Understanding the temporal effects of bushfire on the ecological communities in the Sydney basin using the koala (Phascolarctos cinereus) populations as an umbrella species

Abstract

Following the unprecedented 2019-2020 bushfires in eastern Australia, the effects of climate change are more apparent than ever. Under the current warming climate, scientists predict that summers will become hotter and drier, increasing the likelihood of more frequent and higher severity mega-fires like the 2019-2020 bushfires. Thus, more research must be done to understand how species react to fire beyond the immediate effects of the flames. So far, knowledge about how fire affects vulnerable native species like the koala in the long-term is poorly understood. This study was conducted following the 2019-2020 fires surveying between December 2020 to January 2022. It aimed to determine if the time since fire affects the biodiversity and vegetation in koala habitats of the greater Sydney region. This study demonstrated that time since fire does affect the ecological communities of the greater Sydney region. It was determined that in many factors time since has a significant effect. Time since fire was shown to have a positive effect on overall animal species richness, arboreal mammal species richness, introduced species richness, bird species richness, wonga pigeon presence, brushtail possum presence and wombat presence. The results showed that there is a negative correlation between time since fire and vegetation understory cover, with the recently burnt sites recording double the amount of relative understory cover than the long-term unburnt sites. This was then shown to be linked to the lower overall animal species richness in recently burnt sites. However, for many other factors in this study, it was revealed that time since fire had no significant impact. Although the findings suggested that koalas prefer long-term unburnt habitats, being found in more long-term unburnt sites than recently burnt sites, this difference was not significant. For other faunal and flora factors, such as overall predator presence, fox presence, weed species, vegetation species richness and the species richness of small, medium, and large-sized native mammals, time since fire also had no significant effect. From this study, it is evident that vulnerable species need unburnt habitats to survive a fire. Many species favour long-term unburnt habitats, even a few years after fire, which highlights the role of unburnt patches during and after bushfires. With the current prediction of more frequent and intense mega-fires like that of the 2019-2020 fires, it is more important than ever that governments protect koala habitats from land clearing and fire wherever possible. Without these unburnt patches, the populations will be at greater risk of extinction.

Date of Award	2022
Original language	English