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1 Livestock and greenhouse gas emissions: the importance of getting the numbers 2 right 3 4 M. Herrero1, P. Gerber2, T. Vellinga3, T. Garnett4, T. McAllister5, A. Leip6, C. Opio2, 5 H.J. Westhoek7, P.K. Thornton1, J. Olesen8, N. Hutchings8, H. Montgomery9, J-F 6 Soussana10, T. Wassenaar11, and H. Steinfeld2 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 1 International Livestock Research Institute, PO Box 30709, Nairobi, Kenya. Food and Agriculture Organization of the United Nations, Animal Production and Health Division, Rome, Italy. 3 Wageningen University and Research Centre, Animal Science Group, Wageningen, The Netherlands. 4 Food Climate Research Network, Centre for Environmental Strategy, University of Surrey, UK. 5 Agriculture and Agri-Food Canada, Lethbridge Research Centre, Alberta, Canada. 6 European Commission, Joint Research Centre, Institute for Environment and Sustainability, Ispra (VA), Italy. 7 Netherlands Environmental Assessment Agency (PBL), Bilthoven, The Netherlands. 8 Aarhus University, Department of Agroecology and Environment, Tjele, Denmark. 9 Ministry of Agriculture and Forestry, New Zealand. 10 Institute Nationale de la Recherche Agronomique, Clermont-Ferrand, France. 11 Centre de Coopération Internationale en Recherche Agronomique pour le Développement, 97408 Saint-Denis Messageries Cedex 9, La Réunion. 2 24 25 Corresponding author : Mario Herrero, [email protected] 26 27 Running Head: Commentary - livestock and greenhouse gas emissions 1 1 Abstract 2 3 Livestock are of significant importance to society. In the process of generating 4 nourishment, income, employment and other benefits, they produce significant amounts 5 of greenhouse gases. The estimated contribution of livestock to global greenhouse gas 6 emissions ranges from 10 to 51% of the global emissions. This wide range suggests 7 significant methodological differences and uncertainties in different studies. This 8 commentary piece examines the main discrepancies between well known and 9 documented studies such as FAO's Livestock Long Shadow report (FAO 2006) and more 10 recent estimates. We advocate for better documentation of assumptions and 11 methodologies for estimating emissions and the need for greater scientific debate, 12 discussion and scrutiny in this area. This is essential to improve our understanding of 13 livestock's contribution to GHG emissions and to design better climate change mitigation 14 and adaptation strategies for the global livestock sector and those depending from it. 15 16 Keywords: 17 climate change, livestock, greenhouse gas emissions, mitigation, adaptation 2 1 Livestock farming plays a critical role in food production across the globe, and has 2 formed part of local landscapes and ecosystems for millennia. The importance of 3 livestock in providing human societies with food, incomes, employment, nutrients and 4 risk insurance is widely recognized (Perry and Sones 2007, Herrero et al. 2009). 5 6 At the same time there is growing awareness within the research and policy communities 7 that the rapid growth in global production and consumption of livestock products is 8 contributing to a range of serious environmental problems, the most notable being the 9 sector’s substantial contribution to climate changing emissions. 10 11 In 2006, the FAO’s Livestock’s Long Shadow report (FAO, 2006), using well 12 documented and rigorous life cycle analyses, estimated that global livestock contributes 13 to 18% of global GHG emissions. According to the study the main contributors to GHG 14 from livestock systems are land use change (carbon dioxide, CO2), enteric fermentation 15 from ruminants (methane, CH4) and manure management (nitrous oxide, N2O). A recent 16 non-peer reviewed report published by the Worldwatch Institute (Goodland and Anhang 17 2009) contested these figures and argued that GHG emissions from livestock could be 18 closer to 51% of global GHG emissions. In our view, this report has oversimplified the 19 issue with respect to livestock production. It has emphasised the negative impacts 20 without highlighting the positives and, in doing so, has used a methodological approach 21 which we believe to be flawed. Even though Goodland and Anhang (2009) do not 22 present detailed methodologies or clear scientific evidence to back their results, the 23 differences between the studies center around the following areas: 3 1 2 Exclusion of carbon dioxide emissions from livestock respiration 3 4 According to Goodland and Anhang (2009), CO2 from livestock respiration was an 5 overlooked source of GHG from the FAO study3. Under 2006 Intergovermental Panel on 6 Climate Change (IPCC) inventory guidelines (IPCC 2006) and under the Kyoto protocol, 7 CO2 from livestock is not considered a net source of CO2 for the following reasons: 8 a) This CO2 is considered to be part of a rapid biological system where the plant material 9 consumed by the animals is created by photosynthesis (which sequesters CO2 in the 10 process). The amount of carbon in feed consumed and CO2 emitted by livestock are 11 considered to be roughly equivalent and part of a short-term carbon cycle. This short 12 term cycle does not lead to a net increase in the concentration of atmospheric CO2 within 13 relevant time horizons. 