Document ID: chunk:federal_register_of_legislation:F2024L00270:body:0:p43
Version: federal_register_of_legislation:F2024L00270
Segment Type: other
Provision Reference: 
Character Range: 117625–120739

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 reduction in habitat quality is due to severe eucalypt dieback caused by altered hydrology of the Cockatoo Creek floodplain and lack of appropriate disturbance regime to promote natural regeneration of eucalypts and Melaleuca and Leptospermum midstorey (Harley 2016; Greet et al. 2020). Browsing by swamp wallabies (Wallabia bicolor), sambar deer (Cervus unicolor) and potentially fallow deer (Dama dama) is also likely to compound the effects of dieback and impact recruitment of seedlings necessary to maintain dense vegetation structure (D. Harley pers. comm.).

4.2.5             Population fragmentation
An ongoing reduction in the extent of suitable habitat is likely to lead to increased fragmentation of the population into a series of variably-sized subpopulations. Subpopulation structuring has recently been examined in the Central Highlands (Zilko 2021) and revealed four distinct genetic groups in the highlands: Northern (encompassing Snob's Creek, Mt Bullfight, Lake Mountain, Arnold Gap, and Marysville), Central (Warburton, Donna Buang, and Ben Cairn), Southern (Powelltown), and Eastern (Baw Baw National Park and Toorongo Plateau). This suggests contemporary isolation of the four groups, highlighting the need to reconnect populations to avoid further erosion of genetic diversity and fitness decline (as has been documented for the lowland population). The southern genetic group (Powelltown population) appears to be most vulnerable based on its size, it also was inferred to have had the most recent gene flow with the extinct Bass River population, which in turn shared genes with the lowland population (Hansen et al 2009). This suggests mixing lowland possums with those of the southern groups should replicate past gene flow and thus be of low risk of outbreeding depression (Ralls et al. 2020). Molecular analyses for the Yellingbo subpopulation indicate that population fragmentation can occur over very small spatial scales, even where continuous vegetation cover exists, suggesting the species is highly sensitive to habitat quality (Hansen 2008; Hansen and Taylor 2008; Zilko et al. 2020).

4.2.6             Climate change
The climate of the Central Highlands is likely to change significantly in future decades, with high-confidence predictions of higher temperatures, a higher frequency of days of extreme heat, increased incidence and longevity of meteorological drought, and harsher fire-weather climate (Grose et al. 2015). These projections largely maintain or accelerate climate trends evident over recent decades, which have contributed to ongoing reduction in the quality and extent of habitat suitable for Leadbeater's possum. Zoos Victoria and Deakin University have recently modelled the impacts of increasing temperatures on the suitable climate space for Leadbeater's possum for four future emission