The declaration has already drawn dozens of signatories among tourist businesses and adds to local calls for climate action from local government such as Douglas Shire council.

Imogen Zethoven, the society's reef campaign director, said the tourism industry had been "in a state of shock" after the first bout of mass coral bleaching in 2016, and had resisted discussing climate change.

But a second bout in 2017 brought a recognition that a warming planet "is an existential threat to the reef and the tourism industry", Ms Zethoven said.

'Overdue'

Tony Fontes, a dive operator based in the Whitsundays since the 1980s, called AMPTO's shift "a huge step".

"It's overdue but it is happening," Mr Fontes said. "Basically we need a mass campaign" to protect the reef.

How far the tourist industry push dovetails with the anti-Adani campaign remains to be seen.

Bob Manning, Cairns Regional Council mayor, doubts opposition to the Indian miner's proposed giant Carmichael mine in the Galilee Basin "gets us anywhere".

Still, "Adani has done us no favour overseas", Mr Manning said. "It’s hard for us to say we are responsibly managing the reef...but at the same time we’re letting those coal ships through."

A spokeswoman for Adani said the company remains "100 per cent committed to the Carmichael project and are confident of securing finance".

"Strict safety and environmental standards already governing shipping along the Queensland coast will ensure there is no impact to the Great Barrier Reef,” she said.

'Global issue'

Ian Macfarlane, chief executive of the Queensland Resources Council, said coal from the basin "is high energy, lower emission coal when compared with lower quality, higher emission coals sourced from Indonesia and India".

"The addressing of climate change is a global issue and requires all countries to be involved in lowering emissions," he said.

Mark Read, acting director of field management at the Great Barrier Reef Marine Park Authority, said the tourism industry's new stance comes even as visitor numbers rebound to record levels.

“These are the people who spend their lives taking people out, [who have] lived and breathed and tried to make a living through these tough times," Dr Read said.

Still, the authority is not in a position to discuss curbs on Australian coal, such as the Adani mine.

Climate change “is the thing that the global community most desperately needs to tackle if we’re going to...give the reef a real possible chance for a long-term future,” Dr Read said.

The author travelled to the Great Barrier Reef courtesy of the Climate Council.