Microbial terroir? The media gets it wrong again (surprise)

As has by now been widely publicized in wine circles and elsewhere, Dr. David Mills and graduate student Nicholas Bokulich of UC Davis have just published a journal article (in the Early Edition of the Proceedings of the National Academy of Sciences here) demonstrating that populations of bacteria and yeast associated with wine grapes vary geographically in organized and predictable ways. Bokulich collected samples across California, isolated bacteria and yeast from those samples, sequenced bits of their DNA, and then looked for patterns.

This is a beautiful, extremely strong study with useful implications. Unfortunately but unsurprisingly, the news headlines are getting much of it wrong. The New York Times article on the subject* sets up the long-standing American skepticism about terroir, then proclaims that “American researchers may have penetrated the veil that hides the landscape of terroir from clear view, at least in part. They have seized on a plausible aspect of terroir that can be scientifically measured – the fungi and bacteria that grow on the surface of the wine grape.” This is the kind of unscientific media hogwash that contributes to people on the street having balderdash-worthy ideas about how science works. I can’t blame the article’s author for being one more journalist who doesn’t understand science (or who knows better but still needs the sexy story). I can blame the NY Times for not having the sense or taking the effort to get someone with enough research knowledge to cover the story well (Inside Scoop SF did, though they do have Jon Bonné). You’re the NY Times; you folks can do this.

Problem #1: Bokulich and Mills’ findings don’t actually say anything about terroir as we typically talk about it: in terms of sensory impact. The paper describes regional variations. The paper doesn’t connect those variations with any element of wine quality, perceptible or otherwise.

Problem #2: This is not the first time researchers have attempted to quantify some element of terroir. Not even close. Geologists and pedologists (soil scientists) have done a lot of good work looking at soil structure, depth, aspect, and so forth. Other microbiologists have looked at differences in bacteria and yeast across space. Bokulich’s study is exceptionally strong, but it’s not as earth-shatteringly unique as the media are making it out to be.

Problem #3: A technical point, but Bokulich and Mills didn’t actually look at microbes on the surface of grapes. They collected grape musts, which for them meant “destemmed, crushed grapes, representing a mixed, aggregate sample of all grapes from an individual vineyard block” collected after ordinary stemming and crushing operations at the winery. The strength of looking at musts is in having a sample that reflects averaging across a vineyard block and does away with potentially idiosyncratic variations between individual grapes. The main weakness is that we’re a lot less sure of where the microbes came from. What if some of the microbes came from the winery equipment or from handling operations instead of being present on the grapes in the vineyard? Significant regional patterns correlated with environmental factors – precipitation and temperature, for example – but we still can’t actually pinpoint where those microbes are originating.

The NY Times article does a pretty good job of summarizing the original PNAS paper. Kudos to it’s author for talking a bit about the methods behind the findings, for observing near the end of the piece that “the Davis scientists still need to prove that these microbes affect the quality of the wine,” and for calling up Dr. Thomas Henick-Kling at Washington State University for a second opinion. The problem is in the headline and the first few paragraphs which are, of course, what get picked up and misconstrued by everyone else.

This is a fine example of a frequent pattern in news science coverage. Researchers publish a paper on a sexy topic like wine or cancer, and – being like other humans – their conclusions about the implications of their findings might take a few steps over the bounds of reasonability. The university and/or the academic journal puts out some kind of press release, highlighting the sexy bits and the in-our-dreams implications. Journalists pick up on the sexy bits and elaborate even sexier hooks and headlines around them. The hooks and headlines get picked up by less reputable news replicators and on Facebook and Twitter. And by now we’re wandering around smack-dab in the middle of unreasonableness territory.

A chicken-and-egg problem: do we get headlines like this because national science literacy is bad, or does poor science literacy stem (in part) from the uncritical quality of our media? Either way, there’s improving to be done here.

  • Wine-Searcher’s coverage has to get an honorable mention, not only for its especially unreasonable tag line – “New research suggests that bacteria and fungi could be as important in the expression of regionality as soil and climate” – but for referring to what we all know and love as Botrytis cinerea or Noble rot by the show-worthy name of its anamorph (another form of the same fungi), Botryotinia fuckeliana.

