How trees talk to each other
-
0:01 - 0:03Imagine you're walking through a forest.
-
0:04 - 0:07I'm guessing you're thinking
of a collection of trees, -
0:07 - 0:10what we foresters call a stand,
-
0:10 - 0:13with their rugged stems
and their beautiful crowns. -
0:13 - 0:16Yes, trees are the foundation of forests,
-
0:16 - 0:19but a forest is much more
than what you see, -
0:20 - 0:23and today I want to change
the way you think about forests. -
0:24 - 0:27You see, underground
there is this other world, -
0:27 - 0:30a world of infinite biological pathways
-
0:30 - 0:34that connect trees
and allow them to communicate -
0:34 - 0:37and allow the forest to behave
as though it's a single organism. -
0:38 - 0:41It might remind you
of a sort of intelligence. -
0:42 - 0:43How do I know this?
-
0:43 - 0:45Here's my story.
-
0:46 - 0:48I grew up in the forests
of British Columbia. -
0:49 - 0:52I used to lay on the forest floor
and stare up at the tree crowns. -
0:52 - 0:54They were giants.
-
0:54 - 0:56My grandfather was a giant, too.
-
0:56 - 0:57He was a horse logger,
-
0:57 - 1:01and he used to selectively cut
cedar poles from the inland rainforest. -
1:02 - 1:06Grandpa taught me about the quiet
and cohesive ways of the woods, -
1:06 - 1:08and how my family was knit into it.
-
1:09 - 1:11So I followed in grandpa's footsteps.
-
1:11 - 1:14He and I had this curiosity about forests,
-
1:15 - 1:17and my first big "aha" moment
-
1:17 - 1:19was at the outhouse by our lake.
-
1:20 - 1:23Our poor dog Jigs
had slipped and fallen into the pit. -
1:24 - 1:27So grandpa ran up with his shovel
to rescue the poor dog. -
1:27 - 1:29He was down there, swimming in the muck.
-
1:31 - 1:34But as grandpa dug
through that forest floor, -
1:34 - 1:36I became fascinated with the roots,
-
1:36 - 1:39and under that, what I learned later
was the white mycelium -
1:39 - 1:43and under that the red
and yellow mineral horizons. -
1:43 - 1:46Eventually, grandpa and I
rescued the poor dog, -
1:46 - 1:49but it was at that moment that I realized
-
1:49 - 1:51that that palette of roots and soil
-
1:51 - 1:54was really the foundation of the forest.
-
1:55 - 1:56And I wanted to know more.
-
1:57 - 1:58So I studied forestry.
-
1:59 - 2:03But soon I found myself working
alongside the powerful people -
2:03 - 2:05in charge of the commercial harvest.
-
2:06 - 2:09The extent of the clear-cutting
-
2:09 - 2:10was alarming,
-
2:10 - 2:13and I soon found myself
conflicted by my part in it. -
2:14 - 2:19Not only that, the spraying
and hacking of the aspens and birches -
2:19 - 2:23to make way for the more commercially
valuable planted pines and firs -
2:23 - 2:24was astounding.
-
2:25 - 2:29It seemed that nothing could stop
this relentless industrial machine. -
2:30 - 2:31So I went back to school,
-
2:32 - 2:34and I studied my other world.
-
2:35 - 2:40You see, scientists had just discovered
in the laboratory in vitro -
2:40 - 2:42that one pine seedling root
-
2:42 - 2:45could transmit carbon
to another pine seedling root. -
2:46 - 2:48But this was in the laboratory,
-
2:48 - 2:51and I wondered,
could this happen in real forests? -
2:51 - 2:52I thought yes.
-
2:53 - 2:57Trees in real forests might also
share information below ground. -
2:58 - 3:00But this was really controversial,
-
3:00 - 3:03and some people thought I was crazy,
-
3:03 - 3:06and I had a really hard time
getting research funding. -
3:06 - 3:07But I persevered,
-
3:08 - 3:12and I eventually conducted
some experiments deep in the forest, -
3:12 - 3:1325 years ago.
