The FAO’s 2006 report Livestock’s Long Shadow: Environmental Issues and Options, led by Henning Steinfeld, provides what is perhaps the most widely-cited statistic on the link between animal agriculture and climate change; that world livestock practices account for about 18% of all anthropogenic greenhouse gases (GHGs) in carbon equivalent.
If livestock were responsible for such a large share of climate change, then it should certainly oblige policy-makers to take drastic mitigating measures or to at least include the issue in any serious debate about combatting global warming. Even though it is now a widely-accepted fact that climate change is manmade and poses a eminent threat to life on earth, most people do not make the connection between diet and climate, instead assuming that transportation and industry are the main contributors to climate change. The FAO’s 18% estimate would make livestock a greater contributor to climate change than transportation, though there is reason to believe that livestock’s contribution to global warming is even higher.
Three years after the FAO report, Robert Goodland and Jeff Anhang co-authored a compelling paper entitled “Livestock and Climate Change” that argues the FAO report was flawed in a few areas and that livestock’s real share of anthropogenic greenhouse gases is more like 51%. They argue that the FAO miscounted, overlooked, or misallocated livestock’s contribution to climate change (see chart below), taking into consideration:
1) Animal respiration – The FAO should have recognized that farm animals are not carbon sinks and included their respiration in its GHG accounting — especially since there are over 60 billion terrestrial farm animals. Though livestock animals are living organisms, the carbon they emit is anthropogenic in the same way exhaust of cars is because humans brought them into existence. Carbon in the atmosphere has a greenhouse effect, regardless of its source.
2) Land-use change -Though the FAO accounts for carbon lost to deforestation, it does not account for the carbon sequestration that is foregone when land is cleared of natural vegetation and used to grow feed crop or graze livestock.
3) Methane – CH4 has a much higher global warming potential (GWP) than CO2. The FAO’s calculations integrate this fact into their accounting, however they use a 100-year time scale, which gives methane a smaller share of total global warming since it has such a shorter half-life in the atmosphere than carbon dioxide. Goodland and Anhang suggest that a 20-year timeframe would be more appropriate for CH4, and that it produces a GWP of 72 times that of CO2 (as opposed to 25 times CO2, which is what the FAO’s calculations produced).
4) Growth in livestock – Since the data underlying Livestock’s Long Shadow was collected, world livestock populations have grown over 12%, which would obviously increase the sector’s effect on climate.
5) Other factors – As other sources of GHGs, the authors point to statistics that are undercounted, data that is outdated, estimates that are based on less carbon intensive farming in Minnesota, data that are included in other categories, and hidden GHG emissions that are connected to other lifecycle activities of livestock products.
Even if Goodland and Anhang’s estimates are off in some areas, the authors provide a compelling argument for why the FAO’s widely-cited 18% figure is far too low. But regardless of whether the figure is 18% or 51% of anthopogenic greenhouses, to be sure, livestock — or rather the consumption of meat, eggs, and dairy — is a major cause of climate change and ought to be treated as such.
Source: Goodland, Robert and Jeff Anhang. “Livestock and Climate Change.” World Watch Magazine, Nov/Dec 2009. Pg. 10.