“The hottest year was even hotter than expected,” read a recent headline in Science. If, like me, you want to do more to stave off the worst, then cast a more critical eye on diet. What we eat has a major climate impact, because food production generates high levels of the greenhouse gases (GHG) that underlie climate change.
In fact, just the livestock sector of the global food supply chain contributes about 14.5% to the total of all the GHG emissions generated by human activities. Livestock contributes 50% of annual methane emissions and 75% of nitrous oxide (N2O) emissions.
By far the biggest dietary culprit is beef. In 2023, Americans consumed more than 57 pounds per person. What brands cattle as bad climate actors? In their burps, flatulence, and manure, cows emit large volumes of methane, a gas far more effective at trapping heat than carbon dioxide. N2O, an extremely potent GHG, is released from bovine urine.
Also driving global warming, 77% of the world’s agricultural land is used either for grazing animals or growing crops to feed them. Recently, physicians have sounded the alarm about the “dual threat” to public health and the climate from our unsustainable meat-based diet. Healthy diets, associated with long and relatively disease-free lives, contain small amounts of lean meat, some fish and seafood, and a predominance of whole grains, fruits, vegetables, legumes, nuts and seeds, and healthy oils (e.g., olive oil).
High in animal products, unhealthy diets are linked to elevated rates of disease, shorter life spans, and planetary harm. At least partly due to diet, the prevalence of obesity in the United States is as much as 42% higher than it was two decades ago, accompanied by a related epidemic of chronic diseases. Half of our adult population now has diabetes or pre-diabetes, both conditions that predispose to cardiovascular diseases. Millennials are showing “startling increases” in obesity-related cancers. Low fiber diets (meat itself has no fiber) adversely affect digestive processes, immunity, and the gut’s defenses against colon cancer.
It’s not all gloom and doom, though. Modest meat restriction, for example, pays handsomely in longevity. If you switch a mere 3% of daily calorie intake (i.e., on average, just 60 calories) from meat to plant-based proteins, your risk of mortality declines, according to a 2020 study. That 3% switch led to a 10% decrease in overall mortality risk and a 11% to 12% decrease in risk of cardiovascular disease in men and women, respectively.
The biggest payoff for health and the planet comes from cutting down on, or eliminating, beef from the diet. Emissions produced from raising plant foods are 10 to 50 times lower than those from animal products, according to the Science article mentioned above.
This is because eating meat is an inefficient way for us to extract calories and protein from the crops fed to farm animals. Most of the feed goes into maintaining the animals’ metabolic processes. Although reported values vary, beef cows, on average, are only about 4% efficient in converting protein in feed to edible protein, chickens about 20%, and pigs intermediate at about 15%.
Health reasons aside, logic alone suggests that human survival will benefit by decreased meat and dairy consumption, because crops for animals are themselves jeopardized by climate change. Given this, growing most crops for direct human consumption makes life-sustaining sense.
Resources
Hottest year: shorturl.at/dknw1
Beef consumption: shorturl.at/jmvT6
Grazing land: shorturl.at/hknW8
Dual threat: shorturl.at/aCLP6
Mortality risk: