This biological approach uses traditional plant breeding and newer biotechnological methods to select and tailor crop varieties with greater carbon sequestration capacity. Improvements in agronomic practices generally have the goal to increase yields. Then humans or livestock usually consume these yields, and subsequently their respiration returns the CO2 to the atmosphere relatively quickly. However, in many cases the improvements have not greatly changed the harvest index of the crops meaning that greater amounts of residue carbon are generated, which can lead to increased carbon storage in the soil (Lal et al., 1998; Smith et. al., 2008). One example is using biotechnology to produce improved crop varieties with greater insect and/or disease resistance resulting in greater yields and in corresponding increases in residues available for sequestration. A second way would be to improve the digestibility of pasture species using gene modification (GM) technology to reduce methane emissions from ruminants and nitrous oxide emissions from animal excreta. A third method to reduce emissions is adopting cropping systems which reduce reliance on pesticides, nitrogenous fertilisers, and other inputs that require fossil fuels to be manufactured. A good example of this is the use of rotations with legume crops.
See also 'Rice: agricultural biotechnology' for the biotechnology approach for methane mitigation technology involves identification of rice cultivars which emit less methane.
Agricultural biotechnology stands out as a promising tool for the development of traits and varieties that help to mitigate and adapt to climate change. GM crops with pest resistance (Bt) and herbicide tolerance and conventionally bred varieties using marker selection in tissue culture have benefited agriculture by improving productivity and disease resistance. Had productivity not been maintained or increased by such GM crops, more land would have to be cultivated, and it is likely such land would come from forest or other more natural ecosystems with sequestered carbon that would be released when tilled for growing crops. There are three ways that a GM crop can reduce GHG emissions: (1) increasing productivity and the amount of residue carbon that can be sequestered, (2) herbicide-resistance crops enable greater use of no-till which helps preserve carbon sequestration, and (3) because of enabled no-till, the amount of fossil fuel use by tractors and other implements is reduced because no-till involves fewer passes of equipment across the field.
Crop varieties that have been created by traditional plant selection methods have no barriers to dissemination, and they are accepted worldwide. On the other hand, plant varieties resulting from GM crops have faced stiff opposition from consumers in several parts of the world, most notably in Europe. Moreover, the resultant seeds are often relatively expensive so they may not be available to the poorest farmers.
- A big advantage of biotechnology is that, besides increasing carbon sequestration, it can help to improve the productivity of crop plants.
- By selecting cultivars that are more responsive to elevated CO2 and more resistant to heat stress, crops will be better adapted to future climatic conditions.
- The method generally requires several years and generations of plants to implement because yield and carbon sequestration are dependent on many abiotic and biotic factors. The pace of variety development may be slower than changes in atmospheric CO2 and climate.
- Whole new research programs are needed for identifying varieties and traits responsive to the increases in atmospheric CO2 and global warming and their interactions on the productivity, grain quality, water relations, and pest resistance of crops, and such research is expensive (e.g., Ainsworth et al., 2008).
- To be successful, selection needs germplasm that differs in many traits, and there may not be enough range in variation of crucial traits needed to adapt to climate change.
- Many varietal crosses require the use of growth chambers or greenhouses with potted plants, which makes it difficult to predict responses under field conditions.
Traditional plant selection is used worldwide to improve plant varieties, often with the aim of matching them to local growing conditions. Newer biotechnology requires specialised equipment and laboratories as well as more trained personnel, therefore it tends to be a technology that is confined to more developed countries. Because of the high cost of facilities that can produce conditions with elevated CO2 and temperature as expected with global change, relatively few field experiments have been conducted (e.g., Ainsworth et al., 2008), and they have tended to be in developed countries, with China and India as exceptions. Approximately 250 million acres of biotechnology engineered maize, canola, cotton, soybeans, papaya, sugarbeets, sweetcorn and squash crops have increased global farmer profits by about $27 billion, reduced pesticides application by 224 million kg, reduced environmental impacts of pesticides by 14% and reduced GHG emissions by 960 million kg of CO2 (Brookes and Barfoot, 2009). On the basis of above advantages of GM crops, several companies such as Monsanto, Syngenta and Pioneer-DuPont have started to use these germplasms in their research and development pipelines.
Varieties with increased yield for whatever reason improve the profitability of farmers. Many commercial seed companies are hugely successful. Therefore, the economics of using improved varieties, whether by traditional plant selection or by biotechnology, have been very positive, and it is very likely that they will continue to be positive with future climate change. As mentioned above, besides benefiting agriculture by improving productivity and disease resistance, improved plant varieties have decreased GHG emissions by reducing demand for cultivated land and fossil-fuel-based inputs. GM crops conserve over 14,200 million kg of CO2 – the equivalent of removing over 6 million cars from circulation in 2007 alone (Brookes and Barfoot, 2009).
Newer biotechnology requires specialised equipment and laboratories as well as more trained personnel, therefore it tends to be a technology that is confined to more developed countries. Because of the high cost of facilities that can produce conditions with elevated CO2 and temperature as expected with global change, relatively few field experiments have been conducted (e.g., Ainsworth et al., 2008), and they have tended to be in developed countries, with China and India as exceptions.
Ainsworth, E.A., C. Beier, C. Calfapietra, R. Ceulemans, M. Durand-Tardif, G.D. Farquhar, D.L. Godbold, G.R. Hendrey, T. Hickler, J. Kaduk, D.F. Karnosky, B.A. Kimball, C. Körner, M. Koornneef, T. Lafarge, A.D.B. Leakey, K.F. Lewin, S.P. Long, R. Manderscheid, D.L.McNeil, T.A.Mies, F. Miglietta, J.A. Morgan, J. Nagy, R.J. Norby, R.M. Norton, K.E. Percy, A. Rogers, J.F. Soussana, M. Stitt, H.-J. Wiegel, and J.W. White (2008). Next generation of elevated [CO2] experiments with crops: A critical investment for feeding the future world. Plant, Cell and Environment 31:1317-1324.
Brookes, G., and P. Barfoot. (2009): “GM Crops: global socio-economic and environmental impacts 1996-2007”. PG Economics Ltd, UK, May.
Lal, R., Kimble, JM, Follet, RF, and Cole, CV. (1998b): The Potential of U.S. Cropland to Sequester Carbon and Mitigate the Greenhouse Effect, Ann Arbor Press, Chelsea, Michigan, USA. Lal, R, Kimble JM, Follett RF, and Stewart BA. (1998c) Soil Processes and the Carbon Cycle. CRC Press LLC.
Smith P, Martino D, Cai Z, Gwary D, Janzen HH, Kumar P, Mccarl B, Ogle S, O’mara F, Rice C, Scholes RJ, Sirotenko O, Howden M, Mcallister T, Pan G, Romanenkov V, Schneider U, Towprayoon S, Wattenbach M and Smith JU (2008): Greenhouse gas mitigation in agriculture. Philosophical Transactions of the Royal Society B 363:789-813.