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Erosion is a geological process in which surface materials like soil, soil parent material, and rock are worn away and transported to new locations. Carbon elements are widely found in the Earth’s surface, including the atmosphere, soil, rock, water, and organisms. Consequently, erosive activities inevitably lead to the movement of carbon elements. Given the pivotal role that erosion-induced carbon plays in maintaining the balance of the global carbon budget, it is important to understand the process by which erosion impacts the carbon cycle.
A new article in Reviews of Geophysics explores the impacts of physical and chemical erosion on carbon dynamics. Here, we asked the lead authors to give an overview of erosion-carbon dynamics, why they are important, and how scientists study them.
What are the main driving forces behind erosion?
Erosion happens through the action of both internal and external forces. Internal forces, like earthquakes, can shift the Earth’s crust, while external forces come from energy provided by the Sun. These include wind, water, glaciers, and ocean waves. Erosion can be either physical, like when soil is carried away by wind or water, or chemical, where materials break down due to chemical reactions, like in chemical weathering. In both cases, the eroded materials eventually settle elsewhere.
What are the main forms of carbon elements in the Earth’s surface?
Carbon on the Earth’s surface exists in two main forms: organic carbon and inorganic carbon. Organic carbon is found in living organisms (from microorganisms to plants and animals), soil organic matter (like humus and plant remains), fossil fuels (such as coal, oil, and natural gas), and rivers (in forms like dissolved organic carbon and particulate organic carbon). Inorganic carbon is found in the atmosphere and soil (e.g., CO2 in soil air), in water bodies (like H2CO3, CO32-, HCO3–), and in rocks (such as carbonates). Specifically, carbon elements in soil organic matter, the atmosphere, water bodies, rivers, and rocks are closely tied to erosion processes, making it important to consider in these contexts.
The terrestrial sources and major transformations of dissolved organic carbon, particulate organic carbon, dissolved inorganic carbon in inland waters. Credit: Zheng et al. [2025], Figure 4
How do erosion processes move different types of carbon around?
Erosion processes move different types of carbon in various ways, but the two most important forms are soil erosion and chemical weathering. In soil erosion, external forces like raindrops detach soil particles containing organic carbon. Runoff then carries this organic carbon downhill. Some of it dissolves in water and can be transported over long distances, while the rest remains as particulate organic carbon, either floating in the water or settling at the bottom of rivers and streams.
In chemical weathering, slightly acidic rainwater (due to dissolved carbon dioxide) plays a key role. When surface soil is removed by erosion, the underlying rocks or soil parent material come into contact with the acidic water, which dissolves carbonate minerals. The resulting bicarbonate (HCO3–) is then transported into rivers by runoff.
Additionally, inorganic carbon in the soil can be carried into water bodies during erosion. In areas with gully erosion of sedimentary rocks, the increased exposure of rock organic carbon due to climate change can result in higher CO2 emissions, which is currently a major research focus.
Why is it important to understand erosion patterns in the context of global climate change?
Climate change is altering regional precipitation patterns, leading to more frequent extreme rainfall events.
Climate change is altering regional precipitation patterns, leading to more frequent extreme rainfall events. Increased rainfall intensity (and erosivity) is expected to raise global soil losses by 30%–66% in the near future. This increase in soil loss accelerates the movement, deposition, and burial of soil organic carbon, which affects the processes of carbon synthesis and decomposition. As a result, the carbon exchange between land and the atmosphere is altered. Additionally, climate change has accelerated glacial erosion, exposing organic carbon in sedimentary rocks to oxidation, which further contributes to carbon emissions, creating a feedback effect.
What are the main factors that influence the balance between carbon sequestration and carbon release during erosion processes?
The balance between carbon sequestration and release during erosion processes is influenced by several key factors. Carbon sequestration involves the burial and replacement of carbon in the soil, while carbon release mainly refers to the decomposition of organic carbon. Key factors that affect this balance include:
Soil erosion intensity: Affects how much carbon is moved and replaced.
Soil temperature and moisture: Influence the rate of carbon decomposition.
Leaching of dissolved organic carbon: Can alter carbon loss and decomposition.
Particle-size selectivity: Smaller particles may decompose more quickly, releasing more carbon.
Carbon enrichment ratio: Higher carbon concentrations in runoff can affect both release and burial.
