The focus of preventing runaway global warming has been on reducing carbon dioxide emissions as it should be, but lost in the discussions seems to be the need to reduce methane and nitrous oxide emissions, particularly from agricultural sources. The accompanying illustration from Global Warming Art shows that a good chunk of greenhouse gas emissions is in the form of methane and nitrous oxide and a good portion of these two greenhouse gases comes from agriculture (light green). The role of agriculture in global warming was emphasized in a report called “Livestock’s Long Shadow” which was issued last year by the United Nations Food and Agricultural Organization. Here is a quote from the Executive Summary:
With rising temperatures, rising sea levels, melting icecaps and glaciers, shifting ocean currents and weather patterns, climate change is the most serious challenge facing the human race.
The livestock sector is a major player, responsible for 18 percent of greenhouse gas emissions measured in CO2 equivalent. This is a higher share than transport.
The livestock sector accounts for 9 percent of anthropogenic CO2 emissions. The largest share of this derives from land-use changes especially deforestation caused by expansion of pastures and arable land for feedcrops. Livestock are responsible for much larger shares of some gases with far higher potential to warm the atmosphere. The sector emits 37 percent of anthropogenic methane (with 23 times the global warming potential (GWP) of CO2) most of that from enteric fermentation by ruminants. It emits 65 percent of anthropogenic nitrous oxide (with 296 times the GWP of CO2), the great majority from manure. Livestock are also responsible for almost two-thirds (64 percent) of anthropogenic ammonia emissions, which contribute significantly to acid rain and acidification of ecosystems.
When it comes to taking action to stop global warming we hear a lot about using renewable energy sources, more energy efficiency, and occasionally practicing energy conservation, but very little is said about taking measures such as eating less meat or even becoming a vegan. Will any of the many candidates running for president in the United States give up eating meat and ask their campaign staff to do the same? Extremely unlikely. However, the more methane and nitrous oxide emissions can be reduced the less reduction of carbon dioxide emissions will be needed which is important because it is very difficult to greatly reduce carbon dioxide emissions since it largely requires replacing coal and oil as energy sources.