The agriculture sector, especially livestock production, accounts for one-fifth of total greenhouse-gas (GHG) emissions globally (McMichael et al, 2007).  Livestock production, including transport and feed, accounts for nearly 80% of the sector’s emissions (McMichael et al, 2007). Although CO2 is the most anthropogenic greenhouse-gas (GHG) emitter, with fossil fuel as the main source, methane, halocarbons and nitrous oxide are also huge contributors (Carlsson-Kanyama and Gonzalez, 2009). Methane itself is 270x more effective as an absorber of infrared radiation than CO2 (Houghton et al 1996). Animal production (mainly cattle and pig) is the largest emitter of methane from enteric fermentation and manure lagoons. However, as meat production, particularly in the form of Concentrated Animal Feed Operations (CAFOs), increases with world market demands, it also requires more agrochemicals, fossil fuel and electricity, resulting to the contributor of CO2 emissions.  Weber and Matthews found that the production of food contributes 83% of the average US households CO2 footprint each year whereas transport and delivery or “food miles” contributes only 11% and 4% respectively. In measuring the impact of food miles, and the climate footprint, it is important to examine individual food groups. Red meat contributes 150% more GHGs than fish and chicken (Weber and Matthews) with meats and fruits transported by air having the highest total GHG emissions (Carlsson-Kanyama and Gonzalez, 2009).

Herder in Timbuktu

Livestock production, at its current level, has intensified with one-third of the world’s entire land surface (FAO) going towards production, and of land dedicated to food crop production, 1/3 of global harvest of crops are eaten annual by animals (enough to feed more than 3 billion people) (Smil, 2002). It is estimated that to produce 1 kg of red meat, 13 kg of grain is needed, whereas with chicken the ratio is 1: 1.8 (USDA). Most of the energy (88-97%) and protein (80-96%) content contained within cereal and leguminous grains fed to animals is not converted to edible protein and fat (Smil, 2002). Yet, despite these statistics, global demand and consumption for meat is increasing, particularly in developing countries. But they have not yet caught up to the American diet. The average American consumes approximately 124 kg of meat each year, compared to the average worldwide consumption of 31 kg per year (FAO, 2006). If current consumption patterns remain, meat consumed in 2030 will be 72% higher than the amount consumed in 2000. Production of this amount of meat will require CAFO systems that will potentially generate an estimated 1.9 billion tons of GHG (Fiala, 2008).

In order to reduce agriculture-related GHG emissions, McMichael et al recommended, in the short term, a reduction of the current global average meat consumption of 100 g per person per day by 10% as a working global target with not more than 50 g per day coming from red meat of ruminants, particularly in high-income countries. Some have argued that this recommendation is conservative, and does not address long term issues of the animal production process itself. Whether conventional and organic systems of livestock productivity differ, in terms of GHG emissions, remains inconclusive and contentious when taking into account methodology, type of high quality grain, grain fed versus pasture fed and post production food miles (McMichael et al., 2007; FAO, 2006b). This dietary recommendation, beyond short-term solutions to climate change mitigation, may impact global health including a reduced risk of colorectal cancer (Norat et al., 2002) and coronary disease (Hu and Willet, 1998).

• Carlsson-Kanyama, A and Gonzalez, AD (2009) Potential contributions of food consumption patterns to climate change. Am J. Clin. Nutr 89(suppl): 1704S-9S.
• FAO (2006). World Agriculture towards 2015/30, an FAO Study. Rome.
• FAO (2006b). Livestock’s long shadow. Environmental issues and options. Rome: FAO.
• Fiala N (2008) Meeting the demand: An estimation of potential greenhouse gas emissions from meat production. Ecological Economics 67: 412-419.
• Houghton et al. editors. (1996) Climate change 1995. New York: Cambridge University Press.
• Hu, FB and Willett WC (1998) The relationship between consumption of animal products (beef, pork, poultry, eggs, fish and dairy products) and risk of chronic disease: a critical review. Cambridge, MA: Harvard School of Public Health.
• McMichael, AJ, Powles, JW, Butler, CJ and Uauy, R (2007) Food, livestock production, energy, climate change and health. Lancet 370: 1253-63.
• Norat T, Lukanova, A, Ferrari, P et al. (2002) Meat consumption and colorectal cancer risk: dose response meta-analysis of epidemiological studies. Int. J. Cancer 98: 241-56.
• USDA
• Weber, CL and Matthews, HS (2008) Food Miles and the Relative Climate Impacts of Food Choices in the United States. Environ. Sci, Technol. 42: 3508-3513.