Coral reefs pushed to brink as bleaching crisis worsens
4 Min Read
A record coral bleaching event has impacted over 84% of the world’s reefs, threatening marine life and coastal communities, driven by climate change.
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A man swims along coral reefs off Verde Island, Batangas province, Philippines on January 24, 2024 (AP)
A record-breaking coral bleaching event, driven by human-caused climate change, has now affected over 84% of the world’s coral reefs, sparking fears of widespread ecosystem collapse. The episode, which began in early 2023, has rapidly become the most intense and widespread bleaching event ever recorded, stretching across the Pacific, Atlantic, and Indian oceans.
Coral reefs are under immense stress due to warming ocean temperatures, caused by the burning of fossil fuels and the release of greenhouse gases, which have remained at historic highs over the past two years.
"The link between fossil fuel emissions and coral mortality is direct and undeniable," said Alex Sen Gupta, a climate scientist at the University of New South Wales in Australia.
The current bleaching is the fourth global event of its kind and the second to occur within a decade, surpassing the 2014–2017 event in scale.
“From 1 January 2023 to 20 April 2025, bleaching-level heat stress has impacted 83.7 percent of the world's coral reef area," the US National Oceanic and Atmospheric Administration (NOAA) said in its latest update on Monday.
Bleaching happens when corals expel the algae that live in their tissues, organisms that provide both color and nutrients. Without them, corals turn ghostly white and become far more vulnerable to disease and death. While reefs can recover, scientists warn that sustained high temperatures are reducing their chances of bouncing back.
In some parts of the world, the conditions are so extreme that they threaten the survival of nearly all coral species in affected areas.
Growing global threat
Conditions in some regions were extreme enough to "lead to multi-species or near complete mortality on a coral reef", said the NOAA.
Explore NOAA’s Coral Reef Watch tool to observe sea surface temperatures and predictions of coral bleaching around the world: https://t.co/RFMvhBi0B0 #CoralReefs @noaasatellites @CoralReefWatch pic.twitter.com/3mjKn6Y7gJ
— NOAA Coral Program (@NOAACoral) April 4, 2025
The situation has grown so dire that the NOAA had to extend its widely used bleaching alert scale by three additional levels.
“It's the coral reef equivalent of adding Category 6 and 7 to the tropical cyclone scale,” said Sen Gupta.
Melanie McField from the Healthy Reefs for Healthy People initiative, which monitors Caribbean reefs, noted that even resilient corals are now succumbing.
“If you continue to have heatwave after heatwave, it's hard to see how that recovery is going to happen,” the veteran reef scientist told Agence-France Presse (AFP) from Florida.
She described a particularly stark example in Honduras, saying, “By February 2024, all of that died, and it was down to five percent living coral... We never saw that before, these mass mortalities."
Since the 1950s, global live coral cover has halved due to the twin threats of climate change and local environmental degradation, according to the International Coral Reef Initiative.
These ecosystems are critical, not just for marine biodiversity, but also for the millions of people worldwide who depend on them for food, storm protection, and economic livelihood.
Scientists warn that if global warming reaches 1.5°C above pre-industrial levels, an internationally agreed-upon limit under the Paris Agreement, up to 90% of coral reefs could be lost. The planet has already warmed by at least 1.36°C, according to data from the EU's Copernicus climate monitor.
Projections suggest the 1.5°C threshold could be crossed as early as the next decade. At 2°C, nearly all coral reefs could vanish. If governments follow through on their current climate pledges, global temperatures could rise as much as 3.1°C by the end of the century, a level that would spell near-total devastation for reefs worldwide.
Mass coral bleaching was first recorded in the 1980s and has since become one of the clearest and most devastating consequences of rising ocean temperatures. What once were occasional events are now happening with increasing frequency and severity, and each new episode leaves less time for reefs to recover.
