A review of existing tools for citizen science research on soil health

Soil-related citizen science projects have gained significant interest driven by the prominence of soil within public policy agendas. Amongst others, this includes the EU Soil Strategy for 2030, which contributes to the objectives of the EU Green Deal and proposes specific actions to increase citizen engagement on soils. Increasing citizen engagement is also one of the building blocks in the EU Mission: A Soil Deal for Europe. In this work, we reviewed over 60 citizen science projects, across the globe, that considered soil health. We collected citizen science projects based on literature search, expert interviews, suggestions from project partners and through the mailing lists of the European Network for Soil Awareness (ENSA) and the European Soil Data Centre (ESDAC). We then screened all projects for the following characteristics: geographic coverage, duration, scientific factors (e.g. soil properties considered, fieldwork), technological factors (e.g. applications used) and their citizen engagement (e.g. target groups). Two-thirds of the reviewed studies were based in Europe and mostly conducted at regional- or national scales. We recommend to align the citizen science methodology with the desired level of participation. We also identified a need for the development of standardised, user-friendly and cost-effective methodologies to generate soil data. Engagement of citizen can be facilitated through, i.) providing feedback protocols on their scientific contribution and, ii.) assigning qualified mediators or activity leaders to support participants throughout the project. All collected information has been made available as an open-access repository and can inform future citizen-science projects on soil health.