When extreme weather rewrites the soil carbon cycle
Soil carbon storage is moving centre stage in climate policy, and a 2026 review published in Carbon Research explains why. Extreme weather is now directly altering how much carbon soils can hold. Droughts, floods, and wildfires are disrupting the balance between what plants put into the ground and what microbes release back into the atmosphere.
For UK businesses with land holdings, supply chains that depend on agriculture, or carbon offsetting commitments, this matters commercially. Soil carbon projects underpin many nature-based removal strategies. If extreme weather undermines those stores, the accounting changes.
Professor Nanthi Bolan of the University of Western Australia led the research. His team examined how climate shocks alter carbon flows in terrestrial and aquatic systems. The central finding is blunt: soil carbon is not static. Weather events can trigger rapid losses through microbial activity, erosion, and leaching into waterways.
Weather extremes disrupt carbon inputs and microbial processes
The review identifies three primary disruption pathways. Each one affects how carbon enters, stays in, or leaves the soil.
Drought cuts plant biomass. Less vegetation means fewer roots, less leaf litter, and lower carbon inputs overall. When rain eventually returns, dried microbial communities reactivate quickly. This rewetting can produce sudden pulses of CO2 as dormant microbes consume accumulated organic matter.
Flooding creates waterlogged conditions. Oxygen levels drop, which changes the types of microbes that dominate. Anaerobic bacteria take over, shifting decomposition chemistry. Floodwater also leaches dissolved organic carbon from mineral surfaces and carries it into rivers and streams.
Wildfire removes surface vegetation and litter in one event. Heat alters soil structure, sometimes making it water-repellent. Exposed soil loses carbon through erosion when rain arrives. Fire-damaged ground often releases more carbon than intact systems for months or years afterward.
Consequently, compound disturbances can tip soils from net carbon sinks into sources. A drought followed by flooding, or fire followed by heavy rain, multiplies the disruption. The review emphasises that these combinations are becoming more common as global temperatures rise.
Croplands and grasslands face repeated drought-rewetting cycles
Agricultural soils are particularly vulnerable. Croplands and managed grasslands experience frequent wetting and drying as rainfall patterns shift. Each cycle can trigger microbial flushes that release CO2.
The published paper notes that repeated drought-rewetting cycles reduce long-term soil organic carbon storage. Farmers may see declining soil health over successive seasons. This affects water retention, nutrient availability, and ultimately crop yields.
Meanwhile, related global research supports the broader trend. One analysis found that most extreme weather types accelerate soil organic carbon loss under 1.5°C of warming. That threshold is already being approached in many regions.
For businesses relying on consistent agricultural output, these changes introduce new supply chain risks. Lower soil carbon often correlates with reduced fertility. Suppliers may face higher input costs for fertilisers or water. Quality and volume variability can increase.
Moreover, companies using soil carbon credits for offsetting need to consider permanence. If extreme weather increases the likelihood of reversal, the carbon accounting becomes less reliable. Verification protocols may tighten, and insurance costs could rise.
Climate models now need to account for soil carbon feedbacks
Soil carbon was once treated as a relatively stable pool in climate models. The assumption was that land management controlled most of the variation. However, this review frames extreme weather as a direct driver of the carbon cycle itself.
If soils lose carbon faster under extreme conditions, atmospheric greenhouse gas concentrations rise more quickly. This creates a feedback loop: warming intensifies weather extremes, which destabilise soil carbon, which accelerates warming further.
Climate mitigation plans typically count on natural carbon sinks to offset some industrial emissions. Forests and soils are the two largest terrestrial stores. When one becomes less reliable, pressure increases on emissions reduction targets.
Businesses setting net zero pathways often include nature-based solutions. Soil restoration, regenerative agriculture, and peatland rewetting all depend on stable or increasing carbon stocks. If those stocks become volatile, the trajectory to net zero shifts.
Therefore, risk assessments need updating. Physical climate risk now includes potential carbon losses from land assets. Transition risk encompasses tighter rules around carbon credit quality and permanence guarantees.
Erosion and leaching move carbon into waterways
Soil carbon does not always return to the atmosphere as CO2. Fire and flood can transport it physically into rivers, lakes, and coastal waters. This dissolved organic carbon can degrade further downstream or settle in sediments.
The review highlights that flooding mobilises mineral-bound carbon. Normally, clay particles protect organic matter from microbial breakdown. When floodwater saturates soil, some of that protection dissolves. Carbon moves laterally rather than vertically.
Erosion works differently but produces similar outcomes. Wind and water lift topsoil rich in organic matter. That material ends up in watercourses, where oxygen levels and microbial communities differ. Some carbon degrades rapidly; some persists in new forms.
For catchment managers and water companies, this has practical consequences. Dissolved organic carbon affects water treatment costs. It can bind with chlorine to form disinfection byproducts, requiring additional filtration stages.
Additionally, businesses with environmental permits tied to watercourse quality may see compliance costs rise. Increased carbon loads can influence nutrient balances and aquatic ecosystems, triggering stricter discharge limits or monitoring requirements.
Key facts from the 2026 Carbon Research review
- Droughts reduce plant biomass and lower carbon inputs into soil, while rewetting triggers sudden microbial CO2 pulses.
- Flooding creates low-oxygen conditions that alter decomposition and release dissolved organic carbon into waterways.
