Biological isolation is a contributing factor to the unique difference the Australian environment has. The biological isolation over the past 40 million years since the separation for Australia from Gondwanaland has allowed the flora and fauna to evolve to fit the Australian environment. But the flora and fauna from other continents that Australia has been connected to, still share some similar qualities and shared their flora and fauna. An example of similarities from the formation of Gondwanaland is shared banksia species that are found in Australia, Southern Africa and India. Also the southern beech is found in Australia, New Guinea and South America, and there are fossil remains in Antarctica. The African ostrich, Australian emu and the South American rhea are very closely related flightless birds. This shows that biological isolation is a major point of the uniqueness of the Australian environment.
The Australian environment also has relative geological stability. The last volcanoes were active many years ago, and the last of the glaciers shrank and melted many years ago. We only had volcanoes and glaciers because of the separation of Pangaea therefore making the Continental Drift Theory. There is little geological activity to create or refresh fertile soils. The majority of Australia is very old rock therefore means that we have very poor soils and recently alluvial soils which also have poor nutrients.