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Imagine you're walking through a forest.

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I'm guessing you're thinking
of a collection of trees,

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what we foresters call a stand,

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with their rugged stems
and their beautiful crowns.

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Yes, trees are the foundation of forests,

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but a forest is much more
than what you see,

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and today I want to change
the way you think about forests.

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You see, underground
there is this other world,

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a world of infinite biological pathways

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that connect trees
and allow them to communicate

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and allow the forest to behave
as though it's a single organism.

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It might remind you
of a sort of intelligence.

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How do I know this?

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Here's my story.

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I grew up in the forests
of British Columbia.

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I used to lay on the forest floor
and stare up at the tree crowns.

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They were giants.

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My grandfather was a giant, too.

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He was a horse logger,

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and he used to selectively cut
cedar poles from the inland rainforest.

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Grandpa taught me about the quiet
and cohesive ways of the woods,

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and how my family was knit into it.

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So I followed in grandpa's footsteps.

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He and I had this curiosity about forests,

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and my first big "aha" moment

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was at the outhouse by our lake.

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Our poor dog Jigs
had slipped and fallen into the pit.

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So grandpa ran up with his shovel
to rescue the poor dog.

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He was down there, swimming in the muck.

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But as grandpa dug
through that forest floor,

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I became fascinated with the roots,

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and under that, what I learned later
was the white mycelium

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and under that the red
and yellow mineral horizons.

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Eventually, grandpa and I
rescued the poor dog,

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but it was at that moment that I realized

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that that palette of roots and soil

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was really the foundation of the forest.

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And I wanted to know more.

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So I studied forestry.

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But soon I found myself working
alongside the powerful people

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in charge of the commercial harvest.

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The extent of the clear-cutting

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was alarming,

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and I soon found myself
conflicted by my part in it.

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Not only that, the spraying
and hacking of the aspens and birches

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to make way for the more commercially
valuable planted pines and firs

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was astounding.

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It seemed that nothing could stop
this relentless industrial machine.

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So I went back to school,

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and I studied my other world.

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You see, scientists had just discovered
in the laboratory in vitro

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that one pine seedling root

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could transmit carbon
to another pine seedling root.

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But this was in the laboratory,

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and I wondered,
could this happen in real forests?

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I thought yes.

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Trees in real forests might also
share information below ground.

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But this was really controversial,

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and some people thought I was crazy,

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and I had a really hard time
getting research funding.

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But I persevered,

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and I eventually conducted
some experiments deep in the forest,

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25 years ago.

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I grew 80 replicates of three species:

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paper birch, Douglas fir,
and western red cedar.

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I figured the birch and the fir
would be connected in a belowground web,

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but not the cedar.

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It was in its own other world.

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And I gathered my apparatus,

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and I had no money,
so I had to do it on the cheap.

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So I went to Canadian Tire --

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(Laughter)

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and I bought some plastic bags
and duct tape and shade cloth,

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a timer, a paper suit, a respirator.

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And then I borrowed some
high-tech stuff from my university:

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a Geiger counter, a scintillation counter,
a mass spectrometer, microscopes.

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And then I got some
really dangerous stuff:

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syringes full of radioactive
carbon-14 carbon dioxide gas

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and some high pressure bottles

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of the stable isotope
carbon-13 carbon dioxide gas.

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But I was legally permitted.

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(Laughter)

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Oh, and I forgot some stuff,

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important stuff: the bug spray,

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the bear spray,
the filters for my respirator.

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Oh well.

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The first day of the experiment,
we got out to our plot

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and a grizzly bear and her cub
chased us off.

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And I had no bear spray.

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But you know, this is how
forest research in Canada goes.

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(Laughter)

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So I came back the next day,

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and mama grizzly and her cub were gone.

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So this time, we really got started,

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and I pulled on my white paper suit,

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I put on my respirator,

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and then

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I put the plastic bags over my trees.

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I got my giant syringes,

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and I injected the bags

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with my tracer isotope
carbon dioxide gases,

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first the birch.

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I injected carbon-14, the radioactive gas,

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into the bag of birch.

