The State Government will today release a new 10-year draft forest management plan, setting the stage for the most significant clash between conservationists and the timber industry since the ban on old-growth logging in 2001.
Under one scenario put forward by the Conservation Commission in the plan, logging of prime jarrah in the South West would be cut by a quarter.
But the forests watchdog has refused to make a definitive recommendation on logging quotas, instead suggesting a range for first and second-grade jarrah anywhere from 95,000 cubic metres to 137,000cum a year - representing a 27 per cent cut or 5 per cent increase on the current level of 131,000cum.
Total logging of jarrah, karri and marri, including lower-grade logs, could rise 32 per cent or be cut by about 16 per cent in two scenarios in the plan. Low-grade karri logging could increase up to 50 per cent to 240,000cum a year.
Conservation Commission chairman Brian Easton said there was no intention to end native timber logging or to return to logging old-growth forest.
But the commission would not commit to defining a sustainable yield because of uncertainty about the impact of climate change and how the forests would cope.
Mr Easton said the Department of Environment and Conservation had done extensive modelling of conditions that affected growth of timber and revegetation.
He said the two scenarios in the draft were based on computer modelling using 2007 CSIRO projections of climate change.
Mr Easton said declining rainfall and climate change meant the forest was under pressure.
"It's a document which is planning to run for 10 years about the responsible management of our whole forest system, at a time when declining rainfall will be continuing and unknown factors around climate change," he said.
The report recommends adding 2370ha to the conservation reserve at Whicher Scarp, near Busselton.
The Conservation Council of WA supports an end to native timber logging.
The Forest Industries Federation has been pushing for a small increase in the amount of native timber it can take.
Preston Environment Group spokesman Peter Murphy said he had serious doubts whether the new plan would protect the forest.
Environment Minister Bill Marmion has said the Government is committed to a sustainable native timber industry and encouraged submissions on the draft plan.
The plan will be open for public comment for three months and will be reviewed by an independent expert panel before formal assessment by the Environmental Protection Authority.
The final plan is expected to be considered by the Government next year.