The Great Barrier Reef, thought to have been in recovery after three mass coral bleaching events in quick succession, has been devastated for a fourth time in six years. The Marine Park Authority has confirmed a new mass bleaching event through aerial surveys of 750 separate reefs across the 1,400-mile-long stretch of corals, the New York Times reports. About 60% of corals were found with severe bleaching. Only two mass bleaching events were recorded prior to 2016—in 1998 and 2002. Subsequent bleaching in 2016, 2017, and 2020 followed record-breaking temperatures. But this episode is the first to occur during the La Niña weather phenomenon, when Australia's sea-surface temperatures are typically cooler than normal.
Sea-surface temperatures are currently less than 0.5 degrees Celsius above average throughout most of the reef. Earlier this month, however, the Marine Park Authority warned that water temperatures in some parts were as much as 4 degrees Celsius above average, the BBC reports. Similar trends were observed prior to other mass bleaching events, including in 2020. "We're in concerning times," Dr. Neal Cantin, a coral biologist who led a team of observers, tells the Times. "We're seeing that coral reefs can't cope with the current rate of warming and the frequency of climate change," he adds, noting this year's bleaching appears to cover a wider area than in 2016 and 2017. It's "truly heart-breaking," says the Australian Conservation Foundation.
Bleaching is a processed in which corals, stressed by environmental changes, push out the algae living within. But the coral itself remains alive, the Marine Park Authority says. "If conditions moderate, bleached corals can recover from this stress, as was the case in 2020." It adds "weather patterns over the next couple of weeks continue to remain critical in determining the overall extent and severity of coral bleaching across the marine park." UNESCO intends to label the site as in danger, arguing Australia's government isn't doing enough in terms of protection. Just this week, UN Secretary-General Antonio Guterres "used an address to a sustainability summit to take an extraordinary public swipe at Australia's climate efforts," per the Guardian. (Read more Great Barrier Reef stories.)