The WA government has moved to end logging in native forests by investing in softwood timber plantations, a plan Premier Mark McGowan says will save around 400,000 hectares that would otherwise have been at risk of being felled.

In a pre-budget announcement, Mr McGowan said the government would spend $350 million on softwood plantations across the state's south-west to preserve karri, jarrah and wandoo forests.

From 2024, timber taken from native forests will be limited to forest management activities that improve forest health and clearing for approved mining operations, such as Alcoa.

"By saving 400,000 hectares of forests from logging, that is 1,000 times Kings Parks that would have been logged that now will be preserved for future generations," Mr McGowan said.

"What that will mean is these wonderful forests, the trees, the creatures that live within them, the ecosystems, will be saved.

Mr McGowan said the $350 million to be spent on planting new softwood estates, predominately pine, would ensure ongoing supplies of timber for industry.

He said the money would be forthcoming over the next 10 years, creating around 140 jobs and preserving around another 2,000.

Forestry workers to get 'transition plan'

Mr McGowan said it would be the biggest-ever single investment in softwood plantations.

It would see an additional 33,000 hectares of softwood timber plantation, with up to 50 million pine trees planted, sequestering between 7.9 and 9.5 million tonnes of carbon dioxide equivalent.

"We will also be putting in place a $50 million transition plan for people who work in forestry in native forests," the Premier said.

Mr McGowan said logging would finish at the end of 2023-24, when the state's Forest Management Plan ended.

"We are providing advice today to industry that that is the approach that will be adopted," he said.

"We will work with these people and these communities to make sure people can transition into other jobs across the community.

"Saving these forests is important. They should not be lost."

A Native Forestry Transition Group will be established, to assist in the development and implementation of the plan, and will be comprised of local industry, union and government stakeholders.

'Important step in climate change fight'

Climate Action Minister Amber Jade Sanderson said the plan would bring the total amount of state forests protected from logging to around two million hectares.

"This will not only ensure this important asset can be enjoyed for its beauty, Aboriginal cultural heritage and ecotourism for years to come, but it is an important step in the fight against climate change," she said.

"Globally, deforestation is a major contributor to climate change.

"WA's South West native forests are storing approximately 600 million tonnes of carbon dioxide equivalent, or roughly 116 years' worth of annual emissions for every car in Western Australia."

About 9,000 hectares of high conservation-value karri will also receive immediate protection, with other high-value forest areas to be recommended for national park status.

Rushed move will cost jobs: industry 

Forest Industries Federation of WA executive director Melissa Haslam told ABC Radio the industry was in a "total state of shock".

"I am heartbroken for the families in the South West who have relied on this industry for generations.

"It's a sustainable industry and we have been harvesting less than 1 per cent of the forest and regenerating all of it.

"We have got thousands of people employed in this industry in the South West and some of those businesses are generational.

"They're hearing about it for the first time on the radio that come 2023, you won't have your family business anymore."

Shire fears for local economy

Manjimup Shire President Paul Omodei said the decision would be devastating for his town's local economy, which was still reliant on native forest logging.

"Just paying out cash to cash out small timber mills will mean that the jobs will go out the door with those people," he said.

Mr Omodei said the government's commitment to invest $350 million towards the expansion of WA's softwood timber plantations fell short.

"[It] is over 10 years, so $35 million a year will not compensate anywhere near what's needed," he said.

"The softwood timber expansion which most of the funding will go towards will be mainly outside of the Manjimup district."

Industry faces wipe-out, opposition says

Shadow Forestry Minister Steve Martin said the government's announcement had come "out of the blue" and without meaningful consultation with industry.

"They [industry] are completely blindsided by this announcement," he said.

"The jobs, the families and the businesses that this industry supports will be shocked.

"It will have devastating news for places like Nannup, Greenbushes, Manjimup and more broadly across the South West.

"There are jobs all over the South West which rely on the responsible harvesting of our native forests.

Mr Martin described the ban on logging as "arrogant".

"This is an appalling lack of consultant and engagement with a sector which provides jobs and export income right across WA," he said.

WA 'leading the pack': conservationists

Jessica Beckerling, campaign director of the WA Forest Alliance which has long lobbied for an end to native logging in the South West, described the ban as a "historic moment".

"Victoria has a plan to phase out native logging but that doesn't come into effect until 2030. This is historic because WA is leading the pack."

Ms Beckerling said it was a win for conservationists.

"We've been seeing 10 football fields of karri and jarrah forests falling every day," she said.

"It's become less and less profitable over time, fewer people employed, and it's been having increased impacts on wildlife, climate, biodiversity, water, and it's started to have impacts on other sectors which have been speaking out about the need to protect native forests for their industries to grow.

"It's protecting habitats for countless flora and fauna species that live here and nowhere else on Earth.

"This is absolutely profound and it just couldn't have come soon enough."