ISTE’s scientific publications include a pluridisciplinary editorial sphere entitled “Earth Systems – Environmental Sciences” and, within this domain, we are now pleased to release a series of works entitled Soils, coordinated by Christian Valentin, as part of the activities of the working group on soils at the Académie d’Agriculture de France (French Academy of Agriculture).

The general title of this series of works, “Soils as a Key Component of the Critical Zone” merits a number of comments.

The Critical Zone (CZ), a concept which is now globally recognized, designates the location of interactions between the atmosphere, the hydrosphere, the pedosphere – the outermost layer of the Earth’s crust, made up of soils and subject to the processes for soil formation, derived from interactions with the other surface components – the lithosphere and ecosystems. Within this zone, there are vital exchanges of water, matter and energy, such exchanges interacting with those of other layers, both oceanic and atmospheric, within the Earth system. Its extreme reactivity, whether physical, chemical or biological, is an essential factor of the overall regulation of this Earth system.

Supporting all forms of life, this thin layer has a high level of interaction with human activities. Examples of these are agriculture, urbanization, resource extraction, waste management and economic activities.

This concept of the Critical Zone (CZ) entirely revives the environmental approach, simultaneously enabling an integrated, descriptive, explanatory and predictive view of the Earth system, of its major biogeochemical cycles and their interaction with the climate system. The view becomes dynamic, explaining all interactions, and opens the way for predictive modeling. Such processes are necessarily integrated with given models, paying special attention to the hydrological cycle as well as the carbon and nitrogen cycles.

Within the CZ, soil is a key component, playing a prominent role in the storage, dynamics and conversion of biogenic elements (carbon, nitrogen, phosphorous – C, N, P) and of all inorganic, organic or microbiological contaminants. This contributes to significantly affecting the quantity and the quality of the essential resources for human activity, these being soils, water and air quality.

Soils thus return to the top of the international agenda, as a result of the major challenges for any civilization. These include agricultural production, climate change, changes and conflicts over land use (deforestation, urbanization, land grabbing and others), biodiversity, major cycles (water, carbon (C), nitrogen (N) and phosphorous (P)), pollution, health, waste, the circular economy, and so on. They appear therefore legitimately within the United Nations’ “sustainable development goals” by 2030 (SDG 15: “Protect, restore and promote sustainable use of terrestrial ecosystems, sustainably manage forests, combat desertification, and halt and reverse land degradation and halt biodiversity loss”).

The study of soils, as a key component of the Critical Zone, should thus not only be tackled by soil science but also within the highly numerous disciplines of Earth and life sciences, humanities and social sciences. Soils, being as they are at the center of multiple interactions, are an intricate array of systems, a nexus joining the essential parameters. These are food, water, energy, climate and biodiversity.

Soils, in terms of structure and dynamics, with complex processes, are sensitive to global changes that induce developments, which themselves obey threshold processes and issues of resilience. These involve, with regard to their study, taking into account not only short but also long time spans. This aspect was stressed in a white paper on soils published by the CNRS in 2015 (available at the address: www.insu.cnrs.fr/node/5432). The dynamics of major biogeochemical cycles, in particular with timescale characteristics which can be centuries old, indeed even go further back beyond that and so on.

It is clear that among the major components of the environment discussed earlier, soils are the least understood by the general public, by the authorities and even in academic circles. Consequently, it becomes of prime importance to provide the conceptual bases to the greatest number of university teachers and students so as to tackle soils with the complexity of their nature, their mechanics, their diversity and their interactions with other components, within the Critical Zone.

This is what is achieved with the reflections, analyses and the prospective studies carried out by all of the authors in this series. They are top scientists with a high level of international expertise within their discipline, and are mindful of adopting a holistic approach to soil study. The authors of this series pay specific attention to aspects able to be concluded through an open interdisciplinary science, beyond the single scientific community, policymakers, managers and to all those who are interested in the evolution of our planet. These authors also support their scientific reflection in line with training demands and, of course, the broadest dissemination of knowledge.

The series takes the form of six volumes:

• – Soils as a Key Component of the Critical Zone 1: Functions and Services, a volume which will serve as a general introduction;
• – Soils as a Key Component of the Critical Zone 2: Societal Issues;
• – Soils as a Key Component of the Critical Zone 3: Soils and Water Circulation;
• – Soils as a Key Component of the Critical Zone 4: Soils and Water Quality;
• – Soils as a Key Component of the Critical Zone 5: Degradation and Rehabilitation; and
• – Soils as a Key Component of the Critical Zone 6: Ecology.

Finally, it is worth mentioning again that this series was prepared essentially within the working group “Soils” at the Académie d’Agriculture de France, under the debonair, yet tenacious and assertive, stewardship of Christian Valentin. We are grateful to this group of scientists and their leader for producing this series.

André MARIOTTI

Professor Emeritus at Sorbonne University

Honorary Member of the Institut Universitaire de France

Coordinator of the series

“Earth Systems – Environmental Sciences”, ISTE Ltd