Urban green roofs promote metropolitan biodiversity: A comparative case study

Urban green spaces can provide habitat and resources for urban dwelling fauna. Suburban green spaces occur most commonly as parks and roadside vegetation, but as human populations grow and space in cities becomes increasingly limited, space-efficient green solutions like green roofs and walls in metropolitan areas are becoming increasingly common. However, the efficacy of these forms of green infrastructure in attracting and promoting biodiversity remains limited. To address this, we compared arthropod, gastropod, and avian species richness and diversity between green and conventional roofs on neighbouring and identical buildings in metropolitan Sydney, Australia. By monitoring local biodiversity using motion sensing camera traps and regular insect surveys, we found that the green roof supported four times the avian, over seven times the arthropod, and twice the gastropod diversity of the conventional roof. Only the green roof attracted locally rare species including blue banded bees (Amegilla Cingulata) and metallic shield bugs (Scutiphora pedicellata). Our results suggest that green roofs, like other urban green spaces, can have ecological significance by attracting and supporting urban fauna that may then add important functional capacities to previously depauperate spaces. This study demonstrates the potential for the widespread adoption of green roofs to create more biologically diverse cities.