Corals, one of the greatest natural wonders, face their biggest crisis to date

During the so-called ‘Third Global Coral Bleaching Event’, which occurred from 2014 to 2017, 15% of reefs around the world also experienced significant mortality, according to research by an international team led by researchers from STRI, James Cook University in Australia and former Coral Reef Watch director of the National Oceanic and Atmospheric Administration (NOAA) in the United States C. Mark Eakin.

This study combined satellite images of ocean water temperature from the Coral Reef Watch system with observations of reefs obtained through underwater and aerial surveys around the world to estimate the extent of coral bleaching during a global marine heat wave.

“It is the most geographically broad analysis of coral bleaching studies to date. Nearly 200 co-authors from 143 institutions in 41 countries and territories contributed data,” said Sean Connolly, senior scientist at the Smithsonian.

Eakin, former director of NOAA Coral Reef Watch and chief scientific advisor for the Netflix documentary Chasing Coral, said that “thermal stress levels were so extreme during this event, that Coral Reef Watch had to create new, higher bleaching alert levels that had not been necessary in previous events.”

“Our results show that the third global bleaching event was by far the most severe and widespread on record. However, the reefs are currently suffering a fourth, even more serious event, which began in early 2023,” Conelly said.

Scott Heron, from James Cook University, explained that “about half of the reefs affected by thermal stress at bleaching levels were exposed two or more times during the three-year event, often with devastating consequences. That included consecutive events on Australia’s Great Barrier Reef.”

“Since then, three more bleaching events have been recorded there. We are seeing that the reefs do not have time to recover properly before the next bleaching event occurs,” he added.

A coral is made up of a small animal related to jellyfish that secretes the hard structure and even smaller algae that convert sunlight into the energy that the animal needs to live, the STRI explained in its statement.

Bleaching occurs under thermal stress, when the association is broken, the energy source is lost and it turns white, causing reduced growth, reduced reproduction and even death when it is especially severe or prolonged.

In the last 30 years, the Earth has lost 50% of its corals because the oceans absorb most of the heat generated by burning fossil fuels. If the oceans did not absorb heat, the air temperature would be around 50°C (122°F). Data from around the world shows that the planet is now in the fourth global coral bleaching event, STRI said.

The global decline of coral reefs affects many of the services they provide, such as tourism and food supply.

“The benefits that coral reefs bring to society – including fishing, tourism, coastal protection, drug discovery and others – are estimated at about $9.8 trillion per year,” added the scientific entity.