Soil Carbon Sequestration: What Is It and Why Is It Important?
Posted by Chris Ann Lunghino | June 4, 2021
Putting atmospheric carbon back into the soils where it belongs to mitigate impacts of climate change
Soil carbon sequestration is a naturally occurring process that involves atmospheric carbon dioxide capture and storage in soils.
Carbon atoms constantly move from the atmosphere to the Earth and then back to the atmosphere. The world’s soil, along with forests and oceans, is a major carbon sink—it has the ability to absorb and store massive amounts of carbon from the atmosphere.
Because our planet and its atmosphere are a closed environment, the amount of carbon in this system does not change. Where the carbon is located, however, in the atmosphere or on Earth, is constantly changing. Since the industrial revolution, human activities, including conversion of grasslands and other ecosystems to industrial agriculture uses, have degraded soils and led to the release of billions of tons of carbon from soils into the atmosphere.
Humans can help put carbon back into the soil where it belongs.
According to a strong and growing international scientific consensus, humans can help put carbon back into soils where it belongs through intentional restorative land use practices. Accelerating the removal of carbon from the atmosphere and its sequestration back into soils deep underground is critically important to slowing the rapid rise of carbon dioxide in the atmosphere, reducing carbon to safe levels, and avoiding the most catastrophic impacts of climate change.
Returning carbon to the soils rebuilds soil organic matter and soil organic carbon. This results in numerous other benefits, including revitalized soils and improved soil structure, leading to reduced erosion and stormwater runoff (increased retention of water and nutrients), improved water quality in groundwater and surface waters, and increased biodiversity. Healthier soils also means greater productivity of plants in both natural environments and agricultural settings, which ultimately leads to increased food security.
How Soil Carbon Sequestration Works
Soil carbon sequestration is a vital ecosystem service that results from interactions of ecological processes, including photosynthesis, respiration, and decomposition.
Photosynthesis draws carbon out of the air.
Through photosynthesis, a plant draws carbon out of the air to form carbon compounds—photosynthesis fixes atmospheric CO2 into plant biomass. Some of the carbon sequestered in the plant is stored in the plant biomass above and below ground. It combines with water and converts into sugars that fuel more plant growth. The carbon the plant doesn’t need for growth is secreted through its roots into the soil, where it feeds soil microorganisms.
Some of that carbon is released back into the atmosphere when dead roots and leaves decompose, and some is stored deep in the soils for the long-term.
Part of the carbon that the plant secretes into the soil is lost to the atmosphere (or water) due to microbial respiration and decomposition of biomass, including dead roots and leaves. A small proportion of the carbon secreted into the soil is made stable and stored underground for the long-term. “Stable” pools of carbon housed in soils can be stored deep underground for thousands of years. “Active” soil carbon, on the other hand, which lives in topsoil, flows continuously between microbial organisms and the atmosphere. Thus, establishing deep-rooted perennial grasses that nurture deep, fertile soils to store stable carbon for the long-term is an important strategy for reversing the massive loss of soil carbon stock into the atmosphere that has occurred.
Wrapping it up: Soil carbon sequestration is the process of transferring carbon dioxide from the atmosphere into the soil.
Human activities since the industrial revolution affecting ecological processes have led to a massive net carbon loss from soils. Human activities can restore lost carbon to the soils. Implementing intentional land use practices, including regenerative agriculture, to restore degraded and eroded lands can accelerate the removal of atmospheric carbon and its sequestration back into soils where it belongs and contribute significantly to reducing CO2 to safe levels to avoid the most serious long-term impacts of climate change. And sequestering carbon in soils has important co-benefits—it restores soil health and makes our water purer, air cleaner, and ecosystems more diverse.