Green roofs and green walls are no longer niche design features but proven, scalable nature-based solutions that can significantly enhance biodiversity, climate resilience, energy efficiency and human well-being in European cities. This is a central finding of a new knowledge synthesis report prepared by the Science Service for Biodiversity that is being developed by BioAgora in response to a relevant knowledge request submitted by DG Environment to the EC Knowledge Centre for Biodiversity (KCBD).