Green roof ecosystem services in various urban development types: A case study in Graz, Austria

In this paper, we describe how different urban development types and environmental conditions could affect the broad distribution of green roofs in Graz (Austria). A GIS-based mapping method was applied along the lines of four ecosystem services (i.e., regulation of microclimate temperature regulation, support of air quality improvement support, stormwater retention and biodiversity enhancement). The results are rather positive and indicate that green roofs are fit on 87 % of the investigated roof area (172 out of 203 buildings) based on roof dimensions and constructional measures. Among the investigated roof area, 63 % was classified as having a 'high need' for greening and, thus, a need to generate ecosystem services in urban environments. These results present a paradox: Roofs on block and row development are more appropriate for greening purposes than roofs on historical perimeter block development, but the latter is often found in environments where green roofs are needed more (i.e., inner-city centres). Therefore, city planners should consider using different greening strategies for distinct urban development types under diverse environmental conditions and prioritise the greening actions accordingly. These findings may be relevant in other historically grown, centrally compact European cities.