Australia has downgraded the outlook for Great Barrier Reef to 'very poor' for the first time.
In its latest five-yearly report on the health of the world's largest coral reef, the agency charged with managing the world heritage said the situation was becoming desperate.
The reef is facing a triple threat according to the report, with climate change, over-fishing and land clearing all leading to the downgrade.
The Great Barrier Reef Marine Park Authority said the health of the world's largest coral reef system, off the northeast coast of the Queensland state, had deteriorated since its last review, in 2014.
The latest findings, which have been compiled over five years, paint an alarming picture of mass coral bleaching and habitat loss because of both rising sea temperatures and heavy industry.
Queensland is home to some of Australia's largest mining operations, which the report says is affecting local water quality. Coastal land clearing for grazing by farmers is also being blamed for the death of coral in the region.
A global warning on global warming
In sounding the alarm, the marine park authority said immediate action was required to help save the reef.
"The significant and large-scale impacts from record-breaking sea surface temperatures have resulted in coral reef habitat transitioning from poor to very poor condition," the government agency said.
"Climate change is escalating and is the most significant threat to the Region's long-term outlook.
"Significant global action to address climate change is critical to slowing deterioration of the Reef's ecosystem and heritage values and supporting recovery."
Keeping a close watch
UNESCO's World Heritage Committee last year called for global action on climate change to protect five large coral reefs, including the Great Barrier Reef.
The committee is due to consider the reef's world heritage listing, considering its health and a possible "in danger" status.
"The Great Barrier Reef is one of the globe's most famous World Heritage Areas yet the report finds that its integrity is challenged and deteriorating," environmentalist group Australian Marine Conservation Society said in a statement.
"This is now the third Outlook Report. We've had ten years of warnings, ten years of rising greenhouse emissions and ten years watching the Reef heading for a catastrophe," said the group's director of strategy, Imogen Zethoven.
The Great Barrier Reef stretches more than 2,300 km and is home to 400 types of coral, 1,500 species of fish and 4,000 types of molluscs.