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Introduction to Special Section on Greenhouse Gases and Carbon Sequestration in Agriculture and Forestry

Department of Agronomy, Kansas State University, 2004 Throckmorton Plant Sciences Center, Manhattan, KS 66506-5501

^* Corresponding author (cwrice{at}ksu.edu)

Received for publication June 5, 2006.

	INTRODUCTION

TOP INTRODUCTION Agriculture and Forestry... Agriculture and Forestry... Co-effects Third USDA Symposium on... REFERENCES

 
AGRICULTURAL cropland, forest, rangeland, wetlands, and urban ecosystems have significant potential to offset large amounts of greenhouse gases (GHGs) through improved land management and increased productivity. To fully realize this potential, we must understand how to implement the proper management practices and technologies to mitigate carbon dioxide (CO₂), nitrous oxide (N₂O), and methane (CH₄); conduct appropriate national, regional, and local inventories of soil carbon levels; develop sound measurements and monitoring techniques; and apply the appropriate practices and technologies within economic constraints. Considerable research is currently ongoing in these areas and is the subject of this special section.

	Agriculture and Forestry Contribution to Greenhouse Gases

TOP INTRODUCTION Agriculture and Forestry... Agriculture and Forestry... Co-effects Third USDA Symposium on... REFERENCES

 
The atmospheric concentration of three GHGs—O₂, CH₄, and N₂O—has increased during the past 100 to 150 yr (IPCC, 2001). Since the late 1800s fossil fuel use, expansion of cultivated agriculture, and forest clearing have led to an increase in atmospheric CO₂ from 260 µL L^–1 (260 ppmv) to current levels > 370 µL L^–1 (370 ppmv) (IPCC, 1995). Most of the recent increase in CO₂ has been attributed to combustion of fossil fuels for energy and transportation. This increase in atmospheric CO₂ potentially impacts climate, as it is a greenhouse gas. In 1992, the USA signed and ratified the United Nations Framework Convention on Climate Change (UNFCCC) with the provision that stabilization of GHG concentrations allow ecosystems time to adapt to climate change, ensure food production, and enable sustainable economic development. In 2004, total U.S. GHG emissions were 7074 Tg CO₂ equivalent (eq.), a 15% increase since 1990 (USEPA, 2006). In the USA, emissions from agriculture and forestry represented approximately 447 Tg CO₂ eq., 6% of the U.S. total GHG emissions. Globally, agriculture accounts for about 14% of the total GHG emissions.

Agriculture contributes to GHG emissions through enteric fermentation, livestock manure management, rice cultivation, agricultural soil management, and burning of crop residues. Methane and N₂O are the primary greenhouse gases from agriculture. Agriculture in the USA represented 27% of the anthropogenic CH₄ emission in 2004 and 68% of the N₂O emission. Globally agriculture accounts for 47% of the CH₄ emissions and 84% of the N₂O (USEPA, 2006). Forestry contributed approximately 2% to the overall N₂O emissions due to N fertilization of forests.

At the same time agriculture and forestry were contributing to the overall U.S. greenhouse gas emissions, land use, land use change, and forestry represented a sink of 780 Tg CO₂ eq. or 11% of the total U.S. emissions (USEPA, 2006). The agricultural and forestry sinks represented net carbon accumulation by forest and agricultural soils.

	Agriculture and Forestry Contribution to Mitigation

TOP INTRODUCTION Agriculture and Forestry... Agriculture and Forestry... Co-effects Third USDA Symposium on... REFERENCES

