Most of Australia’s estimated 500,000 species are invertebrates, and half are insects. Invertebrates are the ecological glue that holds ecosystems together; they are a food source for many vertebrates, and provide ecological services such as nutrient recycling, pest control and pollination. Despite these critically important functions, invertebrates are rarely the iconic or charismatic animals that garner human attention, although some play an important role in Indigenous beliefs (see Box BIO11). In addition, several species transmit diseases to humans and animals.
Unlike plants and mammals that are relatively well known, only about 25–30 per cent of Australia’s insects have been formally catalogued and named by scientists. Many invertebrate species are small, have restricted distributions, have precise ecological requirements, and are difficult to identify without specialist knowledge and techniques. However, because of these attributes, many species are sensitive to very subtle environmental changes.
The main pressures on Australia’s invertebrate biodiversity—habitat reduction and fragmentation, altered fire regimes, invasive species, and climate change—are increasing. There have been few direct measures of the status of Australia’s invertebrate biodiversity. Indirect evidence from estimates of forest cover, and the distributions of rare and threatened vertebrates and plants suggests that invertebrate populations continue to be at increased extinction risk, especially along the east coast of Australia and in the south-west of Western Australia.
The IBRA regions containing the highest number of EPBC Act–listed invertebrates are in eastern Tasmania (Figure BIO23) and on Australian islands that cannot be seen in this figure. The Pacific Subtropical Islands IBRA region, including Lord Howe Island and Norfolk Island, contains 8 listed invertebrates, including 6 that are critically endangered. Flinders Island to the north-east of Tasmania also contains 8 listed species, including 5 that are endangered.
Seven of the 8 listed fauna on Norfolk Island (1 species) and Lord Howe Island (6 species) are land snails; the remaining species is Lord Howe Island phasmid (Dryococelus australis). Lord Howe Island fauna have suffered significantly from the introduction of exotic animals and human disturbance.
Listed species from eastern Tasmania and Flinders Island include insects (e.g. Tasmanian chaostola skipper—Antipodia chaostola leucophaea; endangered), crayfish (e.g. Furneax burrowing crayfish—Engaeus martigener; endangered), beetles (e.g. broad-toothed stag beetle—Lissotes latidens; endangered) and other invertebrates (e.g. blind velvet worm—Tasmanipatus anophthalmus; endangered).