Half the Great Barrier Reef’s Coral has Died in the Past 25 Years

The Great Barrier Reef, the world's largest coral reef system, has lost more than half of its coral in the past 25 years. That’s according to a new report from the Australian Research Council’s Centre of Excellence for Coral Reef Studies, published this week, which found that mass bleaching events are irreversibly devastating small, medium and large coral populations along the 2,300 kilometre length of the reef.

Andreas Dietzel, lead author of the report, blames human-induced climate change.

“Coral colony abundances on reef crests and slopes have declined sharply across all colony size classes and in all coral taxa compared to historical baselines,” the report states. “Declines were particularly pronounced in the northern and central regions of the Great Barrier Reef, following mass coral bleaching in 2016 and 2017.”

The impact of bleaching events in 2020 still haven’t been accounted for, Dietzel added—meaning the destruction of the reef, which is situated just off Australia’s northeastern coast, could be even more catastrophic than current evidence indicates.

"We can clearly correlate the rising temperatures to coral mortality and bleaching on the Great Barrier Reef,” he told the ABC. “We've had large-scale bleaching events in 1998 and 2002, but they were absolutely dwarfed by the more recent ones in 2016 and 2017. The decline occurred in both shallow and deeper water, and across virtually all species."

Larger species are the worst affected, according to researchers, who found that they had disappeared almost entirely from the far northern outskirts of the reef. Terry Hughes, a co-author of the report and a professor at Queensland’s James Cook University, told the AFP news agency that large corals were “typically depleted by 80 or 90 percent compared to 25 years ago.”

“They make the nooks and crannies that fish and other creatures depend on,” he said, “so losing big three-dimensional corals changes the broader ecosystem.”

Meanwhile, the Australian government continues to commit to environmentally destructive energy policies and projects, and the construction of the Adani Carmichael coal mine—which is slated to produce 60 million tonnes of coal a year, and requires the dredging of over a million cubic metres of the Reef’s seafloor to give passage to coal ships—is underway.

In response to this week’s report, a spokesperson for Australia’s Federal Department of Environment said that “the findings reinforce the Australian Government's commitment to global action on climate change through the Paris Agreement and through new energy technologies.”

And yet Prime Minister Scott Morrison recently refused to commit to a target of net zero carbon emissions by 2050—a decision that puts Australia out of step with more than 70 other countries that have adopted the target—while stubbornly pursuing a “gas-led” economic recovery and investing in coal seam gas wells and power stations, projects that experts have denounced as “dinosaur” technologies.

Dietzel lamented the country’s reckless inaction around climate change, and the seeming ambivalence among politicians towards the ongoing destruction of the UNESCO World Heritage site.

"It's very frustrating to see that there's not much done," he said. "In many cases it's even denied that it happens at all."

Follow Gavin on Twitter