Ten years on – a decade of intensive biodiversity research after the 2009 Black Saturday wildfires in Victoria’s Mountain Ash forest

ABSTRACT The catastrophic 2009 wildfires in the Mountain Ash (Eucalyptus regnans) forests of the Central Highl&s of Victoria provided an opportunity to gain new insights into the responses to fire by various elements of the biota. Ongoing long-term monitoring at a large number of permanent field sites for up to 25 years prior to the fire, together with 10 years of post-fire monitoring, has provided an unparalleled series of datasets on mammal, bird, & plant responses on burned & unburned sites. The empirical studies briefly summarized in this paper show patterns of steep declines in large old trees & declines in site occupancy by arboreal marsupials & birds. These changes contrast markedly with the responses of the two most common species of small mammals (the Agile Antechinus [Antechinus agilis] & Bush Rat [Rattus fuscipes]), which recovered within two generations after the fire. Declines in arboreal marsupials, birds & large old trees have also occurred on unburned sites, indicating an ecosystem-wide trend. In general, logging had a greater impact than fire on the majority of groups of birds & plants, particularly post-fire salvage logging that occurred in some areas following the 2009 wildfires. Beyond interactions between fire & post-fire (salvage) logging & their effects on forest biota, we have uncovered evidence of other kinds of interactions in Mountain Ash forests. These include interactions between: (1) the severity of fires & logging history, (2) post-fire bird population recovery & long-term climate & short-term weather conditions, & (3) impacts on forest soils. The structure & l&scape composition of the Mountain Ash ecosystem has been radically altered over the last century. This has resulted from the combined impact of several large fires, including the 2009 fires as well as widespread clearfell logging that has been conducted within state forests over the last 50 years. The ecosystem now supports old growth cover that is 1/30th to 1/60th of what it was estimated to have been prior to European settlement. The ongoing decline of key components of the Mountain Ash ecosystem has led to it being classified as Critically Endangered & at high risk of ecosystem collapse. We argue that current forest policy & practices need to better mitigate the effects of fire on this already highly disturbed forest & enhance the possible persistence of species in this ecosystem. Several key strategies are required to do this. First, there is a need to significantly exp& the extent of old growth within the Mountain Ash forest estate. This is because fire severity is diminished in such areas. Spatial contagion across old-growth dominated l&scapes also may be suppressed relative to l&scapes composed primarily of young forest. Allied management strategies include the protection of more mesic parts of Mountain Ash l&scapes as these are less likely to burn or at least burn at high severity. Such enhanced protection should include an exp&ed network of buffers around drainage lines & waterways as these are where fire severity is likely to be lowest & also where old growth elements like large old hollow-bearing trees are more abundant. In addition, all existing living & dead hollow-bearing trees need to be protected by buffers of unlogged forest within wood production forests to promote their st&ing life & better conserve cavity-dependent fauna such as the Critically Endangered Leadbeater’s Possum (Gymnobelideus leadbeateri) & other declining taxa like the Greater Glider (Petauroides volans).