Severe Flooding in Indonesia Threatens Survival of Rare Great Apes

WHO:

The Guardian - Prof Serge Wich, a primatologist at Liverpool John Moores University, co-author of the study.

The Guardian - Prof Jatna Supriatna, a conservation biologist at Universitas Indonesia.

The Guardian - Researchers from Borneo Futures, World Weather Attribution, and Liverpool John Moores University.

WHAT:

The Guardian - 58 out of the remaining 800 critically endangered Tapanuli orangutans were killed due to extreme rainfall and landslides.

The Guardian - The rainfall amounted to more than 1,000mm (39in) over four days.

The Guardian - Approximately 8,300 hectares (20,510 acres) of forest habitat were destroyed by landslides, equating to 11.7% of the key forest habitat.

Phys.org - Nearly one in 10 remaining members of the Tapanuli orangutan species were wiped out by the storm.

WHERE:

The Guardian - North Sumatra province, Indonesia.

The Guardian - Batang Toru ecosystem, Indonesia.

WHEN:

The Guardian - The extreme rainfall event occurred in November 2025.

WHY:

The Guardian - Human-induced climate change caused by the burning of fossil fuels increased rainfall intensity by up to 50%.

The Guardian - The loss of 58 Tapanuli orangutans represents a devastating demographic shock to the species, which is already threatened by mining, palm oil plantations, and a large hydropower project.

HOW:

The Guardian - Scientists used satellite imagery and estimates of ape density to assess the impact of Cyclone Senyar on the orangutan population.

(UPDATED June 10, 2026 19:52 UTC)

A recent study reveals that extreme rainfall and landslides in North Sumatra, Indonesia, led to the tragic loss of 58 critically endangered Tapanuli orangutans, nearly ten percent of the remaining population. This catastrophic event, which occurred in November 2025, resulted in over 1,000 millimeters of rain falling within just four days, destroying approximately 8,300 hectares of forest habitat. Researchers from Liverpool John Moores University and other institutions found that human-induced climate change significantly intensified the rainfall, compounding the threats already faced by this vulnerable species from mining and agricultural expansion.