Document ID: chunk:federal_register_of_legislation:F2022L00555:body:0:p59
Version: federal_register_of_legislation:F2022L00555
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Although not yet identified as a threat to the Koala, emerging diseases like Myrtle Rust that impact the health of eucalypt ecosystems may indirectly affect the Koala via decline in habitat quality, although impacts are likely to be minor compared to other threatening processes (Fensham et al. 2020). The potential arrival of other strains of the pathogen in Australia poses an increased risk to susceptible species that are habitat for the Koala.

20. Ecological threatening processes

20.1 Habitat loss and fragmentation
Land use practices causing the loss and fragmentation of habitat are considered the primary ecological threatening process to Koalas, to which they are particularly sensitive (McAlpine 2006a and b; Reed and Lunney 1990; Rhodes et al. 2006, 2008). The Koala depends on trees, forests and woodlands for food and shelter (section 28), and has limited capability to traverse the intervening matrix safely, especially in built environments (section 27.3; Lunney et al. 2002; McAlpine et al. 2006a and b).
Open grey-box woodlands (E. microcarpa) cleared for cropping resulting in habitat loss, scattered paddock trees, narrow corridors and small patches, central NSW. Image: © S. Brown.
Since European settlement, Australia has lost nearly 40% of its forests, with the loss disproportionately occurring on productive fertile soils near the coast. This also coincides with preferred Koala habitat (Bradshaw 2012; Lindenmayer and Fischer 2006; McAlpine et al. 2002, 2006a and b). Since the 1970s, substantial forest loss has occurred in high-density Koala populations of south-eastern Queensland and northern New South Wales (Bradshaw 2012), although the majority of habitat loss within the Koala range occurred within the large but low-density Koala populations of the Brigalow Belt and Mulga Lands (Evans 2016). There appears to be a threshold of habitat coverage below which Koalas rapidly decline from landscapes, which ranges from 10–60% depending on the region (McAlpine et al. 2002, 2005; Rhodes et al. 2008).
Landscape configuration changes disrupt metapopulation processes for the Koala (McAlpine et al. 2006a and b) by directly decreasing population sizes or causing localised extinction through reduced carrying capacity within the landscape via reduced resource availability (Zanette et al. 2001; McAlpine et al. 2006a and b); increasing the isolation of populations (McAlpine et al. 2006b); reducing connectivity between populations (Lunney et al. 2002; McAlpine et al. 2006b; Thompson 2006; TSSC 2012a and b); increasing mortality risk from dogs and vehicles (Lunney et al. 2002; McAlpine et al. 2006b; Rus et al. 2021; see below); disrupting social systems (Thompson 2006); and influencing movement patterns (McAlpine et al. 2006b; Rus et al. 2021). Chronic stress to Koalas from these factors is thought to also increase their susceptibility to disease (Davies et al. 2013; Narayan and Williams 2016) (Figure 4).
Extinction debt (Tilman et