Green roof vegetation for North American ecoregions: A literature review

A green roof is a vegetated roof or deck designed to provide urban greening for buildings, people, or the environment. Made popular across Europe over the past few decades, green roofs are now becoming more familiar to North Americans as some cities have built green roof pilot projects and adopted incentives for using green roofs or even require their use. Green roof standards and guidelines are also emerging to be used for governance and project specification. Although much is known about the application of green roofs across Europe, much less is known about their application across North America's diverse ecological regions. When considering the many decisions required in applying green roof technology to a specific place, there are few choices more critical to their success than the selection of appropriate vegetation. We conducted a review of green roof research to investigate what is known about the application of plants on green roofs across North America and their ecological implications. Results indicate that investigation sites across ecoregions begin to reveal differences in plant survival. Although ecological investigations are limited, their results show improved plant performance and ecological services with diverse green roofs. We conclude that as green roofs continue to become regulated and adopted in policy, further development of standards and guidelines is needed. To date, there is no common ground for reporting of green roof research, and we make recommendations for facilitating such efforts for improved research, policy development and their management across North America's diverse ecological regions.