Western Australia will end the logging of native forests from 2024, protecting nearly two million hectares of land in a bid to help fight climate change.
About 9000 hectares of high conservation-value karri forest will also receive immediate protection.
The new policy will exclude forest management activities and clearing for approved mining operations, including Alcoa.
Premier Mark McGowan says forestry workers in the state's southwest will be supported through a $50 million transition plan to be funded in Thursday's budget.
"This is a historic moment for the protection of our magnificent forests and the creation of sustainable WA jobs," he said on Wednesday.
"This builds on the legacy of the Gallop Labor government's decision to end old-growth logging in 2001.
"By transitioning more of the forestry industry to sustainable timber products like softwood, we are investing in WA's future - supporting the construction and forestry industries, and our regional communities.
"Protecting this vital asset is critical in the fight against climate change."
The budget will include a $350 million investment over 10 years in new softwood plantations across the region.
Mr McGowan said the new plantations would provide at least an additional 33,000 hectares of softwood timber. Up to 50 million pine trees will be planted, "sequestering between 7.9 and 9.5 million tonnes of carbon dioxide equivalent".
"It will also create about 140 timber industry jobs, protect about 1,980 existing jobs, mostly in the South-West timber industry, and support the many thousands of jobs in the state's construction industry that depend upon the reliable supply of softwood timber," he said.
A transition group to assist in the plan's implementation will include local industry representatives, union and government stakeholders.
Mr McGowan said existing contracts would be honoured through to their natural close at the end of 2023.
"We understand that ending logging of native forests will cause uncertainty and disruption for workers and communities. This is not a decision we have taken lightly," he said.
WA aspires to achieve net-zero greenhouse gas emissions by 2050.
The government is still considering whether to legislate the target, amid warnings a dramatic reduction in carbon pollution is needed over the next decade.
Environment Minister Amber-Jade Sanderson said WA's southwest native forests stored about 600 million tonnes of carbon dioxide equivalent, "roughly 116 years' worth of annual emissions for every car in Western Australia".
