Transcript

Intro

0:04 Imagine you’re walking through a forest.
0:07 I’m guessing you’re thinking of a collection of trees,
0:10 what we foresters call a stand,
0:13 with their rugged stems and their beautiful crowns.
0:16 Yes, trees are the foundation of forests,
0:20 but a forest is much more than what you see,
0:23 and today I want to change the way you think about forests.
0:27 You see, underground there is this other world,
0:30 a world of infinite biological pathways
0:33 that connect trees and allow them to communicate
0:37 and allow the forest to behave as though it’s a single organism.
0:41 It might remind you of a sort of intelligence.
0:45 How do I know this?
0:46 Here’s my story.

My story

0:49 I grew up in the forests of British Columbia.
0:52 I used to lay on the forest floor and stare up at the tree crowns.
0:55 They were giants.
0:57 My grandfather was a giant, too.
0:59 He was a horse logger,
1:00 and he used to selectively cut cedar poles from the inland rainforest.
1:05 Grandpa taught me about the quiet and cohesive ways of the woods,
1:09 and how my family was knit into it.
1:12 So I followed in grandpa’s footsteps.
1:14 He and I had this curiosity about forests,
1:18 and my first big “aha” moment
1:20 was at the outhouse by our lake.
1:23 Our poor dog Jigs had slipped and fallen into the pit.
1:27 So grandpa ran up with his shovel to rescue the poor dog.
1:30 He was down there, swimming in the muck.
1:34 But as grandpa dug through that forest floor,
1:37 I became fascinated with the roots,
1:39 and under that, what I learned later was the white mycelium
1:43 and under that the red and yellow mineral horizons.
1:46 Eventually, grandpa and I rescued the poor dog,
1:49 but it was at that moment that I realized
1:52 that that palette of roots and soil
1:54 was really the foundation of the forest.
1:58 And I wanted to know more.
2:00 So I studied forestry.
2:02 But soon I found myself working alongside the powerful people
2:06 in charge of the commercial harvest.
2:09 The extent of the clear-cutting
2:12 was alarming,
2:13 and I soon found myself conflicted by my part in it.
2:17 Not only that, the spraying and hacking of the aspens and birches
2:22 to make way for the more commercially valuable planted pines and firs
2:26 was astounding.
2:28 It seemed that nothing could stop this relentless industrial machine.
2:33 So I went back to school,
2:35 and I studied my other world.

My other world

2:39 You see, scientists had just discovered in the laboratory in vitro
2:43 that one pine seedling root
2:45 could transmit carbon to another pine seedling root.
2:49 But this was in the laboratory,
2:51 and I wondered, could this happen in real forests?
2:54 I thought yes.
2:56 Trees in real forests might also share information below ground.
3:01 But this was really controversial,
3:03 and some people thought I was crazy,
3:06 and I had a really hard time getting research funding.
3:09 But I persevered,
3:11 and I eventually conducted some experiments deep in the forest,
3:15 25 years ago.
3:17 I grew 80 replicates of three species:
3:20 paper birch, Douglas fir, and western red cedar.
3:23 I figured the birch and the fir would be connected in a belowground web,
3:27 but not the cedar.
3:29 It was in its own other world.
3:31 And I gathered my apparatus,
3:33 and I had no money, so I had to do it on the cheap.
3:37 So I went to Canadian Tire —
3:38 (Laughter)
3:40 and I bought some plastic bags and duct tape and shade cloth,
3:43 a timer, a paper suit, a respirator.
3:47 And then I borrowed some high-tech stuff from my university:
3:50 a Geiger counter, a scintillation counter, a mass spectrometer, microscopes.
3:55 And then I got some really dangerous stuff:
3:58 syringes full of radioactive carbon-14 carbon dioxide gas
4:02 and some high pressure bottles
4:04 of the stable isotope carbon-13 carbon dioxide gas.
4:09 But I was legally permitted.
4:10 (Laughter)
4:12 Oh, and I forgot some stuff,
4:14 important stuff: the bug spray,
4:17 the bear spray, the filters for my respirator.

