Assessment of the impact and scope of biogeochemical cycles


Biogeochemical cycles describe the flow of elements in the earth systems. They are strongly influenced by biological and anthropogenic activities and in turn influence other aspects of the earth system and the human environment. Biogeochemical cycles: ecological drivers and environmental impacts, a book published by AGU, shows how biogeochemical cycles have evolved over time and how they manifest themselves in different environments, and presents new methods of quantifying and predicting the flux of the elements. Here the editors of the book give an overview of our understanding of biogeochemical cycles and summarize current challenges and opportunities for research.

What makes biogeochemical cycles such an interesting field of study?

The biogeochemical cycles of the elements influence most of the abiotic factors that determine life. Studying biogeochemical cycles is important to understand how natural ecosystems withstand the pressures of the Anthropocene, and also to anticipate and model the sustainable functioning of human-influenced ecosystems such as agricultural soils.

Example of the application of isotope analysis to elementary cycles. Source: Nägler et al. [2020], Figure 8.7

What is the interest of the Critical Zone Concept in studying biogeochemical cycles?

The critical zone is a porous skin of the earth’s surface that extends from the top of the vegetation crown to the lower limits of the freely circulating groundwater (NRC, 2001). It’s a useful concept in biogeochemistry because it brings together soils, vegetation, rocks, and water. Geologically, it is a very thin layer, but it is the layer that protects life, including humans.

Diagram showing the links between structure and function in the critical zone.
Link between structure and function in the critical area. Photo credit: Moravec and Chorover [2020], Figure 6.1

What are some of the challenges in determining cause and effect relationships within biogeochemical cycles?

Earth systems are incredibly complex and interconnected, which means that one change can trigger multiple abiotic and biological responses and feedbacks. This can, for example, make it difficult to study the effects of climate change on the conservation of organic carbon and the cycle in soils.

Series of three illustrations showing the structure of microbial degradation models.
Structure of microbial decomposition models. Credit: Abs and Ferrière [2020], Figure 5.1, adapted from Georgiou et al. [2017]

How do human activities affect biogeochemical cycles and how are they influenced by them?

It is difficult to name anything in the environment that is not influenced by humans, including biogeochemical cycles. Climate change is a big issue now and the effects of climate change and feedback are particularly dramatic in regions of permafrost. Herndon et al. [2020] demonstrated the influence of warming on the cycles of redox-sensitive elements in permafrost-influenced ecosystems. One of the biggest concerns is the positive feedback on global warming from the release of CO2 and methane, but many other elements such as P, N, S and Fe are affected.

Why is it urgently necessary to examine the interconnectedness of different ecosystems?

The earth is a system with numerous sub-systems such as the biosphere, hydrosphere, atmosphere and the tectonic system that constantly interact. Different ecosystems cannot be fully understood when viewed in isolation because they are not closed systems. There is a constant exchange of materials, energy and living matter between them, and they are all connected by the biogeochemical cycles.

To understand complex relationships, processes and feedback loops within landscape developments, we need to understand how different ecosystems are interconnected in space and time.

The urgency of the investigation of the networking of different ecosystems arises from the use of the current possibilities offered by the Critical Zone Exploration Network by providing locations for the studies and the collaboration of different experts.

What are some of the major gaps in our understanding of biogeochemical cycles that require additional research?

Our book lists nine major gaps, the two most important of which are: quantifying the effects of biological weathering across the scales and applying biogeochemical knowledge to solve societal problems.

Spanning the spatial and temporal scales of processes is challenging for geosciences, and adding the related biological processes makes understanding it even more complex. The establishment of the Critical Zone Observatories and their exploration network provides opportunities to study processes of various magnitudes in numerous locations.

Title page of the book Biogeochemical Cycles: Ecological Drivers and Environmental ImpactThe application and transformation of knowledge to solve societal problems is becoming more and more urgent and relevant as humans exert a significant influence on the environment, including biogeochemical cycles.

The interdisciplinary nature of biogeochemistry and the existing uncertainties in the research results make it difficult to directly influence decision-making. Increased cooperation between areas of biogeochemistry, humanities and social sciences can deliver results and apply solutions to societal problems such as sustainable food production, food security, carbon management and sequestration.

Biogeochemical cycles: ecological drivers and environmental impacts, 2021, ISBN: 978-1-119-41331-8, list price $ 199.95 (print), $ 160.00 (e-book). AGU members get 35 percent off all books at Log in to your AGU member profile to access the discount code.

—Katerina Donzova ([email protected], ORCID logo 00000003-2177-8965), University of Arizona, USA; Zsuzsanna Balogh-Brunstad (ORCID logo 00000002-5749-1213), Hartwick College, USA; and Gaël Le Roux (ORCID logo 00000002-1579-0178), National Center for Scientific Research, France

Editor’s Note: It is AGU Publications ‘policy to invite the authors or editors of newly published books to write an abstract for Eos Editors’ Vox.


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