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Terrestrial Sinks

In contrast to geological sequestration where carbon dioxide (CO₂) gas is injected and stored in geologic layers deep in the Earth, terrestrial sequestration occurs at the Earth's surface through management practices that increase the amount of the carbon portion of the CO₂ that can be stored in roots and vegetable matter aboveground and in the soil. The soil layer that covers the landscape can be thought of as a thin carbon "sink." The amount of carbon that can be stored in the soil through terrestrial sequestration depends on vegetation type and other factors.

Promising land and water management practices that lead to terrestrial sequestration of carbon include adopting conservation tillage, reducing soil erosion, and minimizing soil disturbance; using buffer strips along waterways; enrolling land in conservation programs; restoring and better managing wetlands; eliminating summer fallow; using perennial grasses and winter cover crops; and fostering an increase in forests.^1,2

Vegetation Types Click for larger image (380 KB PDF)

Soil can only take in and store a limited amount of carbon. After a 50- to 100-year time frame, the soils will have reached equilibrium and will not accept any more carbon.³ Once this "steady state" has been reached, the carbon will remain sequestered in the soil as long as the land remains undisturbed or conservation land management practices are continued.

The PCOR Partnership region has an agrarian history founded on fertile soils stretching from the Central Lowlands forests and cropland in the southeastern portion of the region, through the expansive grasslands and croplands of the northern Great Plains, to the northern boreal forests of Canada. However, as central North America developed into the pattern of land use seen today, much of the original soil carbon was lost to the atmosphere. As a result, the vegetation and land in the region could be managed to replace this lost soil carbon with carbon from CO₂ in the atmosphere. The greatest potential would be in converting marginal agricultural lands and degraded lands to grasslands, wetlands, and forests under appropriate conditions.¹

Terrestrial sequestration is important because it can be implemented immediately and can begin to reduce atmospheric CO₂ levels in the next few years. Using terrestrial sequestration now means we can get started on reducing CO₂ levels in the atmosphere while we adopt other carbon control measures.

Terrestrial Carbon Sink Variables

References:

1. Paustian, K.H., and Cole, C.V., 1998, CO₂ mitigation by agriculture - an overview: Climatic Change, v. 40, p. 135-162, Netherlands, Kluwer Academic Publishers.
2. Peterson, E.B., Bonnor, G.M., Robinson, G.C., and Peterson, N.M., 1999, Carbon sequestration aspects of an afforestation program in Canada's prairie provinces: Submitted to Joint Forest Sector Table/Sinks Table, National Climate Change Process, published by Nawitka Renewable Resource Consultants Ltd., p. 1-98, www.nccp.ca/NCCP/pdf/Afforest_Prairies.pdf (accessed September 2004).
3. de Silva, L.L., Cihacek, L.J., Leistritz, F.L., Faller, T.C., Bangsund, D.A., Sorensen, J.A., Steadman, E.N., and Harju, J.A., 2005, The contribution of soils to carbon sequestration: Plains CO₂ Reduction (PCOR) Partnership topical report for U.S. Department of Energy and multiclients, Grand Forks, North Dakota, Energy & Environmental Research Center, June.