Solid Energy also had licences in the area but was not currently pursuing open-cast mining there.
At the moment, the Denniston land is classed as 'stewardship' which gives it "very little protection".
Dr Backes said that although parts of the plateau had been mined in the past, that was by underground mining.
DOC had run an extensive mapping programme of the plateau and found it was home to four ecologically rare ecosystems.
"The West Coast Tai Poutini Conservation Board is not against mining per se, but it does think that areas like the Denniston Plateau with such high conservation values should be protected," she said.
Minerals West Coast general manager Peter O'Sullivan said the area had always been identified as State coal reserve.
The conservation values of the plateau were being thoroughly investigated through the current Environment Court process.
But Forest and Bird top of the south field officer Debs Martin welcomed the move by the conservation board, saying it was never too late "until something has been mined".
"It's fantastic the board recognised its values and it's asking the Conservation Authority."
- The Greymouth Star
