It is generally argued that livestock are the cause of about 18% of worldwide greenhouse gas emissions. The figure comes from a 2006 United Nations Food and Agriculture Organisation report titled “Livestock’s Long Shadow”. A new study by Robert Goodland and Jeff Anhang, published in Worldwatch magazine, argues that this greatly understimates the impact of livestock and that the real figure should be about 50%.
Robert Goodland and Jeff Anhang argue that the FAO underestimated the impact of livestock in serveral ways:
- The FAO excluded the amount of carbon dioxide produced by the livestock’s respiration on the grounds that this is just part of the natural cycle. Goodland and Armstong argue that, since livestock were not part of pre-human nature, their respiration should be regarded as a human-caused greenhouse gas. Including livestock respiration, increases their contribution to greenhouse gas enmissions by 13.7% of the total.
- The FAO counted the loss of carbon dioxide when land is cleared for livestock only in the year in which the clearing occurs. It did not count the amound of carbon dioxide which would have been absorbed in each following year had the land been left uncleared. Robert Goodland and Jeff Anhang estimate that this would add at least another 4.2% of total emissions.
- Methane has a much shorter half-life than carbon dioxide – about 8 years compared with 100 years for carbom dioxide. As a result, reducing methane production would have a much more rapid effect on reducing global warming than reducing carbon dioxide emissions. Robert Goodland and Jeff Anhang argue that, because the FAO only modelled a 25-year period, they greatly underestimated the effect that reducing methane emissions would have over a longer period. They estimated that over a 100-year period the contribution of methane emission from livestock should be increased by another 7.9% of the total.
- The FAO’s estimate was based on 2002 livestock production and did not factor in the rapid increase (by about 12%) which has occurred between 2002 and 2009. This would add another 4% to emissions.
- Robert Goodland and Jeff Anhang point out that the FAO livestock production figures are lower than those from other sources and that many of their calculation are based on farming practices in Minnesota, which are much more efficient than in many other parts of the world.
- Finally, Robert Goodland and Jeff Anhang argue that the FAO omitted many minor sources of emissions such as the fact the meat is usually cooked at a higher temperature than vegetables, that disposal of animal waste releases greenhouse gases, that for health reasons meat distribution involves more packaging than vegetables and that treatment of farm-animal-borne diseases (such as swine flu) and diseases linked to the consumption of animal fat is carbon-intensive.
The researchers conclude that the development of plant-based replacements for meat and dairy products and the marketing of these “analogue” products should be seen as at least as significant as developing renewable energy technology in the fight abainst global warming.