'Embarrassing about-face': Govt admits shire tree canopy loss may not be real

The department has added a notation to data on its website, advising caution in analysing comparative figures for tree canopy in Sydney council areas.

"The department's canopy datasets for 2016, 2019 and 2022 were captured and processed using different methods, technologies and resolutions," the notation says.

"Care should be taken when comparing canopy cover between datasets, especially in LGAs with a lower proportion of Metropolitan Urban Area, as some observed differences may be a result of variations in methodologies rather than actual change in canopy cover."

Mayor Carmelo Pesce hit out at the department's "hopelessly misleading" report, which provided the comparative figures.

"The department has been forced into an embarrassing about-face, begrudgingly admitting they got it wrong with their alarmist findings," he said.

Cr Pesce said diligent work by Sutherland Shire Council staff had uncovered glaring deficiencies in the department's tree canopy mapping after noticing major discrepancies with figures recorded by the council.

Council figures put the canopy decline at just 0.40 per cent between 2016 and 2020.

"Failings in the department's methodology effectively renders their comparative data, collected across studies conducted in 2016, 2019 and 2022, unreliable," he said.

Cr Pesce said figures for places like Woronora Heights and Woronora were "hopelessly out of whack".

"The department recorded an almost 6000 per cent greater decrease in tree canopy cover in Woronora Heights and around 3000 per cent greater decrease in Woronora than that which was recorded in a more detailed analysis by council," he said.

"The fact the department's aerial observations had recorded significant tree canopy loss in protected bushland which will never be logged should have been cause enough for them to double check their homework."

A department spokesman said the data set for 2022, released in October 2023, was "far more sophisticated that those published in 2019 and 2016".

"As an example, the 2022 data uses the best available technology and acquisition methods and captures a resolution of less than 50 centimetres, whereas the 2019 data was accurate between 2 and 30 metres," the spokesman said.

"Given the significant data improvements, the canopy data hub includes advice on how to use the data. The department issued a notation about interpreting datasets across years."