Carbon Sequestration in Soils

From The USGS Web Site:

Carbon enters the soil as roots, litter, harvest residues, and animal manure. It is stored primarily as soil organic matter (SOM). The density (weight/volume) of carbon is highest near the soil surface. But much of the most recently deposited SOM decomposes rapidly, releasing CO2 to the atmosphere.

Some carbon becomes stabilized, especially in the lower part of the soil profile. Balanced rates of input and decomposition determine steady state carbon fluxes. However, in many parts of the world, agriculture and other land-use activities have upset the natural balance in the soil carbon cycle, contributing to an alarming increase in carbon release from soils to the atmosphere in the form of CO2.

Carbon sequestration in soils is a climate-change-mitigating strategy based on the assumption that movement, or flux, of carbon from the air to the soil can be increased while the release of carbon from the soil back to the atmosphere is decreased. In other words, certain activities can transform soil from a carbon source (emits carbon) into a carbon sink (absorbs carbon). This transformation has the potential to reduce atmospheric CO2, thereby slowing global warming and mitigating climate change.

At the same time, carbon sequestration can confer substantial benefits on the people in a region, such as farmers and small landholders, who directly manage the soil carbon pool. Improved land and soil management practices that help sequester carbon in soils can lead to higher soil fertility, increased yields, and other outcomes that aid local populations economically, environmentally, and socially. Carbon sequestration in soils also has great potential in regard to the international trading of carbon credits, where one nation may offset its carbon emissions by supporting carbon sequestration in some other part of the world.

Currently, researchers at the USGS/EROS Data Center are involved in collaborative carbon sequestration projects in West Africa and Central Asia.