Global soil organic carbon levels on the rise due to climate change

A recent study published in Engineering has shed light on the increasing trend of global land surface soil organic carbon (SOC) driven by climate change. The research, conducted by a team of scientists including Yanli Liu, Xin Chen and Jianyun Zhang, utilized a random forest model to analyze historical data and predict future trends of SOC levels based on climate scenarios from the Coupled Model Intercomparison Project Phase 6 (CMIP6).

The study examined global land surface SOC trends from 1981 to 2019 and identified the driving factors behind these changes. The results indicate that the global surface SOC content is on the rise, with temperature and precipitation emerging as the primary climate drivers at the global scale. Vegetation cover was also found to be a crucial local factor influencing the increase in SOC. However, the research highlights that relying solely on natural carbon sinks to achieve global carbon neutrality is a high-risk strategy, as the projected increase in SOC is far from the ambitious targets set by the Paris Agreement.

The historical analysis revealed that the global SOC stock increased by 6.392 petagram carbon (PgC) from 1981 to 2019. This increase was particularly notable in middle- and low-latitude regions, where vegetation cover is more extensive. The study also found that high-latitude regions, such as parts of North America, Asia, and Europe, experienced a significant decrease in SOC, which could be attributed to the effects of global warming on frozen soils.

The researchers employed the geographical detector model to analyze the driving factors of global SOC change. The results showed that temperature, leaf area index (LAI), and rainfall days are the main factors affecting SOC variation globally. The study also highlighted the complex interactions between these factors, which can either enhance or diminish the impact on SOC levels depending on the region.

Using the random forest model, the researchers projected future SOC trends under different climate scenarios. The model predicted that the global SOC stock will continue to increase under all scenarios, with the most significant growth expected in Africa and South America. However, high-emission scenarios, such as SSP5-8.5, could lead to notable declines in SOC in North America, Asia, and Oceania by 2100.

The study emphasizes the importance of implementing mitigation and removal strategies to reduce greenhouse gas emissions, as natural land-based mitigation alone is insufficient to meet the Paris Agreement's target of a four out of one thousand increase in soil carbon stocks per year over the next 20 years. The findings suggest that achieving global carbon neutrality will require a combination of natural carbon sequestration and human-induced measures.

The research underscores the need for comprehensive monitoring systems and advanced data processing techniques to improve the accuracy of SOC projections. It also highlights the potential risks associated with over-reliance on natural carbon sinks and the urgency of developing effective land and soil management strategies to enhance soil carbon sequestration.

The study provides valuable insights into the dynamics of global SOC levels and the role of climate change in driving these changes. The findings emphasize the importance of a balanced approach to carbon mitigation, combining natural processes with human-induced strategies to achieve global carbon equilibrium.

The paper “Nature-Based Global Land Surface Soil Organic Carbon Indicates Increasing Driven by Climate Change,” is authored by Yanli Liu, Xin Chen, Jianyun Zhang, Xing Yuan, Tiesheng Guan, Junliang Jin, Guoqing Wang. Full text of the open access paper: https://doi.org/10.1016/j.eng.2025.03.031. For more information about Engineering, visit the website at https://www.sciencedirect.com/journal/engineering.