LIMOUSIN TODAY LimToday_AugSept19_WEB | Page 80

industry Are Cattle in the U.S. Causing an Increase in Global Warming? By Alan Rotz, USDA and Alex Hristov, Penn State Extension Over the past decade, we have seen the media place blame for our changing climate on cattle. Scientific evidence does not support this claim though for cattle in the United States. Cattle produce a lot of methane gas, primarily through enteric fermentation and fermentation of their manure. Methane is a powerful greenhouse gas that, along with nitrous oxide, carbon dioxide and some other compounds in the atmosphere, create a blanket around our planet. This is good; without this atmospheric blanket, the earth would be too cold for us to survive. The current problem is that concentrations of these gases in the atmosphere are increasing, which is thickening our blanket. Greenhouse gases and the atmosphere The methane that cattle produce is part of a natural carbon cycle that has been happening since the beginning of life on our planet. Through photosynthesis, carbon dioxide is extracted from the atmosphere and fixed as carbohydrates in plant material. Cattle consume and digest these carbohydrates, where some of the carbon is transformed to carbon dioxide and methane gases that are respired back to the atmosphere. This methane is oxidized in the atmosphere through a series of reactions, transforming that carbon back to where it started as carbon dioxide in the atmosphere. In contrast, when we burn fossil fuels, we are 78 | AUGUST / SEPTEMBER 2019