Oceans
Water changes in the oceans

Half of the Great Barrier Reef Has Died Since 2016

Burgess COMMENTARY

Peter Burgess

Half of the Great Barrier Reef Has Died Since 2016

Scientists have known that Australia's iconic Great Barrier Reef is in trouble, but they are just starting to realize the extent of the damage that's been brought on by climate change.

The reef is one of the largest living structures on earth, stretching 1,400 miles, but despite being so massive it can be seen from space, it's still incredibly fragile. Scientists who have been studying the reef have been raising concerns about its future, but now a new study has shed even more light on the damage that's been brought about by climate change.

Scientists studied satellite maps and examined individual species of coral, and found the reef has been forever altered. The changes they documented are the result of a massive coral bleaching event, brought on by higher ocean temperatures.

According to their work, which was just published in the journal Nature, an extreme heat wave in 2016 caused a catastrophic die-off that killed more than half of the corals in the northern third of the reef, but that wasn't even the extent of the damage. They also found that 30 percent of the coral across the entire reef had been lost.

Coral has a symbiotic relationship with tiny algae, known as zooxanthellae, that provide it with food and give it its color. When coral is stressed because of high ocean temperatures, or other causes like pollution and acidification, it expels the algae living in its tissues, which exposes its white skeleton, leaving corals to starve.

Corals may recover over time if stressors are reduced, but if they continue the coral will die. Unfortunately, a second marine heat wave hit in 2017, causing another damaging bleaching event that led to the death of another 20 percent of corals.

In all, about half of the corals in the reef have been wiped out in just two years. Some of the corals didn't even live long enough to starve, they just died almost immediately from heat stress.

Even if some corals recover, it will take years and the ecosystem won't resemble what it once was. If there's any good news here, it's that some species are a bit tougher than others, and have survived in the damaged areas affected by heat, but scientists believe the reef has been forever altered.

'The coral die-off has caused radical changes in the mix of coral species on hundreds of individual reefs, where mature and diverse reef communities are being transformed into more degraded systems, with just a few tough species remaining,' said the study's co-author Professor Andrew Baird, of the Australian Research Council Centre of Excellence for Coral Reef Studies (Coral CoE) at James Cook University in Queensland.

Losing a coral reef ecosystem like the Great Barrier Reef wouldn't just be a tragedy in and of itself, it would be devastating blow to biodiversity. The reef provides a home for thousands of species, and it draws millions of people every year who want the opportunity to experience it in person.

Sadly, bleaching events are becoming more common, putting the Great Barrier Reef, and other reef ecosystems, at risk. While the Great Barrier Reef may be different in the future, scientists believe there's still time to save what's left with quick action on our part to limit carbon emissions.
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ALICIA GRAEF Alicia Graef is a lifelong animal lover with a BS in animal and veterinary science and years of experience working and playing in the equine industry.