-
3:14 - 3:17I grew 80 replicates of three species:
-
3:17 - 3:20paper birch, Douglas fir,
and western red cedar. -
3:20 - 3:24I figured the birch and the fir
would be connected in a belowground web, -
3:24 - 3:26but not the cedar.
-
3:26 - 3:27It was in its own other world.
-
3:28 - 3:30And I gathered my apparatus,
-
3:30 - 3:33and I had no money,
so I had to do it on the cheap. -
3:34 - 3:35So I went to Canadian Tire --
-
3:35 - 3:37(Laughter)
-
3:37 - 3:40and I bought some plastic bags
and duct tape and shade cloth, -
3:40 - 3:43a timer, a paper suit, a respirator.
-
3:44 - 3:47And then I borrowed some
high-tech stuff from my university: -
3:47 - 3:52a Geiger counter, a scintillation counter,
a mass spectrometer, microscopes. -
3:52 - 3:54And then I got some
really dangerous stuff: -
3:54 - 3:59syringes full of radioactive
carbon-14 carbon dioxide gas -
3:59 - 4:01and some high pressure bottles
-
4:01 - 4:05of the stable isotope
carbon-13 carbon dioxide gas. -
4:06 - 4:07But I was legally permitted.
-
4:07 - 4:09(Laughter)
-
4:09 - 4:10Oh, and I forgot some stuff,
-
4:11 - 4:13important stuff: the bug spray,
-
4:14 - 4:16the bear spray,
the filters for my respirator. -
4:17 - 4:18Oh well.
-
4:20 - 4:22The first day of the experiment,
we got out to our plot -
4:22 - 4:25and a grizzly bear and her cub
chased us off. -
4:26 - 4:27And I had no bear spray.
-
4:29 - 4:32But you know, this is how
forest research in Canada goes. -
4:32 - 4:34(Laughter)
-
4:34 - 4:35So I came back the next day,
-
4:35 - 4:38and mama grizzly and her cub were gone.
-
4:38 - 4:40So this time, we really got started,
-
4:40 - 4:42and I pulled on my white paper suit,
-
4:42 - 4:44I put on my respirator,
-
4:46 - 4:47and then
-
4:47 - 4:50I put the plastic bags over my trees.
-
4:51 - 4:53I got my giant syringes,
-
4:53 - 4:55and I injected the bags
-
4:55 - 4:58with my tracer isotope
carbon dioxide gases, -
4:58 - 5:00first the birch.
-
5:00 - 5:03I injected carbon-14, the radioactive gas,
-
5:03 - 5:04into the bag of birch.
-
5:04 - 5:05And then for fir,
-
5:05 - 5:09I injected the stable isotope
carbon-13 carbon dioxide gas. -
5:09 - 5:11I used two isotopes,
-
5:11 - 5:12because I was wondering
-
5:12 - 5:16whether there was two-way communication
going on between these species. -
5:18 - 5:20I got to the final bag,
-
5:20 - 5:22the 80th replicate,
-
5:22 - 5:24and all of a sudden
mama grizzly showed up again. -
5:24 - 5:26And she started to chase me,
-
5:26 - 5:28and I had my syringes above my head,
-
5:28 - 5:31and I was swatting the mosquitos,
and I jumped into the truck, -
5:31 - 5:32and I thought,
-
5:32 - 5:34"This is why people do lab studies."
-
5:34 - 5:35(Laughter)
-
5:37 - 5:39I waited an hour.
-
5:39 - 5:40I figured it would take this long
-
5:40 - 5:43for the trees to suck up
the CO2 through photosynthesis, -
5:43 - 5:46turn it into sugars,
send it down into their roots, -
5:46 - 5:49and maybe, I hypothesized,
-
5:49 - 5:52shuttle that carbon belowground
to their neighbors. -
5:53 - 5:55After the hour was up,
-
5:55 - 5:56I rolled down my window,
-
5:56 - 5:58and I checked for mama grizzly.
