The Great Barrier Reef may be at a "terminal" point after being hit with unprecedented bleaching events in consecutive years, scientists warned Monday.
According to new aerial surveys conducted by the Australian Research Council's Centre of Excellence for Coral Reef Studies, two-thirds of the reef have now been affected, up from one-third last year. This year's mass bleaching occurred even in the absence of an El Niño event.
Professor Terry Hughes, who led the surveys, told the Guardian, "The significance of bleaching this year is that it's back to back, so there's been zero time for recovery."
"It's too early yet to tell what the full death toll will be from this year's bleaching, but clearly it will extend 500km (310 miles) south of last year's bleaching," he said.
Australia now faces a rapidly approaching deadline for saving the reef by addressing climate change, Hughes added.
"It takes at least a decade for a full recovery of even the fastest growing corals, so mass bleaching events 12 months apart offers zero prospect of recovery for reefs that were damaged in 2016," said Dr. James Kerry, who also took part in the surveys.
Bleaching occurs when overly warm ocean waters cause coral to get rid of its internal algae, which turns the coral white and erodes its structures. The loss of structure makes shorelines more vulnerable to extreme weather and destroys natural habitats for marine life.
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A groundbreaking study published last year found that climate change is the primary cause of coral reef degradation around the world.
Jon Brodie, a water quality expert, told the Guardian that the reef was now at a "terminal stage" and that many scientists have lost hope that it can be salvaged.
"We've given up. It's been my life managing water quality, we've failed," Brodie said. "Even though we've spent a lot of money, we've had no success."
Others remained hopeful that the reef had a future, but warned that time was of the essence.
"You've got to be optimistic, I think we have to be," said Jon Day, former director of the Great Barrier Reef Marine Park Authority. "But every moment we waste, and every dollar we waste, isn't helping the issue. We've been denying it for so long, and now we're starting to accept it. But we're spending insufficient amounts addressing the problem."
Hughes continued, "The sooner we take action on global greenhouse gas emissions and transition away from fossil fuels to renewables, the better."