Tree Secrets Unveiled: The Social Network

A mushroom walks into a bar. The bartender says “We don’t serve mushrooms here”. The mushroom stops, shocked and says “Sorry I think you’re mistaken, I’m a fun-guy!”

Although arguably one of the lamest jokes in the world, it does nicely set the scene for the tree secrets we are going to unveil today; fungi, or more specifically, the Wood Wide Web. For this, we will have to dive deeper into the thriving world of organisms beneath the soil. In doing so, we tuck into the complex underground world of the roots, fungi and bacteria that enable trees to communicate with each other. This is their secret social network; 500 million years old and more complex than Facebook, Twitter and LinkedIn combined, let’s dig in. 

For years scientists pondered many different factors about trees, but the underground world remained in the unknown. Fast forward to the 1988 paper by the plant scientist E. I. Newman, “Mycorrhizal Links Between Plants: Their Functioning and Ecological Significance,”  in which Newman argued boldly for the existence of a “mycelial network” linking plants in a unique network of communication. From there, our knowledge has slowly gathered to a point where we can tell the story of a kind of secret, communicative trading system between fungi and trees. 

As trees go through photosynthesis, they leak sugars into the ground. Sugars are transported from the photosynthesizing leaves, via the stem to the roots, to support energy-consuming root activities, such as nutrient uptake. This sugar leakage provides energy for our subterranean fungi. They get sugar. In turn, they respond by giving the plants nutrients. Through this, the trees are able to tune into the fungal network and connect to each other. This system of communications has been coined “The Wood Wide Web.” 

The Wood Wide Web can be a way for trees to help each other. A mother tree can provide more nutrients to shaded seedlings to give them strong and healthy growth. A dying tree can dump its nutrients into the network and provide for other trees so its energy doesn’t go to waste. If being attacked by pests, the trees can send a chemical into the network that acts as a message, warning other trees to put up their defenses. There are “bad” guys in this story too. The network can be hacked by certain species who steal the nutrients to ensure their survival and sabotage others’ growth. This information has allowed us to look at forests in a different way, rather than seeing trees as lonely, individual species, we can look at them as part of a much bigger system, chatting and trading in a similar way to humans.

So, trees are whispering important information and sharing resources through this impressive network of mycorrhizal fungi, which are estimated to connect roughly 90% of all land plants. One scientist famous for his work to unveil the Wood Wide Web is Thomas Crowther and his team from the Crowther Lab at ETH Zurich alongside Stanford University in the US. These researchers used machine learning to map out this network. Dr. Thomas Crowther explained, “just like an MRI scan of the brain helps us to understand how the brain works, this global map of the fungi beneath the soil helps us to understand how global ecosystems work.” They used the Global Forest Initiative database, covering 1.2 million forest tree plots with 28,000 species from more than 70 countries. Their international study has produced the first map, which details the global mycorrhizal fungi networks that empower the secretive world of the Wood Wide Web. This information is useful in many ways, it aids researchers and conservationists in understanding how to restore certain bioregions around the world, and allows them to see the effects of climate change at a microscopic level.

Something really important to consider is that these kinds of fungi are some of the most vulnerable species to temperature rise. The ectomycorrhizal fungi (EM) is generally found in cold, dry climates and surrounds a tree’s root without penetrating them, thus allowing them to soak in what they need without disturbing the flow of information between trees. They store carbon and release it more slowly than their counterparts, the arbuscular fungi (AM). AM fungi infiltrates tree roots, is found in hotter, wetter climates and produces a faster carbon cycle. As the global temperature heats up, we are seeing a switch in some higher latitude forest areas from EM to AM, meaning forests lose parts of the network they rely on to communicate. This change can be considered as indirect, as the tree species composition shifts with the temperature rise. Climate change and the loss of chunks of the Wood Wide Web could result in accelerated warming, as the AM fungi spews carbon into the atmosphere. With roughly 60% of trees connected to and reliant on EM fungi, this would be a massive problem. 

However, as we gain more information about the importance of the fungi supporting trees, we can ensure we keep this in mind as we restore areas of forest. The data set we now have on these fungi allows scientists to not only see what is happening in ecosystems now, but also make accurate predictions for the future. So the social network that allows trees to communicate could also be vital in providing us with information on how to reverse and avoid its destruction. 

This intriguing social network that allows trees to communicate with each other and fungi to carry the messages does somewhat reiterate the importance of both respecting nature and being humbled by the fact that the technology that has developed organically as part of an ecosystem through millennia is the most intelligent technology out there, and always will be.