Scientists have confirmed the ongoing fourth global coral bleaching event is the most intense and widespread on record, continuing from early 2023 through March 2025.

• This bleaching-level heat stress impacted 84% of the world’s reefs while previously first event (1998) affected 21% reefs, second event (2010) affected 37% reefs and third event (2014-17) affected 68% reefs. 

About Corals and Coral Bleaching

• Corals are invertebrate animals that live in colonies of polyps formed by a process called budding (original polyp growing copies of itself). 
• Corals are generally classified as either hard coral (reef-building corals) or soft coral.
  • Hard corals build massive reef structures through calcium carbonate secretion.
• Corals have a symbiotic relationship with algae called zooxanthellae that provide them with nutrients through photosynthesis.
• Coral bleaching occurs when corals expel their colourful zooxanthellae due to environmental stress (primarily rising ocean temperatures), leaving them white and deprived of their main food source.
  • This can lead to mass coral death if prolonged.

Significance of Coral Reefs

• Biodiversity Hotspots: Support approximately 25% of all marine species.
• Coastal Protection: Act as natural breakwaters protecting coastlines from storms, erosion, and flooding.
• Economic Value: Estimated $10 trillion in economic benefits globally through tourism, fisheries, and coastal protection.