The main objective of this study is understand how the adoption of Nature-based Solutions depend on contextual factors, which can in turn impact the operationalization of these actions. The paper tries to propose a taxonomy for Nature-based Solutions (NbS), and identify and examine the potential contribution of various types of urban NbS to climate change adaptation, particularly stormwater regulation.
The authors conducted a systematic literature review to propose a taxonomy which aims to better understand the process and hierarchies involved in developing NbS. They reviewed 582 empirical studies that introduced, designed, modelled, implemented and discussed the benefits of NbS. They used Deductive Content Analysis (DCA), a method that utilises predefined categories or concepts derived from existing theories, frameworks or criteria to analyse qualitative data. They then developed the taxonomy, represented in the figure below, by combining the connections between the different criteria. The taxonomy links each type of NbS to contextual factors. Thus, by understanding the contextual factors and linking them to interventions, planners and policymakers can take into account the current state of practice in the implementation of NbS across across different cities, countries, regions, scales, and climates, and the potential of these interventions in terms of adaptation, ecosystem services, and other co-benefits.
Based on the 582 empirical studies analysed, Sustainable Urban Drainage Systems (SUDS) are the most dominant approaches of NbS for adaptation. The authors specify that in many African countries, water secuirty and management through rainwater harvesting and adaptation to extreme weather is an area of primary focus. The results also show that urban governance/policy/planning, urban blue-green infrastructure, forestry, water resources and management, land use planning, and disaster management are the key sectors that can effectively plan and implement NbS.
The authors, however, argue in favour of a more holistic approach in the development of strategic plans which integrate various governance structures and policy instruments based on local circumstances and priorities. Doing so will help planners and implementers of NbS understand the short and longer term responses under climate-induced pressures, as well as identify the barriers and enablers to scaling up NbS interventions in different areas and socioeconomic conditions. Thus, a first key takeaway from the study is the need or a holistic approach to NbS based on different geographies. The authors suggest that each region adopt its own type of NbS at different scales and climatic conditions to contribute to adaptation, particularly in the context of stormwater management.
A second takeaway of the study covers the planning and management of NbS. Broadly, urban, city and urban catchments are the three dominant scales for NbS. The authors argue that the city scale is preferable for research and development because NbS are generally more effective when incorporated into large-scale, landscape-based and interconnected interventions. Additionally, by taking into account these broader scales, it enables planners of NbS to consider the potential of surrounding and suburban ecosystems that need to be engaged in the planning and implementation of NbS.
All in all, this proposed taxonomy highlights the potential for urban NbS, which can be diverse, pursue multiple objectives and be multi-functional. It allows planners and policymakers to gain an overview of NbS implementation by categorising different types of NbS and understand their association in different contexts.
