The Critical Zone of Earth remains enigmatic without the presence of its inhabitants.

Editors’ Vox is a blog from AGU’s Publications Department.

The critical zone is a narrow layer of the Earth’s surface that stretches from the highest points of trees to underground aquifers. This is where the physical landscape meets the realm of living organisms. Critical zone (CZ) science focuses on studying the development of landscapes from the depths of the Earth to the canopy of trees, which ultimately support life on our planet. It acknowledges that a multidisciplinary approach to science is crucial in comprehending the complex movement of water, nutrients, and sediment through landscapes. These processes are essential for maintaining healthy ecosystems and the benefits they offer to human society.

A recent publication in the September 2023 edition of Earth’s Future introduces a novel approach to critical zone science that takes into account the impact of human behavior. This approach is then put into practice in a companion paper, which examines smallholder farming communities in rural China.

We requested the authors to provide a summary of the development of critical zone science, the key discoveries from their investigation in China, and the potential applications of their research.

What are the “critical zone observatories” and how has their area of focus changed over time?

Collaborative groups of Earth researchers have created comprehensive understanding of the development of natural landscapes in the initial critical zone observatories (CZO). These were particular regions on land that underwent extensive examination of their hydrology, geochemistry, geomorphology, soils, and ecology. These unspoiled natural environments are uncommon in our current society. More recent CZOs have been set up in landscapes that have been damaged by human actions and are now tackling significant issues such as climate change, water shortages, and food sustainability. The discovery of five new CZOs in China has revealed the impact of farmers’ land management on the entire critical zone, from surface soils to deep groundwater.

Studies conducted by CZO have advanced our comprehension of the relationship between natural processes, ranging from the uppermost part of the canopy to the bedrock. However, these studies have neglected to include the significant influence of human activity, which greatly impacts CZ processes in agricultural areas worldwide. On the other hand, research conducted by agronomists, soil scientists, and social scientists on agricultural landscapes has primarily concentrated on the surface layer and at the field or farm level. Our goal is to combine both approaches in order to fully understand CZ processes in environments affected by human intervention and effectively achieve Sustainable Development Goals.

Our proposed approach aims to study the critical zone (CZ) in human-modified landscapes, which are prevalent in our world. To demonstrate the significance of this approach, we have reimagined a crucial diagram that explains the functioning of the CZ, incorporating the role of human activities. Through this new visual representation, we highlight the extensive effects of human activities on CZ function, providing a more accurate understanding of how both natural processes and human actions shape the Earth’s critical zones. Understanding the impact of human activities on CZ function is crucial in preventing ecosystem degradation, supporting local communities, achieving UN Sustainable Development Goals, and promoting climate resilience in these landscapes and the people who rely on them.

What are the main justifications for incorporating the human element in CZS?

The Earth’s critical zone has been significantly changed by agricultural landscapes. There is a increasing global demand for sustainable agriculture in order to mitigate human effects on the environment and to enhance the well-being of farmers and their communities who reside and work in these strained environments. In order to assist local individuals in improving their livelihoods through sustainable agricultural methods, it is necessary to gain a better comprehension of how knowledge about sustainable agriculture is generated, exchanged, and utilized among various groups, such as farmers, scientists, agricultural companies, and government.

The research team’s social scientists provided valuable perspectives on the ways in which farmers engage with their land. This included examining the impact of traditional farming techniques, government training programs, agricultural corporations, and changes in land ownership rights. By directly communicating with farmers, the team gained insight that was crucial in interpreting earth science data in areas where humans have modified the landscape. Without taking into account the local community’s practices and beliefs surrounding land usage, as well as political and social factors, scientists can only grasp a limited understanding of the situation.

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What motivated you to study smallholder farming communities in China?

The traditional farming methods in China have significantly influenced the rural areas over the years. Unfortunately, these landscapes and the resources that support natural processes, agricultural practices, and people’s lives have been greatly damaged due to human actions. This has a direct effect on the ecosystems and landscapes that support these communities, especially in terms of having access to clean water and proper sanitation (SDG 6), reducing poverty (SDG 1), eradicating hunger (SDG 2), taking action against climate change (SDG 13), preserving life on land (SDG 15), and creating sustainable cities and communities (SDG 11).