Bear spray

4:20 Oh well.
4:23 The first day of the experiment, we got out to our plot
4:25 and a grizzly bear and her cub chased us off.
4:29 And I had no bear spray.
4:32 But you know, this is how forest research in Canada goes.
4:35 (Laughter)
4:37 So I came back the next day,
4:38 and mama grizzly and her cub were gone.
4:41 So this time, we really got started,
4:43 and I pulled on my white paper suit,
4:46 I put on my respirator,

The next day

4:49 and then
4:50 I put the plastic bags over my trees.
4:54 I got my giant syringes,
4:56 and I injected the bags
4:58 with my tracer isotope carbon dioxide gases,
5:01 first the birch.
5:03 I injected carbon-14, the radioactive gas,
5:06 into the bag of birch.
5:07 And then for fir,
5:08 I injected the stable isotope carbon-13 carbon dioxide gas.
5:12 I used two isotopes,
5:14 because I was wondering
5:15 whether there was two-way communication going on between these species.
5:21 I got to the final bag,
5:23 the 80th replicate,
5:25 and all of a sudden mama grizzly showed up again.
5:27 And she started to chase me,
5:29 and I had my syringes above my head,
5:31 and I was swatting the mosquitos, and I jumped into the truck,
5:34 and I thought,
5:35 “This is why people do lab studies.”
5:37 (Laughter)
5:40 I waited an hour.
5:42 I figured it would take this long
5:43 for the trees to suck up the CO2 through photosynthesis,
5:46 turn it into sugars, send it down into their roots,
5:49 and maybe, I hypothesized,
5:52 shuttle that carbon belowground to their neighbors.
5:56 After the hour was up,
5:58 I rolled down my window,
5:59 and I checked for mama grizzly.
6:02 Oh good, she’s over there eating her huckleberries.
6:05 So I got out of the truck and I got to work.
6:07 I went to my first bag with the birch. I pulled the bag off.
6:11 I ran my Geiger counter over its leaves.
6:14 Kkhh!
6:16 Perfect.
6:18 The birch had taken up the radioactive gas.
6:21 Then the moment of truth.
6:22 I went over to the fir tree.

The moment of truth

6:24 I pulled off its bag.
6:26 I ran the Geiger counter up its needles,
6:29 and I heard the most beautiful sound.
6:31 Kkhh!
6:34 It was the sound of birch talking to fir,
6:37 and birch was saying, “Hey, can I help you?”
6:40 And fir was saying, “Yeah, can you send me some of your carbon?
6:44 Because somebody threw a shade cloth over me.”
6:47 I went up to cedar, and I ran the Geiger counter over its leaves,
6:51 and as I suspected,
6:54 silence.
6:56 Cedar was in its own world.
6:58 It was not connected into the web interlinking birch and fir.
7:03 I was so excited,
7:05 I ran from plot to plot and I checked all 80 replicates.
7:09 The evidence was clear.
7:11 The C-13 and C-14 was showing me
7:14 that paper birch and Douglas fir were in a lively two-way conversation.
7:19 It turns out at that time of the year,
7:21 in the summer,
7:22 that birch was sending more carbon to fir than fir was sending back to birch,
7:26 especially when the fir was shaded.
7:28 And then in later experiments, we found the opposite,
7:31 that fir was sending more carbon to birch than birch was sending to fir,
7:35 and this was because the fir was still growing while the birch was leafless.
7:39 So it turns out the two species were interdependent,
7:42 like yin and yang.
7:44 And at that moment, everything came into focus for me.
7:47 I knew I had found something big,