-
5:59 - 6:01Oh good, she's over there
eating her huckleberries. -
6:02 - 6:04So I got out of the truck
and I got to work. -
6:04 - 6:08I went to my first bag with the birch.
I pulled the bag off. -
6:08 - 6:11I ran my Geiger counter over its leaves.
-
6:11 - 6:12Kkhh!
-
6:13 - 6:15Perfect.
-
6:15 - 6:18The birch had taken up
the radioactive gas. -
6:18 - 6:19Then the moment of truth.
-
6:19 - 6:21I went over to the fir tree.
-
6:21 - 6:23I pulled off its bag.
-
6:23 - 6:25I ran the Geiger counter up its needles,
-
6:25 - 6:28and I heard the most beautiful sound.
-
6:28 - 6:30Kkhh!
-
6:31 - 6:33It was the sound of birch talking to fir,
-
6:34 - 6:37and birch was saying,
"Hey, can I help you?" -
6:37 - 6:41And fir was saying, "Yeah,
can you send me some of your carbon? -
6:41 - 6:43Because somebody
threw a shade cloth over me." -
6:44 - 6:48I went up to cedar, and I ran
the Geiger counter over its leaves, -
6:48 - 6:50and as I suspected,
-
6:51 - 6:52silence.
-
6:53 - 6:55Cedar was in its own world.
-
6:55 - 6:59It was not connected into the web
interlinking birch and fir. -
7:00 - 7:01I was so excited,
-
7:02 - 7:06I ran from plot to plot
and I checked all 80 replicates. -
7:06 - 7:08The evidence was clear.
-
7:08 - 7:11The C-13 and C-14 was showing me
-
7:11 - 7:15that paper birch and Douglas fir
were in a lively two-way conversation. -
7:16 - 7:18It turns out at that time of the year,
-
7:18 - 7:19in the summer,
-
7:19 - 7:23that birch was sending more carbon to fir
than fir was sending back to birch, -
7:23 - 7:25especially when the fir was shaded.
-
7:25 - 7:28And then in later experiments,
we found the opposite, -
7:28 - 7:32that fir was sending more carbon to birch
than birch was sending to fir, -
7:32 - 7:35and this was because the fir was still
growing while the birch was leafless. -
7:36 - 7:39So it turns out the two species
were interdependent, -
7:39 - 7:40like yin and yang.
-
7:41 - 7:44And at that moment,
everything came into focus for me. -
7:44 - 7:46I knew I had found something big,
-
7:46 - 7:51something that would change the way
we look at how trees interact in forests, -
7:51 - 7:53from not just competitors
-
7:53 - 7:55but to cooperators.
-
7:56 - 7:58And I had found solid evidence
-
7:58 - 8:02of this massive belowground
communications network, -
8:02 - 8:03the other world.
-
8:04 - 8:06Now, I truly hoped and believed
-
8:06 - 8:09that my discovery would change
how we practice forestry, -
8:10 - 8:11from clear-cutting and herbiciding
-
8:11 - 8:14to more holistic and sustainable methods,
-
8:14 - 8:17methods that were less expensive
and more practical. -
8:18 - 8:19What was I thinking?
-
8:20 - 8:21I'll come back to that.
-
8:24 - 8:28So how do we do science
in complex systems like forests? -
8:29 - 8:32Well, as forest scientists,
we have to do our research in the forests, -
8:32 - 8:34and that's really tough,
as I've shown you. -
8:34 - 8:37And we have to be really good
at running from bears. -
8:39 - 8:40But mostly, we have to persevere
-
8:40 - 8:43in spite of all the stuff
stacked against us. -
8:43 - 8:46And we have to follow our intuition
and our experiences -
8:46 - 8:48and ask really good questions.
-
8:48 - 8:51And then we've got to gather our data
and then go verify. -
8:51 - 8:56For me, I've conducted and published
hundreds of experiments in the forest. -
8:57 - 9:01Some of my oldest experimental plantations
are now over 30 years old. -
9:02 - 9:03You can check them out.
