"We're consistently getting reports of losses of parks, open space and urban bushland. We think it has reached a crisis stage," said Jeff Angel, executive director of the Total Environment Centre, which says there has been a 23.5 per cent decline in open space in NSW in the past ten years. CEO of the Nature Conservation Council Kate Smolski described the loss of open space "incredibly alarming". "There are clear risks that the current government is bending to the will of property developers who want more land transferred into private hands and cleared for development," she said. The Total Environment Centre's ​2015 Urban Sanctuary Toolkit says the biggest threats to open space are housing and infrastructure, rezoning of community land as operational land and a review into the state's Crown land, which could potentially result in the sale or commercialisation of Crown lands.

It also attributes recent losses of urban bushland to the controversial 10/50 "bushfire zone" rule, which allows eligible homeowners to clear trees on their property within 10 metres of a home. As secretary of the Cumberland Conservation Network Wayne Olling knows the struggle of protecting open space well, having spent the last ten years trying to protect the Shanes Park Woodland from a road reservation. "When you're talking about something as big as a motorway it has a huge impact on a high conservation value area." While the Total Environment Centre claims a loss of more than 20 per cent, the Office of Local Government states the loss at 2.57 per cent due to a change in reporting procedures. The 2.57 per cent estimate in the June Profile & Performance of the NSW Government Local Sector report was a dramatic improvement on the previous year's report, which showed a 20.10 per cent decline.

Changes to council land management systems have resulted in movements, "both up and down, in the amount of open space reported," an Office of Local Government spokesperson said, but added that there is "no standardised way of measuring open space. It is a matter for each council." ​Mr Angel said inconsistent reporting methods by individual councils are skewing the measurement of open space. "There are serious statistical inconsistencies," Mr Angel said. "Some councils appear to take account of land not under council control, for example, national parks and state forests, which are not urban open space."

Three councils out of 152 showed significant increases in open space in the 2013/14 report compared to the previous years findings.

In one year Wyong increased its total open space by 23,057 hectares, Newcastle by 9,634ha and Gosford by 26,768ha. ​A Wyong council spokesperson confirmed that the sizeable increase was due to a new measurement method, which includes "national parks, nature reserves and conservation areas". The Shanes Park Woodland and the old Air Services Australia site, some of which is now under threat due to a proposed highway. Photo: Steven Siewert.

While the Office of Local Government report claims there is 30,768ha of open space in Gosford, a Gosford council spokesman said total open space amounted to 4,130ha and did not include national parks or state forests. Both Gosford council and the Office of Local Government were unable to explain the origin of the 30,768ha figure. Mr Angel said there is an urgent need for a review of reporting methods, because some land being counted "is not managed by local councils and isn't urban open space". "I think the OLG present an entirely false and unhelpful picture about whether open space has increased or decreased. The numbers are useless," he said.​ The Office of Local Government said it is currently working with the local government sector on "a new performance measurement framework".

A Department of Planning and Environment spokesperson rejected the Total Environment Centre's concerns, arguing that "more than 90 per cent of Sydney's residents live within a five to ten minute walk of green space". She added, that 28,000ha of this land has been transferred by the government to councils and other bodies like the Western Sydney Parklands Trust "'for open space, conservation and parklands".

