Where the ‘Wood-Wide Web’ Narrative Went Wrong

Lambert: Disappointing (?).

By Melanie Jones, professor in the Biology Department at the University of British Columbia’s Okanagan campus, Jason Hoeksema, a professor in the Department of Biology at the University of Mississippi, and Justine Karst, an associate professor in the Department of Renewable Resources at the University of Alberta. Originally published at Undark.

Over the past few years, a fascinating narrative about forests and fungi has captured the public imagination. It holds that the roots of neighboring trees can be connected by fungal filaments, forming massive underground networks that can span entire forests — a so-called wood-wide web. Through this web, the story goes, trees share carbon, water, and other nutrients, and even send chemical warnings of dangers such as insect attacks. The narrative — recounted in books, podcasts, TV series, documentaries, and news articles — has prompted some experts to rethink not only forest management but the relationships between self-interest and altruism in human society.

But is any of it true?

The three of us have studied forest fungi for our whole careers, and even we were surprised by some of the more extraordinary claims surfacing in the media about the wood-wide web. Thinking we had missed something, we thoroughly reviewed 26 field studies, including several of our own, that looked at the role fungal networks play in resource transfer in forests. What we found shows how easily confirmation bias, unchecked claims, and credulous news reporting can, over time, distort research findings beyond recognition. It should serve as a cautionary tale for scientists and journalists alike. 

First, let’s be clear: Fungi do grow inside and on tree roots, forming a symbiosis called a mycorrhiza, or fungus-root. Mycorrhizae are essential for the normal growth of trees. Among other things, the fungi can take up from the soil, and transfer to the tree, nutrients that roots could not otherwise access. In return, fungi receive from the roots sugars they need to grow.

As fungal filaments spread out through forest soil, they will often, at least temporarily, physically connect the roots of two neighboring trees. The resulting system of interconnected tree roots is called a common mycorrhizal network, or CMN.

When people speak of the wood-wide web, they are generally referring to CMNs. But there’s very little that scientists can say with certainty about how, and to what extent, trees interact via CMNs. Unfortunately, that hasn’t prevented the emergence of wildly speculative claims, often with little or no experimental evidence to back them up.

One common assertion is that seedlings benefit from being connected to mature trees via CMNs. However, across the 28 experiments that directly tackled that question, the answer varied depending on the trees’ species, and on when, where, and in what type of soil the seedling is planted. In other words, there is no consensus. Allowed to form CMNs with larger trees, some seedlings seem to perform better, others worse, and still others seem to behave no differently at all. Field experiments designed to allow roots of trees and seedlings to intermingle — as they would in natural forest conditions — cast still more doubt on the seedling hypothesis: In only 18 percent of those studies were the positive effects of CMNs strong enough to overcome the negative effects of root interactions. To say that seedlings generally grow or survive better when connected to CMNs is to make a generalization that simply isn’t supported by the published research.

Other widely reported claims — that trees use CMNs to signal danger, to recognize offspring, or to share nutrients with other trees — are based on similarly thin or misinterpreted evidence. How did such a weakly sourced narrative take such a strong grip on the public imagination?

We scientists shoulder some of the blame. We’re human. Years ago, when the early experiments were being done on forest fungi, some of us — the authors of this essay included — simply got caught up in the excitement of a new idea.

One of us (Jones) was involved in the first major field study on CMNs, published more than 25 years ago. That study found evidence of net carbon transfer between seedlings of two different species, and it posited that most of the carbon was transported through CMNs, while downplaying other possible explanations. This is what’s known as “confirmation bias,” and it is an easy trap to fall into. As hard as it is to admit, it was only due to our skepticism of the recent extraordinary claims about the wood-wide web that we looked back and saw the bias in our own work.

Over decades, these and other distortions have propagated in the academic literature on CMNs, steering the scientific discourse further and further away from reality, similar to a game of “telephone.” In our review, we found that the results of older, influential field studies of CMNs have been increasingly misrepresented by the newer papers that cite them. Among peer reviewed papers published in 2022, fewer than half the statements made about the original field studies could be considered accurate. A 2009 study that used genetic techniques to map the distribution of mycorrhizal fungi, for instance, is now frequently cited as evidence that trees transfer nutrients to one another through CMNs — even though that study did not actually investigate nutrient transfer. In addition, alternative hypotheses provided by the original authors were typically not mentioned in the newer studies.

