How (Not) to Conserve Tropical Forests

A devastating cyclone that struck Indonesia last November has led to the tragic loss of more than 7% of the world's rarest great apes—the Tapanuli orangutans. According to a recent study published in Current Biology, the cyclone, named Senyar, brought catastrophic flooding and landslides to Sumatra, wiping out nearly 60 individuals from a population of around 800. This represents a significant blow to a species already teetering on the brink of extinction due to habitat loss and human encroachment.

The cyclone, which hit the Indonesian island of Sumatra, brought more than 16 inches of rain, marking it as one of the most intense rain events in recent years. The Tsunami and Disaster Mitigation and Research Center noted that climate change played a role in intensifying the storm, potentially increasing the amount of rainfall by between 9% and 50%. This extreme weather event not only claimed over 1,000 lives but also displaced more than a million people, while wreaking havoc on the natural environment.

The impact on the Tapanuli orangutans' primary habitat, located in the West Block of the Batang Toru ecosystem in North Sumatra, was particularly severe. Researchers identified over 20,000 acres of landslide scars using satellite data, indicating that nearly 12% of the forest cover in this region was lost. These landslides occurred as heavy rainfall saturated the ground, leading to sudden collapses of hillsides that left little time for the orangutans to escape.

Erik Meijaard, the lead author of the study and managing director of Borneo Futures in Brunei, highlighted that the estimated number of dead orangutans might be conservative. He suggested that the actual toll could be as high as 120, given the limitations of using population density estimates and the lack of consideration for other factors such as reduced food availability and forest canopy destruction following the cyclone.

The implications of these losses are profound for the Tapanuli orangutan, a species known for its slow reproductive rate. Females typically give birth every six to nine years, making it challenging for the population to recover from such a significant loss. Additionally, the isolation of their populations across Sumatra means that even minor disruptions can have lasting effects on their survival.

Experts warn that the Tapanuli orangutans are now facing increased risks of extinction, especially if annual mortality rates exceed 1% and if their habitats remain fragmented. Friederike Otto, a climate science professor at Imperial College London, emphasized the need for immediate action to prevent further decline. She called for halting deforestation, reconnecting fragmented forest habitats, and fostering collaboration among governments, local communities, and industries to support conservation efforts.

Despite the grim outlook, there is still hope for the Tapanuli orangutans. Conservationists urge the Indonesian government to implement stronger measures to protect the species. They argue that the current crisis could serve as a catalyst for renewed commitment to preserving these unique primates and their fragile ecosystems. However, the threat posed by climate change remains a looming challenge, necessitating urgent and sustained efforts to mitigate its impacts on both the orangutans and their habitats.