Summary

Australia is biologically diverse, with around 150 000 described species, representing perhaps 25% of the total number present. However, this biota is more notable for its endemism than its richness (e.g. 94% of Australian frog species are found nowhere else). Australia is distinctive, not only in terms of endemism, but also in terms of evolutionary adaptations (e.g. large hopping mammals) and ecological processes (e.g. nutrient cycling by fire). Distinctiveness is attributed to three principal factors: (1) a long period of geographic isolation; (2) the preponderance of ancient soils low in key nutrients; and (3) an increasingly arid and inherently unpredictable climate. Australia is also unfortunately distinctive in the scale of biodiversity loss since European settlement with 98 species and subspecies listed as extinct, and a further 1700 threatened with extinction. Both for historical extinctions and currently threatened species, habitat loss and introduced species are the key threats, while climate change is the emerging and possibly most significant threat of the twenty-first century. In the face of these perils, Australia’s distinctive wildlife needs special attention because it makes such a large contribution to the biodiversity and cumulative evolutionary history of the planet.

Introduction

Australia is a biologically unusual continent. This is easily shown by a few examples such as the presence of large hopping marsupials, the prevalence of fire-adapted vegetation, and the sheer diversity of arid-zone lizards. Entire groups of organisms are found nowhere else. Many more are largely confined to the Australian continent, with only a few representatives on nearby islands, such as New Guinea. While visiting Australia and pondering the unusual Australian animals, Charles Darwin wrote in his diary: “An unbeliever in everything beyond his own reason, might exclaim ‘Surely two distinct creators must have been at work …’” (p. 402 of Darwin, 2001). The Australian fauna was so different from that found in Europe, Asia or the Americas, it was as though it was created completely separately from that elsewhere. Of course, Darwin was essentially correct in that Australian wildlife, to a large extent, have been ‘created’ separately. This separateness, however, was not the work of a separate supernatural entity, but rather the result of a long period of independent evolution on an isolated continent subjected to significant and unusual environmental change.