Alex Rosenthal: The world's largest organism

Recorded atDecember 07, 2020
Duration (min:sec)06:03
Video TypeTED-Ed Original
Words per minute154.99 slow
Readability (FK)53.98 medium
SpeakerAlex Rosenthal

Official TED page for this talk


The largest animal in the world is the blue whale, which weighs a massive 150 metric tons. Even so, it's not remotely close to being the largest organism by weight. That title goes to an organism so huge that it's estimated to weigh the equivalent of 40 blue whales. So what is this behemoth? And... where is it? Alex Rosenthal shares the story of the enormous and ancient Pando. [Directed by Lisa LaBracio, narrated by Jack Cutmore-Scott, music by AIM Creative Studios].

Text Highlight (experimental)
100:06 This is Goliath, the krill.
200:09 Don’t get too attached.
300:11 Today this 1 centimeter crustacean
400:13 will share the same fate as 40 million of his closest friends:
500:18 a life sentence in the belly of the largest blue whale in the world.
600:22 Let’s call her Leviatha.
700:25 Leviatha weighs something like 150 metric tons,
800:29 and she’s the largest animal in the world.
900:33 But she’s not even close to being the largest organism by weight,
1000:38 which is estimated to equal about 40 Leviatha’s.
1100:41 So where is this behemoth?
1200:44 Here, in Utah.
1300:46 Sorry, that’s too close.
1400:48 Here.
1500:49 This is Pando, whose name means “I spread out.”
1600:54 Pando, a quaking aspen, has roughly 47,000 genetically identical clone trunks.
1701:01 Those all grow from one enormous root system,
1801:05 which is why scientists consider Pando a single organism.
1901:09 Pando is the clear winner of world’s largest organism by weight
2001:14 an incredible 6 million kilograms.
2101:18 So how did Pando get to be so huge?
2201:22 Pando is not an unusual aspen from a genetic standpoint.
2301:26 Rather, Pando’s size boils down to three main factors:
2401:30 its age, its location, and aspens’ remarkable evolutionary adaptation
2501:36 of self-cloning.
2601:38 So first, Pando is incredibly expansive because it’s incredibly old.
2701:43 How old exactly?
2801:45 No one knows.
2901:47 Dendrochronologist estimates range from 80,000 to 1 million years.
3001:54 The problem is, there’s no simple way to gauge Pando’s age.
3101:58 Counting the rings of a single trunk will only account for up to 200 years or so,
3202:03 as Pando is in a constant cycle of growth, death, and renewal.
3302:09 On average, each individual tree lives 130 years,
3402:13 before falling and being replaced by new ones.
3502:17 Second: location.
3602:19 During the last ice age, which ended about 12,000 years ago,
3702:23 glaciers covered much of the North American climate
3802:26 friendly to aspens.
3902:28 So if there were other comparably sized clonal colonies,
4002:32 they may have perished then.
4102:35 Meanwhile, Pando’s corner of Utah remained glacier-free.
4202:39 The soil there is rich in nutrients that Pando continuously replenishes;
4302:44 as it drops leaves and trunks,
4402:46 the nutrients return to nourish new generations of clones.
4502:50 Which brings us to the third cause of Pando’s size: cloning.
4602:55 Aspens are capable of both sexual reproduction
4702:59 which produces a new organism
4803:01 and asexual reproduction— which creates a clone.
4903:05 They tend to reproduce sexually when conditions are unfavorable
5003:10 and the best strategy for survival is to move elsewhere.
5103:14 Trees aren’t particularly mobile, but their seeds are.
5203:18 Like the rest of us, sexual reproduction is how Pando came into the world
5303:23 in the first place all those tens or hundreds of thousands of years ago.
5403:28 The wind or a pollinator carried pollen from the flower of one of its parents
5503:32 to the other, where a sperm cell fertilized an egg.
5603:36 That flower produced fruit, which split open,
5703:39 releasing hundreds of tiny, light seeds.
5803:42 The wind carried one to a wet spot of land in what is now Utah,
5903:46 where it took root and germinated into Pando’s first stem.
6003:51 A couple of years later, Pando grew mature enough to reproduce asexually.
6103:56 Asexual reproduction, or cloning,
6203:59 tends to happen when the environment is favorable to growth.
6304:03 Aspens have long roots that burrow through the soil.
6404:08 These can sprout shoots that grow up into new trunks.
6504:12 And while Pando grew and spread out, so did our ancestors.
6604:16 As Hunter-gatherers who made cave paintings, survived an ice age,
6704:20 found their way to North America, built civilizations in Egypt and Mesopotamia,
6804:26 fought wars, domesticated animals, fought wars, formed nations,
6904:30 built machines,
7004:31 and invented the internet, and always newer ways to fight wars.
7104:37 Pando has survived many millennia of changing climates and encroaching ice.
7204:42 But it may not survive us.
7304:45 New stems are growing to maturity much more slowly than they need to
7404:50 in order to replace the trunks that fall.
7504:53 Scientists have identified two main reasons for this.
7604:56 The first is that we’ve deprived Pando of fire.
7705:00 When a fire clears a patch of forest, Aspen roots survive,
7805:05 and send shoots bursting up out of the ground by the tens of thousands.
7905:10 And secondly, grazers like herds of cattle and mule deer
8005:14 whose natural predators we’ve hunted to the point of local elimination
8105:18 are eating Pando’s fresh growth.
8205:21 If we lose the world’s largest organism, we’ll lose a scientific treasure trove.
8305:27 Because Pando’s trunks are genetically identical,
8405:30 they can serve as a controlled setting for studies
8505:33 on everything from the tree microbiome
8605:36 to the influence of climate on tree growth rates.
8705:39 The good news is, we have a chance to save Pando,
8805:43 by reducing livestock grazing in the area
8905:46 and further protecting the vulnerable young saplings.
9005:50 And the time to act is today.
9105:53 Because as with so many other marvels of our natural world,
9205:57 once they’re gone it will be a very, very long time before they return.