The hamburger is suddenly embroiled in a political dispute.
Supporters of the Green New Deal, according to a Republican talking point, are anti-patty. “They want to take away your hamburgers,” Sebastian Gorka, a former adviser to President Trump, said last week at the Conservative Political Action Conference.
Other Republicans, including Mr. Trump, have made similar claims. But the Green New Deal, a broad climate policy proposal, makes no mention of hamburgers, cows or beef.
Instead, the resolution, introduced by Representative Alexandria Ocasio-Cortez of New York and Senator Edward J. Markey of Massachusetts, underscores the role of agricultural emissions in climate change.
Among its many goals, it calls for “working collaboratively with farmers and ranchers in the United States to remove pollution and greenhouse gas emissions from the agricultural sector as much as is technologically feasible.”
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Cows have been a focus of some agriculture policy discussions because they release methane, a powerful planet-warming gas. A fact sheet about the Green New Deal that Ms. Ocasio-Cortez’s office published last month, then withdrew, said it would be hard to “get rid of farting cows.” But some critics of the plan saw that as a suggestion that getting rid of cows entirely would be a good thing.
“It’s not to say you get rid of agriculture,” Ms. Ocasio-Cortez later clarified on the Showtime show “Desus and Mero.” “It’s not to say you are going to force everybody to go vegan or anything crazy like that. But it’s to say, listen, we’ve got to address factory farming, maybe we shouldn’t be eating a hamburger for breakfast, lunch, and dinner.”
The back and forth has raised some tricky questions for burger lovers. Are they really that bad? And would it be good for the planet to get rid of cows?
The beef with beef
Agriculture was responsible for 9 percent of greenhouse gas emissions in the United States in 2016, according to the Environmental Protection Agency. While the sectors with the most emissions were transportation and electricity generation, at 28 percent each, United States agricultural emissions were still greater than Britain’s total emissions in 2014, according to data from the World Bank.
Cows and other ruminants are responsible for two-thirds of those agricultural emissions. Their guts produce methane, a powerful greenhouse gas that’s more potent at trapping heat in the atmosphere than carbon dioxide, though it also dissipates faster. Cows release some of that methane through their flatulence, but much more by burping.
Deer, camels and sheep also produce methane. But in the United States, it’s cows that primarily account for the 26.9 percent of methane emissions, more than any other source. Natural gas accounts for 25 percent.
The end of cows?
If cows are such a problem, should we get rid of them?
It’s not that easy, said Robin White, an assistant professor of animal sciences at Virginia Tech.
She was a co-author of a 2017 study that looked at an extreme case — what would happen if all animals were removed from farming. It found that total United States greenhouse gas emissions would be reduced by only a modest amount, while nutritional deficiencies would increase.
Other studies of possible agricultural changes “often don’t consider what we currently produce in terms of food in the United States,” Dr. White said. When those studies remove meat, eggs and dairy from the equation, she said, they tend to assume that other foods will be available.
But today’s agricultural system relies on a suite of crops that researchers have spent decades fine-tuning for specific niches. It isn’t clear that the country could easily grow a new set of crops that would make up for the lost nutrition from meat for the entire population. (Many individuals, of course, already opt against eating meat for ethical, religious or other reasons.)
“We don’t make that assumption,” Dr. White said. “We kind of ask the inverse question: Given the food that’s available, how do we feed people?”
Christian Peters, an associate professor at the Friedman School of Nutrition Science and Policy at Tufts University, said much of the country’s current agricultural output was used to feed animals. “There is a large amount of what we call co-products that come out of the food production system,” he said. “We have these things that we would otherwise turn into a waste, and we use them to raise animals.”
In addition, grazing cows are able to wrest calories from grasslands that are not suitable for growing food for humans.
Cows are also a source of fertilizer, Dr. White said. Her analysis looked at livestock manure that is used as fertilizer and assumed that it would have to be replaced with synthetic fertilizers, which are often made from natural gas. The main component of natural gas is methane, the same gas that makes cows so problematic in the first place.
How many burgers is too many?
From a greenhouse gas emissions perspective, this doesn’t mean that it is sustainable to eat all the burgers we want.
In addition to greenhouse gas emissions, the food system has environmental challenges, like overtaxed agricultural lands; the dead zones that form each year in the Gulf of Mexico, fueled by nutrient runoff from Midwestern fields growing animal feed; and the pollution associated with concentrated animal feeding operations, or so-called factory farms.
Consuming lots of meat is also making people in the United States and other affluent nations unwell, according to a recent report on sustainable diets in the medical journal The Lancet. People in the United States would be better off eating much less red meat, the report said, while those in undernourished parts of the world, like South Asia, would benefit from eating more.
The World Cancer Research Fund has said that limiting red meat to 3.5 ounces — a little less than a quarter-pound burger — no more than three times a week reduces cancer risk. Going lower than that, sticking to one 3.5-ounce serving of red meat a week, reduced related greenhouse gas emissions by nearly half, the Lancet report said.
Dr. Peters published a study in 2016 that suggested that a lacto-ovo diet, which contains dairy and eggs, might be the most sustainable while also providing proper nutrition.
But at a high level, even a lacto-ovo diet necessitates the creation of at least some meat. A laying hen can live six years or longer, but stops laying eggs efficiently after a year. A cow can live up to 20 years, but milk production for most cows drops somewhere between the ages of 5 and 8. Not slaughtering them for meat would mean a commitment to keeping them alive — and committing the resources to do so — for quite some time. It may be more efficient to simply eat them.
If all of this sounds messy, it is. Researchers generally agree that agriculture is one of the hardest parts of the economy to decarbonize; it’s not just about lowering greenhouse gas emissions, but also about keeping the world fed.
The question, Dr. Peters said, boils down to finding sustainable ways of producing food that meet both the food security needs of the United States and the many other nations that depend on it for exports.
“It would be very safe to say that eating less meat is going to make it easier to accommodate a larger number of people on the planet, and every study I’ve seen is pointed to that,” Dr. Peters said. “The question is by how much, and how quickly does that need to change?”
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