More than 4,000 pounds of beef have been recalled over fears that they could be contaminated with mad cow disease. Reuters

If climatologists had their way, we’d be living on a diet of nuts and grains instead of beef and pork. Their reasoning? Livestock and the methane they produce are a major source of greenhouse-gas emissions around the globe. And now more than ever, many scientists are arguing for us to reduce our reliance on livestock to mitigate the effects of global warming.

A new study published Dec. 20 in the journal Nature Climate Change makes the case for cutting back on our consumption of meat from cows, sheep, goats and buffalo, the production of which contribute large amounts of methane gas to our atmosphere. The Environmental Protection Agency has previously stated that, globally, livestock are the “largest source of methane from human-related activities.”

“Greenhouse-gas emissions from ruminant meat production are significant,” the new study notes. “Reductions in global ruminant numbers could make a substantial contribution to climate-change mitigation goals and yield important social and environmental co-benefits.”

Of course, scientists have known for some time that livestock dirty up our atmosphere. A World Watch report from 2009 noted that when people discuss the causes of climate change, they often cite fossil fuels but forget to mention cattle. “Oil, natural gas, and especially coal are indeed major sources of human-caused emissions of carbon dioxide and other greenhouse gases,” the authors wrote. “But we believe that the lifecycle and supply chain of domesticated animals raised for food have been vastly underestimated as a source of [greenhouse gases], and in fact account for at least half of all human-caused [greenhouse gases].”

And for a long time, the amount of methane produced by livestock was grossly underestimated. In November, a study emerged that suggested livestock are producing about twice as much methane gas as scientists previously believed.

Researchers note that about one-fourth of all land area on Earth is dedicated to livestock grazing. The world’s population of livestock numbers in the billions, and nearly 33 percent of all arable land is used to grow feed crops for livestock. According to the study, the global production of cattle and sheep is responsible for 19 to 48 times more greenhouse-gas emissions, based on pounds of food produced, than the global production of protein-rich plant foods like beans or soy products.

"Because the Earth's climate may be near a tipping point to major climate change, multiple approaches are needed for mitigation," William Ripple, a professor in the College of Forestry at Oregon State University and study leader, said in a statement. "We clearly need to reduce the burning of fossil fuels to cut CO2 emissions. But that addresses only part of the problem. We also need to reduce non-CO2 greenhouse gases to lessen the likelihood of us crossing this climatic threshold."

Co-author Pete Smith of the University of Aberdeen in Scotland argued that cutting back on our consumption of livestock could have additional benefits for food security, human health and environmental conservation. After all, meat-based diets require more energy, land and water resources to maintain than plant-based diets do.

There’s no easy solution to curbing climate change, and the effort involves several variables. But scientists think reducing our dependence on livestock is key to cutting back on greenhouse-gas emissions. The difficulty will be in convincing consumers to change their eating habits.

"On a large scale, motivating humans to change their diet to consume less meat would be challenging, and unlikely to happen voluntarily without incentives," Ripple told Nature World News. "Employing a tax or emission-trading scheme on livestock's greenhouse-gas emissions would be one alternative that would modify consumer prices and affect consumption patterns."

Last week, the U.S. State Department released its 2014 Climate Action Report. In it, the Obama administration made clear how it plans to cut U.S. greenhouse-gas emissions to 17 percent below 2005 levels by 2020. The good news is, we’re already well on our way. According to the report, in 2011, U.S. greenhouse-gas emissions were 6.5 percent below 2005 levels, in part because of improved energy efficiency, the development of cleaner and renewable energy sources, and the recession.

The administration believes that by further regulating carbon-dioxide and methane emissions, and putting in place stricter energy efficiency measures for vehicles and major appliances, the U.S. can meet its emissions goal by 2020.

Maybe cutting out that weekly fast-food burger won’t hurt, either.