Revisiting the meanings of the Critical Zone through the OZCAR research infrastructure example, definitions and evolutions

Since its first definition by the National Research Council in 2001, the concept of Critical Zone has known undeniable success over the last quarter of a century. A success that is often reflected by the evolution and diversification of its meanings. Recently, Lee et al. (2023) proposed a review that literally focuses on “the meanings of the Critical Zone”. Through an extensive review of the literature across the disciplines and journals, they have identified three loosely overlapping meanings. An ontological meaning, where the Critical Zone is mostly seen as the Earth’s spatial interface where geochemical and biological activity sustains life. An epistemic meaning, where the Critical Zone is considered a product of collaborative efforts between scientific communities to build a whole-system knowledge data-base and library. And finally, an anthropocenic meaning, where the Critical Zone is the vulnerable home of the human species. In this contribution, we aim at revisiting these three meanings through the creation and development of the French network OZCAR (Critical Zone Observatories: Research and Application).Created in 2015 to enhance the collaborations between Critical Zone observatories (Gaillardet et al., 2018), OZCAR is a French Research Infrastructure that gathers 23 national observation services and +120 study sites in metropolitan France and on 5 continents. If most observation services existed prior to the creation of OZCAR, we have seen major evolutions over the last decade as the OZCAR community developed and bloomed. Originally conceived as a spatial definition (ontological meaning), the “Critical Zone” words in OZCAR became a vast collaborative effort to develop the whole system approach and data base (epistemic meaning). It is now also fostering transformative research aimed at preserving our planet’s habitability, i.e., the giant spaceship in which we all live together (anthropocenic meaning).References:Lee, R. M., Shoshitaishvili, B., Wood, R. L., Bekker, J., & Abbott, B. W. (2023). The meanings of the Critical Zone. Anthropocene, 42, 100377.,doi:10.1016/j.ancene.2023.100377.Gaillardet, J., Braud, I., Hankard, F., Anquetin, S., Bour, O., Dorfliger, N., et al. (2018). OZCAR: The French network of critical zone observatories. Vadose Zone Journal, 17(1), 1-24, doi:10.2136/vzj2018.04.0067.