Ongoing unraveling of a continental fauna: decline and extinction of Australian mammals since European settlement

Abstract

The highly distinctive and mostly endemic Australian land mammal fauna has suffered an extraordinary rate of extinction (>10% of the 273 endemic terrestrial species) over the last ∼200 y: in comparison, only one native land mammal from continental North America became extinct since European settlement. A further 21% of Australian endemic land mammal species are now assessed to be threatened, indicating that the rate of loss (of one to two extinctions per decade) is likely to continue. Australia's marine mammals have fared better overall, but status assessment for them is seriously impeded by lack of information. Much of the loss of Australian land mammal fauna (particularly in the vast deserts and tropical savannas) has been in areas that are remote from human population centers and recognized as relatively unmodified at global scale. In contrast to general patterns of extinction on other continents where the main cause is habitat loss, hunting, and impacts of human development, particularly in areas of high and increasing human population pressures, the loss of Australian land mammals is most likely due primarily to predation by introduced species, particularly the feral cat, Felis catus, and European red fox, Vulpes vulpes, and changed fire regimes.

Keywords: biodiversity; conservation; feral animal; marsupial; predation.

Fig. 1.

The cumulative number of extinct mammal taxa in Australia. Open circles denote species; filled squares also include subspecies. Note that dates could not be estimated for some extinct taxa, so the tally given here is less than the total number of extinct taxa. Note also that the decade value refers to the 10 y following the date given (i.e., 2000 is the period 2000–2009 inclusive). Reproduced with permission from ref. .

Fig. 2.

Change in the Red List Index for Australia’s endemic terrestrial mammal fauna over the period 1992–2012. Note that this index varies from 0 (if all taxa are Extinct) to 1 (if all taxa are Least Concern). Reproduced with permission from ref. .

Fig. 3.

Comparison of the extent of extinction and threatened status across different taxonomic groups in Australia. Data relate to numbers on the formal Australian list of threatened species (24). Abbreviations: EX, Extinct; CR, Critically Endangered; EN, Endangered; VU, Vulnerable.

Fig. 4.

Example of the distributional retreat of the Australian terrestrial mammal fauna—in this case, the numbat, Myrmecobius fasciatus. Green circles represent current (post-1992) range, red crosses represent records between 1788 and 1992, gray shading indicates presumed range at the time of European settlement, and blue squares represent recent attempts to reintroduce the species to its former range. Reproduced with permission from ref. .