Anniversaries provide great opportunities to celebrate achievements, to look into the future, and to do some self-reflection. I have the honour of doing so in a specific field of science communication that I’m familiar with: the field of citizen science communication, especially with a European focus. I hope this commentary prompts others who are experts in their regions of the world to also reflect on the past and the future for this growing field.

How can citizen science (CS) be engaging? What does engagement entail? Who needs to be engaged? What are the challenges and opportunities of engagement in CS? After two years of lockdown and isolation, these were some of the questions debated by engaged researchers, students, and practitioners at the ‘Engaging Citizen Science Conference 2022’, (CitSci2022), held April 25th–26th at Aarhus University, Denmark. The conference aimed to showcase and share knowledge, ideas, and innovations on engaging citizens in scientific processes to secure the field of citizen science to thrive and expand. Nearly 250 participants, mainly from Europe, participated in an extensive programme with various session formats that provided an interactive and inspirational space for presenting and negotiating experiences, challenges, and enthusiasm for CS. This review presents highlights from the event and some reflections from the reviewer, including thoughts on what engagement means, and concluding with focus points that practitioners, researchers, and students may consider when engaging citizens in science and organizing similar events in future.

Citizen Science (CS) can help change the paradigm of science communication. To test this, 38 ongoing CS projects from Italy, Portugal and Spain have been selected by the H2020 NEWSERA project to act as pilots in the development of communication strategies, specifically targeting stakeholders in the quadruple helix. The projects, together with stakeholder representatives and science communication and journalism professionals participated in a series of workshops — #CitSciComm Labs — where communication strategies were co-designed, using adapted design-thinking methods. The innovative methodological approach is hereby presented and can be an inspiration for others willing to implement improved communication strategies to target different stakeholders.

Despite the societal relevance of energy research, there is a distinct lack of citizen science initiatives in the field. This paper reports the experience of a participatory and innovative strategy to develop a citizen science initiative for solar energy research. A number of stakeholders participated in the definition and implementation of the initiative, and tools such as surveys and a hackathon were employed. The process described aims to provide a blueprint for transforming the relationship between citizens and research into societal challenges. Here we describe the collaborative process and analyse the main opportunities, limitations and future perspectives.

Young children are actors usually excluded from political decisions and also from many science communication projects. Participatory science communication models can help to connect their everyday life with both local policies and science-related content. Using visual methodologies for engagement, we aimed at understanding what preschool children prefer in the city landscape. Results show how young children envision a “better city” and how that construction might defy current scientific knowledge. It further illustrates how science communication can be used to co-produce new knowledge, contributing to the debate about people's needs and perceptions related to science-based options.

Citizen science opens the scientific knowledge production process to societal actors. In this novel collaboration process, scientists and citizens alike face the challenge of new tasks and functions, eventually resulting in changing roles. Role theory provides a way of conceptualizing the roles that people take in communication and interaction. We use role theory to create a framework that identifies scientists' and citizens' tasks in citizen science projects, main aims of communication, spaces they interact in, and their roles — thus providing a structured way to capture communication and interaction in and about CS for further scientific reflection and practical application.

Despite being a critical environmental problem, soil pollution is not usually considered as a relevant issue by the general public. This disinterest derives from traditional procedures to assess soil pollution that are quite complex and costly, not considering any form of citizen involvement. Seeking to challenge this situation, the project “Nuestros Suelos” (Our Soil) aimed at designing and testing a low-cost participative soil pollution assessment toolkit. The final prototype included several participative modules, going from an assessment of the history of local soils to measuring heavy metals such as Arsenic and Copper. Tested with low-income communities in northern Chile, the toolkit was able not only to produce multiple kinds of data but also a public that started to understand and care about the issue.

Co-creation aims at integrating citizens in the entire research process. The citizen linguistics project German in Austria tests this approach in the humanities based on the assumption that language is ubiquitous. The project combines different forms of public participation, including a co-created format, where citizens can raise (and answer) research questions about the German language in Austria and a linguistic treasure hunt, where citizens collect and analyze data on linguistic landscapes. However, co-creation was hard to implement. Despite a high number of participants, their willingness to contribute to more than one research step was low.

In 2021 Sweden’s first national portal for citizen science will be launched to help researchers practice sustainable and responsible citizen science with different societal stakeholders. This paper present findings from two surveys on attitudes and experiences of citizen science among researchers at Swedish universities. Both surveys provided input to the development of the national portal, for which researchers are a key stakeholder group. The first survey (n=636) was exclusively focused on citizen science and involved researchers and other personnel at Swedish University of Agricultural Science (SLU). 63% of respondents at SLU had heard about citizen science (CS) prior to the survey; however a majority of these (61%) had not been involved in any CS initiative themselves. Dominant reasons for researchers choosing a CS approach in projects were to enable collection of large amounts of data (68%), improving the knowledge base (59%), improving data quality (25%), promote participants’ understanding in research (21%) and promote collaboration between the university and society (20%). The other survey (n=3 699) was on the broader topic of communication and open science, including questions on CS, and was distributed to researchers from all Swedish universities. 61% of respondents had not been engaged in any research projects where volunteers were involved in the process. A minority of the researchers had participated in projects were volunteers had collected data (18%), been involved in internal or external communication (16%), contributed project ideas (14%) and/or formulated research questions (11%). Nearly four out of ten respondents (37%) had heard about CS prior to the survey. The researchers were more positive towards having parts of the research process open to citizen observation, rather than open to citizen influence/participation. Our results show that CS is a far from well-known concept among Swedish researchers. And while those who have heard about CS are generally positive towards it, researchers overall are hesitant to invite citizens to take part in the research process.

Undertaking citizen science research in Public Health involving human subjects poses significant challenges concerning the traditional process of ethical approval. It requires an extension of the ethics of protection of research subjects in order to include the empowerment of citizens as citizen scientists. This paper investigates these challenges and illustrates the ethical framework and the strategies developed within the CitieS-Health project. It also proposes first recommendations generated from the experiences of five citizen science pilot studies in environmental epidemiology within this project.