But they agreed on the importance of preserving the state's unique natural bushland and koala habitat at the forum in Sydney on Wednesday evening.
Opposition environment spokeswoman Penny Sharpe and Greens MP Sue Higginson were both against the controversial move to raise Warragamba Dam, which detractors say will impact World Heritage listed wilderness.
Ms Sharpe said a Labor government would not raise the dam.
The Coalition government is continuing to review project assessments and environmental impact studies, with Environment Minister James Griffin coming under fire at the forum for comments by Premier Dominic Perrottet that the state must "put people before plants".
"We all know and have seen the impact of floods on livelihoods, on the environment and on communities. It is a very difficult one," Mr Griffin said.
He also faced heat over reports the number of invasive brumbies in Kosciuszko National Park had grown close to 19,000, and how his party would act to address the damage the horses were doing to the high country environment.
Ms Sharpe said a Labor government would work to reduce the number of horses in the park "as quickly as possible" to the existing Coalition management plan target of 3000.
"The key thing is to get those horses out of the park as quickly as possible," she said.
Mr Griffin said the government remained committed to its stakeholder-formulated plan, with the government putting the increase in number down to two seasons of particularly high rainfall.
"We have been trying to implement the plan as quickly as possible," he said.
"There have been challenges to do with safety that have made that quite complicated, but we are absolutely committed to forging ahead and getting that number down to 3000."
Jacqui Mumford, acting chief executive of the Nature Conservation Council said preserving nature was a deeply important issue that would impact the state for generations to come.
"When we talk about nature and climate, we aren't just talking about a nice bush walk on the weekend," Ms Mumford said.
"We're talking about protecting the air we breathe, the food we eat and the water we drink."
Ms Higginson, and much of the crowd, were in favour of stopping the logging of native forests and transitioning the industry's roughly 1000 workers to other jobs.
Mr Griffin said his government was working to increase timber plantations but said there needed to be discussion with affected communities about how the transition takes place
He backed the Environment Protection Authority in governing what occurs in state forests.
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