Soil carbon sequestration to mitigate climate change: a critical re‐examination to identify the true and the false
Tóm tắt
The term ‘carbon sequestration’ is commonly used to describe any increase in soil organic carbon (SOC) content caused by a change in land management, with the implication that increased soil carbon (C) storage mitigates climate change. However, this is only true if the management practice causes an additional net transfer of C from the atmosphere to land. Limitations of C sequestration for climate change mitigation include the following constraints: (i) the quantity of C stored in soil is finite, (ii) the process is reversible and (iii) even if SOC is increased there may be changes in the fluxes of other greenhouse gases, especially nitrous oxide (N2O) and methane. Removing land from annual cropping and converting to forest, grassland or perennial crops will remove C from atmospheric CO2 and genuinely contribute to climate change mitigation. However, indirect effects such as conversion of land elsewhere under native vegetation to agriculture could negate the benefit through increased CO2 emission. Re‐vegetating degraded land, of limited value for food production, avoids this problem. Adding organic materials such as crop residues or animal manure to soil, whilst increasing SOC, generally does not constitute an additional transfer of C from the atmosphere to land, depending on the alternative fate of the residue. Increases in SOC from reduced tillage now appear to be much smaller than previously claimed, at least in temperate regions, and in some situations increased N2O emission may negate any increase in stored C. The climate change benefit of increased SOC from enhanced crop growth (for example from the use of fertilizers) must be balanced against greenhouse gas emissions associated with manufacture and use of fertilizer. An over‐emphasis on the benefits of soil C sequestration may detract from other measures that are at least as effective in combating climate change, including slowing deforestation and increasing efficiency of N use in order to decrease N2O emissions.
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Tài liệu tham khảo
Angers D.A., 1996, Structure and Organic Matter Storage in Agricultural Soils, 193
Bergstrom L., 2005, Perspectives and challenges in the future use of plant nutrients in tilled and mixed agricultural systems., Ambio, 34, 283, 10.1579/0044-7447-34.4.283
Bhogal A. Chambers B.J. Whitmore A.P.&Powlson D.S.2009.The Effects of Reduced Tillage Practices and Organic Material Additions on the Carbon Content of Arable Soils. Scientific Report for Defra Project SP0561 Defra London. [WWW document]. URLhttp://randd.defra.gov.uk/Document.aspx?Document=SP0561_6892_FRP.doc[accessed December 2010].
Copeland J., 2008, National and Regional Supply/Demand Balance for Agricultural Straw in Great Britain.
Glendining M.J., 1995, Soil Management: Experimental Basis for Sustainability and Environmental Quality, 385
Goulding K.W.T., 2005, The missing link., Geoscientist, 15, 4
IPCC, 2007, Synthesis Report, Summary for Policy Makers, 1
IPCC, 2007, Changes in Atmospheric Constituents and in Radiative Forcing, 131
Jones P.&Crane R.2009.England and Wales Under Organic Agriculture. How Much Food Could be Produced?Centre for Agricultural Strategy Report 18 University of Reading Reading.
Lal R., 2003, Global potential of soil carbon sequestration to mitigate the greenhouse effect., Critical Reviews in Plant Sciences, 22, 151, 10.1080/713610854
Rochette R., 2008, No-till only increases N2O emissions in poorly-aerated soils, 101, 97
Royal Society2009.Reaping the Benefits: Science and the Sustainable Intensification of Global Agriculture. Royal Society Policy Report 11/09 Royal Society London.
Searchinger T., 2008, Use of U.S. croplands for biofuels increases greenhouse gases through emissions from land‐use change., Science Express, 319, 1238
Smith P., 2000, Considering manure and carbon sequestration., Science, 287, 427, 10.1126/science.287.5452.427e
Verheijen F.G.A., 2009, Biochar Application to Soils–A Critical Scientific Review of Effects on Soil Properties, Processes and Functions.