As these biases have spilled over into the media, the narrative has caught fire. And no wonder: If scientists themselves could be seduced by potentially sensational findings, it is not surprising that the media could too.

Journalists told emotional, persuasive, and seductive stories about the wood-wide web, amplifying the speculations of a few scientists through powerful storytelling. Writers imbued trees with human qualities, portraying them as conscious actors using fungi to serve their needs. Fantasy moved to the foreground, facts to the back. In an odd kind of mutual reinforcement, the media blitz may have convinced experts in other subfields of ecology that the claims about CMNs were well-founded.

The episode underscores how important it is for journalists to seek out a broad range of expert opinions, and to challenge us scientists when our assertions aren’t clearly backed up by rigorous research. By directly asking scientists questions such as “What other phenomena could explain your results?” and “How many other studies support this hypothesis?” journalists may be able to better understand and convey some of the uncertainty around scientific conclusions. The best science writing can capture the hearts and minds of the public, but it must be true to the evidence and the scientific process. If not, the consequences can be far-reaching, affecting policy decisions that impact real people.

There are many captivating and scientifically well-grounded stories we can tell about fungi in forests — and we should. Mycorrhizal fungi underlie many of our favorite edible mushrooms, including truffles, chanterelles, and porcinis. And some herbs in the understories of forests, rather than photosynthesizing sugars like a normal plant, use CMNs to connect to trees and steal their sugars. Forests are fascinating places, marked by a rich diversity of interactions between plants, animals, and microbes. The stories are endless. We just have to tell them with care.

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About Lambert Strether

Readers, I have had a correspondent characterize my views as realistic cynical. Let me briefly explain them. I believe in universal programs that provide concrete material benefits, especially to the working class. Medicare for All is the prime example, but tuition-free college and a Post Office Bank also fall under this heading. So do a Jobs Guarantee and a Debt Jubilee. Clearly, neither liberal Democrats nor conservative Republicans can deliver on such programs, because the two are different flavors of neoliberalism (“Because markets”). I don’t much care about the “ism” that delivers the benefits, although whichever one does have to put common humanity first, as opposed to markets. Could be a second FDR saving capitalism, democratic socialism leashing and collaring it, or communism razing it. I don’t much care, as long as the benefits are delivered. To me, the key issue — and this is why Medicare for All is always first with me — is the tens of thousands of excess “deaths from despair,” as described by the Case-Deaton study, and other recent studies. That enormous body count makes Medicare for All, at the very least, a moral and strategic imperative. And that level of suffering and organic damage makes the concerns of identity politics — even the worthy fight to help the refugees Bush, Obama, and Clinton’s wars created — bright shiny objects by comparison. Hence my frustration with the news flow — currently in my view the swirling intersection of two, separate Shock Doctrine campaigns, one by the Administration, and the other by out-of-power liberals and their allies in the State and in the press — a news flow that constantly forces me to focus on matters that I regard as of secondary importance to the excess deaths. What kind of political economy is it that halts or even reverses the increases in life expectancy that civilized societies have achieved? I am also very hopeful that the continuing destruction of both party establishments will open the space for voices supporting programs similar to those I have listed; let’s call such voices “the left.” Volatility creates opportunity, especially if the Democrat establishment, which puts markets first and opposes all such programs, isn’t allowed to get back into the saddle. Eyes on the prize! I love the tactical level, and secretly love even the horse race, since I’ve been blogging about it daily for fourteen years, but everything I write has this perspective at the back of it.


  1. Steve H.

    I don’t care, my mouth still waters when I dig my fingers through my bark-soil.

    have I been assimilated?…

  2. .Tom

    > “As these biases have spilled over into the media, the narrative has caught fire. And no wonder: If scientists themselves could be seduced by potentially sensational findings, it is not surprising that the media could too.”

    I am frequently impressed by the arrogance of scientists, of which this is a nice example.

    1. juno mas

      The article is actually quite circumspect. How is the author being arrogant?

