Impacts of Dietary Recommendations

Following the government's dietary recommendations may lead to . . . climate change?

New research suggests the following:

“if Americans adopted the recommendations in USDA’s “Dietary Guidelines for Americans, 2010,” while keeping caloric intake constant, diet-related greenhouse gas emissions would increase 12 percent.”

Rather than trying to anticipate the unintended consequences of such recommendations, the study authors want to add another layer on top of the nutritional recommendations

“The take-home message is that health and environmental agendas are not aligned in the current dietary recommendations,” Heller said.

The paper’s findings are especially relevant now because the USDA Dietary Guidelines Advisory Committee is for the first time considering food sustainability within the context of dietary recommendations, he said.”

As I've pointed out before, trying to integrate nutritional and environmental objectives into recommendations involves value judgement that go beyond scientific evidence. Moreover, focusing just on C02 emissions or nutritional composition (as if that's easy to characterize) ignores many other factors.  On a per-acre basis, which crops are the biggest users of pesticides or water? You might be surprised to find out that it is not corn, soybeans, or wheat but rather many fruits and veggies like lemons, strawberries, etc. 

Rather than trying to add layer upon layer to the dietary recommendations, why not respect people's choices?  The price of food reflects the resources used and the demands on those resources.  If the problem is that prices don't fully reflect water use or C02 emissions, then the idea is to think about assigning property rights in a way that that information-aggregating markets help allocate those resources.  But, I suppose it's less fun to let markets allocate resources.  That would take away our power to tell others what to eat.  

Buffalo extermination - environmental catastrophe or savior?

Given my Wall Street Journal article earlier this week, I've received a large number of questions and comment about beef cattle production and the environment.  One comment on the piece in the WSJ made an observation that had never occurred to me.

One of the big concerns with beef production is methane emissions.  Methane is a more potent greenhouse gas than carbon.  Cattle are ruminants, and their digestion produces methane (which is released not from the back-end of the cow as is typically asserted but rather the front-end).  

In any event, it seems a common presumption of many who are worried about this issue is that if we got rid of all the beef cattle in the US (or at least drastically reduced their numbers), that would be a great thing because we could significantly cut greenhouse gas emissions and help curb climate change.

In fact, we did something very much like that in the US in the mid to late 1800s, and it is almost universally considered a tragedy.

According to some environmental groups, there was once more than 20 million bison roaming the Great Plains.  This number may not be far fetched.  According to one academic paper, the bison carrying capacity of the Great Plains in 1860 was estimated between 13.78 to 20.67 million bison.   According to EPA calculations, American bison generate as much or more methane as do beef cattle on a per-head basis (compare table A-184 to A-187).  

In 1990, there were only about 50,000 head of bison in the US.  Today there are less than 200,000.  Thus, there has been a 100 fold reduction in bison numbers since the mid 1800s.

Were these bison causing climate change back in the 1800s?  Is it a great victory for the environment that they were almost eradicated?    

Logically consistency would seem to dictate that we think about the methane emissions of the ~20 million American bison in the 1800s the same way we think about the methane emissions of the ~29 million beef cattle in the US today.   I suspect the total amount of methane emissions from 1860s bison population and 2014 US beef cattle population are roughly similar (according to the EPA, feedlot beef cattle have much lower per-head methane emissions than bison - about half as much).  [addendum: a reader subsequently emailed me and correctly pointed out that, including dairy cattle, there are actually more than 90 million cattle in the US today - a figure roughly 3 to 4 times more than the number of bison existing in the 1800s]

So, bison depopulation - environmental boon or ecological travesty?  Neither?  Both?

A food producing machine

Imagine a biologist on an excursion in the Amazon looking for new plant species.  He comes across a new grass he's never seen, and brings it back home to his lab in the U.S.  He finds that the grass grows exceedingly well in greenhouses with the right fertilizer and soil, and he immediately moves to field trials.  He also notices that the grass produces a seed that durable, storable, and extraordinarily calorie dense.  The scientist immediately recognizes the potential for the newly discovered plant to solve global hunger problems and to meet the dietary demands of a growing world population.

But, there is a problem.  Lab analysis reveals that the seeds are toxic to humans.  Despite the set-back, the scientist doesn't give up.  He toils away year after year until he creates a machine that can convert the seeds into a food that is not only safe for humans to eat but that is incredibly delicious to eat.  There are a few downsides.  For every five calories that go into the machine, only one comes out.  Plus, the machine uses water, runs on electricity, burns fossil fuels, and creates CO2 emissions.  

Should the scientist be condemned for his work?  Or, hailed as an ingenious hero for finding a plant that can inexpensively produce calories, and then creating a machine that can turn those calories into something people really want to eat?  

Maybe another way to think about it is to ask whether the scientist's new product can pass the market test; can his new food - despite it's inefficiencies (which will make the price higher than it otherwise would be) - compete against other foods in the marketplace?  Recall, that the new food must be priced in a way that covers the cost of all the resources it uses - from the fertilizer to grow the new seeds to the gasoline required to run the new machine.

Now, let's call the new grass "corn" and the new machine "cow".  The analogy isn't perfect (e.g., the cow is a living-feeling being and not a lifeless machine), but the thought experiment is useful nonetheless.

It's particularly useful in thinking about the argument that corn is "wasted" in the process of feeding animals.  It is one that appears - in one form - in a recent paper in Science.  West et al. write:

“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.””

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.

