By 2080, scientists believe coral bleaching is likely to start in spring, rather than summer, with a high risk of year-round bleaching for some reefs almost inevitable and this, is regardless of any action taken to mitigate climate change.
James Cook University's Professor Scott Heron was co-author of a study analysing when and where coral bleaching is likely to take place in the future.
Professor Heron said scientists are looking for the most likely places for coral to survive so environmental efforts could be concentrated there.
"Even with substantial mitigation of greenhouse gasses almost all of the world's coral reefs are likely to be exposed to more than three months of severe bleaching risk by 2080, with 20 per cent of these reefs being exposed to severe bleaching conditions for more than nine months of the year,'' he said.
"These numbers get even worse if we make little or no effort to curb climate change but that in itself should inspire us toward concerted efforts to reduce emissions."
Professor Heron said the most biodiverse rich coral regions, including the Great Barrier Reef, are the most vulnerable to heat stress and corals in these regions are least likely to benefit from efforts to mitigate climate change.
"There is much lower than average bleaching risk on the northern coasts of Venezuela and Colombia. Other less impacted areas include Socotra Island opposite the Gulf of Aden and Alor Kecil in Indonesia.
"There's variability in risk in the Coral Triangle, roughly from Indonesia to the Philippines to the Solomon Islands, but the future looks bleak for reefs in the Great Barrier Reef and Hawaii," said Professor Heron.
Lead author Dr Camille Mellin from the University of Adelaide said it's also expected longer exposure to heat stress in coming decades will weaken coral.
"By identifying Earth's reef regions that are at lowest risk of accelerated bleaching, our work will show where we can prioritise efforts to limit future loss of coral reef biodiversity.
"Interventions involving assisted evolution, coral translocation, or coral restoration should be maximised in coral refuges with lower risk of bleaching," said Dr Mellin.
