The federal environment minister has been accused in court of failing to protect Australia's natural treasures from the full scope of possible climate harms caused by coal mining.
The Federal Court is hearing the case against Tanya Plibersek in Melbourne this week.
The Environment Council of Central Queensland is pursuing the minister after she refused its request to reconsider plans to expand two NSW coal mines, at Narrabri and Mount Pleasant.
The companies behind the projects - Whitehaven Coal subsidiary Narrabri Coal Operations, and MACH Energy - have joined the proceedings in support of the minister.
The mine expansions are yet to receive final approval, with the current court case considered a final hurdle.
Lawyers for the council say the minister gave two particularly questionable reasons for refusing to reconsider her climate risk assessments for the mine expansions.
The first was that it was "reasonable" for her to assume that if the expansions didn't go ahead, the market would increase supply elsewhere to meet demand for coal.
The second was that she wasn't satisfied there was likely to be a net increase in greenhouse gas emissions, or necessarily an impact on how World Heritage properties were affected by climate change.
As the court case opened on Monday, the council's barrister Emrys Nekvapil SC said the minister had failed to deploy the precautionary principle at the right stage during her climate risk assessment of the projects.
He said the minister was aware of advice from the International Energy Agency, laying out a feasible pathway to achieve net zero emissions and limit warming to 1.5C - the main ambition of the Paris climate pact signed by Australia.
"And that pathway has no new coal approvals," Mr Nekvapil told the court.
He said that in terms of the Great Barrier Reef, for example, there were "really possible futures under which the reef survives, and there are really possible futures under which it doesn't".
"Whether they happen or not would depend on total future emissions," he said, while noting MACH Energy's intention to expand its open-cut thermal coal mine at Mount Pleasant would result in production climbing to 21 megatonnes a year out to 2048.
The other project involved in the case is proposal by Whitehaven Coal subsidiary Narrabri Coal Operations to extend underground mining at the Narrabri thermal coal mine until 2044.
The case continues.
