How do nature-based solutions contribute to biodiversity in cities

Abstract

The multifunctional character of nature-based solutions (NbS) in cities, benefiting both biodiversity and human well-being, is gaining increasing attention. Designing multifunctional NbS requires insights in how NbS contribute to urban biodiversity, since biodiversity supports ecosystem stability, resilience and connected benefits for people. However, while knowledge of urban biodiversity has grown recently, a comprehensive understanding of how NbS contribute to biodiversity is still lacking. We analyzed the outcomes of 185 urban NbS cases in 87 cities across 33 countries, based on data collected in a systematic literature review. Our results show that 78% of NbS cases contribute positively to improving biodiversity when compared to non-NbS and, in some cases, their performance was comparable to that of natural reference sites. Moreover, NbS cases consistently showed positive additional effects on non-biodiversity outcomes, leading to predominantly ‘win-win’ solutions benefiting both biodiversity and human well-being. We showed that current evidence is limited to specific taxa (mostly animals), NbS types (e.g., gardens, forests), and commonly used metrics (e.g., species richness, abundance). We also found a lack of comparative studies integrating baseline data to assess NbS contributions to biodiversity effectively. Our research provides insights for developing effective NbS planning and management for biodiversity, advancing the understanding of multifunctional NbS, and expanding NbS evaluations to provide more accessible information for decision-making and policy.