Prioritizing Urban Nature-Based Solutions to Support Scaling-Out Strategies: A Case Study in Las Palmas de Gran Canaria

Nature-based solutions (NbS) can synergistically improve human well-being and biodiversity in urban areas by enhancing ecosystem functions and services. Scaling out NbS, understood as the widespread application of NbS in multiple contexts, is an important policy ambition to increase the number of people and regions benefiting from NbS. However, designing scaling-out strategies requires considering critical aspects of the nexus between NbS and ecosystem services (ES) supply to yield large-scale benefits effectively. The aim of the study is twofold: (i) to simulate the stepwise implementation of multiple NbS and (ii) to quantify their cumulative impacts on ES supply and beneficiaries. The NbS implementation was guided by a method that prioritizes different NbS types in multiple sites, by combining spatial information on ES demand and land suitability with a qualitative description of ES supply by NbS type. The cumulative impacts were computed stepwise using GIS modeling. The study was conducted in Las Palmas de Gran Canaria (Spain), focusing on five types of NbS (urban forests, urban parks, community gardens, infiltration ponds), and five ES (runoff mitigation, stormwater treatment, soil erosion control, recreation, and food supply). Overall, 179 NbS were simulated in 130 sites distributed in the city. The findings showed an improvement in all services, albeit significant increments occurred only for certain services. We observed a non-linear relationship between NbS and impacts, including constant, positive, and negative trends. We discussed several factors that were determinants of impacts, providing insights on how to design scaling-out strategies from the biophysical perspective. Moreover, we reflected on the role of multifunctionality, social preferences, and economic feasibility as prioritization criteria for NbS. Finally, we addressed the implementation of NbS scaling-out strategies from a broader perspective, deepening governance, economic and planning challenges, and potential actions for the case study.