The impact of urbanisation on the mammals of Melbourne - do atlas records tell the whole story or just some of the chapters?

The impacts of urbanisation on the biodiversity of native plants and animals are typically deleterious and potentially profound. These consequences are likely to increase as the size of the human population and geographic extent of many urban areas continue to expand. Unfortunately, the absence of detailed “before development” data makes it difficult to accurately assess changes in species diversity or abundance over time. In this study, atlas data are used to investigate the impacts of urbanisation of the greater Melbourne area on the composition of the mammal community. The mammal community of Melbourne at the time of European settlement in 1856 was diverse, with 50 species recorded. A broad measure of change in distribution found that 16 species were recorded in fewer local government areas in the last 20 years than in the preceding years to 1856; the majority were small ground-dwelling mammals. The converse was true for the microchiropteran bats, with 14 species being recorded in more local government areas after 1980, probably a reflection of improved survey techniques. There was little to no relationship at the landscape scale between the presence of a species or species group and the amount of remnant vegetation or public open space within a 700 m radius of the survey point. This is probably because species that rely on tracts of native vegetation are unable to persist in the urban mosaic of greater Melbourne, while more generalist species are able to cope with the radical changes associated with urbanisation. This study has highlighted the need for surveys of mammal communities that are stratified across the urban landscape to document the conservation status of species and provide the foundation for future state of the environment reporting.