 
Contributions of agriculture and forestry to mitigation of greenhouse gases can be achieved by (i) decreasing emissions of GHGs and (ii) sequestering C, derived from atmospheric CO₂, within the ecosystem. Thus, effective mitigation strategies involve appropriate measures that decrease emissions while enhancing C storage in biomass and in soil. Recent models of land use suggest terrestrial systems can mitigate the increase of atmospheric CO₂ by sequestering C into vegetation and soils. The estimated amount of C stored in world soils is about 1100 to 1600 Pg, more than twice the C in living vegetation (560 Pg) or in the atmosphere (750 Pg) (Sundquist, 1993). Carbon sequestration in vegetation and soils is one of the mitigation technologies (IPCC, 2000). Caldeira et al. (2004) categorized several mitigation options. Those options that were immediately deployable with major contributions (>0.2 Pg C yr^–1) to mitigation included agricultural soil C storage, non-CO₂ abatement from agriculture (soils and livestock), reforestation, and land restoration. Options that also had significant mitigation contribution but were not immediately deployable included geologic storage, coal technology, and hydrogen fuels. Thus, agriculture and forestry are major mitigation options for reducing GHG emissions in the short term. Forests in the USA are estimated to be currently sequestering 200 Tg yr^–1 with an additional potential of 100 to 200 Tg yr^–1 with appropriate development of technology and practices, and technical assistance to land managers (Birdsey et al., 2006). In agriculture current estimates of soil C sequestration are 11 to 21 Tg yr^–1, primarily due to conservation set-aside, reduced tillage, and increased crop productivity (Lokupitiya and Paustian, 2006). The potential for U.S. cropland to sequester C ranges from 75 to 208 Tg yr^–1 (Lal et al., 1998) and another 18 to 90 Tg yr^–1 for grazing lands (Follett et al., 2001). Current technologies that can be implemented immediately include:

• Cropland management (i.e., reduced tillage, reduced fallow, cover crops)
  
• Grazing land management/pasture improvement
  
• Forestry management
  
• Restoration of degraded lands
  
• Livestock management
  
• Manure/biosolids management
  
• Bio-energy production
  

However, the potential will be reduced by the extent of adoption, which is governed by market and policy forces (McCarl and Schneider, 2001).

	Co-effects

TOP INTRODUCTION Agriculture and Forestry... Agriculture and Forestry... Co-effects Third USDA Symposium on... REFERENCES

 
Several of the mitigation options provide co-benefits. Increasing soil C improves soil structure (McVay et al., 2006), increases soil fertility, soil biodiversity (Schnürer et al., 1985; Hooper et al., 2000), and water availability (Peterson and Westfall, 1997). In addition, retention of residues on the soil surface reduces soil erosion, thus improving air and water quality. Better N management in agriculture and forestry has the potential to improve water quality and N use efficiency.

	Third USDA Symposium on Greenhouse Gases and Carbon Sequestration in Agriculture and Forestry

TOP INTRODUCTION Agriculture and Forestry... Agriculture and Forestry... Co-effects Third USDA Symposium on... REFERENCES

 
The USA and other countries are considering options to respond to global warming. In support of these decisions, basic information about the sources and sinks of greenhouse gases in terrestrial systems, ecosystem management, and the associated variability needs to be synthesized to optimize accounting and verification of greenhouse gases. The papers in this section of the journal are a result of the Third USDA Symposium on Greenhouse Gases and Carbon Sequestration in Agriculture and Forestry. The purpose of this conference was to (i) provide a forum for scientists to present the most recent breakthroughs in science and technology developments relevant to storing carbon and addressing greenhouse gases in managed terrestrial ecosystems; (ii) transfer information about new scientific findings, new technologies, and program information to scientists, program managers, policymakers, and the private sector; and (iii) enhance collaboration and partnerships within the USDA and with other federal, state, and private organizations.

The symposium organizers were Kansas State University, Soil Science Society of America, and the Consortium for Agricultural Soils Mitigation of Greenhouse Gases (CASMGS). The CASMGS provides information and technology necessary to develop, analyze, and implement agricultural soil greenhouse gas mitigation strategies and is supported by a grant from USDA–CSREES. The consortium consists of scientists from Colorado State University, Iowa State University, Kansas State University, Michigan State University, Montana State University, Ohio State University, Purdue University, Texas A&M University System, University of Nebraska, and Pacific Northwest National Laboratory.