-
9:03 - 9:05That's how forest science works.
-
9:06 - 9:09So now I want to talk about the science.
-
9:09 - 9:12How were paper birch
and Douglas fir communicating? -
9:12 - 9:16Well, it turns out they were conversing
not only in the language of carbon -
9:16 - 9:19but also nitrogen and phosphorus
-
9:19 - 9:24and water and defense signals
and allele chemicals and hormones -- -
9:24 - 9:25information.
-
9:26 - 9:29And you know, I have to tell you,
before me, scientists had thought -
9:29 - 9:33that this belowground
mutualistic symbiosis called a mycorrhiza -
9:33 - 9:34was involved.
-
9:34 - 9:38Mycorrhiza literally means "fungus root."
-
9:38 - 9:42You see their reproductive organs
when you walk through the forest. -
9:42 - 9:44They're the mushrooms.
-
9:44 - 9:47The mushrooms, though,
are just the tip of the iceberg, -
9:47 - 9:51because coming out of those stems
are fungal threads that form a mycelium, -
9:51 - 9:54and that mycelium
infects and colonizes the roots -
9:54 - 9:56of all the trees and plants.
-
9:56 - 9:59And where the fungal cells
interact with the root cells, -
9:59 - 10:02there's a trade of carbon for nutrients,
-
10:02 - 10:05and that fungus gets those nutrients
by growing through the soil -
10:05 - 10:07and coating every soil particle.
-
10:08 - 10:12The web is so dense that there can be
hundreds of kilometers of mycelium -
10:12 - 10:14under a single footstep.
-
10:15 - 10:20And not only that, that mycelium connects
different individuals in the forest, -
10:20 - 10:26individuals not only of the same species
but between species, like birch and fir, -
10:26 - 10:28and it works kind of like the Internet.
-
10:30 - 10:32You see, like all networks,
-
10:32 - 10:34mycorrhizal networks have nodes and links.
-
10:35 - 10:39We made this map by examining
the short sequences of DNA -
10:39 - 10:44of every tree and every fungal individual
in a patch of Douglas fir forest. -
10:44 - 10:48In this picture, the circles represent
the Douglas fir, or the nodes, -
10:48 - 10:52and the lines represent the interlinking
fungal highways, or the links. -
10:53 - 10:57The biggest, darkest nodes
are the busiest nodes. -
10:57 - 10:59We call those hub trees,
-
10:59 - 11:02or more fondly, mother trees,
-
11:02 - 11:06because it turns out
that those hub trees nurture their young, -
11:07 - 11:09the ones growing in the understory.
-
11:09 - 11:11And if you can see those yellow dots,
-
11:11 - 11:15those are the young seedlings
that have established within the network -
11:15 - 11:16of the old mother trees.
-
11:16 - 11:21In a single forest, a mother tree can be
connected to hundreds of other trees. -
11:22 - 11:24And using our isotope tracers,
-
11:24 - 11:26we have found that mother trees
-
11:26 - 11:29will send their excess carbon
through the mycorrhizal network -
11:29 - 11:31to the understory seedlings,
-
11:31 - 11:34and we've associated this
with increased seedling survival -
11:34 - 11:35by four times.
-
11:36 - 11:39Now, we know we all
favor our own children, -
11:39 - 11:42and I wondered, could Douglas fir
recognize its own kin, -
11:44 - 11:46like mama grizzly and her cub?
-
11:47 - 11:48So we set about an experiment,
-
11:48 - 11:52and we grew mother trees
with kin and stranger's seedlings. -
11:52 - 11:55And it turns out
they do recognize their kin. -
11:55 - 12:00Mother trees colonize their kin
with bigger mycorrhizal networks. -
12:00 - 12:03They send them more carbon below ground.
-
12:03 - 12:05They even reduce
their own root competition -
12:05 - 12:08to make elbow room for their kids.
