Development of an integrative approach for the assessment of ecosystem services and environmental impacts of urban nature-based solutions

Research shows the potential of nature-based solutions (NBS) to provide various ecosystem services (ES) in an urban context (e.g., stormwater management, summer comfort). However, few studies provide multi-criteria indicators based on a mechanistic approach (i.e., modelling process). Furthermore, holistic methodologies that assess both ES and environmental impacts are lacking. To address these shortcomings, a performance assessment method called HIBOU (Hybrid evaluation of Interactions between urban nature, BiOdiversity, and Urban systems) is being developed. It aims to support urban planners in making informed decisions about integrating nature into their projects and optimizing the design of NBS to avoid greenwashing. The aim of the study is to complement this method with NBS and ES, using green roofs and urban trees as proof of concept on the one hand, and stormwater management and functional diversity on the other. The most appropriate models and indicators available in the scientific literature are selected based on operational and validity criteria: water balances calculating runoff as an indicator for stormwater management and the Functional Attribute Diversity (FAD) indicator for functional diversity. The models are then refined and validated with experimental data where available. The generalizability of our approach to other services and urban nature-based solutions is discussed. The challenges of this approach are debated: balancing the diversity and complexity of indicators and the number of input parameters with the operational simplicity of the method.