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.  

Nutritional Guidelines Redux

By now, I'm sure many readers have seen the announcement that the secretaries of the USDA and HHS have announced that the latest dietary guidelines will NOT include issues of sustainability.

This is a topic I've commented on several times in the past, and I was interviewed by Stewart Varney on the Fox Business Network yesterday about the development (I haven't found a link yet to post).

Here are just a few scattered thoughts and comments.

First, it is a bit odd that the nutritional guidelines don't consider behavioral responses of consumers.  That is, if it is recommended not to eat food type X, then what will consumers switch to eating instead?  Note that the question isn't: what do we wish consumers would eat instead, but rather what substitutions will actually occur?  This issue was highlighted in a post by Aaron Carroll on the NYT Upshot blog when discussing a large study that showed reducing saturated fat intake didn't produce noticeable health benefits: 

“The study also resulted in a reduction of unsaturated fats and an increase in carbs. That’s specifically what the committee argues shouldn’t happen. It says that bad fats should be replaced with better fats. However, people did reduce their saturated fats to 10 percent of intake, and didn’t see real improvements in outcomes. This has led many to question whether the quantitative recommendation made by the committee is supported by research.”

In a day and age when behavioral economics is all the rage, and is even being required by the White House, it is a bit absurd to believe consumers will follow all the guidelines and recommendations to-a-tee.  A more pragmatic approach is to realize most people will devote enough attention to get a couple take-home messages, and then act.  We need to study how consumers will actually substitute given their preferences and the messages they digest.  This isn't necessarily a critique of information behind the guidelines themselves (after all, we do want some systematic, scientific summary of the state of nutritional knowledge), but rather a call for research on how the guidelines are actually implemented and communicated and are ultimately used by consumers.

Second, this article by Tania Lombrozo at NPR touches on an issue I addressed several months ago: when guidelines mix nutrition and "sustainability", it necessarily involves value judgments not  science.  She writes:

“Science can (and should) inform our decisions, but you can’t read off policy from science. Invoking science as an arbiter for questions of values isn’t just misguided, it’s dangerous — it fails to recognize what science can (and can’t) provide and it fails to make room for the conversations we should be having: conversations about the kinds of lives we ought to live, the obligations we have to each other, to future humans and to other animals, and — among other things — what that means for the food choices we make every day.”

Finally, looking at a lot of discussion surrounding this issue, while the guidelines purportedly discuss "sustainability" - the issue is often boiled down to a single issue: greenhouse gas emissions.  While it is clear that beef is a larger emitter of greenhouse gasses than most other animal and plant-based food, the impacts need to be placed in context.  In the US, livestock production probably accounts for a very small percentage of all all greenhouse gas emissions.  Telling people to eat less meat will likely have small effects on greenhouse gas emissions.  My gut feeling is that further investments in productivity-enhancing research will have a larger effect on greenhouse gas emissions than cajoling consumers.  

In other places discussing "sustainability" the issue of food security is mentioned, as is resource use.  To an economist's ears, when I hear "resource use", I immediately think of prices.  Prices are the mechanism by which resources get efficiently allocated in a market-based economy.  As such, it gives me pause when I think of a report by a a group of nutritionists making recommendations on proper resource use.   I'd never trust a dictator (or even a group of economists) on having enough knowledge to making optimal decisions on resource use.  Beef is a relatively expensive food.  That tells us it is using a lot of resources, and that higher price causes us to eat less than we otherwise would.  

But, what about externalities?  To the extent beef production uses a lot of corn or land, that's already reflected in the price of beef.  But, does the price of beef reflect water use and potential (long run) impacts of greenhouse has emissions?  Probably not fully.  So, the key there is to try to get the prices right.  Well functioning water markets would be a start.  Greg Mankiw recently had an interview on getting the price of carbon right.  Once the prices are right, then "recommendations" regarding resource use are somewhat meaningless: you're either willing to pay (and able) the price to buy the items you like to eat or not.