Ms McKenzie said she told Environment Minister Mark Speakman of her concerns when he rang her on Tuesday, just as the state's upper house was debating the new package of biodiversity conservation laws that will replace existing native vegetation protections.

Mr Speakman's tone was pleasant and thorough, but his explanation of the four tiers of codes and other regulations intended to discourage farmers from stepping up broadscale land clearing without associated conservation measures failed to reassure her, she said.

"I'm concerned that it seems all too complicated," Ms McKenzie told Fairfax Media. "I don't see how they are going to enforce them."

The new bills passed the upper house early on Wednesday morning and are set to be voted into law in the lower house on Thursday afternoon.

The government pressed ahead with its plan to overhaul the native vegetation and threatened species laws - long demanded by its Nationals coalition members - despite calls that Mr Turner's murder should stop the process in its tracks.

Mr Turner, an Office of Environment staffer, was inspecting land clearing at Croppa Creek, north-east of Moree, with a colleague in July 2014 when he was gunned down by farmer Ian Turnbull.

In June this year, the octogenarian farmer was found guilty of murder and jailed for 24 years, and one of his sons ordered to carry out remediation of the land potentially costing millions of dollars.

Ms McKenzie said she was not convinced the new laws would curb habitat destruction and, if anything, would be more complex and frustrating for farmers and harder for government workers to implement.

"How are they going to enforce it with the skeleton staff they have?" Ms McKenzie said.

No 'free kick'

The government has argued the existing laws were failing to prevent extinctions and placing an unfair burden on farmers to conserve habitat compared with other developers.

Mr Speakman said the package of reforms was "not a free kick for landholders to do the wrong thing".

Farmers would have "an incentive to do the right thing by the environment", including having access to a $240 million fund over five years for private conservation.

"We are putting in legal safeguards to prevent broadscale land clearing, meaning that what happened in Queensland simply cannot happen here," he said, referring to that state's tripling of annual land-clearing rates to 300,000 hectares after an easing of curbs by then Liberal National Party premier Campbell Newman.

The maximum that can be cleared under the new NSW codes is 625 hectares over three years, with a requirement to set aside two to five times the area for conservation, Mr Speakman said.

Among the critics, though, has been Liberal MP Bruce Notley-Smith, who warned the changes could trigger "further irreversible land degradation".

Ecologist Hugh Possingham, who had served on a review panel of existing laws, resigned his advisory role over concerns that land-clearing rates would double in NSW because of the new codes.

Researchers such as Philip Gibbons, a biodiversity expert at the Australian National University, estimates land-clearing may already be as much as six times larger than now tracked by the NSW government.

No watering down

Ms McKenzie said Mr Speakman insisted to her that farmers facing fines or other sanctions under current laws "would not have their penalties watered down".

The minister's comments come as OEH has ongoing legal action pending against two of Mr Turnbull's sons in the Land and Environment Court, among others involving native vegetation.

"If found guilty, the court would sentence the Turnbulls under the laws that were in place at the time the alleged offences were committed," Mr Speakman told Fairfax Media.

Sue Higginson, principal solicitor with the Environmental Defenders Office NSW, said "the law at the time is the law that applies".

There is, however, "a slight openness" in the law for judges to apply discretion in sentencing to take into account subsequent legal changes, Ms Higginson said. "If you were a defence lawyer, you'd be mad not to [argue for leniency]."

Todd Alexis, a barrister acting on behalf of the Turnbulls, declined to comment.

"Like Mr Alexis, we are not in a position to address your inquiry any further at this stage," said Sylvester Joseph, a solicitor from Cole & Butler in Moree, also acting for the Turnbulls.

Mixed response

Derek Schoen, president of industry group NSW Farmers, is a supporter of the new laws, describing them as "a marked improvement" from the draft versions, including the final self-assessable codes.

"There are aspects however, that will require [Local Land Service] officers to apply flexibility and common sense, which government has afforded flexibility in the system," Mr Schoen said.

The group has dropped its early demands for the bills to be delayed until updated native vegetation mapping is ready to guide farmers on what they can clear.

Opponents, though, say the final tweaks to the laws do not counter its basic flaws.

"These laws will increase land clearing, harm native wildlife, increase erosion and salinity, and drive up greenhouse gas emissions," Penny Sharpe, Labor's environment spokesman, said.

"The passage of these laws occurs without the support of scientists, of farmers or environment groups," Ms Sharpe said, adding Labor would overhaul the laws if elected in 2019.

Mehreen Faruqi, the Greens environment spokeswoman, said the passage of the bills would amount to "the biggest act of environmental vandalism we have ever seen in NSW".

"We have no final codes, no biodiversity offset methodology, no native vegetation map, no codes of practice for managing wildlife interactions, and no urban vegetation policy," Dr Faruqi said.

Mr Speakman defended the new laws, saying the changes "were always intended to be implemented in multiple stages", with the public able to provide feedback as subordinate legal instruments are developed.

smh.com.au