The influence of cultural burns on the density and stress response of koalas on Minjerribah, North Stradbroke Island.

Asitha Samarawickrama

doi:10.25907/00726

Australia is the most fire prone continent on earth and Australian ecosystems have been influenced by fire for millennia. Although fires are typically considered a natural disturbance, humans have influenced the frequency and intensity of fires. Sediment cores confirm an increased frequency of fire coinciding with the arrival of First Nations Peoples to Australia. First Nations Peoples have utilised low intensity fire in mosaic patches, to manage resources and maintain biodiversity, and have accumulated and transferred traditional fire knowledge across multiple generations. However, the suppression of traditional fire management, mainly due to the European colonisation of Australia and the removal of First Nations Peoples from their lands, and the loss of cultural knowledge, contributed to a change in fire regimes across the continent. In addition, anthropogenic climate change is also contributing to unparalleled fire activity, and the frequency of high intensity, severe wildfire events is expected to increase across Australia in future. After centuries of suppression, the reestablishment of patch mosaic cultural burning has resulted in ecological, social and environmental benefits, especially in Australia’s northern savannas and western deserts. Cultural burning is also abating greenhouse gas emissions, by preventing and mitigating large wildfires in flammable ecosystems, hence demonstrating that traditional fire management is an effective tool for mitigating climate change impacts. Following the megafires of 2019-2020, which burnt over 12 million hectares in eastern Australia, there have been calls for the reestablishment of cultural burning to mitigate the impacts of high intensity wildfires on koalas and their preferred eucalypt habitat. However, research on cultural burns in eastern Australia is limited. If cultural burns are to be supported in fire prone eucalypt habitat, the impacts of such burns on native fauna requires investigation. This thesis aimed to bridge this gap, by investigating the effects of cultural burning on koalas, a species that was recently uplisted as an endangered species under federal law (EPBC Act, 1999) in three eastern states. Our work took place on Minjerribah, North Stradbroke Island, a sand island off southeast Queensland, which has been impacted by destructive wildfires previously, and where cultural burns are now conducted under the guidance of the Quandamooka Yoolooburrabee Aboriginal Corporation. Minjerribah has been identified as a haven for koalas due to the limited prevalence of major threats impacting southeast Queensland’s koala populations. However, severe wildfires remain a key threat, and effective fire management remains critical for the conservation of the island’s koalas. In chapter two of this thesis, we used a drone fitted with a thermal camera to obtain density estimates of koalas before and after low intensity cultural burns. Our statistical model showed that cultural burns did not negatively impact koala density at our study sites. Our research revealed a decline in mean density across our study sites after the burns, regardless of treatment. However, the reasons for this decline are currently unclear and long-term monitoring may provide evidence that koala density on the island is subject to seasonal variation. Density varied between sites, and the presence of preferred feed trees may have influenced this variation. Future research incorporating remotely sensed data would be useful in determining factors influencing koala density on the island. Although low intensity cultural burns were not responsible for changes in density, subtle impacts such as koala’s stress response to the burns cannot be overlooked. Non-invasive sampling of faecal glucocorticoid metabolites is now a preferred method to gain insights into the koalas’ stress response. In chapter three, we investigated the influence of low intensity cultural burns on faecal cortisol and corticosterone metabolite (faecal glucocorticoid metabolite) concentrations of koalas on Minjerribah. Mean faecal glucocorticoid metabolite concentrations decreased across all sites after the cultural burns. However, our linear mixed model did not associate this decrease with the cultural burns. The monthly variations in mean faecal glucocorticoid metabolite concentrations revealed in our research is likely explained by seasonal factors and the above average rainfall due to La Nina weather conditions. We aim to build on our work in the future, by incorporating genetics to link hormonal profiles to individual koalas, as individual variations in stress are known to be large. Our work has major implications for the conservation of the endangered koala. We have provided evidence that cultural practices, traditional knowledge, and new technology can be combined to study and protect the koala in fire prone eucalypt habitat. Furthermore, our work has provided a case for cultural burns to be re-established across the koalas’ entire distributional range, and we support and encourage increased collaboration between First Nations Peoples, researchers, governments, managers and other stakeholders for the benefit of koala conservation. Although some management interventions are helping to minimise the decline of this iconic species, it is clear that policies and environmental legislation have failed to protect the koala across much of its range. Immediate and effective action on anthropogenic climate change is vital and cannot be delayed if the extinction of the koala is to be prevented. Our work adds to the mounting body of evidence which suggests that low intensity cultural burns implemented in mosaics, incorporating the traditional fire knowledge of First Nations Peoples, can maintain biodiversity, provide ecosystem benefits, and mitigate the impacts of climate change. However, if cultural burns are to be reinstated across continental Australia, significant barriers such as restricted access to Country, lack of sufficient funding and logistical support, and high levels of bureaucracy, need to be addressed. We support the call for increased funding and more applied fire workshops led by First Nations Peoples to generate support for traditional fire management and increase the potential for partnerships between First Nations Groups and other stakeholders. In conclusion, we hope that the results of this study will support the case for cultural burning by First Nations Peoples to be utilised across the entire Australian continent, to mitigate the impact of large wildfires on not just koalas, but for all species, including humans.

The influence of cultural burns on the density and stress response of koalas on Minjerribah, North Stradbroke Island.

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