Melbourne has a lot of things that need fixing. It needs a light rail from the city to the airport. Train line/tram line extensions to universities a connection between the two partial ring roads. High speed rail connecting all the eastern cities
I live in a high density burb on a train line and every time a warehouse or shop comes down, an apartment building goes up, and that's good because owning a car is entirely optional here, but day and night main roads are clogged by thousands of people heading into the city in cars owned by those who live further out because there are no trains, or there is no parking near their train stop or the trains are too full, I'm on a "sardine" line and often have to let one or two trains go by because they're too full. They need the infrastructure, and the people buying up and selling off the land are only there to make a profit, they can't control the infrastructure.
Also the selling off of the land around the cities pushes the crops needed to feed the city further out... or out of business. Then we're importing food, adding to pollution, losing control of the quality of the food. Our major crisis in the next 40 years will be how to feed the 2 billion more people in the world, and if each city does not become more or less self-sufficient in terms of producing food, then each city is at the mercy of world wide food shortages.
75% by 2050 is how much our food production will have to rise world wide. It's a crisis we're racing towards blindly, investors are pouring money into growing biofuel to power rich people's cars as poor people starve. All the grain crops produced in all the world in one year could not drive the USs cars for one year... so what the hell are the policy makers thinking?