Itwas an arresting statistic in an otherwise not very statisticky (and highly entertaining) New Yorker profile of the founder of fake-meat pioneer Impossible Foods: “Every four pounds of beef you eat contributes to as much global warming as flying from New York to London—and the average American eats that much each month.”
That last bit is actually an understatement: per-capita beef consumption in the U.S. was 4.7 pounds per month in 2017, according to the U.S. Department of Agriculture. Whether that is too much for the good of our hearts and other body parts is of course a matter of continuing debate, with a big new study out this week claiming that it isn’t so bad after all. Whether it’s really that bad for the climate turns out to be a matter of dispute as well, with knowledgeable people taking to Twitter soon after the New Yorker article went online last week to dispute its beef-to-air-travel comparison.
“An uncharacteristic howler from the @NewYorker,” wrote Washington Post food columnist Tamar Haspel. University of California at Davis animal science professor and air-quality expert Frank Mitloehner, who was quoted in the article, called out the number and said he was “seeking … clarification.” And I, who had little previous knowledge of such matters, reported that after spending some time poring through the scientific literature “the closest I could get was that eight pounds of beef might do it.”
With help from an explanation by the article’s author, Tad Friend, I have since been able to get to four, although only by using a flight-emissions calculator that delivers much lower numbers than the others I consulted. The source of Friend’s estimate for beef’s climate impact was one I had already come across: a December 2018 article in the journal Nature that put it at 188 kilograms of carbon-dioxide-equivalent emissions per kilogram of beef. That’s based on the weight of the carcass, about 70% of which actually makes it onto people’s plates, so 269 kilograms of emissions per kilogram of beef was the number Friend used.
At either 188 or 269, this is a lot higher than other estimates of beef’s per-kilogram impact that have been making the rounds. The Food and Agriculture Organization of the United Nations (whose estimates are discussed in more detail below) says it’s 48.7 kilograms, carcass weight. Researchers at the U.S. Department of Agriculture recently put it at 21.3 kilograms for U.S. cattle operations. A 2012 survey of past studies by Dutch government researchers found a range of 9 to 122 kilograms. Nine kilograms carcass weight is about 13 at the grocery store. Compare that to the flight-related emissions calculated by the Swiss nonprofit myclimate and it would take 70 kilograms, or 154 pounds, of such beef to equal the climate impact of an economy flight from New York to London.
Why do the estimates vary so widely? A lot depends on how the cattle are raised. Modern intensive agricultural methods are usually judged to be more climate-friendly than traditional or organic ones — a finding that deserves a separate exploration. But in the case of “Assessing the efficiency of changes in land use for mitigating climate change,” the title of the 2018 Nature article, the really big differences have to do with, you guessed it, assessing the efficiency of changes in land use. Which is worth diving into, because it so nicely illustrates the complications of any such calculation.
Lead author Timothy Searchinger of the World Resources Institute and Princeton University and his co-authors estimated the carbon-dioxide-capturing capability of native vegetation on land that is now being farmed or grazed, then counted the difference between that and its current capability as its “carbon opportunity cost.” Measured this way, the global opportunity costs of livestock farming turn out to be staggeringly large.
The numbers are so much higher for the meat of sheep, goats, beef and buffalo than for pork and poultry because the former are ruminants whose multi-chambered stomachs digest food in a very different way than the stomachs of hogs and chickens (and humans) do. One product of ruminant digestion is enteric methane, which comes out mainly as belches and accounts for about 60% of the estimated production emissions for beef and buffalo meat in the chart above. Another is an insatiable appetite for grasses and other plants that means ruminants usually require either lots of pasture or lots of land planted with forage crops such as alfalfa.
Methane is a potent but short-lived greenhouse gas, and it is standard practice in such calculations to average its warming impact over 100 years to convert it into a CO2-equivalent. There are climate scientists who argue that this is misleading, and that a fairer accounting would reduce the warming impact assigned to existing methane emissions. But in any case, that impact pales next to the land-use demands of grazing: planet-wide there’s about twice as much land devoted to livestock pasture as to growing crops.
