Nathan Johnson, Director of Public Lands, March 26, 2019
Who doesn’t love a good science fiction story? Sometimes fantasy is closer to reality than we may realize. As many readers may recall, the eco-conscious 2009 blockbuster film “Avatar” transported viewers to a lush alien moon whose forest ecology formed a vast connected neural network. The lanky, blue-skinned alien protagonists of the film, the “Na’vi,” lived in a massive, ancient tree (the “Tree of Souls”) that anchored the network and dominated the surrounding landscape.
As it turns out, this neural network-like interconnection of forests is not fantasy — it’s the norm. Natural forests are communities of trees and plants that communicate with one another, nurture one another, and protect one another. Their “neural” interconnection comes in the form of fungal networks. At the micro level, fungi form bonds with and sheath tree roots. At the larger level, these same fungi can extend over vast distances, connecting hundreds and even thousands of trees to one another. Emerging science has dubbed this phenomenon the “Wood Wide Web.” The technical term is “mycorrhizal network.”
In any healthy forest, mycorrhizal fungi and trees rely on each other. Trees convert sunlight and carbon from the atmosphere into sugars that they then pass along to the fungal network. In exchange, the fungi send water and soil nutrients to the trees. The network also enables trees to pass along biochemical and electrical signals to other networked trees. This resulting inter-tree communication, or “tree talk,” includes warning signals about insect predators. When under attack by hungry insects, trees send chemical signals into the network. Connected trees get the message and pump bitter tannins into their tissues and leaves, discouraging would-be leaf-munchers.
And, this may sound strange, but some trees can and do form family units. Emerging science has shown that “mother trees” can use the fungal network to selectively share nutrients with their own seedlings at a greater rate than they do with other seedlings of different species or even with non-kin seedlings of the same species. Similarly, dying trees have been found to rapidly shuttle their nutrients into the system, thereby providing a burst of legacy energy and information to younger generations of trees in the network.
Much like the “Tree of Souls” featured in Avatar, large old trees tend to serve as especially important network hubs, surrounded by dense fungal networks. These ancient trees have far more numerous and robust mycorrhizal connections than younger, smaller trees. Older forests are also more biodiverse and have more well-established and diverse fungal communities. High mycorrhizal fungal diversity can help trees resist disease and drought, help them grow faster, and help them store more carbon.
In short, intact and well networked forests are resilient forests. These forests are in close communication. They’re sharing resources. Their constituent parts are warning and defending each other. Our forests will need to be resilient to survive and succeed through the coming (and already arriving) ravages of climate change. In Part II, we’ll talk about the role of old forests in capturing and storing carbon (our climate-fighting super-weapons), and what happens to complex fungal networks and forest resiliency when heavy logging enters the picture.
In the meantime, you may want to ask yourself what the trees are chatting about when you’re next in the woods.