Why Are Coral Reefs Turning White? Oceans Never Saw A Mass Bleaching Event 'This Big Before', Report Says

Climate Change Impact: The world's coral reefs are experiencing the most widespread bleaching event ever recorded, with 77% of global coral reef areas affected, Reuters reports.

The mass bleaching of coral reefs around the world, which is said to have begun in February 2023, has become the most widespread ever recorded, according to the National Oceanic and Atmospheric Administration (NOAA). A staggering 77% of global coral reef areas have experienced bleaching-level heat stress, spanning the Atlantic, Pacific, and Indian oceans, as soaring ocean temperatures driven by climate change continue to escalate, a Reuters report said.

Satellite data has shown the current event has already surpassed the previous mass bleaching record, affecting over 11% more coral reefs, and doing so in nearly half the time. "This could potentially have serious ramifications for the ultimate response of these reefs to these bleaching events,” Derek Manzello, NOAA’s Coral Reef Watch coordinator, told Reuters. 

NOAA officially declared the global bleaching event in April 2024, marking the fourth such occurrence since 1998. The last major bleaching event, which took place between 2014 and 2017, impacted just under 66% of the world’s coral reefs, and at least 14% of the world's coral died as a result of the previous two global bleaching events.

What Is Coral Bleaching?

Coral bleaching occurs when rising ocean temperatures force corals to expel the symbiotic algae that provide them with their vibrant colours and nutrients. Without these algae, the corals turn pale and are highly vulnerable to disease and starvation. Though bleaching does not immediately kill corals, they can only recover if ocean temperatures drop, which may get increasingly unlikely given current climate trends.

NOAA, however, is not calling it the "worst" on record yet, despite the vast extent of the bleaching. According to the Reuters report, scientists are still conducting underwater assessments to measure the full impact on coral mortality, but it seems likely that this event could break records for damage as well. 

"It seems likely that it is going to be record-breaking in terms of impacts," Manzello was quoted as saying. "We’ve never had a coral bleaching event this big before," he said.

While the corals in the Thailand seas are bleaching at a fast pace, the phenomenon has been confirmed in regions such as Palau, Guam, and Israel in the last six weeks alone, and heat stress remains high in areas like the Caribbean and the South China Sea.

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COP16 Summit In Colombia To Discuss Heat Stress On Coral Reefs  

The situation has prompted urgent global discussions, with a special emergency session on coral reefs set to take place during the United Nations Convention on Biological Diversity (COP16) summit in Colombia starting on October 21. The session will focus on potential strategies to prevent the functional extinction of corals, including financial support and additional protections. “The meeting will bring together the global funding community to say we’re still in the fourth bleaching event, these are happening back to back... What are we going to do about it?” Emily Darling, head of the Wildlife Conservation Society’s coral reef conservation program, was quoted as saying in the Reuters report.

The ongoing bleaching has been exacerbated by the recent El Niño climate pattern, which raises ocean temperatures. With 2024 likely to be the hottest year on record, and concerns that the world may be entering a state of “chronic global bleaching”, there are fears that even a shift to the typically cooler La Niña pattern may not be enough to help corals recover. 

This record-breaking event signals alarming consequences not just for coral reefs but also for the ecosystems and economies that rely on them. Coral reefs contribute an estimated $2.7 trillion annually to global goods and services, through tourism, fisheries, and marine biodiversity. Scientists have long projected that the survival of coral reefs is at risk if global temperatures exceed 1.5°C of warming. With the latest bleaching occurring at just 1.3°C of warming, concerns are mounting that many of the world’s reefs may have already passed a point of no return.