An evaluation framework to assess multiple benefits of NBS: innovative approaches and KPIs

Nature-based solutions (NBS) generate different impacts at the urban scale, such as the ability to regulate water or store carbon, comparable to traditional, gray infrastructures in a more cost-efficient way. On the other hand, by their intrinsic nature, NBS do deliver a series of other services that are commonly defined as social, economic, and environmental cobenefits. These benefits are not always valued in a consistent and complete way, so there is the need to compile a more comprehensive evidence base on the social, economic, and environmental effectiveness of NBS. The chapter attempts to identify a categorization of the existing NBS and define the ecosystem services (ES) provided by them. Furthermore, starting from the results achieved through the definition of the existing NBS frameworks assessment, the chapter will identify a set of key performance indicators KPIs, based on the ES produced by NBS, to measure the economic, social, and environmental benefits generated in by NBS at the urban level taking into account their multifunctional character. In total, 66 key performance indicators have been individuated: 3 for provisioning services, 38 for regulating services, 17 for cultural services, and 8 for supporting services. Each indicator has been associated to a category of ES in order to measure and evaluate the performances of NBS implemented in cities.