Listening to Coral Reef Health
Healthy coral reefs don’t just look vibrant — they also sound alive. A recent study in Indonesia’s Sangkarang Archipelago revealed that machine learning can distinguish between the soundscapes of healthy, degraded, and restored reefs. Led by Ben Williams of University College London, the research shows that reef sounds — from snapping shrimps to parrotfish crunches — can act as reliable indicators of ecosystem recovery.
From Proof of Concept to Machine Learning
Earlier studies had already shown that restored reefs can sound similar to healthy ones, but analyzing recordings manually was slow. Williams developed an algorithm that successfully classified reef soundscapes. Recordings from older restored reefs were mostly identified as healthy, while newly restored sites still resembled degraded reefs. This automated method offers a faster and more scalable way to monitor reef recovery.
Why Soundscapes Matter
The findings have wide implications. Juvenile fish and coral larvae use reef sounds to decide where to settle, meaning that lively soundscapes help attract new generations of marine life. As Cornell scientist Aaron Rice explains, bioacoustics could answer a key question in restoration: how to measure progress effectively and know when a reef is truly recovering.
Global Applications and Next Steps
Researchers are now deploying low-cost hydrophones like the open-source HydroMoth to sites worldwide, including the Great Barrier Reef and the Maldives. Since coral reefs differ regionally, the team is testing whether one global model or several regional models will be needed to classify reef health. Future work also aims to identify exactly which sounds signal healthy reefs.
Hope and Challenges Ahead
Listening to reefs is emerging as a viable conservation tool, capable of providing round-the-clock data in conditions where divers cannot work. However, restoration is not a silver bullet. Williams stresses that without tackling climate change and greenhouse gas emissions, global coral reefs remain at grave risk of collapse by the end of the century. Restoration and climate action must go hand in hand to secure the future of these ecosystems.
