In a paper published on Thursday in the journal Nature, researchers led by Terry Hughes from James Cook University argue a narrowing window remains to preserve what's left of the world's reefs that have already been altered significantly over the past three decades.

The urgency is driven in part by unprecedented bleaching from marine heatwaves that have triggered the death of about 50 per cent of the Great Barrier Reef's corals in the past two summers alone.

The impacts have come even though tropical waters have warmed by about 0.57 degrees between 1880 and 2015, well shy of the average global temperature increase of 0.88 degrees. Assuming nations fulfil their Paris climate summit pledges to keep warming to well below 2 degrees, reefs "will be able to secure a future," Professor Hughes said.

"There's really no time to lose and the further beyond those [Paris] targets we go, the worse it will be for reefs," he said.

"Biodiversity is not what needs to be preserved," Professor Hughes said. "It's the function of the reef and its capacity to continue to be useful to people, particularly those in poor, developing countries."

Efforts in Australia had focussed largely on local issues, such as culling coral-munching crown-of-thorns starfish and improving water quality of nearby rivers.

Such spending has to continue because "a dead coral can't survive climate change," Stephen Palumbi, director of Stanford University's Hopkins Marine Station, said.

Instead, management had to extend involvement to limit wider threats, such as from poverty limiting the opportunities of local communities, or coastal development and tourism, Professor Palumbi, one of the paper's authors, said.

"If you were pick an ecosystem on which human wellbeing pivots, coral reefs would be up there in the top three," he said, noting half a billion people depend on them.

Professor Palumbi, a geneticist, said scientists should redouble efforts to identify the genes of the most resilient corals to the heat and other stresses and ensure those reefs survive.

Professor Hughes, who is also director of the ARC Centre of Excellence for Coral Reef Studies, said scientists had tended to study the impacts of acidification and warming on corals separately. They had also typically assumed fossil fuel emissions would remain at business-at-usual levels.

Research should focus more on how those threats act in concert. Scientists should take a more optimistic view that societies won't permit temperature increases to hit the 4-6 degrees the higher emission scenarios imply.

At that level it "would certainly be the end of coral reefs but that wouldn't be too good for people either," Professor Hughes said.

Expectations are increasing that the Turnbull government will announce further action to address the recent mass die-off of corals.

"The federal government remains concerned about the impacts we are seeing to the Great Barrier Reef from global coral bleaching," Josh Frydenberg, Minister for the Environment and Energy," said.

"In light of recent reports of additional bleaching, now - more than ever - all parties must focus on protecting this iconic environmental asset for its intrinsic beauty and its wider value to the nation," he said, adding the Australian and Queensland governments are planning to spend more than $2 billion over the coming decade as part of the Reef 2050 Plan.

Joshua Cinner, another of the paper's authors and also at the ARC Centre, said it made little sense to subsidise new coal mines - such as the proposed Adani Carmichael in Queensland - and hope the reef will make it.

"If they're trying to promote the largest coal mine in the world, and then saying we're going to invest in killing starfish to offset that, it's inadequate," Professor Cinner said. "There needs to be some policy coherence."

"The majority of people oppose things like the Adani mine and an enormous number of people love the Great Barrier Reef," he said. "As a society, we're going to have to make a choice."