Study: World on Precipice of Fourth Global Coral Bleaching Event

From 2014-2017, heat waves hammered oceans across the globe. They caused at least 80% of the world’s coral reefs to see at least moderate bleaching. Scientists labeled the widespread damage the “Third Global Coral Bleaching Event.” Now, a new study of over 15,000 reefs suggests we may be heading for a fourth major bleaching cycle. It could cause permanent damage.

Corals are tiny marine invertebrates. They live in complex structures. The structures are formed from calcium carbonate. Over time, they can build so many of these “skeletons” that it forms a "reef." It's a whole underwater habitat. Coral reefs provide shelter to thousands of other species. They also work as a buffer. They guard against ocean currents and storm surges that would batter coastlines. 

Normally, corals live symbiotically with algae. Algae is a type of underwater plant within the coral structures. They lend the corals their unique colors. They also provide a source of food. But when water temperatures rise, the algae are expelled. Corals turn white as a result. It's a process known as bleaching. Without the algae as a source of food, many corals don’t survive.  

In the new study, published this month in the journal Nature Communications, oceanographers used data from 2014-2017 to run AI-assisted models of what current heat patterns might do to coral reefs. More than 88% of the trials showed that, should current warming persist, reefs may suffer a Fourth Global Coral Bleaching event. 

The models show that the impacts of a warming ocean on coral reefs are speeding up, the report’s authors wrote. They added that they were nearly certain that continued ocean warming will cause widespread damage to reefs that likely cannot be reversed.

“Our findings demonstrate that the impacts of ocean warming on coral reefs are accelerating,” the report’s authors wrote.

Reflect: What is one natural place or environment you would miss most if it were gone or changed forever, and why does it matter to you?