Designing nature to be a solution for climate change in cities: A meta-analysis.

Nature-based solutions (NbS) are designed as a win-win strategy to address societal challenges while providing biodiversity, social, and economic benefits. However, uncertainties and gaps persist, particularly regarding the criteria that define a NbS measure and the specific requirements for a solution to be fully recognized as such, which limit the full potential of these strategies in practice. Another persistent issue is the lack of data on strategy responses across different implementation scales (local, city, regional) and climatic zones (temperate, arid, tropical). This article provides an overview of the potential of NbS to promote climate adaptation in cities. Our meta-analysis, which compiled 7163 records from 89 articles worldwide, indicates that integrating NbS strategies with traditional approaches (gray infrastructure and sustainable technologies) is the most effective response to concurrently address multiple climate-related hazards. Flooding had the highest impact at 35.7 %, followed by increased runoff at 30.5 %. Peak flow and water pollution both had an impact of 10.3 %, while temperature increase accounted for 5.7 %, and decreases in thermal comfort made up 5.0 %. We concluded that all evaluated strategies reduced the impact of climate-related hazards, but this reduction was twice as large when incorporating NbS (18.6 % vs 8.1 %). We also demonstrate that this effect is observed under projected climate scenarios, reinforcing the role of NbS in making cities more resilient and sustainable.