Document ID: chunk:federal_register_of_legislation:F2024L00270:body:0:p37
Version: federal_register_of_legislation:F2024L00270
Segment Type: other
Provision Reference: 
Character Range: 101471–104476

Powelltown (McComb et al. 2019). It is unclear whether habitat disturbance, fragmentation and road construction alter predation risk in the Central Highlands, however it is conceivable that they increase predation risk.
Disturbance events that dramatically alter the environment can result in direct mortality of individuals. For example, the 2009 bushfire resulted in greater than 95% mortality for Leadbeater's possums on the Lake Mountain plateau (Harley 2016).
Predation has not been a major cause of adult mortality for the Yellingbo subpopulation (Harley 2015a). Of a large number of individuals radio-tracked at Yellingbo, there were only three adult mortality events. All coincided with the dispersal of new animals into established colonies: one was from female-female aggression; another attributable to predation by a powerful owl (Ninox strenua), and; the third from predation by either a cat or fox (Harley 2005). Some juvenile mortality at Yellingbo (0.5 in the first 12 months) may be attributable to predation but the population decline there is principally due to severe decline in habitat conditions (Harley 2015a).
The main ultimate cause of mortality across the possum's range is episodic habitat loss or gradual reduction in habitat quality associated with disturbance events (Harley 2023). These are discussed in more detail in the Threats section below.

    4               Threats
The major threat to the Leadbeater's possum is the ongoing reduction in the extent, quality and connectivity of suitable habitat (especially large or hollow-bearing trees), with this threat in part a historical legacy, in part a consequence of ongoing actions, and in part a future expectation based mostly on factors which are difficult to control (bushfire).

4.1                 Historical causes of decline
Fossil, sub-fossil and historical records demonstrate that the species was formerly more widely distributed (Lindenmayer et al. 1991d; Lindenmayer et al. 1993d; Harley 2004c; Bilney et al. 2010), however the pattern and timing of historical decline is poorly resolved. Some decline probably occurred prior to European settlement, due to changes in climate and hence fire regimes and habitat extent, but the rate of decline has most likely accelerated since European settlement.
Extensive clearing and landscape modification (including draining of wetlands) – mostly in the decades from the late nineteenth to early twentieth century – removed almost all suitable habitat from the type locality and across the species' lowland range (Brazenor 1950; Macfarlane et al. 1997; Harley 2004c; Harley et al. 2005; Greet et al. 2020).
The extent of suitable montane ash forest has varied markedly over time in response to variation in climate and fire regimes (McKenzie 2002; Worth et al. 2014). Since European colonisation fire management practices (and hence fire regimes) have changed, including in montane ash forests, and along with cumulative impacts of timber harvesting have led to decline