Cows have digestive bacteria in their stomachs that cause them to belch methane, the second-most-significant heat-trapping emission associated with global warming after carbon dioxide. Although it is far less common in the atmosphere than carbon dioxide, it has 20 times the heat-trapping ability.
With worldwide production of milk and beef expected to double in the next 30 years, the United Nations has called livestock one of the most serious near-term threats to the global climate. It estimated that cows might be more dangerous to Earth’s atmosphere than trucks and cars combined.
Scientists are looking at everything from genetics — cows that naturally belch less — to adjusting the bacteria in the cow’s stomach for a way to have the cows emit less methane.