Friends of Dianella Bushland spokesman Rick Denniston said the group became aware of some tree loss during summer of 2014-15.
“It’s been in such good condition for so long and all of a sudden there was incredible decline, it was really once considered the jewel in the crown and the crown is beginning to lose its jewels,” he said.
“Given bushland usually looks after itself doing nothing is not an option, we believe this is now more serious.
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READ NOW“To evaluate the extent of the losses we undertook a survey in May 2016 and the results were worrying.”
The group said they had concerns about the impacts of dust and run-off from the adjacent Seven Hills housing development by Satterley Property Group.
A Satterley spokeswoman said the group had worked with the City of Stirling to ensure protection of the reserve.
“A complete Bushland and Tree Management Plan, with specific protection requirements, was prepared by our environmental consultant and approved by the City of Stirling prior to any clearing of trees in close proximity to Cottonwood Reserve,” she said.
“The only trees that have been cleared were located outside of the reserve land under the supervision and approval of the City of Stirling.
“Conservation fencing as specified by the City of Stirling will be installed in the coming months along the Cottonwood Reserve boundary.”
Stirling parks and reserves manager Ian Hunter confirmed the City’s environmental officers had noticed dying trees and bushland in the area.
“We are waiting on the analysis results of recent sampling to determine whether Dieback is present,” he said.
“Other reasons could be water stress from the decline of the groundwater table owing to insufficient winter rainfalls over past years to replenish aquifers.”
Mr Hunter said ongoing issues that threatened the reserve were public access into the bush areas rather than staying on the tracks provided and the dumping of rubbish.
Mr Denniston said he hoped the City would undergo a range of tests to establish the cause of the problem.