-
12:08 - 12:12When mother trees are injured or dying,
-
12:12 - 12:16they also send messages of wisdom
on to the next generation of seedlings. -
12:17 - 12:19So we've used isotope tracing
-
12:19 - 12:21to trace carbon moving
from an injured mother tree -
12:21 - 12:24down her trunk
into the mycorrhizal network -
12:24 - 12:26and into her neighboring seedlings,
-
12:27 - 12:29not only carbon but also defense signals.
-
12:29 - 12:31And these two compounds
-
12:31 - 12:35have increased the resistance
of those seedlings to future stresses. -
12:35 - 12:37So trees talk.
-
12:39 - 12:41(Applause)
-
12:41 - 12:42Thank you.
-
12:45 - 12:48Through back and forth conversations,
-
12:48 - 12:50they increase the resilience
of the whole community. -
12:51 - 12:54It probably reminds you
of our own social communities, -
12:54 - 12:56and our families,
-
12:56 - 12:57well, at least some families.
-
12:57 - 12:59(Laughter)
-
13:00 - 13:01So let's come back to the initial point.
-
13:02 - 13:05Forests aren't simply
collections of trees, -
13:05 - 13:08they're complex systems
with hubs and networks -
13:09 - 13:12that overlap and connect trees
and allow them to communicate, -
13:12 - 13:16and they provide avenues
for feedbacks and adaptation, -
13:16 - 13:18and this makes the forest resilient.
-
13:18 - 13:23That's because there are many hub trees
and many overlapping networks. -
13:23 - 13:25But they're also vulnerable,
-
13:25 - 13:28vulnerable not only
to natural disturbances -
13:28 - 13:32like bark beetles that preferentially
attack big old trees -
13:32 - 13:34but high-grade logging
and clear-cut logging. -
13:35 - 13:38You see, you can take out
one or two hub trees, -
13:38 - 13:40but there comes a tipping point,
-
13:41 - 13:44because hub trees are not
unlike rivets in an airplane. -
13:44 - 13:47You can take out one or two
and the plane still flies, -
13:47 - 13:49but you take out one too many,
-
13:49 - 13:52or maybe that one holding on the wings,
-
13:52 - 13:54and the whole system collapses.
-
13:55 - 13:58So now how are you thinking
about forests? Differently? -
13:58 - 13:59(Audience) Yes.
-
13:59 - 14:00Cool.
-
14:01 - 14:02I'm glad.
-
14:03 - 14:07So, remember I said earlier
that I hoped that my research, -
14:07 - 14:10my discoveries would change
the way we practice forestry. -
14:10 - 14:14Well, I want to take a check on that
30 years later here in western Canada. -
14:23 - 14:25This is about 100 kilometers
to the west of us, -
14:25 - 14:28just on the border of Banff National Park.
-
14:29 - 14:31That's a lot of clear-cuts.
-
14:31 - 14:32It's not so pristine.
-
14:34 - 14:39In 2014, the World Resources Institute
reported that Canada in the past decade -
14:39 - 14:43has had the highest forest disturbance
rate of any country worldwide, -
14:44 - 14:45and I bet you thought it was Brazil.
-
14:47 - 14:51In Canada, it's 3.6 percent per year.
-
14:51 - 14:55Now, by my estimation, that's about
four times the rate that is sustainable. -
14:57 - 15:01Now, massive disturbance at this scale
is known to affect hydrological cycles, -
15:01 - 15:03degrade wildlife habitat,
-
15:03 - 15:06and emit greenhouse gases
back into the atmosphere, -
15:06 - 15:09which creates more disturbance
and more tree diebacks. -
15:11 - 15:14Not only that, we're continuing
to plant one or two species -
15:14 - 15:16and weed out the aspens and birches.
