Posted on
August 17, 2010 by
The VRG Blog Editor
by Jeanne Yacoubou, MS
VRG Research Director
Background: Dr. Frank Mitloehner's October 2009 scientific paper, co-authored with Dr. Maurice Pitesky and Dr. Kimberly Stackhouse, and his presentation at the March 2010 American Chemical Society meeting, titled Clearing the Air: Livestock’s Contribution to Climate Change (Adv. in Ag. 103: 3-40), have raised questions about the validity and accuracy of the United Nations' (UN) Food and Agricultural Organization's (FAO) 2006 report titled Livestock's Long Shadow: Environmental Issues and Options (herein noted as Long Shadow). In response to many inquiries about the impact of this criticism on the claims made in Long Shadow, The VRG addresses some questions on this issue.
Q. How legitimate is Mitloehner's assertion that Long Shadow significantly overestimates the contributions of livestock to anthropogenic (i.e., human-caused) greenhouse gases (GHGs) that in turn contribute to global climate change when Long Shadow states that globally, 18% of anthropogenic GHGs come from livestock? In other words, does Mitloehner's criticism that FAO conducted a "lopsided analysis" to derive the 18% figure, calling it a "classical apples-and-oranges analogy that truly confused the issue" mean that FAO cannot accurately claim that emissions from livestock are greater than those generated from transport? (Note: The GHGs include carbon dioxide (CO2), methane (CO2), and nitrous oxide ((N2O), which together are expressed in the calculations as carbon dioxide equivalents. This way of grouping the three major greenhouse gases accounts for the different global warming potential of the three gases (i.e., molecules of methane and nitrous oxide retain heat much better than molecules of carbon dioxide (respectively and approximately, 23 and 296 times better), meaning methane and nitrous oxide contribute more to climate change on a per molecule basis than carbon dioxide itself.)
A. Long Shadow's 18% figure is based on a comprehensive life cycle analysis (LCA) considering both direct and indirect sources of global GHG emissions due to all activities related to livestock production. Direct sources include nitrous-oxide producing animal manure and methane-producing enteric fermentation. Indirect sources include land use changes (e.g., deforestation) and animal feed production.
Mitloehner's major criticism of Long Shadow is that it did not conduct a comprehensive LCA of the transport sector. Instead, FAO used the value calculated by the Intergovernmental Panel on Climate Change (IPCC) value without modification. The IPCC value only considered direct sources of fossil fuel burning and not indirect ones such as GHGs emitted due to crude oil extraction, road construction, or the manufacturing of cars. Thus, asserts Mitloehner, FAO cannot claim that livestock produces more GHGs than transportation.
FAO's Pierre Gerber, an author of Long Shadow, has admitted to BBC News: "I must honestly say that he has a point" about the different LCAs used to calculate livestock's and transportation's contributions to climate change and accepts Mitloehner's criticism. However, Gerber contends, "But on the rest of the report, I don't think it was really challenged." In other words, the different methodologies do not invalidate the conclusions of Long Shadow, including the conclusion that livestock production contributes 18% to total global climate change in both direct and indirect ways. Gerber told the Columbia Journalism Review that "We stand entirely behind the 18 percent figure."
Gerber stated that the data needed to perform a LCA for the transport sector, such as detailed emissions numbers for every country, are not available. But the IPCC calculations were done as carefully as possible (with an uncertainty of less than five percent for carbon dioxide emissions from fossil fuel use, which make up approximately 75% of all GHGs), despite the uncertainties in calculating values for all other GHGs in the atmosphere. What is most difficult to assess is the proportion of the subtotals (from each sector) coming from anthropogenic versus natural sources. What complicates matters even more is the overlap between sectors revealed most easily when comprehensive LCAs are done for every sector such that the sum of all emissions could be over 100%.
Gerber also stated that the total GHG determination won't change significantly by a comprehensive LCA of the transport sector. All that may occur is a rearrangement by sectors of the total. In other words, a LCA for the transport sector may change the relative amount of GHGs contributed by that sector. Later reports by FAO will include more "disaggregation" by sector (i.e., livestock, transport, industry, etc.) of the total value as more data are collected.
