malthusista, I never denied that population growth has costs. But new railways benefit the existing population as well, and it would be difficult to fund them without population growth.

From the article:
"When the bubble eventually bursts and the economy sours, the scheme spirals downward with higher unemployment, depressed wages, falling incomes, more people sinking into debt, more homeless families"
The Australian government would not let it get to the stage of homeless families, and our laws would limit how much wages can be depressed. And if the government responds in a sensible way like the Rudd government did, the other negative effects can be avoided too.

And significantly, none of those things depend on increasing population anyway.

Aidan,

Your faith in the ability of our politicians to solve problems while boosting population is touching. In fact, according to the latest figures from Roy Morgan Research, 10% of the working age population is unemployed and another 9.7% is underemployed. People in such a market have very little bargaining power.

Unpaid overtime:

http://www.afr.com/p/national/fewer_staff_more_unpaid_overtime_UsirEtFQf5AZWAObFDtVhP

Homeless families:

http://www.smh.com.au/national/a-new-face-of-homelessness-20130504-2izot.html

Tony Recsei is far from unbiased, but this article has links to serious studies showing negative effects of high density on human welfare.

http://www.newgeography.com/content/003945-health-happiness-and-density

This paper from Nature discusses the mental health aspects:

http://www.nature.com/nature/journal/v474/n7352/full/nature10190.html

You have been given evidence that the politicians are ignoring, and in some cases censoring, the advice of their own scientists against boosting the population, and that population growth is an important factor in the deterioration of our environment and quality of life. I can only assume that you are still pushing population growth for one of two reasons. One possibility is that you have a religious or quasi-religious faith in it, much like Runner on creationism, Jardine on Austrian economics, or Arjay on 9/11 Truthism. The other is that you or people close to you are personally making money from it.

Aidan wrote "... new railways benefit the existing population as well, and it would be difficult to fund them without population growth."

As shown by Divergence above citing Jane O'Sullivan, and affirmed by Kelvin Thomson, the Federal Labor member for Wills, each new immigrant costs Australian taxpayers $200,000, so adding more can only make it a lot more difficult to raise the necessary funds to build new railways.

Aidan wrote, "The Australian government would not let it get to the stage of homeless families, ...".

Yet another unfounded assertion by Aidan not backed by any sources.

There has already been an alarming increase in homelessness. This is hardly surprising given that housing has become so much less affordable that it was in a previous generation. Whether or not the homeless include substantial numbers of families, I cannot say, but if housing costs continue to be driven higher by immigration, I don't see how family homelessness can be prevented.