Shellharbour City Council has removed hundreds of hectares of nature reserve from the care of full-time rangers, in a move described by union representatives as a threat to sensitive environmental and heritage sites.
Until now, four rangers have been employed to exclusively look after the Bass Point Reserve and Blackbutt Forest Reserve.
From this week, council will trial a system whereby the rangers' positions are absorbed into other departments and the reserves are monitored, repaired and maintained by compliance and parks and gardens staff as part of their broader duties.
Council is working to find alternative jobs for three of the rangers, with roles in cleaning, ordinance and tractor-driving looking likely.
The fourth ranger has been given the choice of an alternative position or redundancy.
United Services Union organiser Rudi Oppitz has questioned the environmental impacts of the change, and the safety implications, as the parks will no longer be under the watch of permanent authority figures.
"When you look at the size of these parks, it's quite easy for things to go wrong," Mr Oppitz said.
"Having rangers that are regularly going through the park offers a level of security to the general public.
"If the [state] government was to turn around and say that we no longer need rangers in state-owned heritage parks and national parks, and what we'll do is just send in a lawn mower or a maintenance crew every now and then, what do you think the outcry would be, and how well maintained would these parks be?"
Blackbutt Forest Reserve is home to the last remaining viable remnant of coastal plain forest in the region.
Meanwhile Bass Point Reserve is recognised as an important archaeological site due to its Aboriginal and European heritage.
Mr Oppitz said council representatives had couched the changes as cost-cutting, but it remained unclear how money would be saved, given all four rangers have been offered alternative positions within council.
In a statement to the Mercury, a council spokeswoman said the change was aimed at improving "the effective and efficient delivery of services" and providing "better services for the benefit of the whole community", but did not explain what budget saving would result, if any.
"The available funding is utilised within the parks and gardens team to better manage public spaces across the city," she said.
Council pledged community safety and protection of the area's natural environment would not be compromised under the new staffing arrangements.
"Council will still provide the same services via other roles in council," the spokeswoman said.
"Surveillance will be performed at each site at intervals during the day to regulate any illegal activities including issues relating to parking and activities by council compliance officers. Cleaning and emptying of the bins will be conducted daily by cleaning staff and bush regeneration and management will be continued by parks and gardens team staff."
Mr Oppitz said the four rangers were all long-term employees. The longest serving had worked at the reserve for 25 years.
He said the four were "devastated" at the change.
"All of them put in well over and above what would normally be expected of any employee of council in looking after and maintaining the parks," he said.
"To see [their work] being unravelled and going down the path that it is, it's devastating for them."