      I have a science background in plant biology and soils. I’ve always been skeptical of the concept of “wood-wide web”. The transfer of nutrients between plants and the soil micro-biome has always been dominated by chemical reactions not sentience

      1. Henry Moon Pie

        My guess is that there is in many of us, from the scientists to the media to the reader, among those who have some understanding of our situation, a longing for Nature to be our magical, helping friend as we enter this catastrophe. It will be hard for us to hold onto that as the Nature we’ve distorted unleashes some of that energy we’ve packed into it with our “runnin’ ’round on fossil fuel.” We may long just to feel that Nature is indifferent to us rather than determined to destroy us.

        Heaven and earth aren’t humane.
        To them, the ten thousand things
        are straw dogs.

        Tao te Ching #5 (Le Guin rendition)

  3. Joe Well

    There is a major omission in this wonderful piece on how unsupported and even false narrative about science take root:

    The role of university, corporate and other institutional PR departments, including house newsletters like the Harvard Gazette, which put out hyped up press releases.

    Everyone knows that a lot of “soft” news is little more than rewritten press releases, so the root of the problem is there.

    But everyone in the food chain from the scientists to the news publishers has an interest in keeping the hype going…until it inevitably dies down and someone can get new hype by debunking it.

    1. Dick Swenson

      This is a perfect example of how the nonsense phrase “artificial intelligence” became so pervasive.

      This phrase created around 1959 by John McCarthy at MIT to describe a summer school for which he wanted funding became a keyword when discussing computer enhanced activities, e.g., game playing (chess, checkers, GO, etc.), Language efforts (translation, speech to script or v. v. such as SIRI), and every sort of computer effort. All these efforts were sophisticated, complicated to implement, and often requiried large amounts of time and data. Music was also being “enhanced. Think of itms such as the MOOG synthesizer.

      BUT none ever evidenced “intelligence.” They are all just computer programs. Many of the developers (and advocates) assume that “thinking” and “intelligence” are mechanical processes that can be programmed on computers. If you start with this assumption then computer programs will some day be intelligent. This is an example where results confirm assumptions used in developing the results.

      Science is no different than politics and the other social activities, e. g., economics, sociology, etc. And scientists (real ones, at least) are also human beings. They are subject to the same kinds of infuences to which we all succumb which include a desire for fame and fortune and the desire to be noticed while still alive.

      Myths and generalizations are all part of the human process. Admitting them when they go awry is seldom rewarded.

  4. jefemt

    Not to worry, the good news is all this data will be incorporated into AI and future decision making!

    Garbage in, Garbage out— Upcycle to AI!

    And I don’t think the fungi are the type that cause hallucinations to which AI seems prone.


  5. Michael

    So, just the facts m’am?

    It seems the story tellers performed their role admirably.

    Now the scientists have to excise their biases and poor trade craft.

    and the band played on!

  6. New Okie

    While it is always frustrating to hear about arrogance in any field (and come on, the supposed experts in a field with a whole 26 studies to read–some of which they wrote themselves– are only now going over them with a critical eye?) I still applaud the authors for having the humility to course correct. So much science nowadays starts with a conclusion, and when the conclusion proves false (or at least not conclusively true) the authors seem terrified to even admit it. Which, as many have noted before me, is not science, but a religion.

  7. The Rev Kev

    Maybe the real story is that we are now nearly a quarter of the way through the 21st century and we still don’t know how things like soil and fungi and trees really work. I find that rather remarkable.

    1. Henry Moon Pie

      That is both remarkable and sad. I’m reminded of a famous Wendell Berry quote:

      We have lived by the assumption that what was good for us would be good for the world. And this has been based on the even flimsier assumption that we could know with any certainty what was good even for us. We have fulfilled the danger of this by making our personal pride and greed the standard of our behavior toward the world – to the incalculable disadvantage of the world and every living thing in it. And now, perhaps very close to too late, our great error has become clear. It is not only our own creativity – our own capacity for life – that is stifled by our arrogant assumption; the creation itself is stifled.

