Like humans, trees are extremely social creatures, utterly dependent on each other for their survival. And, as it is with us, communication is key.
After scientists discovered pine tree roots could transfer carbon to other pine tree roots in a lab, ecology professor Suzanne Simard set out to figure out how they did it. What she discovered was a vast tangled web of hair-like mushroom roots — an information super highway allowing trees to communicate important messages to other members of their species and related species, such that the forest behaves as “a single organism.”
The idea that trees could share information underground was controversial. Some of Simard’s colleagues thought she was crazy. Having trouble finding research funding, she eventually set out to conduct the experiments herself, planting 240 birch, fir and cedar trees in a Canadian forest. She covered the seedlings with plastic bags and filled them with various types of carbon gas. An hour later she took the bags off, ran her Geiger counter over their leaves and heard “the most beautiful sound,” she says in the Ted Talk.
“Crrrrr… It was the sound of Birch talking to Fir,” she said. “Birch was saying, ‘hey, can I help you?’” “And Fir was saying yeah, can you send me some of your carbon? Somebody threw a shade cloth over me.”
She also scanned the cedar’s leaves, and as she suspected — silence. The cedar was in its own world. It was not connected into the fungal web linking birches and firs. The birch and fir were in a “lively two-way conversation,” Simard says. When the fir was shaded by the birch in summer, the birch sent more carbon to it. When the birch was leafless in the winter, the fir sent more carbon to it.
The two trees were totally interdependent, Simard discovered, “like yin and yang.”
That’s when Simard knew she was onto something big… In the past, we assumed trees were competing with each other for carbon, sunlight, water and nutrients. But Simard’s work showed us trees were also cooperators.
They communicate by sending mysterious chemical and hormonal signals to each other via the mycelium, to determine which trees need more carbon, nitrogen, phosphorus and carbon, and which trees have some to spare, sending the elements back and forth to each other until the entire forest is balanced. “The web is so dense there can be hundreds of kilometers of mycelium under a single foot step,” Simard says.
The mycelium web connects mother trees with baby trees, allowing them to feed their young. A single mother tree can provide nourishment for hundreds of smaller trees in the under-story of her branches, she says. Mother trees even recognize their kin, sending them more mycelium and carbon annd reducing their own root size to make room for their babies.
This new understanding of tree communication had Simard worried about the implications of clear-cutting. When mother trees are injured or dying, they send their wisdom onto the next generation. They can’t do this is if they are all wiped out at once. “You can take out one or two hub trees, but there comes a tipping point, if you take out one too many, the whole system collapses,” she says. Often clear-cut forests are replanted with only one or two species. “These simplified forests lack complexity making them vulnerable to infection and bugs.”
To ensure the survival of the planet’s lungs at a time when they are most crucial, Simard suggests four simple solutions to end the damage caused by clear cutting :