Furthermore, Gerber said that FAO is currently working on much more comprehensive analyses of emissions from food production that should allow comparisons between diets, including meat-based and vegetarian diets. This report will partition the global 18% into different commodities such as eggs, milk, beef, etc., produced in different farming systems and in different world regions and climatic zones in order to pinpoint the sources of anthropogenic GHG emissions caused by livestock. Equipped with this information, the FAO can propose effective mitigation strategies that are very specific to different segments of the livestock industry in different parts of the world. An updated report should be completed by the end of 2010.
It may be said that both Mitloehner and Gerber agree that reducing emissions in both the livestock and the transport sectors is important for environmental protection. Knowing exactly where these emissions are generated can lead to more appropriate mitigation strategies that will most likely vary among world regions according to livestock subsector type (i.e., eggs, beef, etc.) and farming system (i.e., feedlot, grazing system, etc.).
Q. Dr. Mitloehner implies that Long Shadow is not relevant to local or national public policy discussions about food production and the environment as the popular press leads readers to believe, citing the EPA's calculation from its Inventory of U.S. Greenhouse Gases and Sinks: 1990-2007 published in 2009, which states that livestock's contribution in the United States to anthropogenic GHGs is approximately 3% of all human-created GHGs. Does Dr. Mitloehner's claim make Long Shadow irrelevant to such local or national policy discussions?
A. It is interesting to note that Dr. Mitloehner offers the EPA report and a California EPA report in direct comparison with the UN's although he points out the different scope and assumptions of the three. In some respects, his criticism of Long Shadow's comparative use of a comprehensive LCA to one that is not (i.e., the livestock sector's versus the transportation sector's), referring to it as "a classical apples-and-oranges" problem, may be applied to his analysis as well. For example, one major difference is that Long Shadow determines the indirect contribution to GHGs derived from animal feed production (a large indirect contribution by livestock production) while the EPA does not, but rather groups GHGs from animal feed and human crops together, so that GHGs generated from the production of animal feed crops alone cannot be determined (and, so, cannot be included in their 3% figure).
It should also be noted that the 3% value cited by Mitloehner includes only the GHGs due to enteric fermentation and manure management even though he grants that other aspects of livestock production, such as land use changes, feed production, and on-farm fossil fuel burning, do produce significant amounts of GHGs. These other aspects were considered in Long Shadow and included in its total GHGs produced by the livestock sector (18%).
Despite the different assumptions of the reports, it is noteworthy that they reach many of the same conclusions. For example, enteric fermentation and manure management generate approximately the same amounts of methane (~40% of total anthropogenic GHGs) and nitrous oxide (~65% of total anthropogenic GHGs). The EPA report also points out that methane emissions from manure management increased by 54% since 1990, due mainly to the trend among pig and dairy farmers to store manure as a liquid slurry which produces greater methane emissions that storage of manure as a solid. Both methane and nitrous oxide are gases which have much greater global warming potential than carbon dioxide. Mitloehner also points out that the increasing use on crops of synthetic fertilizers, which reduce methane emissions, tends to increase the production of the more potent nitrous oxide. These facts are not made clearly by Mitloehner but they are important when considering the overall effect of different sectors on total world GHG emissions.
Several of Mitloehner's other statements made at the ACS meeting go beyond his level of expertise as an animal scientist. For example, Mitloehner criticizes Long Shadow by implying that it misleads Americans into believing that dietary changes away from meat-based diets is a major way for climate change reduction in the United States. He states that "We certainly can reduce our greenhouse-gas production, but not by consuming less meat and milk. Producing less meat and milk will only mean more hunger in poor countries." Mitloehner uses the EPA report, which asserts that the US transport sector is responsible for 26% of GHG emissions while livestock rearing contributes only 3% of the total US GHG emissions, to defend his claims. However, based on these points, one cannot rightly claim that reducing milk and meat consumption in the US will not contribute to reducing global climate change. Nor can one make any statement about reducing world hunger.
