Participatory soil citizen science: An unexploited resource for European soil research

Soils are key components of our ecosystems and provide 95%–99% of our food. This importance is reflected by an increase in participatory citizen science projects on soils. Citizen science is a participatory research method that actively involves and engages the public in scientific enquiry to generate new knowledge or understanding. Here, we review past and current citizen science projects on agricultural soils across Europe. We conducted a web-based survey and described 24 reviewed European citizen science projects in the light of the 10 principles of citizen science and identified success factors for citizen science. Over 66% of the projects generated soil biodiversity data; 54% and 42% of the projects generated data on vegetation cover and soil organic carbon, respectively. Our findings show that soil citizen science projects aligned with the 10 principles of citizen science offer an unexploited resource for European soil health research. We conclude that promoting co-creation, fostering knowledge-sharing networks and enabling long-term communication and commitment with citizens are success factors for further development of citizen science on soils.