How bad, really, is meat eating?

Last week, Scientific American published a piece on how to get people to eat less meat.  Apparently, the science is settled and we now only need to come up  with the right "messages." 

There are an awful lot of apocalyptic pronouncements about the adverse effects of meat eating on the environment.  In a widely viewed TED talk, Mark Bittman likens meat production to a nuclear explosion and says it is leading to a "holocaust of a different kind," pointing directly to impacts on climate change.  As another example, Bill Maher, comedian and host of an HBO talk show, has written, “But when it comes to bad for the environment, nothing—literally—compares with eating meat. . . . If you care about the planet, it’s actually better to eat a salad in a Hummer than a cheeseburger in a Prius.”   I could, quite literally, provide dozens of these sorts of quotes from well known journals, writers, actors, etc, but I think you get the point.  The overall message is pretty clear: we should become increasingly more vegetarian.  

Let's take a look at one of the outcomes people are most worried about and where externality is relatively clear: climate change.   I went to the EPA's calculations, and surmise the following carbon equivalent impacts for the US attributable to beef cattle, swine, and poultry production during the year 2014 (MMT is million metric tons):

• beef cattle: 116.7 MMT C02 (from digestion) + 4 MMT C02 (from waste management) = 119.7 MMT C02;
• swine: 1 MMT C02 (from digestion) + 22.4 MMT C02 (from waste management) = 23.4 MMT C02; and
• poultry: 0 MMT C02 (from digestion) + 3.2 MMT C02 (from waste management) = 3.2 MMT C02.

Elsewhere, the EPA suggests using using a social cost of carbon of $36/metric ton of C02 (assuming a discount rate of 3%) for cost benefit analysis and rule making.  Multiplying the C02 impacts above by the price tag of $36 implies the following total carbon costs in 2014.

• beef cattle: $4.3 billion;
• swine: $842 million; and
• poultry: $115 million.

That seem like a lot, but keep in mind that we also eat a lot of meat.  Data from the USDA suggests that in 2014, farmers/ranchers in the US produced 24.32 billion pounds of beef, 22.86 billion lbs of pork, and 44.98 billion lbs of poultry.  Putting the carbon costs on a per-pound basis (i.e., dividing total carbon cost by pounds produced), suggests the following.

• beef: $0.177/lb;
• pork: $0.037/lb; and
• poultry: $0.002/lb.

I don't know about you, but those don't seem like enormous costs.  Let's think about it a different way.  Suppose you wanted to "internalize" the the impacts you're having on climate change by altering how much beef, pork, and poultry you buy.  To do this, take the price you see at the grocery store and add about $0.18/lb to the price of beef, $0.04/lb to the price of pork, and less than a penny to the price of poultry, and act as if these were the prices actually being charged.  Would you change your behavior much based on such price increase?  If not, we'd could say the climate impacts are relatively small.

I saw the following from the economist Bob Lawson on twitter this weekend.

If you have ever said "externality" but don't understand that the optimal amount of pollution >0, then you're doing it wrong.

— Bob Lawson (@doclawson12) April 17, 2016

The key isn't to have zero greenhouse gas impacts, but rather to to make sure you're taking into account the cost of those impacts.  For the case of beef, that means acting as if the price were about $0.17/lb higher.  Do that and you can shop away, guilt free (well, at least the guilt of carbon impacts).

P.S.  USDA data suggests the retail price of beef in 2014 was around $5.60/lb.  An $0.18/lb price increase would represent about a 3% increase in the price of beef.  Assuming the own-price elasticity of demand is, say, -0.6, this price increase would lead to a 1.9% reduction in the quantity of beef demanded. So, to internalize the carbon impacts of beef eating, Americans would reduce beef consumption by 1.9%.   It's not zero but its a far cry from vegetarianism.  

An often forgotten benefit of biotech crops

Discussions on the environmental benefits (or costs) of genetically engineered crops tend to focus on relative volumes and toxicities of herbicides applied, effects of Bt, and possibilities of cross pollinating native plants.  In so doing, what is often missed is an important environmental benefit of herbicide resistant crops.  In particular, if a farmer can control weeds by spraying the entire field with a herbicide like glyphosate, that means they don't have to use other methods of weed control (like plowing) that may lead to soil runoff.  

A new paper just released by the American Journal of Agricultural Economics by Edward Perry, GianCarlo Moschini, and David Hennessy tackles this issue. Here's a portion of the abstract:

“We find that glyphosate tolerant soybeans and conservation tillage are complementary practices. In addition, our estimation shows that farm operation scale promotes the adoption of both conservation tillage and glyphosate tolerant seed, and that all of higher fuel prices, more droughty conditions, and soil erodibility increase use of conservation tillage. We apply our results to simulate annual adoption rates for both conservation tillage and no-tillage in a scenario without glyphosate tolerant soybeans available as a choice. We find that the adoption of conservation tillage and no-tillage have been about 10% and 20% higher, respectively, due to the advent of glyphosate tolerant soybeans.”

It should be noted that herbicide tolerance isn't unique to biotechnology.  There are several "non GM" crops on the market that are tolerant to certain herbicides but are not genetically engineered, at least as the term normally used.