We aimed to assess the impact of China’s national policies on CZO functioning and explore the learning practices of local farmers, including who they learn from, their trust levels, and their capacity and interest in adopting sustainable farming practices. Additionally, we looked at identifying obstacles to training and how this information can inform the dissemination of CZ science.

What were the main discoveries from your study?

Farmers in the area are implementing techniques to enhance the durability of damaged land. By comprehending their own methods of land management, the interpretation of CZ science data has been enhanced.

Our research revealed that learning methods and preferences differed geographically among the three regions studied. In two of these regions, learning primarily occurred through close family connections. This information is crucial for creating effective knowledge-sharing initiatives and offering sustainable agricultural education in diverse areas.

We found the main challenges that small-scale farmers face in maintaining their livelihoods, such as the expensive price of fertilizers. From there, we were able to establish connections between the scientific research on nitrogen pollution and the use of fertilizers as a significant financial burden, pinpointing areas where changes in policies and practices could directly benefit local livelihoods. This enabled us to better connect the CZ science with the Sustainable Development Goals (SDGs).

How could your research potentially be applied?

The Anthropocene critical zone science diagram effectively depicts the relationship between humans and the Earth’s critical zone. This new perspective highlights the influence of human actions on terrestrial landscapes, illustrating the significant role humans play in landscape degradation.

We have proven that effective management of landscapes requires the collaboration of both natural and social scientists in order to develop successful land-use policies that are supported by the local community. We have also devised a useful model for conducting transdisciplinary research, which involves actively involving and working alongside local communities to develop research programs that align with their needs and contribute to achieving the UN Sustainable Development Goals. This model incorporates a combination of scientific, social, and local knowledge, as well as fostering knowledge exchange. It also includes a research cycle and funding model that can be applied by others. This approach is well-suited for addressing major global challenges such as climate change, ecosystem decline, and planetary health, which are crucial for creating a resilient future for our planet.

Our suggestion for future scientific research in strained agricultural areas is to focus on a more community-based approach in order to establish trust and conduct studies that directly address urgent environmental issues at the local level. This involves studying the residents of these landscapes through social science and human geography methods, while also considering the ecological functioning of the landscape. By doing so, we can ensure that environmental science is firmly rooted in, guided by, and beneficial to the local communities.

Our research findings can be utilized by organizations, such as the National Science Foundation (NSF) in the United States, to support their Next Generation Earth Systems Science initiative, which focuses on studying the intricate connections and feedbacks between natural and social processes. It can also contribute to the implementation of global plans, like the Food and Agriculture Organization’s (FAO) Strategic Framework 2022-2031, as well as important policies, such as the European Union’s Soils Strategy for 2030. Our study also serves as a valuable example of how understanding local practices of ecosystem management, adaptation measures, and diverse knowledge can aid in promoting climate resilient development.

—Larissa A. Naylor ([email protected], 0000-0002-4065-2674), University of Glasgow, United Kingdom; Jennifer A. J. Dungait  (0000-0001-9074-4174), University of Exeter and SRUC-Scotland’s Rural College, United Kingdom; Paul D. Hallett (0000-0001-7542-7832), University of Glasgow, United Kingdom

Neil Munro (0000-0001-7542-7832) and the University of Glasgow in the United Kingdom (0000-0001-7542-7832)0000-0001-9694-9701), University of Glasgow, United Kingdom; Alasdair Stanton (0000-0002-6237-8653), University of Glasgow, United Kingdom; and Timothy A. Quine (

I am affiliated with the University of Exeter in the United Kingdom with the identifier 0000-0002-5143-5157.

AGU Publications follows a policy of inviting authors of certain journal articles to compose a summary for Eos Editors’ Vox.

Citation: Naylor, L. A., J. A. J. Dungait, P. D. Hallett, N. Munro, A. Stanton, and T. A. Quine (2023), Earth’s critical zone remains a mystery without its people, Eos, 104, https://doi.org/10.1029/2023EO235025. Published on 19 September 2023.

The views expressed in this article do not necessarily reflect those of AGU, Eos, or any associated organizations. They are the views of the author(s) alone.

Text © 2023. The authors. CC BY-NC-ND 3.0

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