Nearly two-thirds of the world’s coral reefs have experienced severe bleaching due to heat stress over the past year. Reports by the NOAA suggest that world’s 60% coral reefs may have bleached last year.

The U.S. National Oceanic and Atmospheric Administration (NOAA) has been closely monitoring the health of coral reefs globally. The combination of climate change and an El Nino climate pattern has driven ocean temperatures to unprecedented levels. This has further led to widespread coral bleaching.

NOAA’s recent data reveals that approximately 60.5% of the world’s reef areas have been affected. Moreover, this number is continuing to rise. “I am very worried about the state of the world’s coral reefs,” said Derek Manzello, NOAA’s Coral Reef Watch coordinator, in a monthly briefing.

“We are seeing ocean temperatures play out right now that are very extreme in nature,” Manzello said.

Coral bleaching occurs when corals, stressed by high temperatures, expel the algae that live within their tissues. These algae are crucial for the corals’ color and energy. Without them, corals turn pale and become susceptible to starvation and disease.

The current mass bleaching event, the fourth on record, has been documented in at least 62 countries and territories. Nations like India and Sri Lanka have reported significant impacts. This event surpasses previous ones in terms of affected areas.

The last global bleaching event from 2014 to 2017 affected 56.1% of reef areas. On the other hand, earlier events in 1998 and 2010 impacted 20% and 35% of reefs, respectively.

Despite the wider reach of the current event, the 2014-17 bleaching remains the most severe and persistent. However, Manzello warned that the 2023-24 event could soon exceed it. “The Atlantic Ocean has been off the charts,” he stated. He noted that 99.7% of the Atlantic’s coral reefs experienced bleaching-level heat stress over the past year.

Coral reefs in the Atlantic Ocean have been particularly hard hit. An assessment published in April 2024 reported between 50% and 93% coral mortality in Huatulco, Oaxaca, in the Mexican Pacific.

The situation is expected to deteriorate further this summer as heat stress accumulates in the Southern Caribbean. In some areas, the heat stress threshold for bleaching has already been surpassed unusually early in the year.

“This is alarming because this has never happened so early in the year before,” Manzello said. Scientists predict additional bleaching in the Southern Caribbean, around Florida, and at the Mesoamerican Barrier Reef—the world’s second-largest reef—this summer.

Although the El Nino event is dissipating, ocean temperatures remain abnormally high. “It won’t take much additional warming to push temperatures past the bleaching threshold,” Manzello warned.

This extensive coral bleaching highlights the urgent need for global efforts to address climate change. Coral reefs are vital ecosystems, supporting marine biodiversity and protecting coastlines. The loss of these reefs would have severe ecological and economic consequences.

NOAA’s report that the world’s 60% coral reefs may have bleached is concerning. It underscores the critical state of the world’s coral reefs and the ongoing threats they face from rising ocean temperatures. Immediate and sustained action is essential to mitigate these impacts and preserve these crucial marine habitats for future generations.

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