Environmentalists have applauded a move by Rio Tinto and Alcoa to hand back 40-year-old mining rights to the Mitchell Plateau in the Kimberley as part of a proposal by the Western Australian government to create the country’s largest national park.
The West Australian premier, Colin Barnett, announced legislation on Tuesday that would wind back the 1971 agreement and allow the 175,000 hectare reserve to be included in the footprint of the proposed 2m hectare Kimberley national park.
The new national park was announced before the 2013 state election and has bipartisan support. It would form part of a 5m-hectare network of national and marine parks in the state’s north-west, as part of an $81m conservation strategy.
“The Mitchell Plateau and the Mitchell Falls are spectacular and unique landscapes in Australia and will be the jewels in the crown of the new Kimberley national park,” Barnett said. “I am delighted that thanks to this agreement, this extraordinary landscape will now be conserved.”
The legislation, to be introduced in parliament this week, will protect land covered under 14 mining leases and prevent any new exploration licences or mining tenements being granted in or adjacent to the proposed national park.
The Wilderness Society has waged a decades-long campaign against mining on the Mitchell Plateau. WA campaigner Peter Robertson said terminating the mining agreement was “great news” and necessary for the proper development of the national park, which he said would have had a negligible conservation benefit without the inclusion of the Mitchell Plateau site.
“The rest of the areas are really just converting existing conservation areas into a national park, there’s no real impact in conservation at all,” Robertson said. “It was clear from the outset that it had to include the Mitchell Plateau.”
Robertson said the plateau was one of only a few areas in Australia that managed to retain its full complement of animal species after colonisation.
“It has got rare and endemic plant species and rare and endemic animal species that are not found anywhere else in the world,” Robertson said. “And visually it’s incredibly beautiful. It’s certainly special and should have been protected a long time ago.”
Among the species endemic to the plateau are the scaly-tailed possum, Kimberley rock rat and Livistona palms.
There are more than 500m tonnes of untapped bauxite reserves on the Mitchell Plateau, according to Geoscience Australia
The mining rights were secured in 1971 under the Alumina Refinery (Mitchell Plateau) Agreement Act, which gave what was then the Amax Bauxite Corporation rights to mine bauxite on the plateau alongside an alumina refinery, estimated at the time to cost $100m.
But despite successive governments extending the agreement, it never moved past the exploration stage.
Rio Tinto is the lead joint venture partner in the project. In a statement released on Tuesday, the chief executive, Sam Walsh, said the decision to hand back the plateau was made on conservation grounds, but admitted the project was a difficult economic proposition.
“While the Mitchell Plateau bauxite resource is likely to hold value in the future, the State Agreement Act required the development of an alumina refinery which has always proven to be economically challenging,” Walsh said.
“All of us at Rio Tinto are very proud to be able to encourage the government’s ambition to establish a new national park in the Kimberley region, with this significant addition to the conservation area.”
Formalising the newly protected area into a national park will take significant discussion with the three groups of native title holders on the Mitchell Plateau, the Wunambal-Gaambera, Dambimangari and Wilinggin.
They were granted exclusive possession native title rights – the strongest property right available under native title – to 25,909 square kilometres on the plateau in a joint determination in 2011.
Traditional owners in the area opposed mining but some are concerned at giving up exclusive possession rights for a national park to be established.
The Wunambal-Gaambera Aboriginal Corporation already manages the 26,000-hectaure Uunguu Indigenous Protected Area which was handed back by the federal government in 2011.
The bulk of the area released under the Mitchell Plateau deal is Wunambal-Gaambera land. The corporation told Guardian Australia it was not yet making public comment.
The WA environment minister, Albert Jacob, said the government would work with traditional owners to jointly manage the national park.
“This is also generating employment opportunities for Aboriginal communities and supporting environmentally sensitive nature-based tourism,” Jacob said.