Abstract
In May 2024, a workshop was held as part of the European Citizen Science Association (ECSA) 2024 conference in Vienna to explore the creation of transnational communities to upscale citizen science, to address global issues as outlined by the European Union Horizon Missions and their objectives. This report summarises the discussions and issues that were raised during the workshop, from the point of view of a range of different actors in the citizen science discipline. This includes success stories of projects that have upscaled to an international scope, their methodologies for doing so, and the challenges citizen science initiatives face when attempting to contribute to global-scale challenges. The examples shared demonstrate a range of approaches when upscaling citizen science projects, giving rise to discussions regarding project management, shared learning and practice, citizen science tools and resources, scalability and context, and data interoperability. The success and challenges revealed will provide a clear roadmap for current and future citizen science practitioners, especially those with the ambition of upscaling their efforts to tackle challenges at national, regional, or global levels.