      We have been wrong. We must change our lives, so that it will be possible to live by the contrary assumption that what is good for the world will be good for us. And that requires that we make the effort to know the world and to learn what is good for it. We must learn to cooperate in its processes, and to yield to its limits. But even more important, we must learn to acknowledge that the creation is full of mystery; we will never entirely understand it.

  8. Eclair

    Rats! I had been thinking that here was a ‘religion’ I could grok. The word, ‘religion,’ being, maybe, derived from the Latin, religare, ‘to bind. To hold together, to tie fast.

    Up there, in the sky, there resides God, (male, natch), who is actually three Gods (Father, Son, Holy Spirit.) And, the Son was born to a human female, back 2,000 years ago, who had been impregnated by the Holy Spirit, so she was technically still a virgin. This human Son, grew up to be a radical, who agitated against the Roman occupation and the Vichy-like local ruling class, so they killed him in a most barbaric manner. But, being God, he came back from the dead, hung around for a few weeks, then ascended back into the sky, to merge back into his Father and Holy Ghost, and become the One God demanded by monotheism.

    Humans gotta believe in something that will bind them together, otherwise we devolve into individual, self-maximizing consumer units, monetizing the hell out of every object and transaction. (Oops! Are we there already?)

    Me, I prefer the ‘trees talk to each other, feel pain, help their neighbors, nurture their baby seedlings,’ model. Makes me think before I take my nifty chain saw and cut one down. Makes me aware that, as a so-called ‘human,’ I am not so very special.

      1. Arizona Slim

        Me? I am in Tucson, Arizona.

        If I hugged my trees, I would be in some serious pain. In this part of the world, trees have thorns.

      2. lyman alpha blob

        Hug them all except for the Norway maples. Those can go into the chipper.

  9. Cetra Ess

    We’re still left needing to explain how Wohlleben’s 500 year old tree stump had observable chlorophyls despite having no foliage, which I think is where he got the idea that it was perhaps coming from neighbouring trees? Was this the source for the idea that trees support each other?

  10. Sub-Boreal

    For soil fans, here’s a really nice review article (open-access) which lays out the evidence in favour of maintaining a network of living roots in managed forest stands. It makes a strong case for a style of forestry that keeps a generous number of green trees after extracting some stems for harvest.

    It shows that there’s a multitude of things going on below-ground in the zone around living roots (rhizosphere), and these are quantitatively significant for carbon behaviour at the stand level. There’s a large body of evidence cited, without needing to make more speculative assertions about the kinds of linkages invoked by advocates of the “wood-wide web” model.

    An estimated half of the carbon fixed by trees is transported belowground, a portion of which is exuded into the soil where it fuels a complex belowground food web. The biological transformation of exudates into microbial metabolites and necromass is a major source of soil organic matter (SOM), including persistent mineral-associated organic matter (MAOM). Recent recognition of the fundamental importance of these inputs from living roots for sustaining life belowground and replenishing SOM demands a rethinking of how we harvest forests. By severing the lifeline of living roots, clearcut harvesting devastates much of the belowground biodiversity in forests, and prohibits a principal pathway through which SOM and C stocks are replenished. Retention harvesting retains the influence of living roots within retention patches and potentially throughout the harvested area, but only if inter-tree distances are 15 m or less. Retention trees sustain and support the re-establishment of belowground life and function following forest harvest and may mitigate post-harvest soil C losses. Sustaining the belowground ecosystem via inputs from living roots is an underappreciated benefit of continuous-cover and retention forestry.

    As a soil scientist, I’ve found this whole controversy quite fascinating, not least because it brings attention to one of the less charismatic back-channels of environmental science. I don’t really have a dog in this fight; I know some of the proponents of different points of view either personally or through their papers, and they’re all top-calibre people, doing their best work. But it’s really complex stuff, and it has important implications for practical decisions about how to manage forests. This work needs all of the capable, inquisitive people it can manage to attract!

  11. Deacon Sieve

    Thanks Sub-Boreal for the citation. I would have liked to see some more citations in the original post supporting the claims.

  12. les online

    Darn ! There goes the idea i had of making loads of money from writing songs, and kids books, about funguys…And you’ve got me wondering if i should dump my copy of Peter Kropotkin’s “Mutual Aid” throughout nature, because he might have only imagined it…

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