From Envirowiki

Bioregions are regions are overarching ecological areas that are distinct from the areas around them. Each region contains many ecosystems (ie. flood plain, gully, and hilltop ecosystems).

[edit] Bioregionalisation of Australia.

The (Interim Bioregionalisation of Australia (IBRA)) establishes units (bioregions and subregions) for measuring the status of natural systems, such as reservation status or clearing status. They are used as the unit of measurement in the National Land and Water Resources Audit, for example, in their 2002 Australian Terrestrial Biodiversity Assessment

Australia has 85 bioregions (not including marine bioregions) and 403 subregions.