Ranking Conservation and Timber Management Options for Leadbeater's Possum in Southeastern Australia Using Population Viability Analysis

The conservation of the endangered Leadbeater's Possum, Gymnobelideus leadbeateri, is one of the most contentious forestry issues in Australia. The challenge is to identify strategies to conserve the species in the significant portion of its range in the central highlands of Victoria (southeastern Australia) where timber harvesting occurs. We used ALEX, a simulation program for population viability analysis, to explore the effectiveness of potential forest management strategies to enhance the persistence of G. leadbeateri in areas of wood production. Our study focused on the relationship between the risk of metapopulation extinction and (1) the number and spatial arrangement of 50-ha logging areas that could be reserved from timber harvesting and (2) the impacts of post-fire salvage logging in reserved areas. We modeled complex patch structures within two forest blocks (Murrindindi and Steavenson) that were based on maps of both existing patches of suitable habitat for G. leadbeateri and the location of potential logging areas. We recorded high values for the probability of extinction of metapopulations of G. leadbeateri when existing strategies for the conservation of the species within the Murrindindi and Steavenson Forest Blocks were modeled. Exclusion of salvage logging operations from burned, old-growth forests significantly improved the species' prospects of survival in both the short and long term. Withdrawal of timber harvesting from some proposed logging coupes made a significant, positive long-term contribution to metapopulation persistence. But there will be a delay of at least 150 years until areas set aside now make a significant contribution to metapopulation persistence. This is the time required for existing stands of regrowth to develop old-growth characteristics that are an essential habitat component for G. leadbeateri. We examined the effectiveness of different designs for setting aside a total reserved area of 300 ha. These ranged from a single 300-ha reserve to 12, 25-ha reserves. Populations in smaller reserves were vulnerable to extinction from demographic stochasticity and environmental variability. Conversely, a small number of larger reserves were susceptible to destruction in a single, catastrophic wildfire, highlighting the need for several dispersed reserves. Analyses of the sensitivity of various management options to variations in fire frequency and extent, movement capability, and a wide range of other factors indicated that the conservation strategy that gave the best relative outcome for G. leadbeateri was both to set aside several 50 to 100-ha reserves in every forest block and to preclude post-fire salvage logging operations from these areas if they burned in a wildfire.

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