The opportunity costs of this pasture depend a lot on what was growing there before it was turned over to the cattle, goats or sheep. Forests, especially tropical forests, can store a lot more carbon per acre than grasslands and deserts can. Here is a map from the Nature article of “above- and below-ground carbon stocks of potential natural vegetation under current climate.” The darker the green, the greater the storage potential:
Raising cattle on Great Plains grasslands in the U.S. that were previously populated by similar numbers of bison (also ruminants) does not have nearly the climate impact, then, of doing so on clear-cut Amazon rainforest in Brazil. Searchinger told me he hasn’t calculated emissions estimates by region yet, but even the FAO’s estimates, which factor in the impact of newly cleared pasture but not the opportunity costs of existing pasture, show much lower per-kilogram impacts from European and North American livestock due to more-efficient farming methods.
For Searchinger, such differences matter a lot in determining where and how to raise livestock and grow crops in a way that minimizes climate impacts. He and his co-authors created a Carbon Benefits Index calculator that allows one to estimate the impact of growing a particular crop or raising livestock in a particular way on a hectare-by-hectare basis around the world.
But for consumers, he argues, “we should be focused on the marginal impact of our demand for beef,” which is best represented by the global average. Only about 11% of the beef consumed in the U.S. is imported (and a similar share of U.S. production is exported), but this is more than enough for consumption shifts in the U.S. to affect farming decisions elsewhere, and vice versa. “You could have only 1% beef trade and it would still have a big effect,” Searchinger says.
In a blog post last week, UC Davis animal scientist Mitloehner and Texas Tech University agricultural economist Darren Hudson took issue with this reasoning:
Would increased U.S. beef exports eventually displace Brazilian beef exports in lower-income countries? Maybe, but it would take a considerable change in consumer choices and income in those countries. We have no evidence to indicate that would occur anytime soon, if at all. The predictions of the huge benefits of reducing U.S. beef consumption are, then, just based on unsupported assumptions.
That all may be true, but assuming that U.S. beef consumption is totally unconnected to what’s going on in the rest of the world also seems misleading. As with just about everything else related to climate change, the problems and solutions don’t stop at national borders.
Per-capita beef consumption in the U.S. has fallen from 94.1 pounds a year in 1976 to 56.8 (which is where the 4.7 pounds-a-month number comes from) in 2017. Couple that with the ever-increasing efficiency of livestock farming in the U.S., and beef-related carbon emissions here have surely fallen over that time. Problem solved, right? Well, per-capita beef consumption is still higher in the U.S. than in any other country except Argentina, and I think it’s pretty clear that we Americans would be just fine if we ate smaller quantities of beef and other meat. Meanwhile, many people in poorer countries with higher livestock-related carbon emissions should probably be eating more meat.
Searchinger argues that the right way to think about this is to “separate how we recognize the climate performance of different actors: If you’re a consumer, we want to recognize that you’re consuming low-carbon goods. If you’re a producer, we want to recognize that you’re producing the same good with less carbon than other farmers.” I get that logic, and I agree that consumers should be made aware that eating beef and lamb comes with much bigger climate impacts than most other foods. What I’m still struggling with is the implication, present in both the Nature article and the New Yorker piece, that it’s as big a climate-change driver as burning fossil fuels (or even bigger).
Humans have been raising livestock for thousands of years, while the rise of coal, oil and natural gas is relatively recent. Carbon-dioxide emissions from fossil-fuel combustion and industrial processes accounted for about 78% of the increase in global greenhouse gas emissions between 1970 and 2010, estimates the UN’s Intergovernmental Panel on Climate Change.
It’s burning fossil fuels that got us into this predicament, in other words. Changing how land is used may be essential to getting us out, but farming didn’t cause the climate crisis. -Bloomberg
Also read: We need climate-friendly cows, and scientists have a suggestion on how to create them
That’s BS. Around 10 years ago they calculated the “climate costs” of beef and realized it’s not that bad. Then they added the CO2 exhaled by the cattle which quadrupled(!) the negative impact of beef. It’s just another ploy by radical eco-fanatics to force ppl to turn to veganism. And yes, it also means that breathing is now also bad too for the climate. This whole climate BS comes with a strong sent of insanity. Don’t let yourself get fooled by them!
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