14 b) It is true that in certain systems the balance between carbon consumed and CO2 15 emitted is not perfectly equal, but these differences are small when overall global 16 rangeland and forage productivity are considered as a carbon sink. There is also a 17 significant body of evidence that suggests that grasslands and their growth more than 18 offset CO2 emissions from livestock (Fisher et al., 1994, IPCC 2006). In any case, if 19 respiration is accounted for, then CO2 absorption related to the growth of forage and feed 20 should also be considered in the overall carbon cycle analysis. 21 22 Emissions from land use and land use change 23 4 1 Goodland and Anhang (2009) claim that emissions from land use and land use change 2 induced by the livestock sector have been grossly underestimated. While the estimates 3 from FAO (FAO 2006) may be conservative in many aspects, the argument and analysis 4 presented by the authors is flawed and overly simplistic on several fronts: 5 6 Firstly, in estimating the “unaccounted for emissions” from land use and land use change 7 the authors utilize a different approach from that used in the FAO report (FAO 2006). 8 The authors use a consequential approach that applies a “what-if scenario” in the 9 estimation of emissions from land use and assess the potential emission reductions arising 10 from the use of land for alternative practices. In other words, it quantifies the amount of 11 carbon that would be sequestered if existing grazing lands were allowed to revert to 12 forest, and then attributes the ‘lost’ opportunity for carbon sequestration to livestock. The 13 FAO assessment (FAO 2006) on the other hand, bases its analysis on actual land use 14 trends, thereby allocating carbon losses resulting from current changes in land use to 15 livestock. While in a land constrained world it is important to consider different future 16 possible uses for land so as to ensure food security, carbon storage and biological 17 diversity, the approach adopted by Goodland and Anhang (2009) is methodologically 18 inconsistent. The authors do not quantify the lost opportunity for carbon sequestration 19 that results from other forms of land use, such as arable crop production for human 20 consumption, or urban development. If they were to do this then overall anthropogenic 21 GHG emissions would be higher, and livestock-related impacts would need to be seen as 22 a percentage of this overall higher figure. 23 5 1 More importantly, the authors advocate that livestock products be replaced with 2 alternative food sources, a strategy that would require a portion of the grazing land used 3 for forage production to be converted to land for annual crop production either for food or 4 for biofuel production. This practice would contribute to habitat destruction of native 5 grasslands, an ecosystem that harbors a number of species at risk. Furthermore, the 6 authors fail to provide any detailed analysis on what alternative protein sources would 7 replace animal protein and what would be the likely implications in terms of land use, 8 land use intensity, food security, human nutrition and livelihoods. In addition, it is 9 erroneously assumed that biofuel production is GHG neutral (Searchinger et al., 2007). 10 11 The proposed biofuel option is also misleading from a land use change perspective. In a 12 hypothetical world without livestock, there could be many potential uses for land 13 currently utilized for livestock with biofuel production being only one of these 14 possibilities. This would depend significantly on alternative opportunity costs of land use, 15 labour and transport costs as well as other factors. These have not been considered 16 systematically in the Goodland and Anhang (2009) paper. At the same time, livestock in 17 most cases occupy large areas of the world where other forms of agriculture are not 18 possible, whether this would be for producing food, biofuels or other uses. This limits the 19 scenario of growing biofuels in all areas occupied by livestock. Production of alternative 20 biofuels may be limited to areas that are close to markets and that possess adequate 21 infrastructure, but even these areas would have competing claims for the land and 22 significant opportunity costs. 