A section of Barrabup Forest near Nannup which is being rehabilitated after old growth was improperly cleared is now under threat from an "invasive" wattle which residents say has spread like wildfire.
In 2017, residents became concerned that old growth was being logged in Barrabup which should have been protected under the Forest Management Plan.
An investigation by authorities later found that an old growth assessment was never carried out and that 1.2 hectares of old growth had been cleared to make way for roads.
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Barrabup Conservation Group spokespeople Ellie and Marty McKie said the Forest Product Commission was required to rejuvenate the area where they cleared old growth forest.
"They were required to rip and reseed these roads in an attempt to restore the area of the old growth forest which was destroyed," they said.
"We have been monitoring the seeds planted during the rehabilitation process and noticed an unusual plant growing which we had not seen in the Nannup area."
A sample of the plant was taken to a Department of Biodiversity, Conservation and Attractions botanist who advised the plant was acacia celastrifolia.
The McKie's said the acacia was now growing prolifically in the reseeded areas, taking over all other native species, and an area where most of the old growth trees were located was "thick with it."
"This acacia is not native to Nannup and does not belong in this pristine old growth forest," they said.
"We are calling for action to be taken immediately to rid this pristine area of this invasive wattle.
"It is unbelievable and seems to be just one stuff up after another.
"To put it in an old growth section which is being managed and should be preserved for its unique characteristics is going against everything they stand for.
"It really shows how the government is not managing our pristine forests like they should be."
A DBCA spokesperson said rehabilitation of the site was conducted in line with the FMP 2014-2023, which allowed for seed to be sourced from the relevant Land Management Unit (LMU).
If seed was not readily available from the relevant LMU, they could use seed mix from an adjacent LMU in its place.
"The Barrabup coupe is dissected by two LMUs, Blackwood Central and Blackwood Plateau. The rehabilitation site is within the Blackwood Plateau LMU," the spokesperson said.
"It is not common to use seed from adjacent LMUs. However, as seed of all species in a vegetation complex is not always readily available, it does occur on occasion.
"In this instance, the rehabilitation of a road was a high priority as winter was approaching and a loss of soil through erosion and stream sedimentation was considered a higher risk than using seed from the adjacent LMU.
"Acacia celastrifolia, commonly known as glowing wattle, is a non-invasive shrub that is used in the regeneration seed mix for the Blackwood Central LMU and is native to that area.
"The species will mature but as regeneration of the site progresses and other species become dominant, it will likely disappear from the vegetation system."
However native flora expert and Geographe Community Landcare Nursery coordinator Rod Cary disagreed, saying a Google search showed that acacia celastrifolia was invasive and had become a weed in many situations, both in WA and overseas.
"The most significant of these is an article titled, Weedy Native Plants in Western Australia, by Greg Keighery (Department of Parks and Wildlife) published in Conservation Science Western Australia 2013," he said.
"Personally, I have seen it escape from gravel pit rehabilitation plantings at many local locations in Whicher Range, and invade nearby bushland.
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"It is principally for this reason that we do not grow it, and I have recently discouraged several agencies and individuals from using it in situations where it could become weedy.
"I would never advocate using it in any habitats which are outside of its natural distribution (or even within it).
"There are numerous other examples of acacia species becoming weedy when used inappropriately, and in many of these cases, the invaders become so dominant as to suppress almost all other plants in their vicinity, seriously threatening biodiversity."
The WA Government recently invited all Western Australians to have their say on how South West native forests are managed in the future, which will inform the next Forest Management Plan due in 2023.
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Environment and Climate Action Minister Amber-Jade Sanderson declined to comment, but has previously said the FMP was crucial to the protection and management of South-West forests into the future.
