Little Evidence That Global Warming Is Causing Extinction of Coral Reefs

Coral reefs, like polar bears, have become a poster child for global warming. According to the climate change narrative, both are in imminent peril of becoming extinct.

But just as polar bears are thriving despite the loss of sea ice in the Arctic, coral reefs are in good health overall despite rising temperatures. Recent research shows that not only are corals capable of much more rapid recovery from bleaching events than most reef scientists thought, but they are a lot more abundant around the globe than anyone knew.

During the massive, prolonged El Niño of 2014-17, higher temperatures caused mass bleaching of coral reefs all across the Pacific Ocean, including the famous Great Barrier Reef that hugs the northeastern coast of Australia. Corals lose their vibrant colors when the water gets too hot, because heat causes the microscopic food-producing algae that normally live inside them to poison the coral – so the coral kicks them out. However, corals have the ability to select from the surrounding water a different species of algae better suited to hot conditions, and thus to survive.

Until recently, it was believed that the recovery process, if it occurred at all, took years. But new studies (see here and here) have found that both the Great Barrier Reef and coral colonies on reefs around Christmas Island in the Pacific were able to recover from the 2014-17 El Niño much more rapidly, even while seawater temperatures were still higher than normal. The authors of the studies attribute the corals’ recovery capacity to lack of exposure to other stressors such as the crown-of-thorns starfish and water pollution from farming runoff.

That corals worldwide are not on the verge of extinction was first revealed in a 2021 study by four researchers at Australia’s James Cook University (JCU). The study completely contradicted previous apocalyptic predictions of the imminent demise of coral reefs, predictions that included an earlier warning from three of the same authors and others of ongoing coral degradation from global warming.

The JCU study included data on more than 900 coral reefs across the Pacific, from Indonesia to French Polynesia, as shown in the figure below. To estimate abundances, the researchers used a combination of coral reef habitat maps and counts of coral colonies. They estimated the total number of corals in the Pacific at approximately half a trillion, similar to the number of trees in the Amazon or birds in the world. This colossal population is for a mere 300 species, a small fraction of the 1,619 coral species estimated to exist worldwide by the International Union for Conservation of Nature (IUCN).

Reinforcing the JCU finding is a very recent discovery made by Scuba divers working with the UN Educational, Scientific and Cultural Organization (UNESCO). The divers mapped out a massive reef of giant rose-shaped corals in pristine condition off the coast of Tahiti, the largest island in French Polynesia. The stunning reef, described as “a work of art” by the diving expedition leader, is remarkable for its size and its survival of a mass bleaching event in 2019.

Approximately 3 kilometers (2 miles) long and 30 to 65 meters (100 to 210 feet) across, the reef lies between 30 and 55 meters (100 and 180 feet) below the surface, about 2 kilometers (1 mile) off shore. The giant corals measure more than 2 meters (6.5 feet) in diameter, according to UNESCO. Studying a reef at such great depths for Scuba divers required special technology, such as the use of air containing helium, which negates hallucinations caused by oxygen and nitrogen at depth and helps prevent decompression sickness.

CREDIT: Alexis Rosenfeld/Associated Press

The existence of this and likely many other deep coral reefs, together with the JCU study, mean that the global extinction risk of most coral species is much lower than previously thought, even though a local loss can be ecologically devastating to coral reefs in the vicinity.

The newly discovered rapid recovery of corals probably helped save the Great Barrier Reef from being added to a list of World Heritage Sites that are “in danger.” This classification had been recommended in 2021 by a UNESCO committee, to counter the supposed deleterious effects of climate change.

But, after intensive lobbying by an angry Australian government keen to avoid a politically embarrassing classification for a popular tourist attraction, the committee members agreed to an amendment. The amended recommendation required Australia to produce an updated report on the state of the reef by this month, when a vote could follow on whether or not to classify the site as being in danger.

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