Coral reefs across Micronesia are under growing threat from warming oceans. As temperatures rise, bleaching events are becoming more frequent and severe, pushing many reefs closer to collapse. Without urgent climate action, scientists warn that nearly all reefs could suffer from degradation in the coming decades.
But recent research offers hope: some reefs in Palau are proving to be less exposed to heat stress than others, thanks to natural conditions that can help corals survive high temperatures. These special areas, known as thermal refugia, can form where cooler currents from the open ocean and unique water flows protect reefs from extreme heat. Other reef refugia can be associated with the presence of healthy coastal ecosystems, like mangroves and seagrass beds, that can naturally shield reefs from pollution and produce murky waters that can help reduce harsh sunlight that can damage corals during heatwaves.
The study, led by Dr. Liam Lachs of Newcastle University and the University of Queensland, mapped potential thermal refugia in Palau and found some surprising results. “The previous science suggested we should expect heat-tolerant corals to be at hotter reefs, but across Palau’s barrier reef we found the highest coral heat tolerance and greatest diversity of tolerances at thermal refugia.” says Dr. Lachs, adding that “These thermal refugia seem to be critical reservoirs of resilience and so we should consider prioritising them in conservation portfolios.”
This unexpected extra buffer at thermal refugia means they could endure heatwaves that might otherwise push them past a tipping point, giving the broader reef system a better chance to recover. These locations may also be critical for preserving and promoting naturally heat-tolerant corals in reef management and restoration.
“This new science gives us a powerful tool to build on our existing network of protected areas,” stated Dr. Yimnang Golbuu, Coral Resilience Director at The Nature Conservancy (TNC) Micronesia and Polynesia and co-author of the study. “By identifying these thermal refugia, we can strategically expand our marine protected areas and focus our restoration efforts to help our reefs not just survive, but thrive, for generations to come.”
TNC is working with partners around the world to identify reef refugia, expand marine protection, safeguard coastal habitats, and restore damaged reefs. By putting this knowledge into action, we can help reefs adapt, recover, and continue supporting communities across the Pacific.
For those interested in learning more, the full research article High coral heat tolerance at local-scale thermal refugia by Lachs, L. et al (2024) is published in PLOS Climate.