The science

7:49 something that would change the way we look at how trees interact in forests,
7:54 from not just competitors
7:56 but to cooperators.
7:59 And I had found solid evidence
8:01 of this massive belowground communications network,
8:05 the other world.
8:07 Now, I truly hoped and believed
8:09 that my discovery would change how we practice forestry,
8:13 from clear-cutting and herbiciding
8:14 to more holistic and sustainable methods,
8:17 methods that were less expensive and more practical.
8:21 What was I thinking?
8:23 I’ll come back to that.
8:27 So how do we do science in complex systems like forests?
8:32 Well, as forest scientists, we have to do our research in the forests,
8:35 and that’s really tough, as I’ve shown you.
8:37 And we have to be really good at running from bears.
8:42 But mostly, we have to persevere
8:43 in spite of all the stuff stacked against us.
8:46 And we have to follow our intuition and our experiences
8:49 and ask really good questions.
8:51 And then we’ve got to gather our data and then go verify.
8:54 For me, I’ve conducted and published hundreds of experiments in the forest.
9:00 Some of my oldest experimental plantations are now over 30 years old.
9:05 You can check them out.
9:07 That’s how forest science works.
9:09 So now I want to talk about the science.
9:12 How were paper birch and Douglas fir communicating?
9:15 Well, it turns out they were conversing not only in the language of carbon
9:19 but also nitrogen and phosphorus
9:22 and water and defense signals and allelochemicals and hormones —
9:27 information.
9:29 And you know, I have to tell you, before me, scientists had thought
9:32 that this belowground mutualistic symbiosis called a mycorrhiza
9:36 was involved.
9:38 Mycorrhiza literally means “fungus root.”
9:41 You see their reproductive organs when you walk through the forest.
9:45 They’re the mushrooms.
9:47 The mushrooms, though, are just the tip of the iceberg,
9:50 because coming out of those stems are fungal threads that form a mycelium,
9:54 and that mycelium infects and colonizes the roots
9:57 of all the trees and plants.
9:59 And where the fungal cells interact with the root cells,
10:02 there’s a trade of carbon for nutrients,
10:05 and that fungus gets those nutrients by growing through the soil
10:08 and coating every soil particle.
10:11 The web is so dense that there can be hundreds of kilometers of mycelium
10:15 under a single footstep.
10:18 And not only that, that mycelium connects different individuals in the forest,
10:23 individuals not only of the same species but between species, like birch and fir,
10:29 and it works kind of like the Internet.
10:33 You see, like all networks,
10:35 mycorrhizal networks have nodes and links.
10:38 We made this map by examining the short sequences of DNA
10:42 of every tree and every fungal individual in a patch of Douglas fir forest.
10:47 In this picture, the circles represent the Douglas fir, or the nodes,
10:51 and the lines represent the interlinking fungal highways, or the links.
10:56 The biggest, darkest nodes are the busiest nodes.
11:01 We call those hub trees,
11:02 or more fondly, mother trees,
11:05 because it turns out that those hub trees nurture their young,
11:10 the ones growing in the understory.
11:12 And if you can see those yellow dots,
11:14 those are the young seedlings that have established within the network
11:18 of the old mother trees.
11:19 In a single forest, a mother tree can be connected to hundreds of other trees.
11:25 And using our isotope tracers,
11:27 we have found that mother trees
11:29 will send their excess carbon through the mycorrhizal network
11:32 to the understory seedlings,
11:34 and we’ve associated this with increased seedling survival
11:37 by four times.
11:39 Now, we know we all favor our own children,
11:42 and I wondered, could Douglas fir recognize its own kin,
11:47 like mama grizzly and her cub?
11:50 So we set about an experiment,
11:51 and we grew mother trees with kin and stranger’s seedlings.
11:55 And it turns out they do recognize their kin.
11:58 Mother trees colonize their kin with bigger mycorrhizal networks.
12:03 They send them more carbon below ground.
12:06 They even reduce their own root competition
12:08 to make elbow room for their kids.
12:11 When mother trees are injured or dying,
12:15 they also send messages of wisdom on to the next generation of seedlings.
12:20 So we’ve used isotope tracing
12:22 to trace carbon moving from an injured mother tree
12:24 down her trunk into the mycorrhizal network
12:27 and into her neighboring seedlings,
12:30 not only carbon but also defense signals.
12:32 And these two compounds
12:34 have increased the resistance of those seedlings to future stresses.
12:38 So trees talk.
12:42 (Applause)
12:44 Thank you.
12:48 Through back and forth conversations,
12:51 they increase the resilience of the whole community.
12:54 It probably reminds you of our own social communities,
12:57 and our families,
12:59 well, at least some families.
13:00 (Laughter)
13:03 So let’s come back to the initial point.

