The future of citizen science for marine litter research: What are the benefits to be realised and the challenges to be overcome?

Public engagement in marine litter research is increasing. Further advancing this approach requires a critical examination of the benefits of citizen science and the primary challenges that we must overcome. A thematic analysis of survey responses from 56 professionals (scientists and project organisers) who use citizen science to investigate marine litter revealed nine significant benefits alongside ten key challenges. Benefits were identified for the citizen scientists (e.g., learning something new), science (e.g., reducing data collection costs), and the environment (e.g., less plastic waste in the environment). Challenges identified fell within three categories related to: 1) involving citizens in science (e.g., in engaging, training, and retaining citizen scientists), 2) conducting effective science (e.g., raising the credibility of citizen science), and 3) bridging the gap between citizens and science (e.g., pragmatic and safety concerns). Reflecting on these findings and the broader literature, five key recommendations are provided to advance the practice of citizen science within marine litter research: 1) acknowledging the strengths and weaknesses of the approach; 2) strengthening collaboration and harmonisation within and between different citizen science projects; 3) increasing the awareness and value of the approach; 4) listening to and supporting citizen scientists better; and 5) securing sustainable funding for citizen science work. By incorporating these recommendations, key actors (e.g., professionals who organise citizen science projects, decision makers, and funding agencies) will be better able to advance citizen science projects to generate robust data that can be shared globally to assist in the assessment and management of marine litter.