Monitoring Nature-based Solutions: A Framework for Assessing the Transformative Potential of Urban Nature-based Solutions

Nature-based Solutions (NbS) are increasingly recognised as key instruments for addressing interconnected urban challenges related to climate change, biodiversity loss, and social well-being. However, their monitoring potential is still difficult to assess due to a lack of comparable monitoring approaches. This paper presents the Monitoring & Evaluation (M&E) framework developed within Task 4.4 (T4.4) of the Horizon Europe project Commit2Green (C2G; Project n.101139598), designed to assess the performance, impacts, and transformative potential of urban NbS. It responds to the need for robust and comparable evidence on how NbS contribute to short-term outputs and mid-term outcomes, while providing cities with a structured and scalable tool to support long-term socio-ecological transformations.
The M&E framework proposed here is grounded on the internationally recognised United Nations Environment Assembly’s (UNEA) definition of NbS and it builds on the European Commission’s Handbook for Evaluating the Impact of Nature-based Solutions. The adopted Theory of Change (ToC) approach helps structuring causal pathways, linking societal challenges, NbS interventions, available resources, outputs, outcomes, and long-term impacts. This approach enables cities to articulate assumptions, identify leverage points for change, and systematically assess whether the implemented NbS are leading to the desired transformations in urban ecosystems and contributing to path-shifting, persistent, and system-wide change.
The framework integrates multiple spatial (pilot, district, city) and temporal (output, outcome, impact) dimensions within a standardised matrix. The Key Performance Indicators (KPIs) are designed to capture environmental, human-related, and biodiversity dimensions. While output and outcome indicators capture delivery quality, transformation KPIs are specifically designed to assess deeper changes in governance arrangements, planning practices, institutional learning, stakeholder engagement, and socio-ecological relationships. KPIs were identified and selected through a mixed-methods approach that combines evidence-based indicator sets from the NbS CataTool, a decision-support system for NbS design and impact monitoring developed by the Italian National Biodiversity Future Center (NBFC), Grant Agreement requirements, and city-specific priorities. The co-design and participatory processes strengthen ownership, contextual relevance, and feasibility, while maintaining a shared reference base for monitoring across different urban contexts.
By embedding feedback loops between monitoring results and decision-making processes, the M&E framework supports an adaptive management strategy. The systematic comparison of baseline, mid-term, and post-intervention data enables the detection of unintended effects, trade-offs, and emerging opportunities. By means of iterative adjustments to NbS design, the cities can therefore use the framework as a driver of learning and institutional change. In doing so, the framework fosters long-term resilience, learning-by-doing, and the gradual reconfiguration of urban governance systems.
The M&E framework developed represents a transferable and scalable model for assessing NbS as drivers of systemic urban transformation. It generates robust and comparable evidence on long-term impacts and transformative change, supports NbS upscaling and replication, and fosters institutionalisation within urban planning. In conclusion, the M&E framework demonstrates how NbS can act as catalysts for transformative change towards climate neutrality, biodiversity conservation and enhancement, and socially equitable futures. In this way, the M&E framework becomes an enabling mechanism for systemic change, supporting cities in navigating sustainability transitions.