The world’s largest organism - Alex Rosenthal
This is Goliath, the krill.
Don’t get too attached.
Today this 1 centimeter crustacean
will share the same fate as 40 million
of his closest friends:
a life sentence in the belly
of the largest blue whale in the world.
Let’s call her Leviatha.
Leviatha weighs
something like 150 metric tons,
and she’s the largest animal in the world.
But she’s not even close to being
the largest organism by weight,
which is estimated to equal
about 40 Leviatha’s.
So where is this behemoth?
Here, in Utah.
Sorry, that’s too close.
Here.
This is Pando, whose name means
“I spread out.”
Pando, a quaking aspen, has roughly
47,000 genetically identical clone trunks.
Those all grow from one
enormous root system,
which is why scientists consider Pando
a single organism.
Pando is the clear winner
of world’s largest organism by weight—
an incredible 6 million kilograms.
So how did Pando get to be so huge?
Pando is not an unusual aspen
from a genetic standpoint.
Rather, Pando’s size boils down
to three main factors:
its age, its location, and aspens’
remarkable evolutionary adaptation
of self-cloning.
So first, Pando is incredibly expansive
because it’s incredibly old.
How old exactly?
No one knows.
Dendrochronologist estimates range
from 80,000 to 1 million years.
The problem is, there’s no simple way
to gauge Pando’s age.
Counting the rings of a single trunk will
only account for up to 200 years or so,
as Pando is in a constant cycle of growth,
death, and renewal.
On average, each individual tree
lives 130 years,
before falling and being
replaced by new ones.
Second: location.
During the last ice age,
which ended about 12,000 years ago,
glaciers covered much
of the North American climate
friendly to aspens.
So if there were other comparably
sized clonal colonies,
they may have perished then.
Meanwhile, Pando’s corner of Utah
remained glacier-free.
The soil there is rich in nutrients
that Pando continuously replenishes;
as it drops leaves and trunks,
the nutrients return to nourish
new generations of clones.
Which brings us to the third cause
of Pando’s size: cloning.
Aspens are capable
of both sexual reproduction—
which produces a new organism—
and asexual reproduction—
which creates a clone.
They tend to reproduce sexually
when conditions are unfavorable
and the best strategy for survival
is to move elsewhere.
Trees aren’t particularly mobile,
but their seeds are.
Like the rest of us, sexual reproduction
is how Pando came into the world
in the first place all those tens
or hundreds of thousands of years ago.
The wind or a pollinator carried pollen
from the flower of one of its parents
to the other, where a sperm
cell fertilized an egg.
That flower produced fruit,
which split open,
releasing hundreds of tiny, light seeds.
The wind carried one to a wet spot
of land in what is now Utah,
where it took root and germinated
into Pando’s first stem.
A couple of years later, Pando grew mature
enough to reproduce asexually.
Asexual reproduction, or cloning,
tends to happen when the environment
is favorable to growth.
Aspens have long roots that burrow
through the soil.
These can sprout shoots that grow up
into new trunks.
And while Pando grew and spread out,
so did our ancestors.
As Hunter-gatherers who made
cave paintings, survived an ice age,
found their way to North America, built
civilizations in Egypt and Mesopotamia,
fought wars, domesticated animals,
fought wars, formed nations,
built machines,
and invented the internet,
and always newer ways to fight wars.
Pando has survived many millennia
of changing climates and encroaching ice.
But it may not survive us.
New stems are growing to maturity
much more slowly than they need to
in order to replace the trunks that fall.
Scientists have identified two main
reasons for this.
The first is that we’ve deprived
Pando of fire.
When a fire clears a patch of forest,
Aspen roots survive,
and send shoots bursting up out
of the ground by the tens of thousands.
And secondly, grazers like herds of cattle
and mule deer—
whose natural predators we’ve hunted
to the point of local elimination—
are eating Pando’s fresh growth.
If we lose the world’s largest organism,
we’ll lose a scientific treasure trove.
Because Pando’s trunks
are genetically identical,
they can serve as a controlled setting
for studies
on everything from the tree microbiome
to the influence of climate
on tree growth rates.
The good news is,
we have a chance to save Pando,
by reducing livestock grazing in the area
and further protecting
the vulnerable young saplings.
And the time to act is today.
Because as with so many other marvels
of our natural world,
once they’re gone it will be a very,
very long time before they return.