The Steering committee included William Hohenstein (USDA Global Change Program Office), Rao Achutuni (USDA Foreign Agricultural Service), Kathryn Bickel (USDA Forest Service), Marilyn Buford (USDA Forest Service), Cheryl Butler (USDA Farm Service Agency), Christopher Farley (USDA Forest Service), Paula Geiger (USDA Office of Budget and Program Analysis), Mike Jawson (USDA-ARS), Jan Lewandrowski (USDA-ERS), Carolyn Olson (USDA-NRCS), Charles Rice (Kansas State University), Steven Shafer (USDA-ARS), Bryce Stokes (USDA Forest Service), and Luis Tupas (USDA-CSREES). The organizing committee members included Charles Rice (Kansas State University), Susan Capalbo (Montana State University), Linda Heath (USDA Forest Service), Cesar Izaurralde (Pacific Northwest National Lab.), Larry Jacobson (University of Minnesota), Cathy Kling (Iowa State University), Blain Metting (Pacific Northwest National Lab.), Steven Shafer (USDA-ARS), Scott Staggenborg (Kansas State University), Bryce Stokes (USDA Forest Service), and Luis Tupas (USDA-CSREES). Special thanks go to Steve Watson and Terry Jo Litchfield (Kansas State University) for their hard work organizing the symposium and this special issue.

	REFERENCES

TOP INTRODUCTION Agriculture and Forestry... Agriculture and Forestry... Co-effects Third USDA Symposium on... REFERENCES

 

• Birdsey, R., K. Pregitzer, and A. Lucier. 2006. Forest carbon management in the United States: 1600–2100. J. Environ. Qual. 35:1461–1469 (this issue).[Abstract/Free Full Text]
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• Follett, R.F., J.M. Kimble, and R. Lal. 2001. The potential of U.S. grazing lands to sequester soil carbon. p. 401–430. In R.F. Follett et al. (ed.) The potential of U.S. grazing lands to sequester carbon and mitigate the greenhouse effect. CRC Press, Boca Raton, FL.
• Hooper, D.U., E. Bignell, V.K. Brown, L. Brussaard, J.M. Dangerfield, D.H. Wall, D.H. Wardle, D.C. Coleman, K.E. Giller, P. Lavelle, W.H. Van Der Putten, P.C. DeRuiter, J. Rusek, W.L. Silver, J.M. Tiedje, and V. Wolters. 2000. Interactions between aboveground and belowground biodiversity in terrestrial ecosystems: Patterns, mechanisms, and feedbacks. Bioscience 50:1049–1061.
• IPCC (Intergovernmental Panel on Climate Change). 1995. Technical summary. Intergovernmental Panel on Climate Change, World Meteorological Organization, Geneva, Switzerland.
• IPCC (Intergovernmental Panel on Climate Change). 2000. Land Use, Land Use Change, and Forestry Intergovernmental Panel on Climate Change Special Report. Oxford Univ. Press, UK.
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• Lal, R., J.M. Kimble, R.F. Follett, and C.V. Cole. 1998. The potential of U.S. cropland to sequester carbon and mitigate the greenhouse effect. Sleeping Bear Press, Chelsea, MI.
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• McVay, K.A., J.A. Budde, K. Fabrizzi, M.M. Mikha, C.W. Rice, A.J. Schlegel, D.E. Peterson, D.W. Sweeney, and C. Thompson. 2006. Management effects on soil physical properties in long-term tillage studies in Kansas. Soil Sci. Soc. Am. J. 70:434–438.[Abstract/Free Full Text]
• Peterson, G.A., and D.G. Westfall. 1997. Management of dryland agroecosystems in the central Great Plains of Colorado. p. 355–342. In E.A. Paul et al. (ed.) Soil organic matter in temperate agroecosystems: Long-term experiments in North America. CRC Press, Boca Raton, FL.
• Schnürer, J., M. Clarholm, and T. Rosswall. 1985. Microbial biomass and activity in an agricultural soil with different organic matter contents. Soil Biol. Biochem. 17:611–618.[CrossRef]
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• USEPA. 2006. Inventory of U.S. greenhouse gas emissions and sink: 1990–2004. Available at www.epa.gov/globalwarming/publications/emissions (verified 5 June 2006). USEPA, Washington, DC.

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