"Australia" has a low population density because most of it has close to no population; it's easy to be mislead by this if you're not aware of how the population is distributed within a huge area, but the areas where most people live do not have low population density. It's heavily urbanised (more so than the UK), with the vast majority of the population living in reasonably dense metropolitan areas.

It's the willingness and ability to take effective measures, not the geography, that matters.