Australia's iconic Great Barrier Reef may be irreversibly damaged by climate change in just 16 years unless immediate action is taken, scientists have warned.

A new report by Selina Ward from University of Queensland highlights the potential ecological and economic damage to the reef from global warming.

"One of the most important functions of the reef is as a wave barrier. That protection will be lost. Without the reef, a lot of islands will be swamped," Ward said.

The reef has lost about half its coral coverage since the mid-1980s, with increased carbon dioxide concentrations contributing about 10 per cent alongside damage from other sources such as invasive species and farm nutrient run-off, Professor Ove Hoegh-Guldberg, a professor of marine science at the University of Queensland, said.

Climate change is fast taking over as the main threat to the world's reefs as warmer waters increase the frequency of coral bleaching, while acidifying oceans weaken or erode coral structures, 'The Sydney Morning Herald' reported.

By 2030, on present projections for the growth of carbon dioxide emissions, conditions will be "getting close to what we understand to be some of the limits in terms of rapidly calcifying reefs", Hoegh-Guldberg said.

The Great Barrier Reef may have shrunk to 10 per cent or less of its previous coverage by 2050 if the present trajectory continues, he said.

Bleaching is caused by corals becoming too warm and dying at a much greater rate than normal.

Also heat-stressed corals are now more likely to succumb to disease after a bleaching event because the role of bacteria is changing.

Ward referred to recent studies that have shown the erosion of the reef from acidification as more carbon dioxide is absorbed by the oceans is happening more rapidly than previously thought.

The reef's plight will be a focus of this year's Earth Hour, expected to be observed in 152 nations around the world.