AHA. So what was the question? Why would a green-ly inclined Premier build a desalination plant in Sydney? The alternative of another dam involves incalculable number of "Not In My Back Yard" ers. The other answer is how the "culled" trees get treated. For general expansion of Sydney all trees are killed humanely (ie. chopped down quickly) and the animals which relied on those native trees could move on (a bit like the early settlers thought about aboriginals). With a dam being built, the imagination is that basically everything gets drowned - a slow and painful death.
This is also why Hydro-electric schemes get fought tooth and nail by environmentalists, despite the incredible number of carbon credits over a number of centuries of likely operation. Meanwhile, fossil fuel powered schemes just find an existing industrial complex to attach themselves to WITHOUT A SINGLE PROTESTER!
ACT LOCALLY - yeah right, as long as no big ugly dam, wind turbine, solar generation stack, farm etc. doesn't end up in my back yard!