Consumer Uncertainty about GMOs and Climate Change

A lot of the debate and discussion surrounding public policies toward controversial food and agricultural issues like GMOs or climate change revolves around public sentiment.  We ask people survey questions like "Do you support mandatory labeling of GMOs?"  However, as I've pointed out, consumers may not even want to have to make this sort of decision; they would prefer to defer to experts.  Thus, we're presuming a level of understanding and interest that consumers may not actually have.  This is related to the recent discussion started by Tamar Haspel in the Washington Post about whether the so-called food movement is large or small.  Are "regular" people actually paying much attention to this food stuff that occupies the attention of so many journalists, researchers, writers, and non-profits?

I had these thoughts in mind as I went back and looked at this post by Dan Kahan who took issue with Pew's survey on public opinions about GMOs (this was the survey that attracted a lot of attention because it showed a large gap in public and scientific opinion on GMOs).  Kahan wrote:

“the misimpression that GM foods are a matter of general public concern exists mainly among people who inhabit these domains, & is fueled both by the vulnerability of those inside them to generalize inappropriately from their own limited experience and by the echo-chamber quality of these enclaves of thought.”

and

“That people are answering questions in a manner that doesn’t correspond to reality shows that the survey questions themselves are invalid. They are not measuring what people in the world think—b/c people in the world (i.e., United States) aren’t thinking anything at all about GM foods; they are just eating them.

The only things the questions are measuring—the only thing they are modeling—is how people react to being asked questions they don’t understand. ”

This let me to think: what if we asked people whether they even wanted to express an opinion about GMOs?  So, in the latest issue of my Food Demand Survey (FooDS) that went out last week, I did just that.  I took my sample of over 1,000 respondents and split them in half.  For half of the sample, I first asked, "Do you have an opinion about the safety of eating genetically modified food?"  Then, only for people who said "yes", I posed the following: "Do you think it is generally safe or unsafe to eat genetically modified foods?" For the other half of the sample, I just asked the latter question about safety beliefs and added the option of "I don't know".  This question, by the way, is the same one Pew asked in their survey, and they didn't even offer a "don't know" option - it had to be volunteered by the respondent.  So, what happens when you allow for "I don't know" in these three different ways? 

When "don't know" is asked 1st in sequence before the safety question, a whopping 43% say they don't have an opinion!  By contrast, only 28% say "don't know" when it is offered simultaneously with the safety question.  And, as the bottom pie graph shows, only about 6% of respondents in the Pew survey voluntarily offer "don't know".  Thus, I think Kahan's critique has a lot of merit: a large fraction of consumers gave an opinion in the Pew survey, when in fact, they probably didn't have one when this option was allowed in a more explicitly matter.  

Moreover, allowing (or not allowing) for "don't know" in these different ways generates very different conclusions about consumers' beliefs about the safety of GMOs.  Conditional on having an opinion, the percent saying "generally safe" varies from 40% in the sequential question to 50% in the simultaneous question to 39% in the Pew format which didn't offer "don't know."  That support can vary so widely depending on how "don't know" is asked is hardly indicative of stable, firm, beliefs about GMOs among the general public. 

In last week's survey I also carried out the same exercise regarding Pew's questions on climate change.  For half of my sample, I first asked whether people had an opinion about the causes of changes in the earth's temperature; for the other half, I included "don't know" as an option simultaneous with the question itself.   Here are the results compared to Pew's, which again did not explicitly offer a "don't know."  

Again, we see big differences in the extent to which "don't know" is expressed depending on question format, varying from 37% in the sequential version to only 2% in Pew's survey.  In this case, it appears that people who would have said "don't know" in the sequential question format are more likely to pick response categories that disagree with scientists, when they are given questions where "don't know" isn't so explicitly allowed.  

What can we learn from all this?  Just because people express an opinion on surveys doesn't mean they actually have one (or at least not a very firmly held one).  

Lettuce a bigger environmental threat than beef?

On Monday a press release began making the rounds claiming that "Vegetarian and 'healthy' diets are more harmful to the environment" and the story has generated provocative headlines like, "Lettuce three times worse than bacon for the environment."  The results are based on this paper published in Environment Systems and Decisions by Michelle Tom , Paul Fischbeck, and Chris Hendrickson.

Here's a portion of the abstract:

“This article measures the changes in energy use, blue water footprint, and greenhouse gas (GHG) emissions associated with shifting from current US food consumption patterns to three dietary scenarios, which are based, in part, on the 2010 USDA Dietary Guidelines . . . . This study finds that shifting from the current US diet to dietary Scenario 1 [same mix of foods but fewer calories] decreases energy use, blue water footprint, and GHG emissions by around 9%, while shifting to dietary Scenario 2 [holding calories consumed constant but shifting away from meat to fruit and veg] increases energy use by 43%, blue water footprint by 16%, and GHG emissions by 11 %. Shifting to dietary Scenario 3, which accounts for both reduced Caloric intake and a shift to the USDA recommended food mix, increases energy use by 38 %, blue water footprint by 10 %, and GHG emissions by 6 %. These perhaps counterintuitive results are primarily due to USDA recommendations for greater Caloric intake of fruits, vegetables, dairy, and fish/seafood, which have relatively high resource use and emissions per Calorie.”

