Assessing the effectiveness of urban nature-based solutions for biodiversity and human well-being

Abstract

In response to multiple ecological, climatic, and social challenges in cities, nature-based solutions (NbS) are increasingly promoted to support sustainable and resilient urban futures. Despite their potential, effective application of NbS requires a clear and systematic understanding of their effectiveness in addressing urban challenges. This thesis assesses the effectiveness of urban NbS for biodiversity and human well-being and examines how evidence can support NbS decision-making. It first builds a global evidence base of 547 empirical urban NbS cases. The assessment shows that NbS generally produce positive effects compared with non-NbS alternatives, although performance varies with NbS type, outcome domain, and comparison design. Evidence on biodiversity remains concentrated on specific taxa, selected NbS types and commonly used metrics, while studies assessing biodiversity and human well-being simultaneously remain scarce. Using The Hague as a local case study, the thesis shows that multifunctionality differs across NbS types, while multifunctionality outcomes are sensitive to indicator selection and aggregation methods. Finally, it develops an evidence-based decision-making framework for NbS that embeds evidence explicitly throughout the process, from planning and implementation to evaluation and learning. The thesis provides insights into how urban NbS effectiveness can be assessed and how evidence can inform planning and implementation decisions.