Greens roofs are often promoted as novel habitats that can be used to increase the biodiversity of cities, particularly in dense urban cores. Many regulatory standards or certification programs for buildings now incorporate green roofs for their biodiversity value. However, the success of green roofs designed for biodiversity has rarely been evaluated and the claims of positive biodiversity outcomes could sometimes be criticised as a ‘green wash’ applied by building developers and architects. Using the scientific literature, books detailing green roof projects and published conference proceedings, we reviewed and quantified the ecological motivations cited by green roof projects that aim to increase biodiversity.
The most frequent was ecological restoration or creation of habitat but provision of habitat for rare species and pollinators, ecological compensation for habitat destroyed at ground level and the development of ecological corridors or linkages were also cited. The validity of these motivations are critically reviewed against current ecological theory and evidence from urban ecology studies. Green roofs can be used to increase urban biodiversity but to do so current green roof industry practices and designs must change.