental shock,” says Dr. Vance. “Physiological data from rescued individuals will inform captive breeding programmes as an insurance policy against in situ extinction.”
The conservation community has long argued that climate change is not a future threat but a present-day killer. The Tapanuli orangutan is merely the most extreme example. In Borneo, the same rainfall patterns have drowned thousands of Bornean orangutans, though exact figures remain unknown due to the vastness of the landscape. The British zoos’ initiative could serve as a template for climate-adaptive conservation.
“We are no longer just protecting habitat from palm oil and loggers,” says Dr. Vance. “We are facing the weather itself. That requires a new paradigm: real-time monitoring, rapid response, and, critically, funding that moves as fast as the climate.”
The fund is open for public donations. But Dr. Vance is characteristically blunt: “This is a stopgap. The long-term survival of the Tapanuli orangutan depends on our ability to rein in emissions. Until then, we are triaging a species while the planet burns and drowns by turns.”
