Concept

Carbon cycle

The global circulation of carbon between atmosphere, oceans, soil, vegetation, fossil reservoirs, and the bodies of all living things. Plants pull atmospheric carbon dioxide into themselves through photosynthesis; respiration, decomposition, and combustion return it. The cycle has been near-balanced over geological timescales but has been substantially disrupted by industrial fossil-fuel combustion since 1850. The regenerative-agriculture case for soil-carbon sequestration sits on the carbon cycle: well-managed soils can hold carbon out of the atmosphere for decades to centuries, providing substantial drawdown potential alongside ecological benefits.

The cycle

Carbon moves continuously between major reservoirs:

Atmosphere — primarily as carbon dioxide (CO₂) and methane (CH₄)
Oceans — dissolved inorganic carbon (the largest mobile reservoir); marine biota; sediments
Vegetation — fixed in plant biomass through photosynthesis
Soil — organic matter (humus, microbial biomass, plant residues); carbonate minerals
Fossil reservoirs — coal, oil, natural gas, methane hydrates; the long-cycle reservoir
Geological reservoirs — limestone, dolomite, kerogen; the longest-cycle reservoir

Pathways

Photosynthesis — plants pull CO₂ from atmosphere → fix into sugars → grow biomass
Respiration — plants and animals oxidize sugars for energy → release CO₂
Decomposition — microbes break down dead organic matter → release CO₂ and methane
Combustion — fire (wildfire, fossil-fuel burning) → CO₂
Marine uptake/release — ocean exchanges CO₂ with atmosphere across air-sea interface
Weathering — slow chemical reactions consume atmospheric CO₂ over [[deep-time|geological time]]
Sedimentation — ocean carbon precipitates into seafloor sediments over [[deep-time|geological time]]

Disruption

Pre-industrial atmospheric CO₂ was approximately 280 ppm and roughly stable across millennia. Industrial fossil-fuel combustion has raised it to ~420+ ppm (2024), with continuing rise. The disruption is primarily one-directional: fossil-carbon reservoirs that took hundreds of millions of years to form are being released to [[air|the atmosphere]] in two centuries.

The carbon cycle has not been broken — it continues to operate — but it has been substantially loaded on the input side, with measurable effects on climate, [[ocean-acidification|ocean acidification]], and biological communities.

Soil-carbon drawdown

Among the most-promising near-term levers for partial atmospheric drawdown is soil organic carbon. Well-managed grasslands, croplands, and forests can pull substantial atmospheric carbon into stable soil-carbon pools — humus, mycorrhizal residues, deep-root carbon — over decades.

The total drawdown potential is debated (estimates range widely), but the co-benefits (soil health, water-holding capacity, biodiversity) are uncontroversial: even if soil-[[carbon-sequestration|carbon sequestration]] is a partial climate solution, it is a foundational regenerative-agriculture outcome regardless.

Practitioners building soil carbon: [[gabe-brown|Gabe Brown]], [[singing-frogs-farm|Singing Frogs Farm]], Polyface, the Holistic Management network, the Marin Carbon Project, and thousands of regenerative farmers worldwide.

Sources

IPCC carbon-cycle assessments (multiple reports)
USDA Climate Hubs published materials
Marin Carbon Project research publications

Rooted in life.

What links here, and how

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Scientific

enables

Biochar moves carbon from short-cycle (atmosphere ↔ biomass ↔ decomposition) to long-cycle (stable soil carbon for centuries-millennia)
Reforestation established forests sequester carbon in biomass and soil; reforestation is among the most-tractable nature-based climate solutions

shares approach with

Carbon sequestration carbon sequestration moves carbon between cycle components; understanding the cycle is foundational
Methane methane is a major component of the carbon cycle; CH4 is converted to CO2 in atmosphere over ~12-year timescale
Ocean acidification ocean absorbs ~25% of anthropogenic CO₂; the chemistry of this absorption produces acidification

5 inbound links · 2 outbound