Co-location and Scientific Collaboration Among Environmental Research Infrastructures: Insight from Hyytiälä SMEAR II and Castelporziano

European environmental research infrastructures (RIs) are strategically positioned to address pressing environmental challenges. However, no single RI can generate the comprehensive knowledge required to support Europe’s transition toward a sustainable future when operating in silos (eLTER RI, 2023). To meet this challenge, co-location of RIs has emerged as a key strategy for fostering integration, collaboration, and joint scientific innovation. Collectively, RIs such as eLTER, AnaEE-ERIC, ICOS, LifeWatch, and ACTRIS provide complementary long-term, high-quality data on ecosystem processes, which are essential for understanding climate change impacts and biodiversity loss. This study examines the concept of co-location across four dimensions: data sharing, funding, physical location and instrumentation, and coordination and governance. Using two European case studies, including Hyytiälä SMEAR II (Finland) and the Castelporziano Presidential Estate (Italy), the study explores how co-location is interpreted and implemented in practice. Data were collected through RI documentation and semi-structured interviews involving principal investigators, scientific advisors, and technical personnel from the five RIs represented at the study sites. Findings show that co-location initially emerged from shared scientific interests, particularly the need to observe interactions between the atmosphere and ecosystems. However, conceptual ambiguities persist, especially regarding spatial proximity, scientific criteria, and terminology. The study identifies key benefits, challenges, and institutional dynamics shaping RI integration, including shared physical infrastructure, staff mobility, governance structures, data management, communication strategies, cost-sharing, collaborative funding, knowledge exchange, team integration, and collective responses to cross-disciplinary scientific questions. Overall, the results offer actionable insights into how collaborative infrastructure models can enhance efficiency, scientific impact, and policy relevance across European environmental monitoring systems. These findings contribute to the broader effort to strengthen coordination and alignment among RIs in addressing global environmental challenges.