NOAA says fourth global coral bleaching event underway

April 15 (UPI) -- The world's oceans are now undergoing the fourth global coral bleaching event on record and the second in the last 10 years, the National Oceanic and Atmospheric Administration announced Monday.

NOAA's scientists have documented "extensive" bleaching-level heat stress on coral reefs across the Atlantic, Pacific and Indian Ocean basins during the past 14 months, leading to their assessment that a new global bleaching event is underway, the agency said in a release.

Mass bleaching has been confirmed in at least 53 countries, territories and local economies, the survey found.

The previous global bleaching event started in the North Pacific in the summer of 2014 and continued for a record three years, only dissipating in 2017.

"From February 2023 to April 2024, significant coral bleaching has been documented in both the Northern and Southern Hemispheres of each major ocean basin," said Derek Manzello, the coordinator of NOAA's Coral Reef Watch program.

NOAA Coral Reef Watch's global 5km-resolution satellite Coral Bleaching Alert Area Maximum map, for January 1, 2023 to April 10, 2024. This figure shows the regions, around the globe, that experienced high levels of marine heat stress (Bleaching Alert Levels 2-5) that can cause reef-wide coral bleaching and mortality. Image courtesy of the National Oceanic and Atmospheric Administration

The scientists make their assessments by monitoring sea surface temperature data from 1985 to the present using a blend of NOAA and partner satellites.

The agency has been able to confirm mass bleaching of coral reefs throughout the tropics since February 2023, including in Florida in the United States, the Caribbean, Brazil, the eastern Tropical Pacific including Mexico, Australia's Great Barrier Reef, large areas of the South Pacific and elsewhere.

NOAA's assessment came less than a week after the Australian government reported that more than 60% of individual coral reefs across the Great Barrier Reef have shown "prevalent bleaching" in the latest survey.

Scientists blame the phenomenon on the overall warming of the Earth's oceans, including last year's unprecedented marine heatwave in Florida, which environmentalists say lasted longer and was more severe than any previous event in that region.

"As the world's oceans continue to warm, coral bleaching is becoming more frequent and severe," Manzello said. "When these events are sufficiently severe or prolonged, they can cause coral mortality, which hurts the people who depend on the coral reefs for their livelihoods."

Generally, widespread coral bleaching does not necessarily mean corals will die, but does lead to impacts on local economies, livelihoods and food security, especially for indigenous populations, according to scientists.

Coral reefs protect coastlines from storms and erosion and provide jobs for local communities -- more than 500 million people worldwide depend on coral reefs for food, income and protection, NOAA says.