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And then for fir,

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I injected the stable isotope
carbon-13 carbon dioxide gas.

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I used two isotopes,

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because I was wondering

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whether there was two-way communication
going on between these species.

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I got to the final bag,

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the 80th replicate,

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and all of a sudden
mama grizzly showed up again.

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And she started to chase me,

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and I had my syringes above my head,

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and I was swatting the mosquitos,
and I jumped into the truck,

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and I thought,

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"This is why people do lab studies."

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(Laughter)

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I waited an hour.

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I figured it would take this long

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for the trees to suck up
the CO2 through photosynthesis,

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turn it into sugars,
send it down into their roots,

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and maybe, I hypothesized,

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shuttle that carbon belowground
to their neighbors.

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After the hour was up,

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I rolled down my window,

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and I checked for mama grizzly.

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Oh good, she's over there
eating her huckleberries.

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So I got out of the truck
and I got to work.

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I went to my first bag with the birch.
I pulled the bag off.

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I ran my Geiger counter over its leaves.

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Kkhh!

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Perfect.

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The birch had taken up
the radioactive gas.

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Then the moment of truth.

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I went over to the fir tree.

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I pulled off its bag.

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I ran the Geiger counter up its needles,

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and I heard the most beautiful sound.

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Kkhh!

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It was the sound of birch talking to fir,

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and birch was saying,
"Hey, can I help you?"

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And fir was saying, "Yeah,
can you send me some of your carbon?

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Because somebody
threw a shade cloth over me."

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I went up to cedar, and I ran
the Geiger counter over its leaves,

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and as I suspected,

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silence.

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Cedar was in its own world.

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It was not connected into the web
interlinking birch and fir.

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I was so excited,

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I ran from plot to plot
and I checked all 80 replicates.

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The evidence was clear.

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The C-13 and C-14 was showing me

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that paper birch and Douglas fir
were in a lively two-way conversation.

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It turns out at that time of the year,

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in the summer,

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that birch was sending more carbon to fir
than fir was sending back to birch,

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especially when the fir was shaded.

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And then in later experiments,
we found the opposite,

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that fir was sending more carbon to birch
than birch was sending to fir,

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and this was because the fir was still
growing while the birch was leafless.

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So it turns out the two species
were interdependent,

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like yin and yang.

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And at that moment,
everything came into focus for me.

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I knew I had found something big,

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something that would change the way
we look at how trees interact in forests,

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from not just competitors

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but to cooperators.

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And I had found solid evidence

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of this massive belowground
communications network,

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the other world.

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Now, I truly hoped and believed

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that my discovery would change
how we practice forestry,

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from clear-cutting and herbiciding

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to more holistic and sustainable methods,

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methods that were less expensive
and more practical.

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What was I thinking?

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I'll come back to that.

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So how do we do science
in complex systems like forests?

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Well, as forest scientists,
we have to do our research in the forests,

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and that's really tough,
as I've shown you.

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And we have to be really good
at running from bears.

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But mostly, we have to persevere

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in spite of all the stuff
stacked against us.

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And we have to follow our intuition
and our experiences

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and ask really good questions.

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And then we've got to gather our data
and then go verify.

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For me, I've conducted and published
hundreds of experiments in the forest.

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Some of my oldest experimental plantations
are now over 30 years old.

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You can check them out.

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That's how forest science works.

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So now I want to talk about the science.

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How were paper birch
and Douglas fir communicating?

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Well, it turns out they were conversing
not only in the language of carbon

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but also nitrogen and phosphorus

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and water and defense signals
and allele chemicals and hormones --

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information.

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And you know, I have to tell you,
before me, scientists had thought

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that this belowground
mutualistic symbiosis called a mycorrhiza

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was involved.

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Mycorrhiza literally means "fungus root."

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You see their reproductive organs
when you walk through the forest.

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They're the mushrooms.

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The mushrooms, though,
are just the tip of the iceberg,

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because coming out of those stems
are fungal threads that form a mycelium,

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and that mycelium
infects and colonizes the roots

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of all the trees and plants.

