W. Daniel Kissling, Tom D. Breeze, Camino Liquete, Anne Lyche Solheim, Ian McCallum, Joachim Maes, Tim Hirsch, Maria Lumbierres, Roy H. A. van Grunsven, Pedro Beja, Bruno Smets, César Capinha, Ana Ceia-Hasse, Néstor Fernández, Francisco Moreira, Jessica Junker, Florian Leese, Eleanor Hammond, Lluís Brotons, Alejandra Morán Ordóñez, Simon G. Potts, Joana Santana, Jose W. Valdez, Ingolf Kühn, Marija Milanović, Astrid Schmidt-Kloiber, Dimitrios Bormpoudakis, Dani Villero, Peter Haase, Kristian Meissner, Helge Bruelheide, Marcel Buchhorn, Irene Calderon-Sanou, Miguel Fernandez, Anna Gamero, Anne Gobin, Irene Guerrero, Ute Jandt, Alena Klvaňová, Martina Marei Viti, S. Jannicke Moe, Aletta Bonn, Henrique M. Pereira

To address the biodiversity crisis, global and regional policy frameworks like the Kunming-Montreal Global Biodiversity Framework and the European Green Deal demand to monitor biodiversity. Despite these efforts, existing approaches for monitoring biodiversity remain fragmented and lack data integration. Here, we review and synthesize crucial information for developing an integrated European-wide biodiversity monitoring framework using Essential Biodiversity Variables (EBVs), with the aim to improve data coverage, enhance transnational coordination, adopt advanced technologies, and better inform environmental policies. Using a participatory approach involving over 1500 stakeholders, we prioritized EBVs for assessing biodiversity status and trends and supporting European policies, identified relevant monitoring technologies, developed recommendations for a spatial sampling design, and estimated the costs of implementing a continent-wide biodiversity observation network that covers terrestrial, freshwater, and marine ecosystems. A total of 84 EBVs addressing genetic, species, community and ecosystem-level biodiversity attributes were prioritized. A broad range of monitoring methods is required, especially structured in-situ monitoring schemes and satellite and airborne remote sensing, complemented with citizen science observations, DNA-based methods, digital sensors, and biological observations derived from weather radar. Our suggestions for a more effective spatial sampling design ensure a broad representation of European biodiversity, especially through stratified random sampling, incorporation of existing monitoring sites, filling of spatial gaps, and co-location of monitoring activities. Developing the prioritized EBVs will require to integrate multiple biodiversity data streams, apply advanced modelling techniques for gap-filling, and account for different sources of uncertainty. A digital infrastructure is required with supporting services, and with data being shared using interoperable standards and published on open platforms. The costs of such a European biodiversity observation network were estimated to be at least 5.7 billion Euro over 10 years, including initial investments and annual maintenance. A European Biodiversity Observation Coordination Centre (EBOCC) is needed to coordinate monitoring activities and data management. The network’s benefits for addressing multiple policies, including improved ecosystem services, will by far outweigh the expenses involved in establishing and maintaining the entire network. The illustrated co-design offers a scalable model for developing biodiversity monitoring networks in other continents, with potential adaptations to local policies and conditions.