The Great Barrier Reef is experiencing back-to-back mass coral bleaching for the first time, according to the Australian Government's Great Barrier Reef Marine Park Authority.
This is the first time the reef hasn't had a few years to recover between bleaching, researchers told USA Today.
Researchers from the Great Barrier Reef Marine Park Authority and the Australian Institute of Marine Science spent six hours last week flying over the reef between Townsville and Cairns.
“Importantly, not all bleached coral will die," said Wachenfeld, the director of reef recovery with the Marine Park Authority. "As we saw last year bleaching and mortality can be highly variable across the 344,000 square kilometer Marine Park an area bigger than Italy.”
The Great Barrier Reef was hit by massive bleaching events in 1998, 2002, 2016 and 2017, with last year's event being the worst on record. It killed an estimated 22 percent of all coral, according to a statement from the World Wildlife Fund.
What is coral bleaching?
Warmer waters, caused by climate change, can lead to bleaching.
"When water is too warm, corals will expel the algae living in their tissues, causing the coral to turn completely white," the National Oceanic and Atmospheric Administration (NOAA) explains on its website.
Corals can survive bleaching, but it does put them under more stress.
“Many coral species appear to be more susceptible to bleaching after more than 12 months of sustained above-average ocean temperatures," said Dr. Neal Cantin from the Australian Institute of Marine Science.
The World Wildlife Fund said in a statement that all nations need to focus on bringing down carbon emissions and scaling-up efforts to reduce the local pressure on reefs. Richard Leck of the WWF added that without sufficient emissions reductions annual mass bleaching may happen by 2050.