Two decades of research shows Indonesia's coral reefs are heat tolerant—but only up to a point
Indonesia is home to the world's largest and most biodiverse coral reef system, spanning more than 32,000 square kilometers across the archipelago. Just like what is happening globally, these reefs are now bearing the brunt ...
Our new study, however, found that despite rising sea temperatures, coral cover at most of our Indonesian study sites remained remarkably stable over the long term.
Our study compiled long-term coral monitoring data from across Indonesia. Spanning from 2004 to 2023, the dataset covers 394 permanent reef sites across 32 locations. This massive effort was made possible primarily through data shared by the National Research and Innovation Agency (BRIN), Yayasan Konservasi Alam Nusantara, the Wildlife Conservation Society Indonesia Program, WWF Indonesia and Operation Wallacea.
Out of the 32 locations, 26 showed no significant overall change in hard coral cover, two actually saw an increase and four experienced a decline. Crucially, this stability persisted even as sea surface temperatures rose significantly across every single study location between 1985 and 2023, with the fastest warming occurring in eastern Indonesia.
While this is undoubtedly good news, it comes with a major warning: stability does not mean safety. Once heat stress becomes too frequent or too severe, coral loss can accelerate rapidly.
Even the toughest reefs have a tipping point
Mass coral bleaching in Raja Ampat, Indonesia, December 2024. Credit: Lauren Sparks/Indo Ocean Project
Sea temperatures around Indonesia have been rising. Data from the study locations show clear temperature spikes in 1998, 2010 and 2016, with consistently warmer conditions since 2020. Credit: Razak et al. 2026