Biosequestration is a naturally occurring process that captures and stores atmospheric carbon dioxide (CO2) within the world’s biological systems. This process, which involves the sequestration of carbon by living organisms like plants and algae, is a fundamental part of the global carbon cycle. By removing excess CO2 from the air and storing it in long-term reservoirs, biosequestration plays a significant role in mitigating rising greenhouse gas concentrations.
The Fundamental Processes of Carbon Capture
The primary mechanism driving biosequestration is photosynthesis, used by plants, trees, and microscopic organisms called phytoplankton. Organisms absorb atmospheric CO2, using the carbon atoms to construct their tissues and biomass while releasing oxygen. On land, this carbon is locked into trunks, branches, leaves, and roots, accumulating over decades as the organism grows.
In marine environments, phytoplankton pull carbon from the surface water. When these organisms and the small animals that feed on them die, their carbon-rich remains sink toward the deep ocean in a continuous process known as the biological pump. This sinking material, often called “marine snow,” transfers carbon from the surface to the deep sea. The biological pump stores carbon away from the atmosphere for thousands of years.
Major Natural Carbon Storage Environments
Terrestrial and aquatic ecosystems serve as the planet’s major carbon reservoirs, storing carbon over various timescales. Forests are visible terrestrial sinks, storing large amounts of carbon above ground in woody biomass. The soil beneath these forests and other landscapes holds an even larger quantity of carbon, often containing more carbon than the atmosphere and all vegetation combined.
Carbon stored in soil is known as Soil Organic Carbon (SOC), a mix of decomposed plant and animal matter. The stability of this carbon depends on soil management and microbial activity; if undisturbed, carbon can remain sequestered for decades or centuries. Coastal ecosystems, often called “blue carbon” habitats, are effective at long-term storage. These include mangroves, tidal marshes, and seagrass meadows, which sequester carbon at a faster rate per area than most terrestrial forests.
Blue carbon storage is unique because 50% to 99% of the carbon is stored below ground in dense, waterlogged sediments. The anaerobic (oxygen-poor) conditions slow decomposition, allowing this carbon to remain stable for millennia. Mangroves, for example, can store carbon at rates up to five times higher than tropical forests per unit area. This stability makes protecting these coastal environments a valuable climate solution.
Enhancing Biosequestration Through Human Action
Human intervention can accelerate biosequestration through strategic land management practices. Reforestation and afforestation (planting trees in existing or new forest areas) directly increase carbon uptake and storage in biomass. These efforts focus on regenerating degraded lands to maximize the growth and long-term carbon accumulation potential of the new vegetation.
In agriculture, regenerative farming techniques are designed to increase Soil Organic Carbon. These practices include:
- No-till farming, which avoids disturbing the soil structure and prevents stored carbon from being released as CO2.
- Cover cropping, where fields are planted outside the main growing season to feed the soil microbiome and contribute new organic matter.
- Agroforestry, which integrates trees and shrubs into crop and animal farming systems to enhance soil health and carbon accumulation.
Protecting and restoring blue carbon habitats is another strategy to leverage biosequestration. Restoration projects for mangroves and salt marshes stabilize these ecosystems, ensuring their immense subsurface carbon stores remain locked away. Preventing the degradation of these coastal areas is paramount, as their destruction can release massive amounts of sequestered carbon, turning a sink into a source of emissions.