The Audit's Terrestrial Biodiversity Assessment used four groups to assess patterns in biodiversity: mammals, birds, acacias and eucalypts. A detailed analysis of mammals and birds can help us understand the impact of land use on biodiversity. An analysis of endemic Acacia and eucalypt species (those that only occur in localised areas) can determine where highly restricted species may be threatened. These analyses for other species groups would help provide a more comprehensive picture of biodiversity priorities.

Mammals

• Since European settlement, there has been a massive contraction in the distribution of mammals in arid and semi-arid parts of Australia, particularly the small to medium critical weight range species.
• 22 Australian mammals have become extinct since European settlement - which is one third of the world's recent mammal extinctions - with 8 other species remaining only on islands.
• Evidence suggests that mammal extinctions in Australia are continuing.
• Cape York Peninsula is a key region that retains a large number of species that have limited distributions.
• The pattern of mammal attrition resembles rainfall patterns, with higher levels of decline in bioregions with lower annual rainfall (Map 1).

Map 1: Attrition of Australia's mammal fauna.

Birds

• 29 species show a significant decrease in south-east and south-west of Australia, eastern Tasmania and the Top End within a 20 year period between the two comprehensive Bird Atlas surveys across Australia (Map 2).
• The greatest decline is in grassland, woodland and ground-nesting species.
• Threatening process include: broad-scale vegetation clearing, urbanisation, intensified agriculture and feral predators.
• There is an extinction lag for birds (when compared with mammals) but bird extinctions will also occur.

Map 2: Trends in reporting rate of Australian breeding species between the first Bird Atlas (1977-1981) and the second Bird Atlas (1998-2001).

Acacias and Eucalypts

• 40 bioregions and 61 subregions were identified to have high irreplacable value in terms of endemism. This assessment identified additional areas of specific importance for the conservation of endemic Acacia and eucalypt species to those identified in previous studies. These include the Pilbara, Carnarvon, Great Victoria Desert, Einasleigh Uplands bioregions
• Map 3 shows bioregions that are priority for the conservation of endemic species and which have high species diversity.
• Important regions for endemic species such as south-west Western Australia, and parts of New South Wales Western Slopes, Brigalow Belt and Victoria coincide with extensive clearing, fragmentation and salinisation. This is of concern for the conservation of Acacia and eucalypt species restricted to these regions and their associated ecological communities.

Map 3: Priority bioregions for the conservation of acacias and eucalypts.

Further Information:

• See Australian Terrestrial Biodiversity Assessment 2002 for more details.
• Or go to the Australian Natural Resources Atlas (www.environment.gov.au/atlas).
• Email: info@nlwra.gov.au