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And where the fungal cells
interact with the root cells,

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there's a trade of carbon for nutrients,

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and that fungus gets those nutrients
by growing through the soil

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and coating every soil particle.

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The web is so dense that there can be
hundreds of kilometers of mycelium

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under a single footstep.

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And not only that, that mycelium connects
different individuals in the forest,

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individuals not only of the same species
but between species, like birch and fir,

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and it works kind of like the Internet.

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You see, like all networks,

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mycorrhizal networks have nodes and links.

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We made this map by examining
the short sequences of DNA

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of every tree and every fungal individual
in a patch of Douglas fir forest.

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In this picture, the circles represent
the Douglas fir, or the nodes,

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and the lines represent the interlinking
fungal highways, or the links.

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The biggest, darkest nodes
are the busiest nodes.

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We call those hub trees,

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or more fondly, mother trees,

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because it turns out
that those hub trees nurture their young,

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the ones growing in the understory.

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And if you can see those yellow dots,

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those are the young seedlings
that have established within the network

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of the old mother trees.

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In a single forest, a mother tree can be
connected to hundreds of other trees.

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And using our isotope tracers,

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we have found that mother trees

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will send their excess carbon
through the mycorrhizal network

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to the understory seedlings,

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and we've associated this
with increased seedling survival

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by four times.

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Now, we know we all
favor our own children,

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and I wondered, could Douglas fir
recognize its own kin,

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like mama grizzly and her cub?

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So we set about an experiment,

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and we grew mother trees
with kin and stranger's seedlings.

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And it turns out
they do recognize their kin.

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Mother trees colonize their kin
with bigger mycorrhizal networks.

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They send them more carbon below ground.

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They even reduce
their own root competition

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to make elbow room for their kids.

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When mother trees are injured or dying,

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they also send messages of wisdom
on to the next generation of seedlings.

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So we've used isotope tracing

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to trace carbon moving
from an injured mother tree

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down her trunk
into the mycorrhizal network

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and into her neighboring seedlings,

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not only carbon but also defense signals.

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And these two compounds

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have increased the resistance
of those seedlings to future stresses.

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So trees talk.

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(Applause)

259
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Thank you.

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Through back and forth conversations,

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they increase the resilience
of the whole community.

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It probably reminds you
of our own social communities,

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and our families,

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well, at least some families.

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(Laughter)

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So let's come back to the initial point.

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Forests aren't simply
collections of trees,

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they're complex systems
with hubs and networks

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that overlap and connect trees
and allow them to communicate,

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and they provide avenues
for feedbacks and adaptation,

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and this makes the forest resilient.

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That's because there are many hub trees
and many overlapping networks.

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But they're also vulnerable,

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vulnerable not only
to natural disturbances

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like bark beetles that preferentially
attack big old trees

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but high-grade logging
and clear-cut logging.

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You see, you can take out
one or two hub trees,

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but there comes a tipping point,

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because hub trees are not
unlike rivets in an airplane.

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You can take out one or two
and the plane still flies,

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but you take out one too many,

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or maybe that one holding on the wings,

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and the whole system collapses.

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So now how are you thinking
about forests? Differently?

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(Audience) Yes.

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Cool.

287
00:14:01,040 --> 00:14:02,240
I'm glad.

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00:14:02,920 --> 00:14:06,776
So, remember I said earlier
that I hoped that my research,

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my discoveries would change
the way we practice forestry.

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00:14:10,200 --> 00:14:14,320
Well, I want to take a check on that
30 years later here in western Canada.

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This is about 100 kilometers
to the west of us,

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just on the border of Banff National Park.

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That's a lot of clear-cuts.

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It's not so pristine.

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00:14:33,980 --> 00:14:39,036
In 2014, the World Resources Institute
reported that Canada in the past decade

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has had the highest forest disturbance
rate of any country worldwide,

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and I bet you thought it was Brazil.

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In Canada, it's 3.6 percent per year.

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Now, by my estimation, that's about
four times the rate that is sustainable.

