Great Barrier Reef at Risk of More Mass Bleaching

A sea turtle in the Great Barrier Reef.
A sea turtle among the corals at Lady Elliot Island in the Great Barrier Reef on Oct. 10, 2019. Jonas Gratzer / LightRocket via Getty Images

After record-high temperatures for the last four months of 2021, the Great Barrier Reef is at risk of another mass bleaching event. Experts are shocked and concerned by the unprecedented levels of heat stress on the corals.

From September through December 14, 2021, National Oceanic and Atmospheric Administration (NOAA) noted more heat stress over the corals than usual. During these months, the minimum temperatures in an area spanning over 80% of the reef system were higher than any maximum temperatures ever recorded.

“There’s never been heat stress like that in our records,” said William Skirving, senior scientist and oceanographer with NOAA’s Coral Reef Watch. “It’s completely out of character and speaks to the fact that the minimum temperatures were higher than the previous maximums. This is almost certainly a climate change signal. Being a scientist in this field in this day and age is sometimes a bit nightmarish. Sometimes I wish I knew a little bit less.”

By mid-December, ocean temperatures were 0.5°C higher than water temperatures immediately preceding previous bleaching events, which could be a warning of what’s to come for the reef this year. Researchers are monitoring the area closely, and not all is doomed yet. Extended cloud cover, rain, and wind over the next several weeks could lower temperatures, and mass bleaching may still be avoided.

Scientists anticipate coral bleaching events to become more frequent in a warming world, but the Great Barrier Reef has already experienced multiple mass bleaching events in 1998, 2002, 2016, 2017 and 2020. 

During a mass bleaching, temperatures cause algae, which provide food and vibrant color to coral, leave, and the coral reefs turn white. While they can recover from these events, the corals come back more vulnerable to diseases and with lower reproduction numbers.

Upcoming elections in Australia have prime minister hopefuls, including the incumbent Scott Morrison, pledging money toward reef conservation. The Morrison administration has pledged $1 billion over the next nine years if he wins re-election, but many critics argue that he has failed to make any significant progress to fight climate change during his time in office since 2018. Others welcome the needed funding for reef conservation, but note that the government needs to stop funding fossil fuel projects and make stronger emissions reduction targets immediately for a greater impact.

“Progress on reducing water pollution has fallen behind the government’s targets to protect the reef, so it’s vital that this investment is applied in a way that markedly improves water quality,” said Richard Leck, head of oceans at World Wildlife Fund Australia. “[But it] needs to be complemented by real action on climate to drive down emissions this decade.”

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