[Targan]

In the vast majority of Australia, if you leave civilisation and walk out into the wilderness without being very fit and knowledgable in bushcraft you will probably die within a week or even a couple of days. Finding water is the biggest problem as most of Australia is arid or desert. Even in the part of Australia where I live, potable water wouldn't be easy to find once the pumps stopped working and the desalination plants shut down.

Then there's being able to find food that won't kill you, and avoiding the various creatures large and small which can kill you (many of them without even really setting out to do so). And then out in the desert there's the terrible heat in the days and aching cold at night. Really, most of the Australian continent seems like a gigantic kill zone specifically designed to make it hard for humans to survive.