Unpicking the ‘Wood-Wide Web’
In November 2017, this magazine reported a study of subterranean meshworks of fungi in northern hemisphere forests. The study, from the University of British Columbia, claimed that trees were exchanging resources across these so-called common mycorrhizal networks (CMNs), and that mature trees were using them to extend a helping hand—and chemical warnings—to surrounding seedlings. The notion that trees talk and co-operate with one another—dubbed the ‘wood-wide web’—was snapped up by storytellers (including me: see The Wood-Wide Web, Issue 148), and soon graced shows like Avatar and The Last of Us. But a recent review, published in the journal Nature Ecology & Evolution, now says that study was flawed: “The claim that mature trees preferentially send resources and defence signals to offspring through CMNs has no peer-reviewed, published evidence.” The reviewers point out that many other field studies never found CMNs: “With current technology, it is difficult to confirm that continuous, non-transient mycelial connections exist between trees in the field.” Reviewers also castigated the original study for ‘citation bias’, in which researchers preferentially reference only other studies, including their own, that support their conclusions. Such bias can snowball: “The number of unsupported claims regarding mycorrhizal networks has doubled in the past 25 years in the scientific literature,” noted the reviewers. It’s a timely reminder—if any were needed—that life doesn’t imitate Avatar.
