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Over the past recent months, I have received dozens of requests from various stakeholders, who were concerned about the carbon footprint of human food and particularly its animal-based portion. Most of us know that the discussion regarding the carbon footprint of animal protein has gained regional, national and international momentum. For example, some of Sweden’s fastfood chains now offer information to their customers including not just prize and nutritional facts, but most recently, the carbon footprint of its tofu-, turkey-, or beef burgers. Since recent, the world’s largest supermarket retailer requests from its suppliers information regarding the carbon footprint of milk. Furthermore, a few months back, San Francisco was officially declared the first ‘Meatless Monday City’ in an effort to protect the climate. While some scientists (especially in agriculture) remain climate change skeptics, it should be clear to everyone that animal agriculture is in midst of a considerable societal debate, which requires all of our attention.

Much of the discussion about livestock agriculture’s contribution to climate change stems from a United Nations Food and Agriculture Organization (FAO) report titled Livestock’s Long Shadow (LLS) (FAO. Steinfeld et al. 2006. http://www.fao.org/docrep/010/a0701e/a0701e00.HTM).

This report determined the climate change impact of global livestock production using a method called Life Cycle Assessment, which sums up greenhouse gas (GHG) emissions from the entire production chain. Included in the LLS’s calculations were crop production, land-use change (e.g., clearing rainforest to establish pastures and cropland), the animals themselves and the transportation of final products. The LLS report concluded that globally 18% of human-caused GHG emissions could be attributed to livestock agriculture, and this was a larger share than transportation. However, the authors of LLS made this claim without actually conducting a similarly comprehensive Life Cycle Assessment for the global transportation sector. Colleagues and I here at UC Davis recently published a paper titled ‘Clearing the Air: Livestock’s Contribution to Climate Change’ (Pitesky et al. 2009 Advances in Agronomy 103, 1–40), which pointed out the flawed LLS comparison between the livestock and transportation sectors, and the FAO has since admitted their mistake.

Additionally, we highlighted that the global percentage is not accurate at the regional, national level because in developed nations, such as the United States, the proportion of GHG emissions from the livestock agriculture sector is dwarfed by that of the energy and transportation sectors of the economy. For example, according to the most recent GHG emission inventory of the United States from 2009, transportation and electricity production account for 26 and 31% of emissions, respectively, while livestock agriculture accounts for approximately 3.4%. However, in countries like Paraguay, the trend is likely reversed because of the small transportation and energy sectors, and a relatively large livestock sector (coupled with associated deforestation), which might contribute to more than 50% of that county’s carbon footprint. These differences in numbers clearly emphasize the need to disaggregate emissions estimates by region and also by livestock species – a step recently undertaken by the FAO and other organizations.

While we differed with the authors of LLS on their carbon footprint comparison of livestock vs transportation as well as with the usefulness and correctness of their 18% figure, we do agree with their overall concern that satisfying the upcoming animal protein supply and demands will pose a challenge to the environment. With global animal protein production projected to more than double the current rate by 2050 and the majority of this livestock production growth occurring in the developing world, assessment of the holistic impacts of food animals in the context of global and regional environmental policy and food security becomes imperative. Much of the growth in the global livestock sector will occur in areas that are currently forested (i.e., parts of South America and South East Asia). It has been well established that significant reductions of carbon sequestering forests will have large effects on global climate change.

The fact that land-use changes associated with livestock (i.e., forested land converted to pasture or cropland used for feed production) are a significant source of anthropogenic GHGs in Latin America and other parts of the developing world is apparent. However, it is likely that any kind of land-use change from the original forestland will lead to great increases in carbon emissions. LLS attributes almost one-third to half of the climate-change impact associated with livestock to the change of land-use patterns. Transformation of land from forest to agriculture has occurred in the developed countries centuries ago to make way for industrialization and general societal wealth. Not surprisingly, numerous developing countries are currently attempting to develop their economies by turning economically marginal land into production for animals.

The United States and most other developed countries have not experienced significant land-use change practices around livestock production within the last few decades. Instead, over the last 25 years, forestland has increased by approximately 25% in the United States and livestock production has been intensified (concentrated geographically), thus reducing its geographical footprint.

Most importantly, livestock production in the developed world has experienced a marked improvement in efficiencies, leading to significantly decreased numbers of animals to produce a given amount product that satisfies the nutritional demands of society. For example, it takes five Holstein cows in Mexico to produce the same amount of milk as one of its peers in California!

According to LLS, intensification of livestock production provides large opportunities for climate change mitigation and can reduce GHG emissions from deforestation, thus becoming a long-term solution to a more sustainable livestock production. Indeed, the authors of LLS are currently working on a follow-up paper titled Shrinking the Shadow, which will focus on ways how advanced biotechnologies, improved genetics, nutrition and comprehensive waste management already utilized in most parts of the developed world can be applied effectively worldwide. Knowledge already exists to improve efficiencies in livestock production, which dramatically reduces GHG per unit of production. What is called for is a global green revolution in animal agriculture, coupled with technology transfers, to supply a growing demand for animal protein using sustainable and modern production practices based on knowledge of animal breeding, nutrition and health care, welfare friendly husbandry practices and comprehensive waste management. This major effort will allow us to satisfy societal demands for animal protein while providing stewardship for valuable natural resources.