Resilient forests

13:06 Forests aren’t simply collections of trees,
13:08 they’re complex systems with hubs and networks
13:12 that overlap and connect trees and allow them to communicate,
13:15 and they provide avenues for feedbacks and adaptation,
13:19 and this makes the forest resilient.
13:21 That’s because there are many hub trees and many overlapping networks.
13:26 But they’re also vulnerable,
13:28 vulnerable not only to natural disturbances
13:31 like bark beetles that preferentially attack big old trees
13:35 but high-grade logging and clear-cut logging.
13:38 You see, you can take out one or two hub trees,
13:41 but there comes a tipping point,
13:44 because hub trees are not unlike rivets in an airplane.
13:47 You can take out one or two and the plane still flies,
13:50 but you take out one too many,
13:52 or maybe that one holding on the wings,
13:55 and the whole system collapses.
13:58 So now how are you thinking about forests? Differently?
14:01 (Audience) Yes.
14:02 Cool.
14:04 I’m glad.
14:06 So, remember I said earlier that I hoped that my research,
14:10 my discoveries would change the way we practice forestry.
14:13 Well, I want to take a check on that 30 years later here in western Canada.
14:26 This is about 100 kilometers to the west of us,
14:28 just on the border of Banff National Park.
14:32 That’s a lot of clear-cuts.
14:34 It’s not so pristine.
14:37 In 2014, the World Resources Institute reported that Canada in the past decade
14:42 has had the highest forest disturbance rate of any country worldwide,
14:47 and I bet you thought it was Brazil.

Massive disturbance

14:50 In Canada, it’s 3.6 percent per year.
14:54 Now, by my estimation, that’s about four times the rate that is sustainable.
15:00 Now, massive disturbance at this scale is known to affect hydrological cycles,
15:04 degrade wildlife habitat,
15:06 and emit greenhouse gases back into the atmosphere,
15:09 which creates more disturbance and more tree diebacks.
15:14 Not only that, we’re continuing to plant one or two species
15:17 and weed out the aspens and birches.
15:20 These simplified forests lack complexity,
15:23 and they’re really vulnerable to infections and bugs.
15:26 And as climate changes,
15:28 this is creating a perfect storm
15:32 for extreme events, like the massive mountain pine beetle outbreak
15:36 that just swept across North America,
15:39 or that megafire in the last couple months in Alberta.
15:44 So I want to come back to my final question:
15:48 instead of weakening our forests,
15:50 how can we reinforce them and help them deal with climate change?
15:55 Well, you know, the great thing about forests as complex systems

Solutions

15:59 is they have enormous capacity to self-heal.
16:03 In our recent experiments,
16:04 we found with patch-cutting and retention of hub trees
16:08 and regeneration to a diversity of species and genes and genotypes
16:12 that these mycorrhizal networks, they recover really rapidly.
16:17 So with this in mind, I want to leave you with four simple solutions.
16:21 And we can’t kid ourselves that these are too complicated to act on.
16:26 First, we all need to get out in the forest.
16:31 We need to reestablish local involvement in our own forests.
16:35 You see, most of our forests now
16:37 are managed using a one-size-fits-all approach,
16:40 but good forest stewardship requires knowledge of local conditions.
16:45 Second, we need to save our old-growth forests.
16:50 These are the repositories of genes and mother trees and mycorrhizal networks.
16:58 So this means less cutting.
17:00 I don’t mean no cutting, but less cutting.
17:03 And third, when we do cut,
17:06 we need to save the legacies,
17:08 the mother trees and networks,
17:10 and the wood, the genes,
17:12 so they can pass their wisdom onto the next generation of trees
17:16 so they can withstand the future stresses coming down the road.
17:20 We need to be conservationists.
17:23 And finally, fourthly and finally,
17:26 we need to regenerate our forests with a diversity of species
17:30 and genotypes and structures
17:32 by planting and allowing natural regeneration.
17:36 We have to give Mother Nature the tools she needs
17:39 to use her intelligence to self-heal.
17:42 And we need to remember that forests aren’t just a bunch of trees
17:45 competing with each other,
17:47 they’re supercooperators.
17:50 So back to Jigs.
17:51 Jigs’s fall into the outhouse showed me this other world,
17:56 and it changed my view of forests.
17:59 I hope today to have changed how you think about forests.
18:02 Thank you.
18:03 (Applause)