So, what's going on here?  Didn't the authors of the latest (proposed) Nutritional Guidelines suggest less meat eating due to "sustainability" concerns?  Haven't we repeatedly read things like this quote from a story in Time in  2008? 

“It’s true that giving up that average 176 lb. of meat a year is one of the greenest lifestyle changes you can make as an individual. ”

A few comments about this latest study and how it relates to the "received wisdom."

First, meat eating often looks bad in aggregate because the industry is so big.  In the US, we eat a lot of meat.  As a group, animal products probably represent the largest share of food expenditures of any food category.  As a result, we need to put the outcomes on some kind of units where foods can be compared on an even playing field.  There are a lot of options: lbs of food produced, dollars spent, acres used, or as the current study uses, calories.  As I've discussed before:

“. . . 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.”

For what it's worth, this discussion is related to the debate on whether eating healthy is more or less expensive.  As it turns out: the answer depends how you measure it ($/lb or $/calorie) .

Second, it is important to think on the margin, or think in terms of changes.  Meat is bad.  Compared to what?  As I discussed in the Food Police,  many fruits and vegetables are big users of water and pesticides.  So, if we eat less meat, what will we eat more of instead, and what are the impacts of the items we switch to?  This recent study produces results that look a bit different because it looks not just at aggregates but at marginal changes.  

Third, as this study makes clear, "the environment" is not a single thing.  It is multidimensional.  Here's a graph from the paper.

Some foods are better water users, others worse in terms of GHS emission, others produce more calories/acre and spare more land, and so on.  Very rarely are there "have your cake and eat it too" moments, and there are typically tough tradeoffs between health, environment, and taste (and even tradeoffs within each of those categories).  One problem with studies like this is that they don't count the consumer welfare cost from eating a different mix of foods or different number of calories from what they normally consume, so we don't have any sense for the tradeoff between taste and cost on the one hand and health and the environment on the other.  

The last comment is that it's tough for me to evaluate the "quality" of this paper, and one should probably be a bit careful of suffering from confirmation bias.  A lot of the assumptions driving the result actually come from other papers and analyses.  Moreover, the work was published in a relatively new journal (started in 2012) and I know nothing about it. [update: a follower on Twitter informed me that the journal has been around since the 1980's but recently changed its name]  However, it does appear that the authors' results are similar to those in another paper that the Nutritional Guidelines Committee actually discussed in their report.  The committee writes: 

“a report from Heller and Keoleian suggests that an isocaloric shift from the average U.S. diet (at current U.S. per capita intake of 2,534 kcals/day from Loss-Adjusted Food Availability (LAFA) data) to a pattern that adheres to the 2010 Dietary Guidelines for Americans would result in a 12 percent increase in diet-related GHG emissions. This result was modified, however, by their finding that if Americans consumed the recommended pattern within the recommended calorie intake level of 2,000 kcal/day, there would be a 1 percent decrease in GHG emissions.”

But, of course, people don't just follow the guidelines to a tee.  That's one reason why these sorts of guidelines and recommendations should consider consumers' behavioral responses to the policies in question.

Is the growth in agricultural productivity slowing?

Last week I gave a talk at the University of Nebraska, and Julian Alston from UC Davis was also there.  He presented some recent research with Matt Anderson and Phil Pardey about productivity growth in agriculture.  While I have seen some discussions about the possibility of a slowdown in productivity growth in developing countries, Alston's research suggest it is a phenomenon alive and well here at home.  This is important stuff.  Falling productivity growth has important implications for sustainability, food security, and research and development. They write: 

“We detect sizable and significant slowdowns in the rate of productivity growth. Across the 48 contiguous states for which we have very detailed data for 1949– 2007, U.S. multifactor productivity (MFP) growth averaged just 1.18 percent per year during 1990–2007 compared with 2.02 percent per year for the period 1949–1990. MFP in 44 of the 48 states has been growing at a statistically slower rate since 1990. Using a longer-run national series, since 1990 productivity growth has slowed compared with its longer-run growth rate, which averaged 1.52 percent per year for the entire period, 1910–2007. More subtly, the historically rapid rates of MFP growth during the 1960s, 1970s and 1980s can be seen as an aberration relative to the long-run trend. A cubic time-trend model fits the data very well, with an inflection around 1962. We speculate that a wave of technological progress through the middle of the twentieth century—reflecting the progressive adoption of various mechanical innovations, improved crop varieties, synthetic fertilizers and other chemicals, each in a decades long process—contributed to a sustained surge of faster-than-normal productivity growth throughout the third quarter of the century. A particular feature of this process was to move people off farms, a one-time transformation of agriculture that was largely completed by 1980.”

Here's a graph from their paper showing the change in proportional growth rate in yields (i.e., the log of yields) over time for 6 crops with the inflection point indicated for when growth rates began decelerating.