Deposition environment: The conditions where carbon is deposited can impact how much is buried.
Carbon burial efficiency: Determines how much carbon is actually buried and stored.
These factors work together to control whether more carbon is sequestered or released during erosion.
The balance between key processes of water‐erosion‐induced carbon sinks and sources in organic carbon processes. The middle pink box lists several important factors affecting the balance. Credit:Zheng et al. [2025], Figure 1
Why is it important to distinguish between “on-site processes” and “off-site processes” when studying erosion-induced carbon flux?
“On-site” and “off-site” processes refer to different stages of carbon movement. On-site processes involve the dynamics of organic carbon at the original location that is being eroded, while off-site processes refer to the carbon after it has been moved from the eroded site, including its transport, deposition, and burial. By distinguishing between these processes, we can better understand how carbon behaves during erosion. Additionally, different methods are used to measure carbon flux at each stage, making this distinction crucial for accurate quantification of erosion-induced carbon changes.
How do scientists observe and measure the carbon flux influenced by chemical weathering?
Scientists observe and measure carbon flux influenced by chemical weathering by studying the breakdown of minerals like silicates (e.g., calcium and magnesium silicates) and carbonates. Several methods are used to measure the rates of weathering and associated carbon absorption:
Kinetic method: This method looks at how product concentrations change over time, helping to determine the reaction speed and mechanisms.
Dissolution measurement: By measuring the amount of mineral dissolution, scientists estimate how much CO2 is consumed in the process.
Chemical equation method: This approach measures solute concentrations (e.g., Ca²⁺, Mg²⁺, K⁺) in water to estimate carbon consumption using mass conservation principles.
Model-based estimates: Models like the Global Erosion Model and weathering front models help estimate CO2 fluxes from weathering.
These methods help scientists quantify the carbon flux related to chemical weathering and its role in carbon sinks.
How do scientists observe and measure the carbon flux influenced by water erosion?
Scientists use various methods to measure carbon flux influenced by water erosion, depending on the research focus and time frame. These methods include:
In-situ monitoring: For short-term events like individual rainfall, researchers set up monitoring plots in erosion-prone areas. Instruments measure vertical carbon flux at different stages: on-site, during transport, and at deposition locations.
Isotope or radioelement tracing: For long-term studies (spanning decades), scientists use isotopes to estimate average erosion rates by comparing organic carbon content between eroded and stable sites.
Model simulations: Process-based models simulate the effects of water erosion on carbon cycling, such as the composition, decomposition, and leaching of soil organic carbon. These models help quantify the carbon flux caused by erosion.
These methods provide insights into how water erosion impacts carbon transport and storage over different timescales.
Why does the new conceptual framework that you propose better quantify erosion-related carbon fluxes?
The new conceptual framework improves the quantification of erosion-related carbon fluxes by addressing the limitations of traditional methods.
The new conceptual framework we propose improves the quantification of erosion-related carbon fluxes by addressing the limitations of traditional methods. Typically, quantifying carbon flux over decades involves tracking changes in organic carbon at erosion sites using mathematical analysis and sampling. This method works well on a small scale, especially when reference sites are carefully selected and the erosion rate is accurately estimated. However, it is challenging to scale this approach due to the difficulty of conducting large-scale surveys.
Our framework builds on this mathematical method but integrates the processes of carbon synthesis and decomposition at both erosion and deposition sites, along with the soil erosion process itself. With large-scale datasets (such as erosion rates and organic carbon content in different soil layers obtained through surveys or remote sensing), our framework allows for broader predictions of erosion-induced carbon flux. The accuracy of these predictions depends on the quality and uncertainty of the datasets used.
—Haiyan Zheng (zhenghaiyan@bjfu.edu.cn), Beijing Forestry University, China; and Chiyuan Miao (miaocy@bnu.edu.cn, 0000-0001-6413-7020), Beijing Normal University, China
Editor’s Note: It is the policy of AGU Publications to invite the authors of articles published in Reviews of Geophysics to write a summary for Eos Editors’ Vox.
Citation: Zheng, H., and C. Miao (2025), Erosion: An overlooked contributor to the carbon cycle, Eos, 106,https://doi.org/10.1029/2025EO255010. Published on 13 March 2025.
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