Analyzing the Principles and Key Features of Nature-based Solutions (NbS) in Urban Greening (UG): A Systematic Review

Problem statement: Climate change and its consequences influence all environmental, social, and economic conditions of cities. One of the most important ideas to overcome urban issues is implementing urban greening (UG) to improve the ecology and sustainability of cities; however, the manner ofadopting this idea is facing numerous challenges. In recent years, Nature-based Solutions (NbS) have proposed an emerging and comprehensive concept for solving the ecological and social challenges of cities at macro and micro levels.Research objective: The main goal ofthe research is to identify and analyze the concept ofNbS in solving the challenge of managing urban green structures from both theoretical and practical dimensions. Based on this concept, the current research to answer the question ofhow and in what dimensions NbS, as a comprehensive concept, may support the process of greening cities.Research mthod: This study investigates the concepts and principles of NBS and extracts its features by applying the systematic review of theoretical foundations and adopting the analytical method; it is followed by targeting the added values and its conceptual and operational obstacles by addressing the concept of UG.Conclusion: NbS as a transdisciplinary and collaborative concept, by considering the dynamics of the environment, suggests planning for long-term projects with specific solutions for each place while preserving natural, biological, and cultural values to solve the complex challenges. Most of the features and principles of these solutions overlap with UG concepts, and from the operational aspect, they are a suitable and relatively comprehensive approach for implementing the desired concepts compared to UG approaches. However, a more precise definition is required to address the conceptual nature of NbS, as they are still encountering theoretical and practical obstacles. These conceptual barriers trigger both basic concepts and explanations of perceptual dimensions, while the implementation barriers consist of weak communication between organizations, and between them and the related stakeholders, which includes the temporal-spatial dimensions as well. According to the three-case method ('concept', 'principles & characteristics', and 'implementation processes'), the study mainly focuses on two main categories to remove obstacles: 1) considering the features of entirety and multiplicity to resolve the conceptual obstacles, 2) defining the principles of Realism and the applicability, process-based concept, and acceptability of solutions in eliminating the implementation obstacles.