A Changing Carbon Balance
Soil organic carbon supports soil health, water retention, nutrient cycling, soil structure, and microbial diversity. A review led by Nanthi Bolan examines how climate change-induced droughts, floods, and wildfires can alter these functions by changing carbon inputs, decomposition, erosion, and the movement of dissolved organic carbon.
The analysis places soil carbon within the wider climate system. Depending on environmental conditions and land management, soils can either store carbon or contribute to greenhouse-gas emissions. The authors argue that protecting soil carbon is important not only for climate mitigation but also for sustaining agricultural productivity and ecosystem services.
Mapping the Evidence
On 14 January 2026, the authors searched Google Scholar, PubMed, and Web of Science using terms related to climate change, extreme weather, soil carbon, microbial activity, decomposition, erosion, dissolved organic matter, and leaching. The initial search produced 14,218 records. After duplicate removal and eligibility screening, 3,754 articles were retained for bibliometric and qualitative analysis.
A set of 187 publications was selected for detailed synthesis according to relevance, methodological robustness, and availability of substantive findings. Bibliometric analysis was conducted with VOSviewer, using keyword co-occurrence patterns to identify major research themes. The article is therefore a critical review supported by structured literature screening and bibliometric assessment, rather than a report of newly generated experimental data.
Drought, Flood, and Fire
Drought generally reduces plant biomass production and total carbon inputs to soil, although plants may temporarily allocate a greater proportion of carbon to roots. Prolonged drought can suppress microbial biomass and litter decomposition, while rewetting may trigger a rapid CO₂ pulse as microorganisms consume accumulated substrates. Across the reviewed evidence, repeated or multiyear drought was associated with declining soil organic carbon, with particularly pronounced reductions reported for grasslands and arable croplands.
Flooding produces a contrasting set of processes. Water saturation restricts oxygen diffusion and shifts microbial metabolism toward anaerobic pathways. Prolonged waterlogging can promote the reduction of iron oxyhydroxides and the release of dissolved organic carbon, while erosion and leaching can transport carbon from soils into aquatic systems. At the same time, wetlands and other flooded ecosystems can retain substantial carbon when plant inputs accumulate and decomposition is constrained.
Wildfires directly remove vegetation, litter, and soil organic matter through combustion. They can also increase erosion, alter soil wettability, modify microbial communities, and expose previously protected carbon to decomposition. Pyrogenic carbon formed during incomplete combustion may persist for long periods, but the balance between carbon loss and retention depends on fire severity, soil moisture, fuel load, ecosystem type, and post-fire recovery.
Priorities for Carbon Stewardship
The review indicates that carbon responses cannot be inferred from the type of extreme event alone. Land use, soil mineralogy, hydrology, salinity, vegetation, microbial composition, and event timing all influence whether carbon is stored, mobilized, or released. Compound events, including drought followed by wildfire or alternating drought and flooding, may create effects that differ from those of isolated disturbances.
The article does not report newly generated datasets or present a separate limitations section. Its conclusions are based on the available literature and on a qualitative synthesis of selected publications; consequently, the authors call for improved evidence across soil types, land uses, terrestrial and aquatic environments, and multiple temporal scales. Greater consistency in measurements of carbon pools, microbial functions, and event intensity would improve comparisons among ecosystems.
Future work should combine high-resolution remote sensing, ground observations, advanced spectroscopy, molecular analyses, and integrated modelling. The authors specifically recommend examining microbial genomic and functional diversity, carbon stoichiometry, iron and aluminium oxyhydroxide interactions, clay-mineral protection, long-term carbon storage, and the sequencing of compound extreme events. Such efforts could strengthen assessments of soil carbon vulnerability and inform climate-resilient land management.
Corresponding Author: Nanthi Bolan
Original Source: https://doi.org/10.1007/s44246-026-00300-5
Contributions: Nanthi Bolan, Kadambot H.M. Siddique, and Santanu Mukherjee conceptualised the scope of the review. Shailja Sharma, M. Jagadesh, and Santanu Mukherjee contributed to Section 2 (Methodology). Nanthi Bolan, Santanu Mukherjee, Shiv Bolan, Shailja Sharma, and M. Jagadesh contributed to Section 3 (Climate change and extreme weather events). Nanthi Bolan, Kadambot H. M. Siddique, and Shiv Bolan contributed to Section 4 (Soil carbon). Aime Jean Messiga, Shailja Sharma, Musfiq Usalehin, Thidarat Rupngam, Nithya Rajan, Tao Zhang, and Yixiao Yang contributed to Section 5 (Extreme weather events and soil carbon). Nanthi Bolan, Kadambot H. M. Siddique, M. Jagadesh, and Santanu Mukherjee provided thorough feedback and contributed to Section 1 (Introduction) and Section 6 (Conclusion).
