The idea that trees communicate and share resources via a huge network of underground fungi is a compelling one. The notion first surfaced in academia in the 1990s and quickly mushroomed — ahem — into popular media from there. But does the data support the idea?
A new paper published in the journal Nature examines 20 years of research and media coverage on the webs of fungi, known as common mycorrhizal networks (CMNs). The paper’s conclusion is — I’m sad to say — that the jury on fungi-facilitated cooperation is still very much out.
Fungal networks like the one shown here provide soil nutrients to trees in return for sugars and fats from photosynthesis. But do they help trees ‘communicate?’ It’s still up for debate. Photo: Shutterstock
“Recently, CMNs have captured the interest of broad audiences, especially with respect to forest function and management. We are concerned, however, that recent claims in the popular media about CMNs in forests are disconnected from evidence, and that bias towards citing positive effects of CMNs has developed in the scientific literature,” the paper’s authors wrote in the abstract.
Luckily there are scientists with a willingness to share their deep knowledge of such technical papers with plebes like you and me.
Unraveling two decades of coverage
Over at The Conversation, a website devoted to clarifying scientific research, soil scientists and break down the paper and its implications.
“In lab and field experiments, the amount of carbon and other resources transferred between plants is typically small and stays mostly in the mycorrhizal roots,” Field and Magkourilou write. “This means that while fungi are receiving carbon from one plant, much of it probably stays with the fungus rather than being transferred to another plant. This raises the question of how important these transfers might actually be to trees in a forest.”
The pair go on to explain that much of the popular media coverage around the subject has focused on tree communication, without taking into account what the fungi are doing (and why).
“It is just as likely that the transfer of food between plants is driven by fungal appetite as it is fungal altruism. These considerations underline the need for more research to understand the role of mycorrhizal networks in transmitting resources and information through communities of plants.”
How positive citation bias distorts perception
Another factor the original paper calls attention to is a concept called “positive citation bias.” Essentially, the media is more likely to report on scientific papers that render positive results over negative ones. The upshot is that papers providing evidence of fungal-driven tree communication are more widely distributed than papers that show no such findings.
“Many papers attribute their observed effects to potential common mycorrhizal networks but are then quoted as offering hard proof of their existence and function. And while the use of anthropomorphic language, such as ‘talk’, ‘share’, and ‘trade’, can help to simplify and communicate findings, it can also distort the complexity and prevent a full understanding of a natural phenomenon,” Field and Magkourilou conclude, echoing the sentiments expressed by the original paper’s authors.
The long and short of it? We still don’t know nearly as much about the natural world and how it works as most people think.
