The authors recognize that the 51% figure put forward “is a strong claim that requires strong evidence,” but stress that if their argument is right, “it implies that replacing livestock products with better alternatives” would have far more rapid effects on the climate than actions to replace fossil fuels with renewable energy.

This partly due to significant reductions in the amount of methane, produced by enteric fermentation from cattle. According to the United Nations’ Food and Agriculture Organization, 37% of human-induced methane comes from livestock. Although methane produced by enteric fermentation from cattle warms the atmosphere much more strongly than CO2, its half-life in the atmosphere is only about eight years, compared to at least 100 years for CO2.

Reviewing the direct and indirect sources of GHG emissions from livestock, the authors argue that contribution of livestock respiration to global CO2 emissions is being underestimated.

“Livestock (like automobiles) are a human invention and convenience, not part of pre-human times, and a molecule of CO2 exhaled by livestock is no more natural than one from an auto tailpipe,” they state.

Another major source of emissions that is overlooked is livestock-related deforestation, the report finds, meaning conversion of natural forest and particularly rainforest into grassland. While rainforest stores “at least 200 tons of carbon per hectare,” the tonnage stored by grassland is only eight, the authors say, adding that another 200 tons per hectare of CO2 may be released from the soil beneath.  See table accompanying article.

Furthermore, current estimates exclude farmed fish from the definition of livestock and neglect to calculate the contribution of several other indirect sources of emissions. These include fluorocarbons needed for cooling livestock products, “carbon-intensive medical treatment” of zoonotic illnesses and disposal of by-products, such as leather, feathers, skins and fur, and their packaging.

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Article by Roger Greenway appearing courtesy of ENN

[photo credit: coincoyote]