Role of substrate properties in the provision of multifunctional green roof ecosystem services

•Green roofs are widely put forward as providing services for urban ecosystems.•The impact of green roof substrate (GRS) type has been so far poorly studied.•Constraints are great on the choice of green roof substrates.•GRS composition and depth are decisive for trade-offs between ecosystem services.•More multifunctionality studies on the role of GRS on ecosystem services are needed. Urban ecosystems are increasingly recognized as key providers of ecosystem services. Among them, green roofs are particularly fashionable, and are in high demand by citizens, politicians, urban planners and architects. Surprisingly, the functioning of green roofs and the impact of substrate type have been so far poorly studied and impede to optimize a green roof and its substrate to provide targeted services. This article thus discusses the different types of substrate that can be used for green roof and outlines the possible consequences for green roof functioning.