Back in the day, notably the 1980s when the mass immigration madness was starting to go manic, the claim was often made by Big Australia supporters that Australia must populate or perish. The idea was that the populated Asian countries to the north would not permit Australia to have a small population and vast resources. Unless the corporate agenda was met, they would invade us, and finish us off; the ultimate blackmail.
I always hoped to be at a public venue to nail a chatterer putting this argument. First, what does it say about the countries to the north, so willing to invade? Second, if that was so, why would they worry about Australians filling up the country, when, they were willing to invade, they could fill the place up with their own kind? But this argument has served its day, and the chattering class have moved on and do not see any need to justify mass immigration at all now; it just is done because it can be done to a weak and passive country, with no resistance.