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How does photosynthesis move carbon from the atmosphere into plants and soils?

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Illustration of various geoengineering techniques to address climate change, including carbon capture and storage methods like artificial trees, industrial scrubbers, and deep ocean CO2 storage, as well as solar reflectance strategies such as sulfur aerosols, reflective crops, cloud whitening, and orbital mirrors. The scene shows these interventions applied to land, sea, and atmosphere, with labeled features explaining each process. — Geoengineering Various geoengineering proposals designed to increase solar reflectance or capture and store carbon.

Through the process of photosynthesis, plants and other vegetation act as natural carbon sinks by extracting carbon dioxide (CO₂) from the atmosphere to use as a feedstock for growth and repair.12

Using sunlight and chlorophyll as a catalyst, plants convert CO₂ and water into oxygen and organic compounds, such as sugars, which are then incorporated into the plant's biomass and tissues. The chemical reaction is represented as:13

$6 C O_{2} + 6 H_{2} O \to C_{6} H_{12} O_{6} + 6 O_{2}$

Once this carbon is assimilated into plant tissues, it is stored in aboveground biomass or transferred into the soil. Soils serve as a critical reservoir, containing significantly more carbon than land vegetation, primarily in the form of organic matter like humus. This carbon remains sequestered in the soil until it is released back into the atmosphere through processes such as decomposition by soil microbes or respiration.421