The relationship between green roofs and urban biodiversity: a systematic review

As a form of green infrastructure, green roofs can enhance urban biodiversity by providing complex vegetation structures, supplying increased foraging and roosting opportunities for animals and increasing habitat connectivity. Although it is widely believed that green roofs can promote urban biodiversity, this idea has not been widely studied on an empirical scale. Therefore, a systematic understanding of the relationship between green roofs and biodiversity from different perspectives is still lacking. Here we provide a systematic review of the empirical literature on the relationship between green roofs and biodiversity. The results suggest that green roofs benefit urban biodiversity to some extent but cannot replace quondam natural habitats or complex artificial greening environments. Additionally, the studies reviewed here focused primarily on the diversity of plants or arthropods and were conducted almost exclusively in the United States and the United Kingdom. Moreover, most studies investigating the factors of green roofs affecting biodiversity focused on roof area, height, age, substrate depth, and plant community. To improve our understanding of the relationship between green roofs and urban biodiversity, more extensive research, particularly in developing countries, as well as more in-depth studies of a greater number of species and taxa, including chordates, mollusks and microbes, from different perspectives (e.g. at the genetic level) and other potential pathways are needed. In the future, the density, distribution pattern, distance and location relationship between different green roofs should be considered in an integrated manner. In order to more effectively support urban biodiversity, green roofs should be used in conjunction with other urban green spaces.