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Cropland, pasture/rangeland, and forested lands represent nearly half of the land use in the United States, and agriculture accounts for 10% of U.S. greenhouse gas emissions. The graphic from a paper by Sanderman et al. entitled Soil Carbon Debt of 12,000 years of Human Land Use describes the global distribution of crop and grazing lands (5).
Global distribution of cropping and grazing (Sanderman et al., 2017)
Sanderman et al (2017) goes on to explain that human interactions with agricultural land have depleted soil organic carbon stocks. In other terms, the organic carbon that took thousands of years to accumulate in the soil has declined, by "[median value] 26% for the upper 30 cm and 16% for the top 100 cm of soil, but ranges of −36 to 78% and −25 to 61%, respectively, have been reported for these two depth increments " (5).
Sanderman et al. 2017 (5)
Human use of landscapes over time has led to depletion of soil carbon. Much of this carbon that is no longer stored in the soil as organic carbon has been returned to the atmosphere, primarily as carbon dioxide.
Modeled SOC change in top 2m, positive values (yellow to red) indicate SOC loss; negative (blue to green) indivates net SOC gains (Sanderman et al., 2017) (5).
❓Check your knowledge!
According to graphs and maps above from Sanderman et al. Soil Carbon Debt of 12,000 years of Human Land Use, as grazing lands and cropland have expanded, the cumulative soil organic carbon has [increased/decreased/no correlation].
Discussion board: If you have any questions throughout Module 1, please use the discussion board to below to post.
Citations
Citations
(1) Soil Management Bank. Australian Soil Management. 2019. https://www.australiansoil.com.au/soil-management-benefits (2) Follett, R., Mooney, S., Morgan, J., Paustian, K., Allen Jr., L., Archibeque, S., … Robertson, G. (2011). Carbon sequestration and greenhouse gas fluxes in agriculture: challenges and opportunities. Ames: Council for Agricultural Science and Technology (CAST). (3)Paustian, K., Six, J., Elliott, E. et al. Management options for reducing CO2 emissions from agricultural soils. Biogeochemistry 48, 147–163 (2000). https://doi.org/10.1023/A:1006271331703(4)L. E. Flint, A. L. Flint, M. A. Stern, A. Myer, W. Silver, C. F. Casey, F. Franco, K. Byrd, B. Sleeter, P. Alvarez, J. Creque, T. Estrada and D. Cameron, California's Fourth Climate Change Assessment, Increasing soil organic carbon to mitigate greenhuose gases and increase climate resiliency, 2018.(5) J. Lavelle, F. Cotrufo, Soil carbon is a valuable resource, but all soil carbon is not created equal. The Conversation (2020), (available at https://theconversation.com/soil-carbon-is-a-valuable-resource-but-all-soil-carbon-is-not-created-equal-129175). (6) The Keeling Curve. The Keeling Curve (2020), (available at https://scripps.ucsd.edu/programs/keelingcurve/). (7) B. Deluisi, ESRL Global Monitoring Laboratory - Education and Outreach. Esrl.noaa.gov (2020), (available at https://www.esrl.noaa.gov/gmd/education/carbon_toolkit/basics.html). (8) Jonathan Sanderman, Tomislav Hengi, and Gregory J. Fiske. 2017. Soil carbon debt of 12,000 years of human land use. Proceedings of the National Academy of Sciences: Sep 2017, 114 (36) 9575-9580; DOI: 10.1073/pnas.1706103114(9)J. Hansen, M. Sato, P. Kharecha, K. V. Schuckmann, D. J. Beerling, J. Cao, S. Marcott, V. Masson-Delmotte, M. J. Prather, E. J. Rohling, J. Shakun, P. Smith, A. Lacis, G. Russell and R. Ruedy, Earth System Dynamics, 2017, 8, 577–616.(10)Paustian, K., Lehmann, J., Ogle, S. et al. Climate-smart soils. Nature 532, 49–57 (2016). https://doi.org/10.1038/nature17174 (11) Hansen, J et al. : Young people's burden: requirement of negative CO2 emissions, Earth Syst. Dynam., 8, 577–616, , 2017
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