Where the ‘Wood-Wide Web’ Narrative Went Wrong
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.
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.
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.
Melanie Jones is a professor in the Biology Department at the University of British Columbia’s Okanagan campus. She and her students have been studying mycorrhizal fungal communities in forests, clearcuts, and wildfire sites in British Columbia for 35 years.
Jason Hoeksema is a professor in the Department of Biology at the University of Mississippi. His research addresses a diversity of questions regarding the ecological and evolutionary consequences of species interactions on populations, communities, and ecosystems.
Justine Karst is an associate professor in the Department of Renewable Resources at the University of Alberta. She has been studying the mycorrhizal ecology of forests for 20 years.