23 6 1 Removal of domesticated ruminants would also have implications with regard to the 2 populations of wild ungulates, and what mixes of species would prevail in these 3 environments. These counterfactuals point to the fact that estimating emissions from 4 livestock systems is very complex and need to be analysed with solid conceptual models 5 of global environmental, social and economic change. 6 7 The authors also omit to acknowledge that many key drivers of land use and land use 8 change such as deforestation are outside of productive land uses and are instead driven by 9 motivations and policies such as infrastructure development, land speculation, 10 urbanization, and development of renewable energy. Many of these polices are driven by 11 the present lack of economic incentive to conserve or maintain natural resources. 12 13 Global Warming Potential of Methane 14 15 Goodland and Anhang (2009) suggest using the 20-year global warming potential (GWP) 16 for CH4, which is 72. The debate on how much warming CH4 causes is an ongoing one 17 (Shindell et al., 2009). Scientific advancements have indeed led to the corrections in CH4 18 GWP values over the past decade. And while IPCC in its 4th Assessment Report (IPCC 19 2007) effectively revised the global warming potential (from 23 to 25) as indirect effects 20 of CH4 on ozone and stratospheric water vapor have been included - it should be noted 21 that at the time of the writing of the FAO report (FAO, 2006) the GWP of 23 over a 100- 22 year time horizon was considered valid and acceptable. CH4 has an atmospheric lifetime 23 of 12 years. In this first period CH4 contributes more to the present global warming than 7 1 the factor 25 suggests, but this effect decays almost completely after 20-30 years. CH4 is 2 therefore a very important gas to achieve short-term reduction of radiative forcing. 3 However, the GWP is a measure to prioritize mitigation practices, for which the scale of a 4 century is currently considered appropriate, even though this is under debate (Shindell et 5 al., 2009). IPCC has acknowledged the value of alternative metrics (e.g. the Global 6 Temperature Potential) and indicated that further research is recommendable (Plattner et 7 al., 2009). Besides, selection of a time horizon is not only a scientific issue, but also a 8 political one based on the relative weight that is given to short- versus long-lived 9 greenhouse gases. 10 11 12 Attribution of greenhouse gases to livestock and others 13 14 Goodland and Anhang (2009) also identify a number of greenhouse gas sources currently 15 excluded from GHG assessments from livestock. 16 17 Of particular importance are issues related to the complexity of attributing certain 18 emissions to the livestock sector. For example cooking in open fires, waste management, 19 use of toxic chemicals, packaging and use of cold chains, and chronic degenerative 20 diseases amongst others, are aspects that not only relate to the production or consumption 21 of livestock products. Methodologies for estimating and adequately attributing these 22 kinds of emissions to specific sectors are still under development and have not been 23 vetted by the international scientific community. 8 1 2 Goodland and Anhang (2009) point to the fact that FAO’s 18 percent estimate presently 3 lacks relevance and is outdated. The authors erroneously assume that a 12 percent 4 increase in the global tonnage of livestock products directly translates into a 5 proportionate increase in GHG emissions. This ignores the fact that production systems 6 can become more efficient. For example, in Europe (EU-12) livestock production 7 increased slightly between 1990 and 2002, while the emissions of CH4 and N2O 8 decreased 8-9% over the same period (European Environmental Agency, EEA, 2009). 9 Some European countries have seen even more dramatic improvements in efficiencies. 10 Denmark thus reduced its emissions of CH4 and N2O by 23% over the period 1990 to 11 2002, while maintaining dairy production output and increasing pig production by 27% 12 (Danish Environmental Protection Agency, 2005). This was due to a higher production 13 per animal (and thus lower animal numbers) and a more efficient use of manures and 14 nitrogen fertilizers. 