Do you claim to care about climate?

If you claim to care about climate change, we need to have a word about food. Specifically, about the fantastically unsustainable way we consume food in the U.S. There’s a number of issues here, but the biggest one is our relationship to meat, and the efficiency of turning food — and, by extension, carbon — into calories.

In the U.S. in particular, food supply is woefully inefficient, and this shows up in a number of ways. For example, according to the United Nations Environment Programme, 30% of food produced for humans in the U.S. ends up not being consumed by humans. The USDA puts the same number at 30% to 40%. This is a shame for the food that’s wasted — unconscionable, in a country where people go hungry, and doubly awful given the global state of things — but from an environmental point of view, most of this food doesn’t go bad at the farm level. It goes through the full supply chain — harvesting, refining, preparing, transporting, packaging and presenting in supermarkets or other food retail outlets — before needing to be discarded. Each step incurs additional environmental cost, such as electricity for processing; plastics for packaging; transportation, which comes with its own carbon footprint; and so on.

Reducing waste is important, obviously, but most of us don’t consider the other side of the food production chain. It turns out that animals are particularly inefficient when it comes to delivering calories. Farmed animals need a lot of food to grow, and in the process they consume feed that needs to come from somewhere — often grown especially to feed animals on land that could have grown food for humans.

Food scientists looking at this sort of thing use a feed conversion ratio, a concept that’s been around at least since the 1980s. In other words, how many calories of feed does an animal need to consume to create a calorie of edible meat? There’s a bunch of different formulae and calculators available online for how to determine this.

Take a cow, for example. For every calorie of edible meat, it needs to eat 25 calories of feed. I get that a hamburger is more exciting than a piece of bread, and there are differences in the type of nutrition, but in a world that’s trending toward having 10 billion human inhabitants that are all upwardly mobile in terms of the foods they consume, eating inefficiently seems like a pretty poor choice to me.

Dairy and beef cows have a second problem as well. They are able to eat grass and other foods that humans aren’t able to eat through a process of enteric fermentation. Essentially, ruminants like cows have bacteria in their stomachs that help break down cellulose-enhanced tough plants and grains. In the process, the bacteria release a huge amount of methane (CH₄), which the cows then expel as gas. According to the EPA, methane is 25 times more harmful as a greenhouse gas than CO₂, and livestock can produce between 250 and 500 liters of methane per day. Multiply that by 25 to get the effect of CO₂, and it quickly becomes clear why cows are a problem before you even put them through the shredder to turn them into tasty morsels of food. Of course, there are wild ruminants as well — antelope, giraffe, deer, bison, and so on — but humans have been raising sheep and cows for thousands of years, adding to the population and causing a significant impact. In fact, meat production represents 60% of the greenhouse gas emissions from food production.

I talk and write about climate a fair bit, and even people who claim to care passionately about climate change and environmental questions often fail to research the food they eat. That’s borderline incomprehensible to me: What you eat is something a lot of us do have control over, and not using that control to have a positive impact on the environment seems bizarre.

In addition, the way animals are treated before they are turned into food is absolutely heart-wrenching. If that statement doesn’t have you nodding in agreement, carve out 90 minutes to watch Earthlings — it’s free and narrated by Joaquin Phoenix. If Earthlings doesn’t convince you, you can always suffer through Dominion, which rams the point home over the course of 2 hours. Yes, also free, also narrated by Phoenix, and also almost certain to make you skip the chicken tendies and beef burgers for a couple of weeks, at least.

If animal welfare doesn’t make you think twice, perhaps the environmental impact can. I’m not even necessarily saying you have to turn vegan — although Al Gore did, after he was faced with the inconvenient truth that consuming animal products was inconsistent with being a poster boy for environmentalism — but cutting down on animal products has a disproportionate environmental impact. Eat meat if you must, but eat better meat, more rarely. Have a steak from your local butcher once per week rather than fast-food hamburgers twice per day. Do your research into the dairy industry, and perhaps cut down on that, too; I had the misfortune of visiting a large-scale dairy farm at some point in the last few years, and it wasn’t pleasant.

At the very least, make sure you educate yourself enough to make informed choices, and be prepared for pesky journalists like myself to get all up in your grill if you’re bragging about how environmentally friendly your solar-charged electric vehicle is while you eat irresponsibly raised meat. As climate-aware environmentalists, we need to take a holistic approach. That has to include the food you eat.