Published on 29 Mar 2025
• The National Oceanic and Atmospheric Administration’s (NOAA) Coral Reef Watch (CRW) and the International Coral Reef Initiative (ICRI) have confirmed the fourth global mass coral bleaching event in 2023- 2024.
• Since mid-2023, sea surface temperatures have been abnormally warm, with record highs in March 2023. This warming is attributed to overall climate change and exacerbated by El Niño.
• Coral bleaching has a devastating effect, impacting not just the coral itself but the entire reef ecosystem and even human communities.
• The first global mass coral bleaching event took place in 1998 in which 20% of the world’s reef areas suffered bleaching-level heat stress.
• The next two global bleaching events occurred in 2010 (35% of reefs affected) and between 2014 and 2017 (56% of reefs affected).
• With global temperatures soaring, such events are expected to become more frequent and longer.
• The world may lose the vast majority of its coral reefs at 1.5 degree Celsius of warming, and virtually all at 2 degree, according to a 2018 report by the Intergovernmental Panel on Climate Change (IPCC).
What is coral bleaching?
???? Corals and zooxanthellae have a symbiotic relationship.
???? Corals provide zooxanthellae a safe place to live, zooxanthellae provide oxygen and organic products of photosynthesis that help corals to grow and thrive and are responsible for the unique and beautiful colours of corals.
???? Corals are very sensitive to light and temperature and even a small change in their living conditions can stress them. When stressed, they expel zooxanthellae and turn entirely white. This is called coral bleaching.
Fourth Global Mass Coral Bleaching Event
Coral ecosystem
Coral bleaching
Ecosystems
Biodiversity