Impact assessment of citizen science: state of the art and guiding principles for a consolidated approach

Over the past decade, citizen science has experienced growth and popularity as a scientific practice and as a new form of stakeholder engagement and public participation in science or in the generation of new knowledge. One of the key requirements for realising the potential of citizen science is evidence and demonstration of its impact and value. Yet the actual changes resulting from citizen science interventions are often assumed, ignored or speculated about. Based on a systematic review of 77 publications, combined with empirical insights from 10 past and ongoing projects in the field of citizen science, this paper presents guidelines for a consolidated Citizen Science Impact Assessment framework to help overcome the dispersion of approaches in assessing citizen science impacts; this comprehensive framework enhances the ease and consistency with which impacts can be captured, as well as the comparability of evolving results across projects. Our review is framed according to five distinct, yet interlinked, impact domains (society, economy, environment, science and technology, and governance). Existing citizen science impact assessment approaches provide assessment guidelines unevenly across the five impact domains, and with only a small number providing concrete indicator-level conceptualisations. The analysis of the results generates a number of salient insights which we combine in a set of guiding principles for a consolidated impact assessment framework for citizen science initiatives. These guiding principles pertain to the purpose of citizen science impact assessments, the conceptualisation of data collection methods and information sources, the distinction between relative versus absolute impact, the comparison of impact assessment results across citizen science projects, and the incremental refinement of the organising framework over time.