The problem
A rise of more than 0.7 °C in the average surface temperature has been seen in the past 100 years and there is increasing evidence that the earth’s climate is rapidly changing in response to increased inputs of carbon dioxide (Henson,2001 IPCC,2007). Global carbon dioxide emissions have increased from an average 6.4 ± 0.4 GtC yr–1 in the 1990’s to 7.2 ± 0.3 GtC yr–1 in the period 2000 to 2005(IPCC,2007).The extent that humans are polluting our atmosphere is at a staggering four metric tonnes per person per year (Henson,2001). Therefore mitigation of carbon dioxide into the atmosphere is essential. One method which has major potential in reducing carbon dioxide emissions is soil carbon sequestration (Peterson et. al, 2013).
What is soil carbon sequestration?
Soil carbon sequestration is the process of transferring carbon dioxide from the atmosphere into soil through organic solids and storing it (Sundermeier, Reeder,Lal,n.d). It is also commonly used to describe any increase in soil organic carbon content caused by a change in land management within the soil to mitigate climate change (Powlson, et al. 2011.) At present the attainable soil carbon capacity sink is only 50-60% of its potential capacity and with the added benefits of increasing food security as well improving soil quality, soil carbon sequestration seems a viable option (Halvorson,Wienhold,Black, 2002; Lal,2004a) . It has been predicted that this technology could offset 2000-5000 Mt C/ yr-1 (Cannel, 2003).
What methods improve soil carbon sequestration?
Managing agricultural land
It has been well recognised that the conversion from natural to agricultural land has resulted in a significant loss of 50% of soil organic carbon globally (Kirkby, et al. 2013). Most of the loss in soil organic carbon to the atmosphere can be explained due to reduced inputs of organic matter, increased decomposability of crop residues and tillage effects that decrease the amount of physical protection. Therefore increasing soil organic carbon through managing agricultural land is vital to increase sequestration (Post and Kwon, 2000).
Case study- Australia
Management of land use in Australia is being adopted throughout many regions and improved management of croplands through rotations, conservation tillage and stubble retention has caused a gain of 0.2-0.3 Mg C ha -1 yr-1 in comparison to conventional management, even though small it can relate to large sequestration rates of up 60 tg CO2 per year (Sanderman, et al. 2010).
Managing peat lands
As well as managing agricultural lands, peat lands should equally be managed due to their wide global distribution and contribution to carbon dioxide emissions. They are unique soil carbon pools made from high densities of carbon which have accumulated over many years because decomposition is suppressed by the absence of oxygen under flooded conditions (Smith,2007b; Lal,2009). However increases in anthropogenic activities such as drainage and deforestation for agricultural land has released carbon to the atmosphere and reduced carbon sequestration function (Page, et al, 2011).
References
- Cannel, M., 2003. Carbon sequestration and biomass offset : theoretical potential and achievable capacities globally , in Europe and the UK. Biomass and bioenergy. Vol 24 (2).
- Halverson,A., Weinhold, B., Black,A., 2002. Tillage, nitrogen and cropping effects on soil carbon sequestration. Soil science society of America Journal. Vol 66 p906-912.
- Henson, R., 2001. The rough guide to Climate Change. 3rd ed. London: Penguin Group.
- IPCC 2007. Climate Change 2007: The Physical Science Basis. Cambridge, UK: Cambridge University Press, 2007.
- Kirkby,C., Richardson, A., Wade,L., Passioura, J., Batten,G., Blanchard, C., Kirkegaard. 2013.Nutrient availability limits carbon sequestration in arable soils. Soil biology and biochemistry. Vol 68 p402-409.
- Lal, R., 2009. Agriculture and climate change: An agenda for negotiation in Copenhagen. The potential for soil carbon sequestration. [pdf]International food policy research institute. Available at : http://www.ifpri.org/sites/default/files/publications/focus16_05.pdf Accessed on 23rd November 2013.
- Page, E., Morrison,R., Mallins,R., Hooijer,A., Rieley,O., Jauhianen, J., 2011. Review of peat surface greenhouse gas emissions from oil palm plantations in South East Asia . [pdf] The international council on clean transportation. Available at : http://www.theicct.org/sites/default/files/publications/ICCT_Peat-Emissions_Sept2011.pdf Accessed on 3rd December 2013
- Peterson ,B., Knudsen, M., Hermansen,J.,Halberg, N., 2013. An approach to include soil carbon changes in life cycle assessments. Journal of cleaner production. Vol 52 p217-244.
- Post,W., Kwon,K.,2000. Soil carbon sequestration and land use change: processes and potential. Global change biology . vol 6 p317-328.
- Powlson, D.,Whitmore,A., Goulding,K., 2011. Soil carbon sequestration to mitigate climate change: a critical re-evaluation to identify the true and false. European journal of soil science. vol 62 issue 1.
- Sanderman, J., Farquharson, ,R., Baldock,J., 2010. Soil carbon sequestration potential : A review for Australian agriculture. (pdf) National Research flagships sustainable agriculture. Available at: http://csiro.au/Portals/Publications/Research–Reports/Soil-Carbon-Sequestration-Potential-Report.aspx Accessed on 2nd December 2013.
- Smith, P., D. Martino, Z. Cai, D. Gwary, H. Janzen, P. Kumar, B. McCarl, S. Ogle, F. O’Mara, C. Rice, B. Scholes, O. Sirotenko, 2007: Agriculture. In Climate Change 2007: Mitigation. Contribution of Working Group III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [B. Metz, O.R. Davidson, P.R. Bosch, R. Dave, L.A. Meyer (eds)], Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.
- Sundermeier,A., Reeder,R.,Lal,R., n.d.Soil carbon sequestation. (pdf) Available at: http://ohioline.osu.edu/aex-fact/pdf/0510.pdf accessed on 23rd October 2013. Accessed on 8th December 2013.
