As many as half of Earth's species may be
already migrating to escape warming temperatures.
Plants are inching northward
and so are many animals.
The Arctic ecosystem is particularly vulnerable to invasion.
Scientists aboard this research ship are hunting
the most important fish in the Arctic: polar cod.
Mixed in with the Arctic fish are invaders
including Atlantic cod and capelin.
The southern species compete for polar cod's food.
So here is a very typical Arctic food web
or food chain.
This food web is changing now.
These fish are among many species
migrating into the warming Arctic.
Relatively few species have evolved
to survive its frigid darkness.
Polar cod have some of the most impressive
adaptations to survive.
They use a trick that's common among arctic animals,
they store lots of fat in their bodies.
Polar cod eat tiny copepods,
which also store fat to survive the long winter.
And a high energy meal is crucial
for surviving the harsh Arctic.
One trawl after another reveals southern interlopers.
Out of a thousand fish caught in this trawl,
roughly 70% by weight are southern species.
It's hard for the scientists to pinpoint precisely
when we cross the boundary
between Atlantic and Arctic waters,
but that boundary has been slowly creeping northward.
Scientists call this process
the 'Atlantification' of the Arctic.
Atlantic waters are saltier and they mostly lack ice.
The biggest difference?
Atlantic water is as much as seven degrees warmer.
The polar Cod likes the colder water,
but it's losing territory.
Polar Cod flourish in the shallow waters
of the Barents Sea, but further north it's too deep for them.
Meanwhile, the warmer waters bring with them
new species that are shaking up the food web.
Along with new fish, there are Atlantic varieties of copepods.
They store much less fat than copepods native
to the Arctic, making them a less nutritious food source.
That means polar cod may have to spend more energy hunting.
For the same amount of animals that are gonna be eaten,
you don't transfer the same amount of energy.
Capelin, as well as Atlantic Cod,
were among the invaders we just caught in the trawl.
Capelin will also feed on the same prey
as the polar cod, so we start adding competition
between these two species.
The Atlantic Cod goes one step further:
it eats the polar cod itself.
Capelin's not as rich as polar cods, so that goes
or diminishes, then these levels will also be impacted.
It's easy to vilify the southern species
threatening the ecological balance here.
But take the Atlantic cod,
in their natural habitat, overfishing and now
rising temperatures have decimated its population.
So here in the Arctic, Atlantic Cod seems like an invader,
but it's also a climate refugee from the south
and its main predator is another
key species advancing northward.
Historically, most humans who have come to the Arctic
have taken a lot more than data and a few samples.
For at least 45,000 years, people have been coming
to this paradoxical region.
Punishing, desolate but rich with resources.
Humans are the Arctic's ultimate apex predator
and yet we're only getting started.
With countries like Norway extracting fossil fuels offshore,
other sectors are also expanding northward.
From tourism, to shipping, to military operations.
So the stressers in the Arctic
are probably going to intensify.
As the climate here changes
so will the meaning of the word Arctic.
For the animals who, for now, call it home.