Many activists and reporters claim we should eat little or no meat to prevent climate change. But instead of presenting arguments, proponents of this radical proposal seek to disqualify their critics with personal attacks.
If you want to win an argument, you can employ one of two strategies: make compelling arguments that convince your audience, or engage in personal attacks designed to disqualify your opponents. Here's a textbook example of the latter approach from Forbes contributor Jeff McMahon: Journalists Are Making The Same Mistake With Dietary Change They Made With Climate Change: Study.
The evidence is clear that developed countries need to reduce their meat consumption to mitigate climate change, McMahon asserted, yet the media has hindered this effort by engaging in “Bothsidesism”:
Scientists agree that developed nations need to eat less meat and shift to a plant-based diet, according to a new study in the journal Sustainability, but newspapers cover the issue as an open debate. Newspaper coverage of dietary change is reminiscent of widely criticized coverage of climate change earlier in this century, the study says, which presented the human causes of global warming as debatable long after scientists had reached consensus.
McMahon is on to something here. The media has dishonestly covered the debate about climate change and agriculture. But the issue is not that reporters have given “industry representatives” the chance to mislead the public. The actual mistake has been to amplify sloppy arguments from busybodies who believe themselves qualified to change how the entire world eats. There is absolutely no evidence behind the proposal that cutting meat consumption will slow climate change.
The consensus that isn't
Let's address the article's primary claim. Do “scientists agree” that developed countries need to move away from animal-based diets? McMahon put that question to the study's lead author, Jillian Fry, professor of health sciences at Towson University. Her answer?
“That is a great question and to my knowledge has not been answered,” she said …
So, after all this squabbling about journalists who falsely balance their coverage of animal agriculture and climate change, we actually don't know if there is a consensus surrounding the view that we need to eat less meat. I daresay that McMahon has painted a falsely imbalanced picture of the situation by asserting that “scientists agree” with a conclusion we don't know that they accept.
Fry seems to have anticipated this objection, noting that “scientists who study diets, environmental footprints, climate, and/or resource use have been coming to the same conclusion for many years, and the evidence continues to get stronger.”
The evidence continues to do no such thing. Here are just some of the data points that don't fit the meat-is-destroying-mother-earth narrative, which I've discussed at length previously:
Studies have shown that the amount of land dedicated to raising animals for food has declined markedly in recent decades. There are 140 million fewer hectares of pasture today than there were in 2000.
All models of greenhouse gas emissions from land-use changes indicate that they have declined by a third over the last two decades.
Technological innovations that improve animal health, produce better feed, and optimize the animals themselves for food production could boost this global sustainability trend.
Dairies and livestock operations can collect methane from animal manure and use it as an alternative energy source, turning a potent GHG into a sustainable fuel source. California's dairy industry has slashed its methane emissions from animal manure by 30 percent using this approach.
McMahon discussed none of this evidence in his Forbes piece, and Fry didn't mention any of it in her paper either. That's unfortunate because accounting for all the available data fundamentally changes the story. Indeed the GHG emissions of animal agriculture have been so exaggerated, the EatLancet Commission has conceded that its recommended low-meat diet is not the “diet to reduce climate change.”
Thought experiment: a meatless America
But let's run a thought experiment. What would happen if all 330 million Americans switched to a plant-based diet? A 2017 study published in the Proceedings of the National Academy of Sciences (PNAS) sought to answer that very question. The researchers identified 36 nutrients (energy, protein, carbohydrates, vitamins, minerals, amino acids, and fatty acids) required “to maintain life and health for humans, with variation based on age and sex.” They estimated how much of each nutrient comes from animal and plant-derived foods, then modeled the GHG emissions of a plants-only agriculture system that provided all the necessary nutritional components.
Results: this massive overhaul of America's food supply might reduce total US greenhouse gas emissions by 2.6 percent, since agriculture accounts for just a fraction of our emissions.  The plants-only system yielded a 28 percent decline in agricultural GHG production, but this wasn't enough to offset the animal contribution to GHGs.
This is because transforming our agricultural system would inevitably carry some opportunity costs. As Science pointed out in its report on the PNAS study, if we eliminated animals from agriculture, we couldn't use their manure as fertilizer. Dwindling manure supplies would require increasing production of "synthetic" fertilizer, which could generate 23 million additional tons of carbon dioxide. Converting all land used by the livestock industry to produce crops for human consumption would also increase plant waste, which couldn't be fed to the animals that no longer exist; burning the excess waste might boost CO2 emissions by another two million tons.
On top of all this, the PNAS authors explained that
… removing animals from US agriculture would reduce agricultural GHG emissions, but would also create a food supply incapable of supporting the US population’s nutritional requirements.
This, of course, undermines the obnoxious assertion that plant-based diets are “good for you and the planet.” Fruits and vegetables are nutritious, and you can follow a healthy vegan diet, but neither of those observations makes veganism a panacea for all our dietary woes. For example, eating more produce will not reduce your chronic disease risk, nor will eliminating animal products help you maintain a healthy weight any better than another nutritious diet.
Returning to McMahon's article as we wrap up, reporters do misrepresent scientific topics to the general public—often for political purposes. Vested interests, both in government and the private sector, do use the media to advance their agendas. Ironically, McMahon and his chosen experts aren't calling attention to this problem; they are perpetuating it by selectively presenting evidence and labeling their opponents climate change deniers.
That raises an important question I'd like the anti-meat zealots to answer: if we're really hastening a climate disaster by eating animals, why do you have to ignore evidence to make your case to the public?
 I say “might” because the authors had to utilize a heavy dose of what Dr. Chuck Dinerstein calls “MathMagic.” Modeling the plant-based diets of millions of people requires lots of assumptions that may or may not correspond to reality. See the study's methods section for all the gory details.