The world's largest coral reef is in serious danger.
A UNESCO World Heritage Site, Australia's Great Barrier Reef has lost more than half its coral in the last three decades, and scientists fear the loss caused by frequent bleaching will compromise its ability to recover.
Professor Terry Hughes - of Australia's James Cook University -- is the co author of a study that surveyed coral along the length of the reef from 1995 to 2017.
''The changes have really been quite shocking. The system today is quite degraded with a few exceptions. Coral cover has declined almost everywhere. The mix of species has changed. There are far fewer three dimensional corals that are important for providing habitat for all the rest of the biodiversity on the reef."
Hughes says that the root cause of the problem is global warming and says swift action needs to be taken on a global scale to reduce greenhouse gas emissions.
"You can argue that after five mass bleaching events, it has managed to absorb those impacts and respond to them - that's a pretty optimistic viewpoint. How many bleaching events can it take - we're not sure."
The Great Barrier Reef runs over 1,400 miles down Australia's northeast coast- spanning an area half the size of Texas.