Streetscape biodiversity and the role of bioretention swales in an Australian urban environment

For the successful development of Water Sensitive Urban Design (WSUD) or Low Impact Development (LID) as a relatively new concept for stormwater management, it is necessary to understand the effect of these systems on urban ecology.This study determined the effect of bioretention swales as a type of vegetated WSUD system on urban biodiversity. The biodiversity potential of nine bioretention swales and nine corresponding green spaces in the Melbourne area were compared. Invertebrates captured by sweep netting were used as biodiversity indicators.The number of species, species richness and diversity were higher in bioretention swales than in gardenbed and lawn-type green spaces, respectively. The invertebrate communities in these landscapes were affected by mid-stratum vegetation coverage, the number of flowering plants, pH and the slope characteristics of the bioretention swales. These effects might be a response of the invertebrate species to increased refuge and food resources available in these landscapes. Changing conventional planting strips in streets to bioretention swales has promising potential for enhancing urban biodiversity. In particular, reducing the area of lawn-type green spaces to promote sustainable development is recommended.The outcomes of this research have practical implications for landscape designers and managers whose aim is to conserve invertebrate diversity in urban settings.

Research highlights
► This paper examines the biodiversity of bioretention systems and the factors affecting their biodiversity.
► The study used above-ground active invertebrates captured by sweep-nets as biodiversity indicators.
► Conventional green spaces were used as control sites.
► The invertebrate communities were affected by mid-stratum vegetation coverage, the number of plants in flower, pH and the slope of the landscapes.
► Changing conventional planting strips in streets to bioretention swales may enhance urban biodiversity.