Overfishing and pollution pose significant threats to coral reef habitats, but these dangers pale in comparison to rising ocean temperatures.
The research institutions associated with the National Coral Bleaching Taskforce are: ARC Centre of Excellence for Coral Reef Studies, Australian Institute of Marine Science, CSIRO, Great Barrier Reef Marine Park Authority, James Cook University, NOAA, University of Queensland, University of Sydney, University of Western Australia, WA Department of Parks and Wildlife. That was the worst die-off of coral ever recorded at the reef.
Hughes said scientists had found no evidence that past exposure to bleaching toughened the corals. If ocean temperatures cool off the next few weeks (Austral autumn), the damage might not be as bad as past year.
Professor Hughes said he hoped the die-off this time would not be as serious as last year's, but "back-to-back bleaching is unheard-of in Australia". Researchers suspect that the fourth one is already underway. This time a year ago, for example, the surprising discovery of a new, large coral reef in the murky waters of the Amazon was immediately tempered with the realisation that it's under threat.
In general, unbleached reefs were located towards the southern end of the reef where waters are cooler.
The UN says it is the "most biodiverse" of all the World Heritage sites, and of "enormous scientific and intrinsic importance". But when the water warms by as little as a couple degrees Fahrenheit, algae spits out chemicals poisonous to the coral. But they are incredibly sensitive to excess heat. Their preservation holds humanitarian interest, too, as hundreds of millions of people depend on reef fish for protein, The New York Times reports.
Warm seas around the reef killed some two-thirds of a 700 kilometre (496.4 miles) stretch of coral past year after warm water caused the coral to expel living algae, triggering it to calcify and turn white, a process known as bleaching. The hotter the waters and the longer they're around, the greater the stresses and the more likely the corals are to succumb to them. Scientists from the Arc Centre of Excellence, who published their findings in Nature on March 16, said the alarming results signalled climate change can no longer be thought of as isolated events, but a crisis which threatens all coral reefs globally.
The study explains that the Great Barrier Reef can not be brought back to its state prior to the 2016 bleaching.
When temperatures pass a threshold, the coral expels its symbiotic algal partner, leaving underwater wastelands of white-washed reefs. The loss of coral reefs could disturb our food supply and lead to a humanitarian crisis.
Scientist Andrew Baird survey healthy reefs between Mackay and Townsville on Australia's Great Barrier Reef in October 2016.
INSKEEP: That's what Mia Hoogenboom saw while exploring the Great Barrier Reef. The ocean absorbs about 93 percent of the Earth's increasing heat.