Evaluating nature-based solutions in urban settings: a life-cycle thinking approach

Green roofs are considered a Nature-based Solution (NbS) to many urban issues by providing multiple Ecosystem Services (ES). Industrial ecology tools, like Life Cycle Assessment (LCA), have proven to be effective in evaluating green roofs’ design, but the integration of ES accounting into LCA is still not systematic. The objective of this study is to apply an integrated ES-LCA methodology to calculate the net environmental benefits and drawbacks of a greening redevelopment at the Milano-Bicocca University Campus (Italy). The scope is to identify sustainable and effective urban restoration alternatives for future similar implementations. At the pilot site, an intensive (and accessible) green roof has been recently built. Here, selected trees, shrubs and herbaceous species have been planted to deliver multiple benefits, with the aim of enhancing and supporting biodiversity in the area. After the collection of foreground life cycle inventory data, a preliminary impact assessment has highlighted the implementation’s hotspots, i.e. the most impactful components. This depends on the upstream production of some construction materials, such as the substrate or the granite for borders and seats. Several scenarios have been developed to evaluate possible improvements of deploying alternative materials, for example recycled or organic ones. Moreover, the NbS benefits have been modelled as “ES supply”, such as mediation of air pollution and carbon sequestration. Finally, the integration of endpoint impacts on ecosystems and positive effects of the greening implementation highlights the importance of species selection and provenance in the NbS planning process.