What we typically do is take our relatively un-tasty corn and soy, and plug them into our machine (the cow or pig or chicken) to get a form of food we want to eat.  Yes, it seems inefficient on the surface of it, but the key is to realize the that the original calories from corn and soy were not in a form most humans find desirable.  As far as the human pallet is concerned, not all calories are created equal; we care a great deal about the form in which the calories are delivered to us.

The grass-machine analogy also helps make clear that it is probably a mistake to compare the calorie and CO2 footprint of the corn directly with the cow.  I suspect only a very tiny fraction of the world's caloric consumption comes from directly consuming the raw corn or soy seeds.  It takes energy to convert these seeds into an edible form – either through food processing or through animal feeding. So, what we want to compare is beef with other processed foods.  Otherwise we're comparing apples and oranges (or in this case, corn and beef).

Is Local Food More Environmentally Friendly?

As should be obvious to anyone who thinks about it a bit, the environmental impacts of consuming a local food depends on how efficient your particular locale is at producing the particular food.  One of the ironies of this insight is that areas that have more intensified livestock operations may, at least in some dimensions, be more environmentally friendly than areas with less intensified production (because greater intensity often means more efficient).

Some empirical support for these these insights was recently provided in an article by  Misak Avetisyan, Tom Hertel, and Gregory Sampson just published in the journal Environmental and Resource Economics.   

The abstract:

“With the increased interest in the ‘carbon footprint’ of global economic activities, civil society, governments and the private sector are calling into question the wisdom of transporting food products across continents instead of consuming locally produced food. While the proposition that local consumption will reduce one’s carbon footprint may seem obvious at first glance, this conclusion is not at all clear when one considers that the economic emissions intensity of food production varies widely across regions. In this paper we concentrate on the tradeoff between production and transport emissions reductions by testing the following hypothesis: Substitution of domestic for imported food will reduce the direct and indirect Greenhouse Gas (GHG) emissions associated with consumption. We focus on ruminant livestock since it has the highest emissions intensity across food sectors, but we also consider other food products as well, and alternately perturb the mix of domestic and imported food products by a marginal (equal) amount. We then compare the emissions associated with each of these consumption changes in order to compute a marginal emissions intensity of local food consumption, by country and product. The variations in regional ruminant emissions intensities have profound implications for the food miles debate. While shifting consumption patterns in wealthy countries from imported to domestic livestock products reduces GHG emissions associated with international trade and transport activity, we find that these transport emissions reductions are swamped by changes in global emissions due to differences in GHG emissions intensities of production. Therefore, diverting consumption to local goods only reduces global emissions when undertaken in regions with relatively low emissions intensities. For non-ruminant products, the story is more nuanced. Transport costs are more important in the case of dairy products and vegetable oils. Overall, domestic emissions intensities are the dominant part of the food miles story in about 90 % of the country/commodity cases examined here.”

Cost of Calories and Protein from Meat

Yesterday I gave a talk for some of the world's largest pork producers as part of an event put on by PIC, the world's largest supplier of pork genetics. 

In my presentation, I touched briefly on the environmental impacts of meat production, and showed the following slide, which made the rounds on Twitter yesterday.

I thought a few points of clarification and expansion were in order.  

First, note that Bailey Norwood and I published a paper a few years ago comparing the costs of producing different meats to producing corn, soybeans, wheat, and peanuts (also note that there was a calculation error in the tables; the corrected tables are here). As we show there, it is generally less expensive to get calories or protein from corn or soybeans or wheat than it is from cattle or hogs.   That's one reason we grow such much corn, wheat, and soy - they are incredibly efficient generators of calories and protein.  

I will also note that there have been many attempt to calculate the retail cost of eating "healthy vs. unhealthy" food.  Here, for example, is a paper by the USDA-ERS.  Adam Drewnowski also has several papers on this subject.  This work often shows that meat is relatively  (relative to many fruits and vegetables) inexpensive on a per calorie or per gram of protein basis, although meat looks more expensive when placed on a per pound basis.   If you want really inexpensive calories eat vegetable oil or crackers or sugar; if you want real expensive calories, eat zucchini or lettuce or tomatoes.

The reason I picked lettuce as an example is to make the point that people often do not reason consistently when they argue we should unduly focus on costs of calories.  I have never once heard anyone say how "inefficient" production of lettuce or tomatoes or peppers are, and yet I have repeatedly heard this argument about meat.  

Another important point is that efficiency or cost isn't everything.  What do we get in return?  Who cares if lettuce is really expensive on a $/kcal basis?  A nice salad is tasty.  And healthy.  The trouble is that many of our most efficient producers of calories or protein (field corn, soybeans, wheat) are not that tasty by themselves.  Given the choice to eat a raw soybean or a raw carrot, I'll take he latter any day despite the fact that the latter is "less efficient."  

This discussion reveals another point that Bailey and I discussed in our paper.  To get corn and soy and wheat into foods we like to eat requires processing, which takes energy and is costly.  Thus, one needs to look at the costs of the foods as we eat them not as they're grown.  And, there is generally much less cost wrapped up in the processing of meat and animal products than there is for grain-based products (based on the farm-to-retail price spreads reported by the USDA).

Finally, note that one of the ways we process corn and soybeans into something we like to eat is by feeding them to animals.  Animals convert relatively untasty grains into tasty milk, eggs, and meat.   And even if some energy is "lost" or "wasted" in that process, we're getting something in return.  Here's what I previously had to say about that:

Almost no one looks at their iPad and asks, "how much more energy went into producing this than my old Apple II." The iPad is so much better than the Apple II.  We'd be willing to accept more energy use to have a better computer.  Likewise a nice T-bone is so much better than a head of broccoli.  I'm willing to accept more energy use to have a T-bone than a head of broccoli.