Measuring the contribution of nature-based solutions beyond climate adaptation in cities

Measuring the contribution of urban nature-based solutions (NbS) to climate change adaptation is an essential, though complex, step towards understanding who benefits from them, as well as when, where, how and why. However, urban NbS are also framed as being able to meet multiple objectives relating to biodiversity conservation as well as associated social challenges. The complexity of addressing multiple challenges, combined with conflicting visions of what climate adaptation means at the local level, further burdens the identification of clear and relevant goals, processes and information to track progress (i.e. contributions) towards urban adaptation. To explore and question how current on-the-ground practices address this complexity, we analysed a global dataset of indicators (n = 750 indicators) from 74 NbS projects in 61 cities across 40 countries based on an assessment of the literature regarding information and processes used for evaluating urban NbS for adaptation. This was combined with interviews with local actors who evaluate these NbS projects (n = 15). Our results indicate that current urban NbS projects do not appear to balance climate adaptation with other goals, nor do they uniformly conform to prevailing technical standards of quality of traditional monitoring, evaluation and learning processes. Currently NbS projects tend to primarily prioritise shorter-term high-quality ecological indicators, mostly related to biodiversity, while generally other longer-term social and technical indicators lack quality despite capturing a diversity of potential medium- to long-term contributions of NbS. Various political and social factors that influence the way urban NbS to adaptation are evaluated typically go beyond evaluation purposes and range from using indicators to promote NbS as cost-effective solutions or particular political agendas. The diversity of what makes good information and processes to measure contributions to urban adaptation bolsters calls for establishing processes for flexible, commonly agreed-upon guiding principles. We suggest locally grounded recommendations to help identify fit-for-purpose information and processes to evaluate the potential of urban NbS to address interconnected climate, biodiversity, and societal challenges.