-
15:17 - 15:20These simplified forests lack complexity,
-
15:20 - 15:23and they're really vulnerable
to infections and bugs. -
15:23 - 15:25And as climate changes,
-
15:25 - 15:28this is creating a perfect storm
-
15:29 - 15:33for extreme events, like the massive
mountain pine beetle outbreak -
15:33 - 15:35that just swept across North America,
-
15:36 - 15:39or that megafire in the last
couple months in Alberta. -
15:41 - 15:43So I want to come back
to my final question: -
15:45 - 15:47instead of weakening our forests,
-
15:47 - 15:50how can we reinforce them
and help them deal with climate change? -
15:52 - 15:56Well, you know, the great thing
about forests as complex systems -
15:56 - 15:59is they have enormous
capacity to self-heal. -
16:00 - 16:01In our recent experiments,
-
16:01 - 16:05we found with patch-cutting
and retention of hub trees -
16:05 - 16:09and regeneration to a diversity
of species and genes and genotypes -
16:09 - 16:13that these mycorrhizal networks,
they recover really rapidly. -
16:14 - 16:18So with this in mind, I want to leave you
with four simple solutions. -
16:18 - 16:22And we can't kid ourselves
that these are too complicated to act on. -
16:23 - 16:26First, we all need
to get out in the forest. -
16:28 - 16:32We need to reestablish
local involvement in our own forests. -
16:32 - 16:34You see, most of our forests now
-
16:34 - 16:37are managed using
a one-size-fits-all approach, -
16:37 - 16:41but good forest stewardship
requires knowledge of local conditions. -
16:42 - 16:46Second, we need to save
our old-growth forests. -
16:47 - 16:53These are the repositories of genes
and mother trees and mycorrhizal networks. -
16:55 - 16:57So this means less cutting.
-
16:57 - 16:59I don't mean no cutting, but less cutting.
-
17:00 - 17:03And third, when we do cut,
-
17:03 - 17:04we need to save the legacies,
-
17:05 - 17:07the mother trees and networks,
-
17:07 - 17:09and the wood, the genes,
-
17:09 - 17:13so they can pass their wisdom
onto the next generation of trees -
17:13 - 17:16so they can withstand
the future stresses coming down the road. -
17:17 - 17:19We need to be conservationists.
-
17:20 - 17:23And finally, fourthly and finally,
-
17:23 - 17:27we need to regenerate our forests
with a diversity of species -
17:27 - 17:29and genotypes and structures
-
17:29 - 17:32by planting and allowing
natural regeneration. -
17:33 - 17:36We have to give Mother Nature
the tools she needs -
17:36 - 17:38to use her intelligence to self-heal.
-
17:39 - 17:42And we need to remember
that forests aren't just a bunch of trees -
17:42 - 17:44competing with each other,
-
17:44 - 17:45they're supercooperators.
-
17:47 - 17:48So back to Jigs.
-
17:48 - 17:53Jigs's fall into the outhouse
showed me this other world, -
17:53 - 17:56and it changed my view of forests.
-
17:56 - 17:59I hope today to have changed
how you think about forests. -
17:59 - 18:00Thank you.
-
18:00 - 18:06(Applause)
- Title:
- How trees talk to each other
- Speaker:
- Suzanne Simard
- Description:
-
"A forest is much more than what you see," says ecologist Suzanne Simard. Her 30 years of research in Canadian forests have led to an astounding discovery -- trees talk, often and over vast distances. Learn more about the harmonious yet complicated social lives of trees and prepare to see the natural world with new eyes.
- Video Language:
- English
- Team:
- closed TED
- Project:
- TEDTalks
- Duration:
- 18:24
Brian Greene edited English subtitles for How trees talk to each other | ||
Brian Greene edited English subtitles for How trees talk to each other | ||
Brian Greene edited English subtitles for How trees talk to each other | ||
Brian Greene approved English subtitles for How trees talk to each other | ||
Brian Greene edited English subtitles for How trees talk to each other | ||
Joanna Pietrulewicz accepted English subtitles for How trees talk to each other | ||
Joanna Pietrulewicz edited English subtitles for How trees talk to each other | ||
Joanna Pietrulewicz edited English subtitles for How trees talk to each other |