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Now, massive disturbance at this scale
is known to affect hydrological cycles,

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degrade wildlife habitat,

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00:15:03,460 --> 00:15:06,356
and emit greenhouse gases
back into the atmosphere,

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which creates more disturbance
and more tree diebacks.

304
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Not only that, we're continuing
to plant one or two species

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and weed out the aspens and birches.

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These simplified forests lack complexity,

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and they're really vulnerable
to infections and bugs.

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And as climate changes,

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this is creating a perfect storm

310
00:15:29,420 --> 00:15:32,996
for extreme events, like the massive
mountain pine beetle outbreak

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00:15:33,020 --> 00:15:35,060
that just swept across North America,

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00:15:35,820 --> 00:15:39,140
or that megafire in the last
couple months in Alberta.

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So I want to come back
to my final question:

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instead of weakening our forests,

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how can we reinforce them
and help them deal with climate change?

316
00:15:51,700 --> 00:15:55,716
Well, you know, the great thing
about forests as complex systems

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is they have enormous
capacity to self-heal.

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In our recent experiments,

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we found with patch-cutting
and retention of hub trees

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00:16:04,620 --> 00:16:08,756
and regeneration to a diversity
of species and genes and genotypes

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00:16:08,780 --> 00:16:12,620
that these mycorrhizal networks,
they recover really rapidly.

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00:16:13,940 --> 00:16:18,276
So with this in mind, I want to leave you
with four simple solutions.

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00:16:18,300 --> 00:16:21,660
And we can't kid ourselves
that these are too complicated to act on.

324
00:16:23,180 --> 00:16:26,380
First, we all need
to get out in the forest.

325
00:16:27,500 --> 00:16:32,036
We need to reestablish
local involvement in our own forests.

326
00:16:32,060 --> 00:16:33,676
You see, most of our forests now

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00:16:33,700 --> 00:16:36,916
are managed using
a one-size-fits-all approach,

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00:16:36,940 --> 00:16:41,300
but good forest stewardship
requires knowledge of local conditions.

329
00:16:42,420 --> 00:16:46,100
Second, we need to save
our old-growth forests.

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These are the repositories of genes
and mother trees and mycorrhizal networks.

331
00:16:54,620 --> 00:16:56,876
So this means less cutting.

332
00:16:56,900 --> 00:16:58,940
I don't mean no cutting, but less cutting.

333
00:16:59,980 --> 00:17:02,635
And third, when we do cut,

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00:17:02,660 --> 00:17:04,460
we need to save the legacies,

335
00:17:05,180 --> 00:17:06,716
the mother trees and networks,

336
00:17:06,740 --> 00:17:08,875
and the wood, the genes,

337
00:17:08,900 --> 00:17:12,796
so they can pass their wisdom
onto the next generation of trees

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00:17:12,819 --> 00:17:15,940
so they can withstand
the future stresses coming down the road.

339
00:17:16,620 --> 00:17:18,700
We need to be conservationists.

340
00:17:19,819 --> 00:17:22,539
And finally, fourthly and finally,

341
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we need to regenerate our forests
with a diversity of species

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00:17:26,820 --> 00:17:29,036
and genotypes and structures

343
00:17:29,060 --> 00:17:31,820
by planting and allowing
natural regeneration.

344
00:17:32,620 --> 00:17:35,516
We have to give Mother Nature
the tools she needs

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00:17:35,540 --> 00:17:38,260
to use her intelligence to self-heal.

346
00:17:39,180 --> 00:17:42,236
And we need to remember
that forests aren't just a bunch of trees

347
00:17:42,260 --> 00:17:43,516
competing with each other,

348
00:17:43,540 --> 00:17:45,460
they're supercooperators.

349
00:17:46,700 --> 00:17:48,356
So back to Jigs.

350
00:17:48,380 --> 00:17:52,836
Jigs's fall into the outhouse
showed me this other world,

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00:17:52,860 --> 00:17:55,556
and it changed my view of forests.

352
00:17:55,580 --> 00:17:58,916
I hope today to have changed
how you think about forests.

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00:17:58,940 --> 00:18:00,196
Thank you.

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00:18:00,220 --> 00:18:05,997
(Applause)