Scoping for potential wildlife crossings for koalas and marsupial gliders in the Sutherland Shire and Campbelltown regions of New South Wales, Australia

Arboreal, or “tree-dwelling”, species such as koalas and marsupial gliders may potentially be more vulnerable to the effects of roads, habitat loss and habitat fragmentation due to their high specialisation. The emerging concept of road ecology attempts to reduce the effects of animals on roads and identifies wildlife mitigation structures, including wildlife crossings and exclusion fencing, as the best methods to combat the issue of habitat fragmentation. The Sutherland Shire and Campbelltown regions of Sydney, Australia are of particular interest due to the populations of koalas and various glider species. These regions also have several major roadways present that can impact on species movement and have the potential to disrupt population dynamics and reduce population numbers from animal-vehicle collisions. Crossing structures and other mitigation measures have been used extensively in Australia and worldwide with various levels of success. Spatial analysis of New South Wales BioNet Atlas data was undertaken using GIS software to find areas of high species presence, or “hotspots”. Within the koala dataset, several hotspots were found which mainly existed along the forested and cleared land edge of Campbelltown that is separated by roads. An area of concern was found on a 3.8km segment of Appin Road whereby 12 koalas roadkills were on record, 10 of which coincided with the previous hotspot analysis. Within the marsupial gliders dataset, two main hotspots of species presence were identified. A basic cost surface was also created to generate a suitability and traversability index within the study area. While both of these methods were effective, some issues with data biases and areas with incomplete data were present. Overall, a range of criteria needs to be utilised in order to effectively determine if a mitigation structure is required at a specific location. It is recommended that this study be used as a foundation for future research.