Evaluating the Socio-economic Impact of Citizen Science: Lessons from 54 European Environmental Initiatives for Urban and Regional Policy

Citizen science (CS) initiatives are increasingly recognised as valuable contributors to environmental monitoring, urban governance, and regional planning. Yet their potential to inform public decision-making is undermined by a persistent evaluation deficit: most projects lack standardised frameworks for assessing their socio-economic impact. This paper presents an empirical analysis of 54 European CS projects drawn from the European Commission's Joint Research Centre inventory of citizen science activities for environmental policies. We examine the extent to which these initiatives adopt socio-economic evaluation methodologies, their documented policy uptake, and their survival beyond initial funding periods. Our findings reveal that half of the analysed projects reported no impact assessment whatsoever, and among those that did, methodological fragmentation (spanning survey-based evaluations, indicator frameworks, and cost-benefit analyses) prevents meaningful cross-project comparison. Despite 65% of projects declaring policy relevance, actual documented policy uptake remains limited. Notably, projects that conducted impact assessments were more likely to continue operating after their initial funding period. These findings have direct implications for urban and regional planning, where the integration of citizen-generated data into decision support systems requires evaluable and comparable evidence. We situate our analysis within recent developments in CS-policy integration and propose directions for standardised evaluation approaches tailored to urban and regional contexts.