Who watches the worms? Motivation and (non-)participation in a contributory citizen science project

Citizen science projects rely on public participation to generate data and promote engagement with science. However, little is known about the motivations of individuals who register for citizen science projects but ultimately do not participate. Understanding non-participation is important for improving recruitment and engagement strategies. This study used Earthworm Watch, a UK-based soil biodiversity citizen science project that ran from April 2016 to August 2018, to explore the motivations of both participants and non-participants, and to examine how these relate to demographic factors and survey completion rates. A total of 1,678 participants registered for Earthworm Watch. The overall survey return rate was 12.75%, with no significant differences by age or gender. The provision of physical survey packs did not significantly affect completion rates. Direct contact with project staff was the only recruitment method associated with a significantly higher survey return rate. Significantly more registrants were female than male across all age groups. Motivations related to understanding and values were most reported, with participants often expressing a desire to learn more or to contribute to the topic, but these participants contributed fewer surveys than those without those motivations. Social motivations were mentioned less frequently but were more commonly reported by women. Younger participants were more likely to cite career-related motivations. The limited impact of physical materials on participation suggests that designing projects for immediate and accessible involvement could be more cost-effective. The significant influence of meeting project members and hands-on experiences at events strengthens the case for including these activities in engagement plans. Motivations to participate in Earthworm Watch varied by demographic factors such as age and gender; however, when significant, they influenced only the number of surveys submitted, not the likelihood of participation. This indicates that a one-size-fits-all approach to engagement may be ineffective. Tailoring recruitment and feedback strategies to align with participant demographics and motivations may enhance engagement and survey return rates in future citizen science projects.