What Alcoa's looming alumina monopoly could mean for WA's jarrah forests

Alcoa's multi-billion-dollar deal to buy South32's alumina operations could unlock swathes of Western Australia's native jarrah forests for bauxite mining, environmentalists say.

The landmark $8.1 billion transaction, which remains subject to shareholder and regulatory approval, would put all of WA's bauxite and alumina supply chain under one company, making Alcoa the world's largest bauxite miner.

Botanist Kingsley Dixon said Alcoa's acquisition of South32's Worsley Alumina refinery, located about 175 kilometres south of Perth near Collie, could be key to accessing untapped ore deposits at the southern end of the northern jarrah forest.

"I'm suspicious this means a major impact for parts of the southern flank of the jarrah forest that were previously out of reach of the current refining capacity of Alcoa,"

Professor Dixon said.

Alcoa's current mining lease covers 7,022 square kilometres from near Chidlow to Perth's east, down to Collie in the South West region.

Its current footprint and expansion aspirations have been confined to the centre of its vast mineral lease at the Huntly and Willowdale mines, close to its Pinjarra and Wagerup refineries.

When asked whether the deal would see it ramping up activity in the south, Alcoa told the ABC all mining activity was subject to relevant regulatory approvals.

"We are confident this transaction will help make Australia's bauxite-to-aluminium value chain more competitive, more resilient, and better positioned to continue supporting local jobs, businesses, and regional communities," a spokesperson said.

Acquisition a 'master play'

With the addition of South32's 2,700 square kilometre lease on the eastern side of the forest, Alcoa would have exclusive rights to explore and extract minerals across about 10,000 square kilometres.

More than 80 per cent of that is high-quality, biodiverse forest, according to Professor Dixon.

The Pennsylvania-based company has already faced intense scrutiny, having cleared about 28,000 hectares of the world's only jarrah forests in WA as part of its existing operations.

In February, Alcoa was fined a record $55 million for illegally clearing areas of native forest.

Professor Dixon said moves to mine the southern flank of the forests would come under less scrutiny than its aborted expansion plans near the major population centre of Perth.

"It's a master play by Alcoa to get a major bauxite lease; it also gives them a very large refining capacity in the southern region of the northern jarrah forest," he said.

"It gives [Alcoa] enormous growth capacity and longevity for alumina supply."

South32 has already secured approval to expand its existing Boddington bauxite mine in the northern jarrah forests.

Consolidation not expansion

But industry analysts are unsure the deal to acquire South32 would realise environmentalists' worst fears.

Curtin University minerals economist Sakshi Hazuria Anderson said Alcoa's purchase of South32's alumina assets meant the supply chain could be streamlined.

She said expansion of mining in jarrah forests was possible, but not a given.

"It would potentially make economic sense if the market continues to be strong, if the demand continues to be strong for bauxite," she said.

"Is not a given that it is going to happen. A lot of things do have to align."

Australian Aluminium Council chief executive Marghanita Johnson said the takeover was about securing supply chains, not expanding mine operations.

"This is mine optimisation; it is not more mining. It's about mining in the best places,"

she said.

"It takes years to develop the right mine plan, optimise those resources. So much work goes into the environmental approvals process, but also ensuring community consultation along the way."

Alcoa's price struggles

Alcoa has mined bauxite in Western Australia since the 1960s and employs about 4,000 people across the state, but its operations have lately struggled to stay profitable.

Bauxite prices plummeted last year due to a global oversupply, largely driven by surging exports from the West African nation of Guinea.

The drop led Alcoa to close the aging Kwinana refinery amid the high costs of processing low-grade ore.

Last month, Alcoa chief financial officer Molly Beerman told an industry meeting the remaining refineries in Wagerup and Pinjarra were also struggling with costs.

"They're running the poor bauxite quality there, so under significant cost pressure," she told the Wells Fargo Industrials & Materials Conference in Chicago last month.

"The [alumina] segment as a whole will be underwater."

WA mining analyst Peter Strachan said acquiring the South32 business would allow greater efficiencies and market clout.

"They might have felt what they had left was sub-economic, so they needed to have something which was of critical mass," he said.

"I suspect these assets are more synergistic with the ones they've got, and that they've closed down the old banger of a plant in Kwinana, and now they've got the existing facilities in South 32, and that puts them in a stronger position."