photo: Ron Dollette | flickr | cc
Food historian Rachel Laudan points us to an insightful but unsatisfying post by ag economist Jayson Lusk on the role of cattle as food processors. Addressing the old idea that it is more efficient for humans to eat the plant calories that we feed animals directly. This idea features prominently in an important new paper in Science on improving food security while lowering the environmental impact of food production. (I wrote about this paper in a different context here.)
From the West, et. al paper:
Although crops used for animal feed ultimately produce human food in the form of meat and dairy products, they do so with a substantial loss of caloric efficiency. If current crop production used for animal feed and other nonfood uses (including biofuels) were targeted for direct consumption, ~70% more calories would become available, potentially providing enough calories to meet the basic needs of an additional 4 billion people (28). The human-edible crop calories that do not end up in the food system are referred to as the “diet gap.”
Lusk responds:
I’m not sure the logic of this sort of argument adds up.
Unlike my hypothetical example, corn is not toxic to humans (although some of the grasses cows eat really are inedible to humans). Nevertheless, few people really want to eat the calories that directly come from corn or other common animal feeds like soybeans.
So, why do we grow so much corn and soy? They are incredibly efficient producers of calories and protein. Stated differently, these crops (or “grasses” if you will) allow us to produce an inexpensive, bountiful supply of calories in a form that is storeable and easily transported.
The assumption in the quote of the Science article seems to either be that the “diet gap” will be solved by: 1) convincing people to eat the calories in corn and soy directly, or 2) that there are other tasty-edible crops that can be widely grown instead of corn and soy which can produce calories as efficiently as corn and soy. Aside from maybe rice or wheat (which also require some processing to become edible), the second assumption is almost certainly false. I’m also skeptical about the first assumption – that large swaths of people will voluntarily consume substantial calories directly from corn or soy.
He then goes on to point out that the correct comparison is not between the plant calories consumed by the animals and the meat calories which are yielded, but rather to compare processed, desirable (marketable) plant calories yielded to meat calories yielded, along with the various environmental impacts. He mentions CO2 but I would add water use as well as reactive nitrogen, methane and phosphorous runoff.
It’s an important point. Corn and soy are incredibly efficient ways of turning solar power into edible calories, and animals are a an efficient (if counter-intuitive) mechanism for processing those calories into palatable, high protein food. It should be further pointed out that pastured animals (and that includes nearly all beef cattle prior to feedlot finishing) convert grasses into edible crops on land unsuited to growing crops. Grass is incredibly prevalent and easy to grow with minimal inputs. We can’t eat grass, but cows can eat it for us. Livestock is fed all sorts of byproducts from food production that cycles back into the food supply instead of becoming waste (see the recent dust up over the FDA nearly ending the ability of breweries to sell or give spent grain as feed to livestock producers.).
Rachel Laudan also makes a great point about how labor intensive it is to make corn tortillas. This is the case with lots of staple crops turned into staple meals around the world. We need a better apples to apples comparison of meat to plant based processed food – apples to apples and turkey to tofurkey in terms of inputs and impacts. I suspect that plant based end products will still come out a head, but the 2000 calories of meat to 2000 calories of soybeans is simply a bogus comparison. Meat has two things going in it’s favor. People like eating it. Just wishing that we could change people’s preferences towards a more plant based diet isn’t going to get us very far. Second, corn and soy really are amazingly productive in the places where they dominate. Black beans just can’t compete.
Sadly, cows eating grass also means methane and methane is an even bigger deal as a greenhouse gas than carbon. So here’s the thing. The West paper singles out beef as much more problematic than pork and poultry because of the greater land and water use as well as the greater greenhouse gas impact because of the methane issue with beef. The water and methane issues are pretty straightforward, but the land issue is tricky.
In a country like the US, most beef cattle are raised on land that isn’t viable for other crops, so the greater land issue is a bit of a red herring. Yes a lot of land is used for corn and soy that gets fed to cows, but as Lusk points out, we need to compare hamburger to veggie burger numbers and then we need the number of people who will eat the veggie burgers to be more than a rounding error.
But…the issue isn’t necessarily land use in here in the US. The issue is deforestation, especially in the Amazon for ranching and soybean farming to meet the demand for meat. As a consumer, I understand that I’m buying beef from a global market. Even if I try to buy local, pastured beef, unless I’m buying directly from the farmer, I’m creating demand for beef on the global market. Thus, I have to assume that I’m contributing to deforestation associated with cattle production. This must give the beef consumer pause.
I believe that beef can be a sustainable part of our diet, but that depends on rightsizing the production to a sustainable footprint. Yes there will always be issues with methane and water, but there is a cost to everything, it seems only agriculture is expected to have zero environmental impact. Right now however, that footprint is too large if it is driving deforestation. And that is only going to get worse as China and the global south increases demand for beef. For me that means less beef in my diet, a few nice steaks a year and a few more black bean burgers.
Just when I thought I had it all figured out…