Global coral bleaching crisis spreads after hottest year, scientists say

23/4/2025 12:51

More than four-fifths of the world's coral reef areas have been affected by devastating mass bleaching spurred by record-high ocean temperatures, turning many once-colourful reefs a ghostly pale hue.



Bleaching is triggered by anomalies in water temperature that cause corals to expel the colorful algae living in their tissues. Without the algae's help in delivering nutrients to the corals, the corals cannot survive.



According to the International Coral Reef Initiative and data from the U.S. National Oceanic and Atmospheric Administration which track reef health, the world's fourth mass bleaching event, which scientists declared one year ago, has shown few signs of slowing down.



Instead, it has grown to be the most widespread on record, with 84% of reef areas - from the Indian Ocean to the Atlantic to the Pacific - subjected to intense heat stress for a duration expected to cause bleaching as of March 2025. Last year was the hottest on record and the first to reach over 1.5 degrees Celsius warmer than pre-industrial times, contributing to unprecedented ocean temperatures and triple the previous record number of marine heatwaves around the world.