Coral reefs around the world experiencing mass bleaching, scientists say

Scientists warn that many of the world’s reefs may not recover from the intense, prolonged heat stress.

Along coastlines from Australia to Kenya to Mexico, many of the world’s colourful coral reefs have turned a ghostly white in what scientists say has amounted to the fourth global bleaching event in the last three decades.

At least 54 countries and territories have experienced mass bleaching along their reefs since February 2023 as climate change warms the ocean’s surface waters, the US National Oceanic Atmospheric Administration’s (NOAA) Coral Reef Watch, the world’s top coral reef monitoring body, said on Monday.

“From February 2023 to April 2024, significant coral bleaching has been documented in both the northern and southern hemispheres of each major ocean basin,” Derek Manzello, coordinator of Coral Reef Watch, told journalists.

Corals are invertebrates that live in colonies. Their calcium carbonate secretions form hard and protective scaffolding that serves as a home to many colorful species of single-celled algae.

Coral bleaching is triggered by water temperature anomalies that cause corals to expel the colourful algae living in their tissues. Without the algae’s help in delivering nutrients to the coral, the corals cannot survive.

“More than 54 percent of the reef areas in the global ocean are experiencing bleaching-level heat stress,” Manzello said.

Like this year’s bleaching event, the last three – in 1998, 2010 and 2014-2017 – also coincided with an El Nino climate pattern, which typically ushers in warmer sea temperatures.

Sea surface temperatures over the past year have smashed records that have been kept since 1979, as the effects of El Nino are compounded by climate change.

In turn, Australia’s Great