A blockade has been established in a forest near Nannup

In what protesters say has been a "massive breach of community trust and expectation" a non-violent protest was set up to defend old-growth.

WA Forest Alliance convener Jess Beckerling said the forest known as Lewin 06 was astoundingly beautiful and one of the most beautiful, ancient karri forest ecosystems in the world.

"We first came across this forest two years ago on a survey. Bulldozers were parked over the weekend, having pushed tracks into what was obviously an old-growth forest," she said.

"We stopped the logging with a community old-growth nomination which found 17-hectares of old-growth forest, a diverse eco-type zone and a large eagle's nest that had been missed in the planning process.

"Over the past two years we have spent a lot of time in Lewin 06, and stayed in conversation with Forest Product Commission and the Government about its incredible value.

"We were shocked and dismayed to hear last week that loggers were returning."

Forest Product Commission director operations Gavin Butcher said the Lewin 05/06 coupe was part of the regrowth native forest available for harvest under the FMP.

"In the Lewin 05/06 coupe, 17 hectares of old-growth has been identified through surveys, the FPC will not harvest in old-growth areas," he said.

"About 32 hectares of regrowth native forest is available for harvest in this coupe. This harvest will predominately supply WA timber mills with high-grade sawlog and peeler billets for laminated veneer lumber."

Mr Butcher said there were 1.4 million hectares of national parks, reserves and other protected areas including old-growth forest were not available for harvest in WA.

He said all stands of old-growth forest were protected in WA, which was set by the Department of Biodiversity, Conservation and Attractions.

"The Forest Products Commission sustainably harvests less than 1 per cent each year of the 850,000 hectares of regrowth native forest which is made available for harvest under the Forest Management Plan 2014-2023," he said.

Ms Beckerling said the forest had been disqualified from an old-growth status "on the most absurd grounds."

"The problem is that the definition of old-growth was written in such a way that it underestimates the true extent of old-growth and fails to protect all of WA's precious old-growth forests."

Ms Beckerling said in karri forests, a stump from a tree cut down in the past 150 years disqualified that area of forest from official old growth status and protection.

She said an additional minimum area rule meant small or irregularly shaped areas of old-growth forest were excluded from protection even when no trees had been cut down in the past.

"This goes against community expectations and an ecological application of the national old-growth forest definition," she said.

"Lewin 06 should be immediately protected. It is a mistake for this forest to be on logging plans. And the old-growth definition should be urgently improved to make sure this doesn't happen again.

"We call on the McGowan Government to urgently to pull loggers out of Lewin forest and correct the definition of old-growth forest being applied by DBCA and the FPC to ensure that our precious old-growth forests are fully protected."

Environment Minister Stephen Dawson said he recognised that protection of old-growth forest was important to the community, and old-growth forest continued to be protected under the Forest Management Plan.

"This Government is committed to managing forests in a way that conserves the environment, protects water catchments, provides recreational opportunities, supports honey production and delivers a framework for a sustainable native forest products industry."