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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 they 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 replica,
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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)
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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.
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I'm glad.
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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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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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In my estimation, there hasn't been
a lot of change in the last 30 years.
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It's not so pristine.
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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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and emit greenhouse gases
back into the atmosphere,
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which creates more disturbance
and more tree diebacks.
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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
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for extreme events, like the massive
mountain pine beetle outbreak
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that just swept across North America,
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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?
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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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and regeneration to a diversity
of species and genes and genotypes
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that these mycorrhizal networks,
they recover really rapidly.
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So with this in mind, I want to leave you
with four simple solutions.
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And we can't kid ourselves
that these are too complicated to act on.
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First, we all need
to get out in the forest.
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We need to reestablish
local involvement in our own forests.
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You see, most of our forests now
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are managed using
a one-size-fits-all approach,
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but good forest stewardship
requires knowledge of local conditions.
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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.
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So this means less cutting.
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I don't mean no cutting, but less cutting.
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And third, when we do cut,
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we need to save the legacies,
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the mother trees and networks,
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and the wood, the genes,
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so they can pass their wisdom
onto the next generation of trees
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so they can withstand
the future stresses coming down the road.
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We need to be conservationists.
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And finally, fourthly and finally,
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we need to regenerate our forests
with a diversity of species
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and genotypes and structures
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by planting and allowing
natural regeneration.
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We have to give Mother Nature
the tools she needs
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to use her intelligence to self-heal.
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And we need to remember
that forests aren't just a bunch of trees
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competing with each other,
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they're supercooperators.
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So back to Jigs.
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Jigs's fall into the outhouse
showed me this other world,
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and it changed my view of forests.
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I hope today to have changed
how you think about forests.
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Thank you.
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(Applause)