15 16 The use of lower figures of animal numbers in the estimation of greenhouse gases and 17 failure to use a correction factor are cited as one of the shortfalls of the FAO report (FAO 18 2006). Specific reference is made to the citation of the production of 33 million poultry 19 worldwide. This however stems from a misinterpretation on the part of Goodland and 20 Anhang (2009) who confound “poultry biomass” for production of poultry meat. It 21 should also be mentioned that despite some shortcomings of the FAO statistics, FAO still 22 remains the only globally recognized source of data on agriculture. 23 9 1 Goodland and Anhang (2009) correctly point out that the FAO assessment (FAO 2006) 2 omits emissions related to the preparation of animal products and that estimates for land 3 use change, transport and processing are deliberately conservative. These methodological 4 decisions were constrained by data availability. 5 6 Concluding remarks 7 8 Livestock undoubtedly need to be a priority focus of attention as the global community 9 seeks to address the challenge of climate change. The magnitude of the discrepancy 10 between the Goodland and Anhang paper (2009) and widely recognized estimates of 11 GHG from livestock (FAO, 2006), illustrates the need to provide the climate change 12 community and policy makers with accurate emissions estimates and information about 13 the link between agriculture and climate. 14 15 Improving the global estimates of GHG attributed to livestock systems is of paramount 16 importance. This is not only because we need to define the magnitude of the impact of 17 livestock on climate change, but also because we need to understand their contribution 18 relative to other sources. Such information will enable effective mitigation options to be 19 designed to reduce emissions and improve the sustainability of the livestock sector while 20 continuing to provide livelihoods and food for a wide range of people, especially the 21 poor. We need to understand where livestock can help and where they hinder the goals of 22 resilient global ecosystems and a sustainable, equitable future for future generations. 23 10 1 We believe these efforts need to be part of an ongoing process, but one that is to be 2 conducted through transparent, well established methodologies, rigorous science and 3 open scientific debate. Only in this way will we be able to advance the debate on 4 livestock and climate change and inform policy, climate change negotiations and public 5 opinion more accurately. 6 7 References 8 9 10 Danish Environmental Protection Agency 2005. Denmark’s Fourth National 11 Communication on Climate Change under the United Nations Framework Convention on 12 Climate Change. Environmental Protection Agency, Danish Ministry of the Environment, 13 Copenhagen, Denmark. 14 EEA 2009. Annual European Community greenhouse gas inventory 1990 - 2007 and 15 inventory report 2009. Submission to the UNFCCC secretariat, European Environment 16 Agency, Brussels, Belgium. 17 Fisher, M.J., Rao, I.M., Ayarza, M.A., Lascano, C.E., Sanz, J.I., Thomas, R.J. and Vera, 18 R.R. 1994. Carbon storage by introduced deep-rooted grasses in the South American 19 savannas. Nature 371, 236-238. 20 Goodland, R. and Anhang, J. 2009. Livestock and Climate Change. What if the key 21 actors in climate change were pigs, chickens and cows? Worldwatch 22 November/December 2009, p 10-19, Worldwatch Institute, Washington DC 11 1 Herrero, M., Thornton, P.K., Gerber, P., Reid, R. 2009. Livestock, livelihoods and 2 environment: understanding the trade-offs. Current Opinion in Environmental 3 Sustainability 1, 111-120. 4 IPCC 2006. IPCC Guidelines for National Greenhouse Gas Inventories. 5 Intergovernmental Panel on Climate Change. NGGIP Publications, IGES, Japan. 6 IPCC 2007. Climate Change 2007: Impacts, Adaptation and Vulnerability. Summary 7 for policy makers. Online at http://www.ipcc.cg/SPM13apr07.pdf 8 FAO 2006. Livestock’s Long Shadow. Environmental Issues and Options. Food and 9 Agriculture Organization of the United Nations, Rome, Italy. 10 Perry, B. and Sones, K. 2007. Poverty reduction through animal health. Science 315: 333- 11 334. 12 Plattner, G-K., Stocker, T., Midgley, P., Tignor, M. (Eds). 2009. IPCC Expert Meeting on 13 the Science of Alternative Metrics. Intergovernmental Panel on Climate Change, Geneva, 14 Switzerland. 15 Searchinger, T., Heimlich, R., Houghton, R.A., Dong, F., Elobeid, A., Fabiosa, J., 16 Tokgoz, S., Hayes, D., and Yu, T.-H. 2008. Greenhouse gases through emissions from 17 use of U.S. croplands for biofuels increases land-use change. Science 319, 1238. 18 Shindell, D. T., Faluvegi, G., Koch, D. M., Schmidt, G. A., Unger, N. and Bauer S. E. 19 2009. Improved Attribution of Climate Forcing to Emissions. Science 326, 716-718. 12