A new study has revealed the extent of damage to the world's largest living organism. Australian scientists say an underwater heatwave has had a devastating effect on the Great Barrier Reef. Greg Navarro has more from Sydney.

GREG NAVARRO SYDNEY "The report's authors say all of this really highlights the impact of global warming - and that the Great Barrier Reef is a great indicator because of its sensitivity to the environment around it. They focused on the 2016 coral bleaching event - caused by the warming of the ocean's waters. This bleaching essentially robs coral of the ability to protect itself. Scientists say the underwater heatwave that bleached roughly a third of the Great Barrier Reef was so severe, it instantly cooked some corals in the northern section of the reef. They also say back-to-back bleaching events in 2016 and 2017 have changed the ecology of the reef, and destroyed key habitats for other marine life. Researchers say the study shows that roughly 30 percent of the reef now meets the criteria for a threatened ecosystem, and that coral bleaching events are becoming more common. It's also important to note that the Great Barrier Reef is a vital economic driver here in Australia, helping to generate more than $6 billion Australian dollars - just under 4.7 billion US dollars - a year. Greg Navarro, CGTN, Sydney."