READ MORE: Unfold, the official UC Davis podcast, examines the bad rap cattle receive as an unfriendly producer of climate-changing greenhouse gas.

Cattle are the No. 1 agricultural source of greenhouse gases worldwide. Each year, a single cow will belch about 220 pounds of methane, which is shorter lived than carbon dioxide but 28 times more potent in warming the atmosphere, said Mitloehner, a professor and air quality specialist in the Department of Animal Science.

With the escalating effects of climate change, that fact has advocates urging the public to eat less beef. They contend it’s an unsustainable diet in a world with a population expected to reach nearly 10 billion by 2050.

Mitloehner has openly challenged this view, writing in a recent commentary for The Conversation that “forgoing meat is not the environmental panacea many would have us believe.”

Cows and other ruminants account for just 4 percent of all greenhouse gases produced in the United States, he said, and beef cattle just 2 percent of direct emissions.

Better breeding, genetics and nutrition have increased the efficiency of livestock production in the U.S. In the 1970s, 140 million head of cattle were needed to meet demand. Now, just 90 million head are required. At the same time, those 90 million cattle are producing more meat.

“We’re now feeding more people with fewer cattle,” Mitloehner said.

The global problem

Shrinking livestock’s carbon hoofprint worldwide is a bigger challenge. Livestock are responsible for 14.5 percent of global greenhouse gases.

India, for example, has the world’s largest cattle population, but the lowest beef consumption of any country. As a result, cows live longer and emit more methane over their lifetime. In addition, cows in tropical regions produce less milk and meat, so it takes them longer to get to market.

“If you have hundreds of millions of cattle to achieve a dismal amount of product, then that comes with a high environmental footprint,” Mitloehner said.

Professor and air quality specialist Frank Mitloehner sits in a trailer at the UC Davis dairy barn examining real-time greenhouse gas emission data coming from cows. (Karin Higgins/UC Davis)

Researchers at UC Davis have projects in Vietnam, Ethiopia and Burkina Faso to boost livestock productivity through better nutrition. That may be critical going forward as demand for meat is rising in developing countries.

"We expect by 2050 there is going to be a 300 percent increase in beef demand in Asia," said Ermias Kebreab, a professor of animal science and director of the UC Davis World Food Center.