- Wildfires remove vegetation and litter, accelerate erosion, and can drive long-term carbon losses through changes in soil structure.
- Repeated drought-rewetting cycles in croplands and grasslands measurably reduce long-term soil organic carbon storage.
- Most extreme weather types exacerbate soil organic carbon loss under 1.5°C warming, according to related global analysis.
- Compound disturbances, such as fire followed by flooding, multiply carbon loss pathways and increase volatility in carbon stocks.
- Soil carbon is now recognised as a dynamic, weather-sensitive component of climate mitigation, not a static reservoir.
What this means for land-based carbon strategies
Businesses developing carbon removal portfolios need to reassess soil-based projects. Permanence risk is higher in regions exposed to drought, flood, or fire. That does not make soil carbon unviable, but it does require more rigorous site selection and monitoring.
Insurance and buffer pools become more important. Many carbon standards already require projects to set aside a percentage of credits to cover potential reversals. If extreme weather increases reversal probability, those buffers may need to grow.
Diversification also matters. Relying solely on soil carbon exposes a portfolio to correlated weather risk. Mixing in afforestation, peatland restoration, or technological removal spreads exposure. Each method responds differently to climate shocks.
Furthermore, businesses with agricultural supply chains should engage suppliers on soil health. Regenerative practices such as cover cropping, reduced tillage, and diverse rotations can improve resilience. However, those practices take time to establish, and returns depend on stable weather patterns.
Procurement teams may want to map supplier exposure to extreme weather zones. If a key ingredient comes from a drought-prone region with declining soil carbon, the quality and price outlook changes. Alternative sourcing or long-term contracts with climate adaptation clauses might make sense.
For companies with land assets, carbon accounting rules are tightening. The review reinforces that soil carbon stocks are not guaranteed. Annual verification and satellite monitoring are becoming standard. Those without robust measurement systems face greater scrutiny from investors and regulators.
We work with businesses on carbon reporting and net zero compliance, including how to account for nature-based carbon stocks under evolving standards. Soil carbon requires different treatment from purchased offsets, particularly when physical risks affect permanence.
Soil health links directly to operational resilience
Carbon storage is only one function of healthy soil. Water retention, nutrient cycling, and structural stability all matter for business continuity. Extreme weather that degrades soil carbon typically harms those other functions too.
Consequently, companies managing estates, golf courses, or outdoor facilities face maintenance cost increases. Compacted, carbon-poor soil sheds water rather than absorbing it. That can mean higher irrigation bills in dry periods and flood damage in wet ones.
Food and beverage manufacturers relying on specific crop regions should watch soil degradation trends. Lower carbon correlates with reduced yields over time. Suppliers may struggle to meet volume commitments, or quality may drift as nutrient imbalances emerge.
Meanwhile, construction firms working on brownfield or agricultural sites encounter different ground conditions than historical surveys predicted. Soil that has lost organic matter behaves differently under load. Foundation designs and drainage systems may need adjustment.
Our training programs on environmental risk cover how changing soil conditions affect site assessments and operational planning. Understanding the physical science helps teams anticipate problems before they reach the critical path.
Policy and disclosure implications for UK businesses
UK sustainability disclosure rules require businesses to report climate-related risks. Physical risks include weather extremes that disrupt operations or supply chains. Soil carbon instability falls squarely into that category.
Task Force on Climate-related Financial Disclosures (TCFD) reporting expects scenario analysis. If your business depends on land-based carbon or agricultural inputs, scenarios should model what happens when soil carbon stores decline. The 2026 review provides evidence that this is a plausible pathway, not a remote tail risk.
Additionally, businesses using carbon credits must disclose their quality and permanence assumptions. If credits rely on soil carbon projects in regions facing increasing weather extremes, that creates a material risk. Audit committees and investors will ask how you are managing it.
Regulatory pressure is also building around nature-based claims. The Advertising Standards Authority has issued guidance on environmental claims, and the Competition and Markets Authority is watching greenwashing closely. Overstating the permanence of soil carbon removals could trigger enforcement action.
Therefore, conservative accounting makes sense. Book soil carbon credits at a discount if they come from high-risk geographies. Maintain larger buffer reserves. Document your assumptions clearly so they can withstand external review.
We support clients with ESG compliance and carbon reporting that reflects emerging physical risks. Disclosure needs to balance ambition with realism, especially when dealing with natural systems exposed to volatile weather.
Independent research and guidance on soil carbon dynamics
The University of Western Australia published the full review in Carbon Research, an open-access journal. Carbon Research focuses on carbon cycle science, climate mitigation, and environmental impacts.
UK government guidance on soil management and carbon storage is available from the Department for Environment, Food and Rural Affairs. Defra publishes evidence reviews and practical resources for land managers.
The Environment Agency provides regulatory frameworks for land and water quality, including how soil erosion and carbon leaching affect watercourses. Their guidance is relevant for businesses with environmental permits.
Additional research on climate extremes and carbon cycles appears regularly in journals such as Nature Climate Change and Global Change Biology. Tracking this literature helps businesses stay ahead of emerging risks and understand the scientific basis for policy changes.
For businesses wanting to assess their own land or supply chain exposure, the UK Centre for Ecology and Hydrology offers spatial data on soil carbon stocks and climate projections. This can inform site-level risk assessments and adaptation planning.