Nature’s Internet: How Trees Talk to Each Other in a Healthy Forest: Suzanne Simard at TEDxSeattle (Transcript)

Suzanne Simard

Suzanne Simard – TRANSCRIPT

The Coast Salish people say, “We are one.” For thousands of years they lived it. But we didn’t pay any attention. Most of us have forgotten that we’re connected to each other, and to nature, that we are one. But nature is not some separate thing, but an intimate part of us. And what we do on this Earth ripples through our ecosystems, our web of connections.

Now, the signs are undeniable: climate change, species extinctions, human suffering. We have forgotten. But for their faith, the people are connected through spirit to forests, and oceans and rivers and bears and salmon, the Coast Salish people were ignored. But truly, it does come down to a matter of faith, to trust and respect the relationships that make up the complexity of nature. But we said that’s unscientific. Western science requires exact measurements, visible proof, statistics. But make no mistake, the Coast Salish people were deeply scientific. How else could they have lived here for over 10,000 years in such prosperity?

In fact, they were more scientific than we. For us to look any deeper, that would have hampered progress. “There are trees in those forests, and our buildings need wood, and our printers need paper. We need to cut down the forests and replant those trees.” Now, how do I fit into this? Well, I come from a family of loggers. And while my family was up on the mountainsides cutting down trees, one here, one there, I was playing in the forest below, in the places that are seen and unseen, in the trees and the logs and the forest floor. And I believed that fairies lived there. And their job was to live in and protect the forest, just like my job. But the fairies couldn’t save that forest, and neither could I; actually, nobody could. Because the owner of the patch had to cut it down to feed his family. And that moment changed me forever. Actually, it motivated me.

And I went to school to study forestry. I wanted to understand the mystery of why forests felt so powerful to me. I wanted to save forests. Ironically though, the first job I got coming out of forestry school was to mark old growth trees for clearcutting, and then to replant those clearcuts with fast-growing firs and pines, and to weed out the unwanted species – the alders, the birches, the aspens. And you know what? Well, it’s because we considered them competitors, interfering with our profits. And I got pretty good at creating these shiny new monocultures. But you know, the questions kept piling up. Why was disease spreading through these plantations? Why was cutting out birch making the fir so sick?

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And I was also increasingly worried about the increasing rate of clearcutting. You see, I’d learned in school that about a century ago, that in Canada, in British Columbia, they developed this cutting plan to cut down all of the old growth trees in the working forest. I knew about it, I’d learned it in school. But it took me a long time to realize that the cutting was not going to stop. Nor the attitude that we could convert these old growth forests into nice marketable, neat plantations. It seemed to me that there was more to the forest than meets the eye. So, I returned to graduate school and I became fascinated with the underground, I wanted to understand the mystery of why these old growth forests were so powerful.

So, I looked at this UK study, and they were examining seedlings growing in the laboratory, and colonized them with this fungus, a mycorrhizal fungus. The fungus connected the seedlings in a web, and they transmitted carbon from one seedling to the other. A mycorrhiza is literally a fungus-root. In this symbiotic association the fungus grows through the soil picking up nutrients and water, and bringing them back to the plant, and trading them for photosynthetic carbon. It’s a symbiotic, mutualistic, reciprocal relationship. And most fascinating to me, these fungi could connect plants below ground.

So, I wondered, I thought back to my fir forests, and I wondered, could the fungi colonizing birch actually connect with fir and protect it? So, I did some research, I wanted to find out. My first question came back to that faith thing again. Even though we can’t see it, could these mycorrhizal fungi be connecting trees below ground? Well, it turns out that they can in real forests. Using DNA microsatellites, we uncovered this network in an old growth Douglas fir forest. In this picture, these circles represent Douglas fir trees. And the bigger and darker the circle, the bigger and older the tree. And those small, light circles in the middle, those are the seedlings growing in the understory. And these lines that are linking the circles, those are the interlinking mycorrhizal fungal highways. And you’ll notice that the biggest, darkest circles, the biggest, oldest trees, are the most highly connected. So, we call these ‘hub trees.’ and later, more fondly, we started to call them ‘mother trees.’ Because as it turns out, those mother trees are nurturing the young seedlings in the understory.

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Now, this map is of only two of what we think are 100 fungal species in the forest. Could you imagine if we’d been able to map all 100 species? Next I wanted to know, what might be flowing through this network? Well, it turns out, the very things that plants need to survive and grow. Things like carbon, and nutrients, and water. So, we use isotopes, carbon isotopes, and we label plants, and we were able to see the carbon transmix back and forth through this network, like messages transmitting through the internet. And when one seedling is under stress, if it’s small, or shaded, or nutrient poor, or senescing, the other plant sends more carbon. We figured out that it follows what’s called a source-sink gradient. From a robust source plant like an illuminated birch tree to a needful sink plant like an understory fir tree, and all this without harming the source plants. The next thing we wanted to know was, so this happens, but what does it really matter in forests? Well, it turns out if you shade one of the plants, if Douglas fir’s shaded in the understory, birch will send ten percent of its carbon, and that’s a lot of carbon. That’s enough for Douglas fir actually to make seeds.

Now, we haven’t figured out precisely what the amounts mean, but we do know that this transfer increases their survival and growth, and health of the seedlings growing in the understory. Now, I published this work in some pretty good journals. This particular article struck a chord. Lots of people were enthused. In fact, there is a whole bunch of new research all around the world that was inspired by this paper. But there were also critics who tried to discredit my work. In fact, there were a lot of papers written, keynote addresses given, press releases. And back home, a professional ethics letter was actually put on my file. And my work was called “a dog’s breakfast.”

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Now, I know that you know that this kind of intimidation is actually not that uncommon with breakthrough science, especially if it challenges the status quo. Knowing this, this didn’t stop me. I knew that my science was sound and rigorous, and I knew that one day it could change the way we view the environment. So, really motivated, I returned to my original question, because I still hadn’t quite answered it yet. And I wondered, could these webs, these networks, serve as more than just avenues of exchange of carbon and nutrients and water. Could a tree that’s under stress, diseased, actually benefit from the health of its neighbors? Could birch be helping fir?

So, I did some more experiments, and it turns out, it does. When Douglas fir is under stress or disease, it sends warning signals to its neighbors, and the neighbors respond by increasing production of their defense enzymes, and they’re more resistant to disease. And if that neighbor is a birch tree, the fir benefits from the antibiotic-producing bacteria that are associated with this shared network. It’s like a public immunization system.

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