Livestock and climate change: what if the key actors in climate change are ... cows, pigs, and chickens?

AuthorGoodland, Robert
PositionEssay

Whenever the causes of climate change are discussed, fossil fuels top the list. Oil, natural gas, and especially coal are indeed major sources of human-caused emissions of carbon dioxide ([CO.sub.2]) and other greenhouse gases (GHGs). But we believe that the life cycle and supply chain of domesticated animals raised for food have been vastly underestimated as a source of GHGs, and in fact account for at least half of all human-caused GHGs. If this argument is right, it implies that replacing livestock products with better alternatives would be the best strategy for reversing climate change. In fact, this approach would have far more rapid effects on GHG emissions and their atmospheric concentrations--and thus on the rate the climate is warming--than actions to replace fossil fuels with renewable energy.

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Livestock are already well-known to contribute to GHG emissions. Livestock's Long Shadow, the widely-cited 2006 report by the United Nations Food and Agriculture Organization (FAO), estimates that 7,516 million metric tons per year of [CO.sub.2] equivalents ([CO.sub.2]e), or 18 percent of annual worldwide GHG emissions, are attributable to cattle, buffalo, sheep, goats, camels, horses, pigs, and poultry. That amount would easily qualify livestock for a hard look indeed in the search for ways to address climate change. But our analysis shows that livestock and their byproducts actually account for at least 32,564 million tons of [CO.sub.2]e per year, or 51 percent of annual worldwide GHG emissions.

This is a strong claim that requires strong evidence, so we will thoroughly review the direct and indirect sources of GHG emissions from livestock. Some of these are obvious but underestimated, some are simply overlooked, and some are emissions sources that are already counted but have been assigned to the wrong sectors. Data on livestock vary from place to place and are affected by unavoidable imprecision; where it was impossible to avoid imprecision in estimating any sum of GHGs, we strove to minimize the sum so our overall estimate could be understood as conservative.

The Big Picture

The table to the right summarizes the categories of livestock-based emissions and our estimates of their size. We begin with the FAO's 7,516 million tons of [CO.sub.2]e per year attributable to livestock, an amount established by adding up GHG emissions involved in clearing land to graze livestock and grow feed, keeping livestock alive, and processing and transporting the end products. We show that 25,048 million tons of [CO.sub.2]e attributable to livestock have been undercounted or overlooked; of that subtotal, 3,000 million tons are misallocated and 22,048 million tons are entirely uncounted. When uncounted tons are added to the global inventory of atmospheric GHGs, that inventory rises from 41,755 million tons to 63,'803 million tons. FAO's 7,516 million tons of [CO.sub.2]e attributable to livestock then decline from 18 percent of worldwide GHGs to 11.8 percent. Let's look at each category of uncounted or misallocated GHGs:

Breathing. The FAO excludes livestock respiration from its estimate, per the following argument:

Respiration by livestock is not a net source of [CO.sub.2]. ... Emissions from livestock respiration are part of a rapidly cycling biological system, where the plant matter consumed was itself created through the conversion of atmospheric [CO.sub.2] into organic compounds. Since the emitted and absorbed quantities are considered to be equivalent, livestock respiration is not considered to be a net source under the Kyoto Protocol. Indeed, since part of the carbon consumed is stored in the live tissue of the growing animal, a growing global herd could even be considered a carbon sink. The standing stock livestock biomass increased significantly over the last decades. ... This continuing growth ... could be considered as a carbon sequestration process (roughly estimated at 1 or 2 million tons carbon per year). But this is a flawed way to look at the matter. Examining the sequestration claim first: Sequestration properly refers to extraction of [CO.sub.2] from the atmosphere and its burial in a vault or a stable compound from which it cannot escape over a long period of time. Even if one considers the standing mass of livestock as a carbon sink, by the FAO's own estimate the amount of carbon stored in livestock is trivial compared to the amount stored in forest cleared to create space for growing feed and grazing livestock.

Uncounted, Overlooked, and Misallocated Livestock-related GHG Emissions Annual GHG emissions Percentage of ([CO.sub.2]e) worldwide total million tons FAO estimate 7,516 11.8 Uncounted in current GHG inventories: 1. Overlooked 8,769 13.7 respiration by livestock 2. Overlooked land use [greater than or equal [greater than or to] 2,672 equal to] 4.2 3. Undercounted methane 5,047 7.9 4. Other four categories [greater than or equal [greater than or (see text) to] 5,560 equal to] 8.7 Subtotal [greater than or equal [greater than or to] 22,048 equal to] 34.5 Misallocated in current GHG inventories: 5. Three categories (see [greater than or equal [greater than or text) to] 3,000 equal to] 4.7 Total GHGs attributable [greater than or equal [greater than or to livestock products to] 32,564 equal to] 51.0 More to the point, livestock (like automobiles) are a human invention and convenience, not part of pre-human times, and a molecule of [CO.sub.2] exhaled by livestock is no more natural than one from an auto tailpipe. Moreover, while over time an equilibrium of [CO.sub.2] may exist between the amount respired by animals and the amount photosynthesized by plants, that equilibrium has never been static. Today, tens of billions more livestock are exhaling [CO.sub.2] than in pre-industrial days, while Earth's photosynthetic capacity (its capacity to keep carbon out of the atmosphere by absorbing it in plant mass) has declined sharply as forest has been cleared. (Meanwhile, of course, we add more carbon to the air by burning fossil fuels, further overwhelming the carbon-absorption system.)

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The FAO asserts that livestock respiration is not listed as a recognized source of GHGs under the Kyoto Protocol, although in fact the Protocol does list [CO.sub.2] with no exception, and "other" is included as a catchall category. For clarity, it should be listed separately in whatever protocol replaces Kyoto.

It is tempting to exclude one or another anthropogenic source of emissions from carbon accounting--according to one's own interests--on the grounds that it is offset by photosynthesis. But if it is legitimate to count as GHG sources fossil-fuel-driven automobiles, which hundreds of millions of people do not drive, then it is equally legitimate to count livestock respiration. Little or no livestock product is consumed by hundreds of millions of humans, and no livestock respiration (unlike human respiration) is needed for human survival. By keeping GHGs attributable to livestock respiration off GHG balance sheets, it is predictable that they will not be managed and their amount will increase--as in fact is happening.

Carbon dioxide from livestock respiration accounts for 21 percent of anthropogenic GHGs worldwide, according to a 2005 estimate by British physicist Alan Calverd. He did not provide the weight of this [CO.sub.2], but it works out to about 8,769 million tons. Calverd's estimate is the only original estimate of its type, but because it involves only one variable (the total mass of all livestock, as all but...

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