Indicator description

Why is it indicative

What does the data show

Data

Acknowledgment

Indicator description

Number of species presumed extinct, endangered, vulnerable or rare, as listed in the Tasmanian Threatened Species Protection Act 1995. This indicator should be reported by major group. This indicator applies to animals and plants both on land and in the water.

The Tasmanian Threatened Species Protection Act 1995 defines 'threatened species' as taxon of flora or fauna that is listed in Schedules 3 (endangered and extinct), 4 (vulnerable) or 5 (rare) of the Act. The endangered category represents those species that are most at risk of becoming extinct in the wild followed by the vulnerable and rare categories.

Why is it indicative

Extinction of species equates to a loss of species diversity. The number of species considered extinct, endangered, vulnerable or rare is the best available surrogate for the loss of species.

Extinct species are those that have not been seen for at least 50 years. Endangered species are those in danger of becoming extinct in the near future. Vulnerable species are those that are likely to become endangered in the near future and rare species are those that are either naturally uncommon species or species that have had their range substantially reduced and are at risk.

However, the number of threatened species it is not an ideal measure and care must be taken with interpretation. The number of species presumed threatened may increase either because more species are, in fact, at risk or because of a better understanding of species that were already at risk. For this reason, the number of extinct, endangered, vulnerable and rare species is reported by major group together with the number of known and fully described species for each major group.

What does the data show

• There has been a slight increase in numbers of threatened species in Tasmania between 1995 and 2000. Much of this is due to a better understanding of the status of Tasmania's native species. Areas of particular improvements in understanding have been in the freshwater fish and invertebrate groups.
   
• Groups requiring substantially greater understanding are the invertebrates and lower plants.
   
• Freshwater fish are the most threatened group, with half of the Tasmanian species being listed, with most of these being Tasmanian endemics. Likewise, 109 of the 116 threatened invertebrates are Tasmanian endemics, being found nowhere else in the world.
   
• Several groups have a significant proportion of the native species listed as threatened. For example, approximately one-third of all native broadleaved plants are threatened, and a quarter of the reptiles and the grasses, sedges, orchids and lilies are also threatened.
   

Data

Changes in the total number of threatened species in Tasmania between 1995 and 2000 are shown in the graph and table below. To view changes in the number of threatened species by major group click on the graph.

Note that some groups (e.g. lower plants and invertebrates) have yet to be studied comprehensively.

Acknowledgment

Adapted from Core Biodiversity Indicator BD6 (ANZECC 2000).