6 thoughts on “Microbial terroir? The media gets it wrong again (surprise)

      • Thanks for the link, Tony. Poor translations of scientific research by the media — very often on account of misplaced emphasis or inappropriate degrees of confidence — are unquestionably a common and serious problem in wine, in medicine, in anything with a catchy story. The problem is even reasonably well-documented in the academic literature…but no member of the casual public reading the news reads the academic literature. Doing a better job of educating journalists (and educating scientists about how to talk to journalists) and making the public more aware of the problem is the biggest hurdle.

  1. Though normally I would tend to agree with criticism of wine-science journalism, I feel impelled to defend them a little bit here. Your first issue, that the findings of the paper don’t say anything about terroir as such, is accurate in terms of the experiment itself, which doesn’t look at the quality or sensory impacts of these differences in microbial population. However, the authors do make plenty of allusions themselves to the kind of influence these differences must have on final wine quality. They have not yet proven it, but they say, outright, that “the nonrandom distribution of key taxa [their findings] with crucial impacts on wine quality supports the potential role of microbial biogeography in shaping wine terroir.” So in this case, justified or not, it doesn’t seem to be the journalists who were sexifying the results, they were taking this material directly from the paper.
    And I think the conclusion they are making here is a logical one, given, as they say, that “The chemicosensory distinction of wines from different growing regions is well established, providing the conceptual basis of wine terroir…” and “Likewise, the formative influences of many key grape-derived microbiota on wine quality characteristics are well described but whether their geographical distribution follows logical patterns—supporting a causative role in regional wine differences—has been unknown.”
    Sure, at this point we have only a correlation, but I think that it is, at least, reason to get excited about, because it is definitely a step closer to an “analyzable” basis for terroir than we’ve come to in the past. As you say, many other researcher have attempted to quantify elements of terroir, but this has often been without much success (we have yet to identify and agree on the underlying basis/bases for terroir), this does put a new spin on this type of research, and, potentially, one that could lead to clearer results – who knows?!

    It is an interesting debate that you bring up.. when communicating scientific results to the public, do we stick directly to the material reported in the paper, or do we boost up the sex-appeal a bit? In this case, I think that the NYTimes handled the story appropriately, as terroir IS a sexy subject, so why not take advantage of that fact to get people interested in the science behind it? I think that this article did justice to the fact that the science is very unclear on this issue, but that it is an interesting one and here we have a new approach that could be a novel way to explore the subject.

    ..Unrelatedly, I agree that it is oddly showy of wine-searcher to use Botryotinia fuckeliana. in place of Botrytis cinerea, but the authors of the paper did so as well (they do indicate the synonymity, but primarily refer to the more “show worthy” name), so again, maybe the journalists are taking more directly from the paper than it might seem..

  2. I had a detailed conversation with one of the leading international scientists in the field of wine yeast. If I told you his name you would know him straight away. He told me that despite extensive research he conducted, he had been unable to demonstrate vineyard yeast could be responsible for fermentation of juice in the winery. He could never find evidence of this. However he also said he couldn’t prove it didn’t occur! He firmly believed it was unlikely and proved that “natural” or indigenous yeast that complete fermentation are sourced from the winery not the vineyard. Like many experts he can’t really be bothered to disagree with the people who insist on believing what they want regardless of the scientific evidence ( and he thinks quaint ideas about wine that don’t have any basis in science are sort of cute)

    So terroir and vineyard microbiology – slim at best.

    • John,
      1. Scientists disagree with each other often, just like any other group of experts.
      2. In microbiology, as in most fields of inquiry, evidence trumps belief. Someone can disagree with the published literature, but the burden of proof is on him; “belief” doesn’t go far.
      3. “Slim at best?” I have no stakes in this game — I just appreciate the Bokulich paper — but this looks like a he-said, she-said scenario unless anyone has additional evidence to add.
      4. Why the secrecy about whom you were speaking to?

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