On a west coast of North America.
An old grizzly ambushes his favorite food.
It's never been easier because it's salmon run time.
The river is boiling with migrating fish on their one way trip upstream.
They fight against the river's flow.
The bears reap the rewards.
And here so do the trees.
Because in this place, trees eat fish.
It's all part of a unique cycle that fascinates scientists.
It's got a lot to do with sloppy eating bears
and salmon habits.
Salmon begin their journey in freshwater lakes streams and rivers
as tiny eggs laden gravel beds after hedging the sac fry
life of a nutritious yolk sac attached to their bodies.
When the yolk is all used up, the young salmon must leave the safety
of the gravel nurseries to venture into a much bigger waterworld.
They swim to where the food is plentiful, the salty sea.
On their way
down, they pass so-called estuaries, places
where freshwater meets and mixes with saltwater.
Here
the salmon must undergo a remarkable change called smoltification.
They develop a dark back and a silvery belly.
These color changes help them hide better in the new environment.
Some stay here, while others will swim thousands of kilometers
across the open ocean.
After 1 to 7 years –when the salmon reach adulthood–
they return to their freshwater homes to spawn.
It's all uphill from here.
To help them get there,
they have imprinted the smell of their birthplace in the memory.
Still, they need to overcome many dangerous challenges
like manmade dams, waterfalls and predators.
They become
so single minded about their goal to reproduce that they even stop eating.
They are part of the salmon run.
And once more, they transform. Their color changes
to brown green or even red.
In some species, the males develop a hook and long, sharp teeth ready
to defend their future, spawning territory or to attract a mate.
When arriving at their birthplace, it's time to spawn and die.
But that's not the end of the story, because they leave behind a gift
Their bodies are packed with essential proteins.
A happy feast for the locals,
especially bears.
And their eating habits at this time of the year
have a remarkable effect on every living creature in the area.
Grizzlies, for example, love the salmon run
and they love to get the best seat in the middle of the spectacle.
But when it comes to eating, they choose take away.
They do have some manners and don't eat on the spot.
Instead, they take the prey away to the banks
of the stream or the forest.
Here's where the good manners stop:
They are really sloppy eaters.
That piece of information may sound like an unimportant detail,
but in this story it's actually the most important part.
When preparing for the long winter hibernation,
these giants can eat up to 58,000 calories a day.
When the salmon run is on,
they can afford to take what they want and leave the rest.
So they go for the fattiest parts of the salmon.
The eggs, belly, brain and skin.
In southeastern Alaska,
scientists observed a female bear catching more than 143 kilograms of salmon
over a course of 8 hours. She consumed only a fraction of them.
Another study found bears eat
only about a quarter of each fish and left the rest.
We are talking tons of leftovers.
This huge amount of salmon becomes available to smaller
mammals and birds and the trees of the forest.
How do we know?
Because scientists have found that trees near
salmon streams have impressively high levels of nitrogen.
Nitrogen is an essential element for plant growth.
And it turns out trees can get it from fish.
In the Pacific North, up to 80% of the nitrogen intake
of some tree species can be traced back to salmon Ttees.
Along the banks of salmon stucked rivers, the trees have been found to grow more
than three times faster than trees along salmon free rivers.
And this truly marvelous relationship doesn't stop here.
Every tree benefits! By looking at the growth rings of individual trees,
researchers found that during years when there were more salmon spawning,
the trees grow thicker rings with the higher nitrogen content.
And where do the salmon get all that nitrogen?
From their years at sea.
Good for the trees and also good for the next generation of salmon,
because shade from big healthy trees cools the water
to the ideal temperature for salmon to spawn.
But don't forget the bears. Bears, salmon and trees
form a perfect running cycle together.
A cycle which is good for us humans too.
Trees, especially old trees, are the best technology
for capturing carbon from the atmosphere and storing it.
Old forests are key weapons for fighting climate change.
But for that to continue, this places must remain intact.
And that means salmon and grizzly populations also need to be intact,
because if one element fails,
it all falls apart.
Hi, friends.
Hey friends, thanks for watching! The incredible cycle between salmon, bears and trees
showed us how interconnected everything is. Unfold more about natures magic and
check out our new series.