The future of critical zone research in Europe imbedded in eLTER research infrastructure

Although scientific disciplines are becoming increasingly specialised and expert, they nevertheless isolate themselves from one another. This is particularly evident in the study of the Earth's surface. Over time, the geosciences have diverged from ecology, despite the fact that the historical concept of ecosystem (Tansley, 1935) included both biotic and abiotic components. With time and investment from also compartmented institutions, this has led to independent communities developing parallel research and equipping themselves with field laboratories (long-term observatories): geosciences focusing on the biophysical components of water, relief, and soils, and ecology focusing on biodiversity. Even within geosciences, disciplines are isolated and have developed their own “dialects”.

The Critical Zone Initiative, which originated in the US in 2003, was an attempt to encourage these different Earth science communities to collaborate at the level of instrumented scales (Critical Zone Observatories). This initiative has expanded further in Europe, particularly through the SoilTrec FP7 programme (2009–2014), the CRITEX program in France (2022-2021) or the OZCAR and TERENO research networks in France and Germany respectively. Today, these divisions are no longer tenable. The deterioration of the planet's habitability means that we need to return to a much more systemic approach to habitats that support life, particularly humans and their societies. While disciplinary expertise, particularly in experimental developments and numerical modelling, is necessary, it is far from sufficient to understand how changes in biodiversity will affect biogeochemical cycles, water and food resources.

The eLTER (Long-Term Ecosystem, critical zone, and socio-ecological) Research Infrastructure represents a unique and even historic achievement to (re)connect scientific communities working in the field of environmental and sustainability sciences on continental surfaces. At a backbone of permanently operated sites, eLTER promotes a holistic approach from the local/regional to the continental and global scales. In this contribution, we will present eLTER and show how the list of eLTER Standard Observations selected, distributed across different layers or “spheres,” and the categorization of sites (with a focus on the geosphere and hydrosphere) make it possible to capitalize on the previous works of the critical zone community and enrich it with ecological measurements or socio-ecological practices (Zaccharias et al., 2025). The services offered by eLTER RI also exploit recent advances in critical zone modeling. They provide access to a network of sites spanning large environmental conditions open to transnational access and an open data base and hence a unique opportunity for the moving forward critical zone science, at the local to global scales.

eLTER is the European future of critical zone science.

Tansley, A. G. (1935). The use and abuse of vegetational concepts and terms. Ecology,16, 284–307.

Zacharias, S., Lumpi, T., Weldon, J., Dirnboeck, T., Gaillardet, J., Haase, P., ... & Mirtl, M. (2025). Achieving harmonized and integrated long-term environmental observation of essential ecosystem variables-eLTER's Framework of Standard Observations. Authorea Preprints.