"Under the worst-case scenario, coral populations will collapse by 2100 and the re-establishment of coral reefs will be highly unlikely over the following 200-500 years," said the report entitled "Implications of Climate Change for Australia's Great Barrier Reef".

The Great Barrier Reef is the world's largest living reef formation stretching 2,000 km (1,300 miles) north to south along Australia's northeast coast.

"Only if global average temperature change is kept to below two degrees Celsius can the Reef have any chance of recovering from the predicted damage," the report said.

Coral has a narrow comfort zone and is highly stressed by a temperature rise of less than one degree Celsius.

Water temperature rises of less than one degree coincided with the world's worst recorded coral bleaching episode in 1988. With bleaching, the warmer water forces out the algae that give coral its colour and, if all are lost, the coral dies and the reef will crumble. In 1998, 16 percent of the world's coral died, with 46 percent of the Indian Ocean coral destroyed.

Scientists project water temperatures to rise this century by between two and six degrees Celsius.

"There is little to no evidence that corals can adapt fast enough to match even the lower projected temperature rise," said the Australian report.

It said that by 2050 the Great Barrier Reef would annually experience stress levels higher than those witnessed in 1998 and, by 2100, stress levels globally for coral would be several times higher than 1998.

"Coral cover will decrease to less than five percent on most reefs (in the Great Barrier Reef) by the middle of the century under even the most favourable assumptions," said the report.

"Reefs will not disappear but they will be devoid of coral and dominated by other less appealing species, such as seaweed."

The report said that over-fishing and pollution from coastal farms were also contributing to the destruction of coral on the Great Barrier Reef.

It estimated that destruction of the Reef's coral could end up costing the Australian economy A$8 billion (3.3 billion pounds) and more than 12,000 jobs by 2020.

The Great Barrier Reef supports huge fishing and tourism industries. Even under favourable conditions tourists would only be able to experience real corals in reef "theme parks", it said.