The Great Barrier Reef is Boiling Alive

How many coral reefs can you name? Meaning, the actual proper noun used to refer to it. You may be able to list plenty of countries and islands with good snorkeling and diving opportunities — the Bahamas, the Maldives, the Philippines, and so on — but it’s a decent guess that the median number of actual reefs we can all name is one: the Great Barrier Reef.

The GBR has been a UNESCO World Heritage site for more than 40 years. “The GBR is of superlative natural beauty above and below the water, and provides some of the most spectacular scenery on earth,” the agency says, calling it “a globally outstanding example of an ecosystem that has evolved over millennia.” It is home to around 400 species of coral, which in turn provide shelter and more for 4,000 species of mollusk, 1,500 species of fish, hundreds of birds, and thousands more of invertebrates of various sorts. It’s a fine place, and worth fighting for.

Unfortunately, that fight is an uphill battle. A study published on Wednesday in Nature found that the water in the Coral Sea around the GBR has been hotter at a few points in the past decade than at any point in the previous 400 years, encouraging mass bleaching events that are already getting harder and harder for coral to adapt to. The January to March warm periods for the Sea in 2024, 2017, and 2020 — in descending order — were the three hottest in at least those four centuries. Another three recent years — 2016, 2004, 2022 — came in just behind.

The authors, led by Benjamin Henley of the University of Wollongong in Australia, summed it up: “the existential threat to the GBR ecosystem from anthropogenic climate change is now realized.”

The GBR has faced a number of bleaching events in recent years as the waters surrounding it have warmed. In April of this year, scientists confirmed the arrival of the fourth-ever global bleaching event — though the second this decade — with hot oceans around the planet stressing corals to the point of collapse. In total, corals in at least 66 countries have been harmed in the ongoing event, though a June update suggests the pending arrival of La Niña and its overall cooling effect on the globe may be starting to ease that pressure.

But there will be another.

“In a rapidly warming world, the temperature conditions that give rise to mass coral bleaching events are likely to soon become commonplace,” the authors of the new study wrote. Some organisms can adapt to the changing water temperatures, but that likely needs a decades-to-centuries time frame, a luxury they no longer have. “Model projections also indicate that rates of coral adaptation are too slow to keep pace with global warming.”

This is bad news for the GBR in particular, given its enormous diversity and both ecological and cultural import. “Even with an ambitious long-term international mitigation goal, the ecological function of the GBR is likely to deteriorate further before it stabilizes,” the authors wrote. “Global warming of more than 1.5 °C above pre-industrial levels will probably be catastrophic for coral reefs.”