The Population Debate

There was an interesting debate on television a couple of nights ago, with Dick Smith and three others offering views on Kevin Rudd's dream of a Big Australia, allowing the population to grow 50% over the next 30 years, or whatever.
As with the recent debate about 5 storey development of Beecroft Shopping Centre, the main debate is about "where shall we build the new high rise buildings.
But to me the most pertinent point was Dick Smith asking "why are we doing this?"
One of the answers was that we were providing a service to the rest of the world, offering accommodation to all those desperate people who wanted to come and enjoy the many blessings of Australia. But as Mr Smith asked, why should the people of Australia give up all that they now enjoy in order to please the tiny fraction of the rest of the world who we can, according to Kevin, find houses for.
Of course the developers are keen to build the houses this next wave of settlers will require, but in the process those who now live in Australia will find themselves with ever more congested streets and trains. Do we really want this?
Dick Smith questioned availability of water and food, and the developers responded that technology would cope. Water tanks at every house to collect rain water, genetically modified food, and other exciting innovations can surely cope? But still one is left wondering, why?