If consent was granted the special features of the plateau may be lost for little economic benefit, because it depended on fluctuating commodity prices, he told the court.
The Escarpment mine would destroy 188ha or 11 per cent of the ecosystem, he claimed.
"The economic benefits will be a small fraction of those that were so pivotal to the Commissioner's decision to grant consent. This contribution to economic wellbeing is relatively modest and insufficient to outweigh the adverse effects."
Forest & Bird would produce 40 expert witnesses and thousands of pages of evidence.
Its economic experts, Geoff Butcher and Peter Clough estimated the total wage bill would be up to $40 million or $6m per year. Other benefits would include tax and dividends to shareholders. But these were uncertain and depended on the amount of coal mined, the cost of extraction, the exchange rate, and the price of coal.
Mr Anderson downplayed Bathurst's promise of pest control and said the area was relatively pest-free.
Furthermore it was impossible to rehabilitate the area post-mining to its original state, Mr Anderson said.
The plateau was largely sandstone which mining operations would break up leading to the risk of acid drainage, he said.
At the beginning of the Environment Court hearing this morning, Bathurst counsel, Jo Appleyard, opened the case for Perth-based Bathurst Resources which owns the planned open-cast Escarpment project.
Ms Appleyard told the court how mining had already been carried out on 20 per cent of the Denniston area since the 1870s and it was romantic to suggest otherwise.
The proposed new mine would use best practice to rehabilitate the area and also mitigate effects with pest control.
Expert witnesses to be called by listed Bathurst Resources would outline why conditions will mitigate effects of an open-cast mine on the Denniston Plateau.
Ecology, planning and policy experts, including West Coast district council staff, would give their reasons why they believed various conditions would be sufficient to allay fears about environmental depredation.
The hearing will take place over the next six weeks with a two week break.