This article was written by Reuters and was published in the Globe & Mail on April 16, 2024.
Along coastlines from Australia to Kenya to Mexico, many of the world’s colourful coral reefs have turned a ghostly white in what scientists said on Monday amounted to the fourth global bleaching event in the past three decades. At least 54 countries and territories have experienced mass bleaching among their reefs since February, 2023, as climate change warms the ocean’s surface waters, according to the U.S. National Oceanic and Atmospheric Administration’s (NOAA) Coral Reef Watch, the world’s top coral reef monitoring body.
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 corals, the corals cannot survive.
“More than 54 per cent of the reef areas in the global ocean are experiencing bleaching-level heat stress,” Coral Reef Watch co-ordinator Derek Manzello said.
Announcement of the latest global bleaching event was made jointly by NOAA and the International Coral Reef Initiative, a global intergovernmental conservation partnership. For an event to be deemed global, significant bleaching must occur in all three ocean basins – the Atlantic, Pacific and Indian – within a 365-day period. 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.
Scientists have expressed concern that many of the world’s reefs will not recover from the intense, prolonged heat stress.