Shade cloth could be a last resort to cool corals and slow bleaching that threatens the survival of the Great Barrier Reef, a marine biologist say.
Ove Hoegh-Guldberg of Queensland University in Brisbane warned that greenhouse gas emissions were creating global warming without parallel in 300 million years.
"The historically unprecedented threats to the marine environment posed by increasing atmospheric carbon dioxide will probably require the use of unconventional, non-passive methods to conserve marine ecosystems," he wrote in the journal Nature Climate Change.
About 900 coral formations make up the Barrier Reef, which stretches 2,600 kilometres down Australia's east coast. It draws 2 million visitors each year and underpins more than 30,000 jobs.
Hoegh-Goldberg proposed parasols to shade vulnerable coral formations and low-voltage direct current to stimulate regeneration and force the upwelling of cooler water from the ocean depths.
But he warned that "the magnitude and rapidity of these changes is likely to surpass the ability of numerous marine species to adapt and survive."
He said the pace of change - warming of at least 2 degrees Celsius and a 60-per-cent rise in surface ocean acidity over the past three centuries - meant it was not sensible to trust international efforts to keep the planet cool. He said it was time to consider mitigation measures as a last resort.
On a per-capita basis, Australia is the world's biggest generator of greenhouse gases, mostly because it relies on coal for power generation.
It has pledged a 5-per-cent reduction in 1990 emissions by 2020.
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