Streetscale bioretention basins in Melbourne and their effect on local biodiversity

Development of water sensitive urban design (WSUD) in Australia is rapidly changing urban landscapes by incorporating engineered stormwater management systems such as bioretention basins. Despite these landscape changes, little is known about their effect on urban biodiversity. The biodiversities of six bioretention basins and six corresponding paired greenspaces (divided into two subgroups) in the Melbourne area were compared using ground-dwelling terrestrial invertebrates as biodiversity indicators. Overall, the number of species, species richness and diversity displayed a decreasing trend from bioretention basins to gardenbed and lawn-type greenspaces. This trend may reflect the possible decreasing habitat resources. Species composition was significantly different in these landscape types. The differences in low-stratum vegetation, pH, leaf litter depth and gravel were the main habitat factors influencing the invertebrate communities of these landscapes. The transition from traditional urban greenspaces to bioretention basins potentially promises to enhance urban biodiversity. Landscape planning at the urban-design scale should consider reducing lawn as environmentally unsustainable urban greenspaces. At the streetscape scale, a combination of bioretention basins and gardenbed-type greenspaces may provide ecologically robust and aesthetically pleasant urban streets. This study was conducted in a summer season only and caution should be taken in generalizing the outcomes over an entire year.