8 Biodiversity | 3 Pressures affecting biodiversity | 3.3 Spatial distribution of pressures
State of the Environment 2011 Committee. Australia state of the environment 2011.
Independent report to the Australian Government Minister for Sustainability, Environment, Water, Population and Communities.
Canberra: DSEWPaC, 2011.
Listings of threatened species under the EPBC Act include identification of the pressures that are considered to cause the threat. Evans et al.87 analysed data on plant, animal and other species to report the numbers of species affected by the main pressures on biodiversity (Figure 8.11). They used a slightly different categorisation of pressures from that used in the current report. Two of their categories—‘native species interactions’ and ‘natural causes’—are not dealt with separately in this report. Evans et al. use ‘native species interactions’ to refer to ‘changes in the interactions with native plants or animals resulting in hybridisation or increased predation or competition’ (p. 282) and ‘natural causes’ to refer to ‘biological factors (low genetic diversity, low recruitment), natural disasters, and extreme weather’ (p. 282). Here we consider these types of interactions to be consequences of other pressures, especially clearing and fragmentation of ecosystems, climate, grazing pressure and altered fire regimes.
Consistent with other data synthesised in this report, habitat loss (clearing and fragmentation of native ecosystems in the current report) and introduced species (invasive species and pathogens in the current report) were the pressures most commonly associated with threatened species and the most widespread (Figure 8.11). Inappropriate fire regimes also affected a high proportion of subcatchments.
Source: Evans et al.87
Figure 8.11 Pressures affecting species listed as threatened nationally under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act)
Only species for which spatial data were available were used (i.e. 1137 of 1298 listed species). At the time of the analysis, there were 1700 species listed under the EPBC Act, 1590 of which were extant. Of these, 1298 had available threat data and 1137 had both threat data and spatial data. Therefore, there were about 300 species that could not be assessed because of a lack of threat data.
Figure 8.12, which is based on the same data as Figure 8.11, shows the proportion of threatened species affected by each of the pressures, for each Australian subcatchment that contains threatened species.87 The three most prominent pressures affecting threatened species at a national scale (habitat loss, inappropriate fire regimes and introduced species) were widespread. The other five threatening processes are distributed more unevenly and less extensively. Although there are limitations to using data on only species that have been listed as threatened (i.e. many other species are likely to be affected adversely by these pressures), these analyses give at least a coarse indication of the magnitude and spread of pressures on biodiversity.
Source: Evans et al.87
Figure 8.12 The percentage of threatened freshwater and terrestrial species in each subcatchment affected by (a) habitat loss, (b) introduced species, (c) inappropriate fire regimes, (d) disease, (e) pollution, (f) overexploitation, (g) native species interactions and (h) natural causes; the distribution of threatened species richness is shown in (i)