The $900 million Ruataniwha water storage project is under scrutiny again today in the Court of Appeal.
Forest & Bird is appealing against a High Court ruling that approved a land swap between the Department of Conservation (DoC) and Hawke's Bay Regional Council to enable the dam to be built.
DoC is proposing exchanging 22 hectares of protected conservation land in Ruahine Forest Park for 170 hectares of farm land.
The protected land is home to several threatened species such as the New Zealand falcon and long-tailed bats.
Forest & Bird said the High Court was wrong to allow the land's specially protected status be revoked for a commercial development.
It said the land swap put into question the protection of nearly one-third of the public conservation estate.
Hawke's Bay Regional Council's investment company has dismissed the appeal as a delaying tactic.