Livestock and greenhouse gas emissions: The importance of getting the numbers right

Abstract

Livestock are of significant importance to society. In the process of generating nourishment, income, employment and other benefits, they produce significant amounts of greenhouse gases. The estimated contribution of livestock to global greenhouse gas emissions ranges from 10 to 51% of the global emissions. This wide range suggests significant methodological differences and uncertainties in different studies. This commentary piece examines the main discrepancies between well known and documented studies such as FAO's Livestock Long Shadow report (FAO 2006) and more recent estimates. We advocate for better documentation of assumptions and methodologies for estimating emissions and the need for greater scientific debate, discussion and scrutiny in this area. This is essential to improve our understanding of livestock's contribution to GHG emissions and to design better climate change mitigation and adaptation strategies for the global livestock sector and those depending from it. Keywords:climate change, livestock, greenhouse gas emissions, mitigation, adaptation At the same time there is growing awareness within the research and policy communities that the rapid growth in global production and consumption of livestock products is contributing to a range of serious environmental problems, the most notable being the sector's substantial contribution to climate changing emissions. b) It is true that in certain systems the balance between carbon consumed and CO 2 emitted is not perfectly equal, but these differences are small when overall global rangeland and forage productivity are considered as a carbon sink. There is also a significant body of evidence that suggests that grasslands and their growth more than offset CO 2 emissions from livestock (Fisher et al., 1994, IPCC 2006. In any case, if respiration is accounted for, then CO 2 absorption related to the growth of forage and feed should also be considered in the overall carbon cycle analysis. The authors also omit to acknowledge that many key drivers of land use and land use change such as deforestation are outside of productive land uses and are instead driven by motivations and policies such as infrastructure development, land speculation, urbanization, and development of renewable energy. Many of these polices are driven by the present lack of economic incentive to conserve or maintain natural resources. Global Warming Potential of MethaneGoodland and Anhang ( the factor 25 suggests, but this effect decays almost completely after 20-30 years. CH 4 is therefore a very important gas to achieve short-term reduction of radiative forcing.However, the GWP is a measure to prioritize mitigation practices, for which the scale of a century is currently considered appropriate, even though this is under debate (Shindell et al., 2009). IPCC has acknowledged the value of alternative metrics (e.g. the GlobalTemperature Potential) and indicated that further research is recommendable (Plattner et al., 2009). Besides, selection of a time horizon is not only a scientific issue...

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