Mitloehner goes on to say that to meet increasing demand for meat and milk, the focus in confronting climate change should be on smarter farming, not less farming. In saying this, Mitloehner implicitly depends in part on the scientific legitimacy of Long Shadow to support his view that developing nations should model their agricultural systems on the United States' intensive systems. Long Shadow, in fact, makes a similar claim, along with recommendations that "sustainable" intensive of livestock and feed crop production occur in conjunction with reduced deforestation and improved animal nutrition and manure management. In Mitloehner's use of and similarities to Long Shadow's conclusions, one cannot rightly assert that Long Shadow is irrelevant to public policy discussions about agricultural practices, nationally or globally.
It is noteworthy to point out that Mitloehner's research was funded in part by the Beef Checkoff Program, which provides research money collected from beef producers to some scientists. Whether this funding reflects a conflict of interest and biases the conclusions drawn by Mitloehner is up to the reader to discern.
Q. In the conclusion to his article Mitloehner briefly considers this question: If livestock were simply eliminated from the global agricultural system, would the 18% figure be eliminated as well? Do you agree with him that the GHG emissions coming from the use of resources, previously dedicated to animal agriculture but now used for other "human activities," could produce even greater GHG emissions?
A. Mitloehner does not explore this topic at length and provides no specific examples of "other human activities" and how they would produce even greater amounts of GHGs. It is left to the reader to speculate.
However, he does rightly point out that non-livestock substitutes for such things as synthetic fertilizer in place of manure; vinyl instead of leather; and synthetic fibers to replace wool, etc. also produce GHG emissions. Mitloehner does not quantify these emissions values. Whether they would be greater or less than those of comparable livestock-generated products remains to be seen.
Some propose that if the world transitions to veganic farming where plant-based compost and inedible crop residues are used as fertilizer instead of animal waste products or synthetic fertilizers, it would be possible that a major reduction in GHGs produced by the agricultural sector could result. Interested readers may learn more about veganic farming at www.goveganic.net.
Q. If there were no animal agriculture and everyone were vegan, how much of a reduction of GHGs could result?
A. To the best of our knowledge, there has not been any comprehensive research done that answers this question. Possibly, the upcoming FAO report mentioned in a previous question will provide an answer or at least a well-reasoned, well-supported partial answer.
Mitloehner cites Bruinsma's 2003 report titled World Agriculture: Towards 2015/2030, an FAO Perspective, that says "Overall, 32% of the world's cereal production (the primary concentrate) is fed to livestock" including corn (52%), barley (19%), and wheat (19%). The United States Department of Agriculture (USDA) states that approximately half of US soybean production (and the US is the world's leader in soybean production and consumption), is fed to livestock. Given these high quantities of foodstuffs given to livestock, it is reasonable to assume that significantly fewer GHGs would be produced in a world where fewer cereals and legumes are needed to support large numbers of livestock, i.e., in a world where everyone, or at least the majority, ate a plant-based diet. Long Shadow states that animal feed production is estimated to account for 33% of agricultural cropland, so an elimination or reduction in the numbers of livestock supported by that land would most likely result in less GHG emissions.
Research is beginning to support this claim. For example, a 2009 study titled Climate Benefits of Changing Diet by Elke Stehfest, et al. published in the peer-reviewed journal Climatic Change (95:83-102), concludes that a global food transition to less meat, or even a total switch to a plant-based diet would have a dramatic effect on land use practices and result in climate stabilization. The researchers determine that up to 2,700 Mha of pasture and 100 Mha of cropland could be abandoned as a result of dietary change that excluded all or most livestock. The change would create large carbon uptake due to vegetation regrowth as the former cropland and pastures return to more natural states. Without livestock or with reduced numbers of livestock, methane and nitrous oxide emissions produced by enteric fermentation and manure would be eliminated or substantially reduced, further contributing to climate stabilization.
The VRG will continue to report on the relationship of diet to climate change as scientists and government bodies publish their findings and statistics. Interested readers may subscribe to our free e-newsletter for updates on this timely topic. Visit our website to read more about vegetarianism and the environment, including our newest brochure titled Save Our Water the Vegetarian Way.
