Madagascar’s Hidden Reefs Emerge as Vital Climate Refuges

The understudied coral reefs of the Mahafaly Seascape in southwest Madagascar have shown remarkable tenacity following the 2024 mass bleaching event. These ecosystems are ecologically vital for the region and crucial for local communities, yet they face increasing pressure from marine heatwaves. A recent study surveying six reef locations revealed that while the heat stress was significant, the permanent damage was not catastrophic.

During the peak of the thermal event, bleaching prevalence reached 38.8 per cent. Bleaching is a stress response where corals expel the symbiotic algae living in their tissues, turning them pale or white. However, subsequent surveys showed a sharp decline in bleaching to just 6.0 per cent, and crucial mortality rates remained low, with only a slight 3.5 per cent rise in dead colonies post-event.

The impact was far from uniform across the seascape. Northern sites generally faced higher thermal stress, yet while some reefs like Beheloke suffered, others such as Ambola displayed impressive resilience. The physical structure of the coral mattered significantly; delicate branching genera were hit hardest, contrasting with the robust tolerance of massive and encrusting forms.

These findings suggest that despite the severity of the 2024 event, the Mahafaly assemblages possess a strong capacity for recovery. Scientists believe these reefs could serve as essential climate refugia—safe havens that persist while others perish—highlighting the urgent need for targeted conservation strategies that recognise site-specific resilience.