Document ID: chunk:federal_register_of_legislation:F2024L00270:body:0:p42
Version: federal_register_of_legislation:F2024L00270
Segment Type: other
Provision Reference: 
Character Range: 114927–117892

fires between 1900 and 1938. These forests are classified as regrowth forests and regenerating trees in them have typically not yet formed hollows.
Thinning of younger regrowth forests (typically 18–30 years old) occurred in some areas, with the aim of increasing the growth rate of the remaining trees. Although not all trees are harvested, thinning opens up the stand, removing the dense midstorey connectivity needed by Leadbeater's possum for movement and foraging. Thinning can accelerate the growth of trees and potentially the formation of hollows (P. Baker, University of Melbourne, unpublished) but may concurrently adversely affect vegetation structure for the Leadbeater's possum.
In addition to the direct impacts that timber harvesting had on habitat availability for Leadbeater's possum, harvesting may have ongoing indirect impacts, although the severity of such impact is not well resolved. Proliferation of the track network associated with harvesting may isolate some Leadbeater's possum subpopulations and reduce dispersal.

4.2.3             Reduction in the abundance of hollow-bearing trees
This factor can be considered to be a consequence of other threats or as a threat itself, but it is included specifically here as a threat as it is such an important consideration for the future of this species. The quality of the montane ash habitat for Leadbeater's possum has declined in recent decades due to a significant loss of hollow-bearing trees. Long-term monitoring over the last 30 years in the Central Highlands has shown that within unburnt areas, approximately 3.5% of dead trees collapsed per year during that period and approximately 1.5% of large, live hollow-bearing trees died per year (Lindenmayer et al. 2012). This severe rate of loss of dead and live hollow-bearing trees is predicted to continue into the future (Lindenmayer and Sato 2018). There is currently negligible natural development of new hollow-bearing trees, as 1939 regrowth trees are yet to form hollows. The combination of the loss of existing hollow-bearing trees and a current lack of development of new hollow-bearing trees is predicted to lead to an increasingly severe shortage of these trees in the next 30–70 years (Lindenmayer et al. 1990b; Lindenmayer et al. 2012; Lindenmayer and Sato 2018).

4.2.4             Eucalypt dieback and altered hydrology (for lowland subpopulation)
Lowland swamp forest habitat at Yellingbo and in nearby areas is experiencing ongoing decline in habitat quality due to eucalypt dieback and reduced regeneration, resulting in an altered, more open forest structure. Largely due to such ongoing habitat deterioration, only about 10% of the 180 ha of lowland swamp forest in the Cockatoo Creek section of Yellingbo Nature Conservation Area now supports high-quality habitat, and the subpopulation of Leadbeater's possum in the reserve has declined severely across the monitored period of 2001 to 2022 (Harley 2016, 2023). This