Urban Bushland Wildfire Adaptation: Lessons From Managing Grassland Biodiversity and Woody Thickening on the Queens Domain, Hobart, Tasmania

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ABSTRACT Urban bushland fragments have important natural and social values. Their management is challenging because they typically have experienced complex historical disturbances, making it difficult to settle on the most appropriate restoration targets. We illustrate these issues by chronicling vegetation and fire regime changes in the Queens Domain, a 230‐ha bushland fragment adjacent to central Hobart, Tasmania. This area is at the southernmost end of the grassy woodlands occupying a rift valley that divides western and eastern Tasmania. The establishment of Hobart in 1804 by the British disrupted millennia of Tasmanian Aboriginal management, which had maintained a balance between grass, trees, fire and marsupial herbivores in these grassy woodlands. In the early 19th century, the Domain was used for grazing by sheep and cattle, and there was ongoing removal of trees for timber and firewood. By the late 1800s, the natural values of the Domain were increasingly appreciated, leading to provision of public amenities and restrictions on grazing and tree clearing. The exclusion of domestic herbivores led to an increase in grass biomass and more frequent uncontrolled fires. By the late 20th century, dense understories of casuarina ( Allocasuarina verticillata ) established. Ecological surveys, which ran from the 1970s to the 2020s, highlighted the need for targeted management of several endangered grassland herb species, and led to a major programme to reverse casuarina encroachment using mechanical clearing and poisoning. Additionally, concerns about increasing fire risk underpinned a programme of prescribed burning in grassy eucalypt woodland. These interventions have been effective in returning the Domain to a more open woodland state. However, there remains uncertainty as to their costs and benefits for biodiversity as well as their effectiveness in reducing fire hazard. To resolve this uncertainty, targeted experimentation is needed. We briefly describe such an experiment we have established to test the effects of thinning and prescribed fire on fire hazard, floristic diversity and wildlife assemblages in a nearby reserve invaded by casuarina. The findings of this experiment are designed to be generalised to other grassy woodlands in southern Australia, especially urban bushland fragments.

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