Engaging the public in plant science: Communication facilitators and barriers of scaling up a citizen science campaign

1. Volunteers have been involved in nature observations for decades through citizen science initiatives, providing large data sets as well as problem identification that allow a more complete understanding of many natural phenomena. Although communication is a core component in citizen science, the key factors that determine its effectiveness in national and transboundary campaigns aimed at broad audiences have remained unclear. 2. Using the pan-European citizen science campaign ‘Looking for Cowslips’ spanning across 31 European countries as an example, we explored the main communication facilitators and barriers campaign organisers face in different European regions when engaging the public in citizen science. To do so, we conducted interviews, questionnaires and discussion groups with the campaign organisers. 3. The results indicate that communication in citizen science initiatives poses a challenge, particularly for researchers, who often do not have sufficient time or means for the necessary engagement and communication efforts. In addition to the ecological characteristics of the focal species in the different regions of Europe, the key aspects that need to be considered for planning effective communication in transboundary citizen science projects include various socio-cultural factors, such as the traditions related to citizen science in different countries as well as local indigenous knowledge. 4. Our study shows that collaboration between academic institutions and environmental non-governmental organisations, but also the contribution by local co-organisers at the national level, is crucial for the effectiveness of international citizen science campaigns. In addition, facilitators and barriers of communication need to be considered in each region separately as even at the European scale, we observed a high variability of environmental and socio-cultural settings. 5. Synthesis. In an era of detrimental consequences of human activities on natural ecosystems, it is vital to include society in observations to determine the impact of environmental change on biodiversity through citizen science approaches. Substantial advances in technological tools have helped to foster these initiatives across vast spatial scales. Nevertheless, it is also crucial to select the right pathways for communication to compete with vast amounts of other information and to reach potential participants in varying socio-cultural contexts of different countries.