Just 2% of the Great Barrier Reef has escaped bleaching over the past three decades, a daunting new report reveals. 

A study on the impact of multiple climate extremes by Australia’s James Cook University says global warming is behind the events that led almost 100% of the 2,300-kilometre region, comprising 3,000 individual reefs and considered one of the seven wonders of the natural world, to have been bleached since 1998. 

Lead author Terry Hughes says 80% of the reef has been “severely” bleached since 2016.

"We no longer have the luxury of studying individual climate-related events that were once unprecedented or very rare,” Hughes said in a media release. “​​Instead, as the world gets hotter, we have to understand the effects of sequences of rapid-fire catastrophes, as well as their combined impacts.”

Bleaching occurs when corals are stressed and can be triggered when the water is too warm. During these events, corals expel the heat-sensitive algae living in their tissues in an effort to protect themselves and leave space for algae that can endure greater temperatures. 

The process leaves the corals vulnerable and, in extreme cases, can cause it to die.

The study, however, does uncover some good news, with some sections of the reef seemingly growing in resilience. 

"To our surprise, we found the threshold for bleaching was much higher on reefs that had experienced an earlier episode of heat stress,” coral reef specialist and study co-author Mark Eakin said. “Consequently, the most vulnerable reefs each year were the naïve ones that had not bleached recently.”

Up to half a billion people worldwide rely upon coral reefs for their protection, income and food. One estimate by the United States Environmental Protection Agency suggests the world’s coral reefs contribute almost US$30 billion per year to global economies. 

The Great Barrier Reef specifically supports 64,000 Australian jobs.

While Australia has just committed to achieving net zero greenhouse gas emissions by 2050, the nation hasn’t updated or tightened its emissions reduction targets for the next decade, which is critical if the world is to limit warming to under 1.5 degrees Celsius. 

On Wednesday, the Climate Change Performance Index ranked Australia last, with a score of zero, in a list of 60 countries for policy response to the climate crisis.

Australia did, however, pledge $500 million for reef protection in 2018, the nation’s largest single injection for reef security. 

Still, Hughes says it’s not enough.

“Ironically, the publication of our study coincides with the COP26 meeting in Glasgow,” he said. “A drastic cut in greenhouse gas emissions by all countries is vital for the future of coral reefs and for the hundreds of millions of people who depend on them.”

In July, Australia blocked a campaign by the World Heritage Committee to categorise the reef as an “in danger” site.


Defend the Planet

Just 2% of the Great Barrier Reef Has Escaped Coral Bleaching Since 1998

By Madeleine Keck