Thanks to CuriosityStream for supporting this episode!
Go to CuriosityStream.com/SciShow to learn more.
[ intro ]
What do you think of
when you imagine giant dunes of sand?
Maybe punishing heat, little water,
and practically no life.
Basically, a desert.
But the northernmost parts of Alberta and Saskatchewan in Canada
are not a desert.
It’s below freezing for half the year.
There’s enough precipitation to sustain
the world’s twentieth largest lake.
And yet here, at a latitude of fifty-nine [59] degrees,
lies the Athabasca dunes.
They’re one of the world’s northernmost dune fields,
and one of planet Earth’s most unique habitats.
Like much of northern North America,
Athabasca sits on the Canadian Shield,
a large expanse of nearly exposed bedrock.
The Shield formed during past periods of glaciation,
when huge sheets of ice covered
what is now Canada and parts of the United States.
This ice basically scraped everything down to that bedrock.
The dunes themselves date to the end of Earth’s last glacial period,
somewhere around ten thousand years ago.
These ice sheets were mind-bogglingly thick --
comparable modern ice sheets like Greenland’s can be three kilometers deep.
And although we think of glaciers as just kind of sitting there,
they actually flow in slow motion.
The material they scrape off --
and by material, I mean stuff like mountains --
gets pulverized down into what’s called till.
As the planet warmed and the glaciers retreated north,
much of that till was carried along for the ride.
Think about how much water must’ve been produced
by the melting of a kilometer-thick ice sheet the size of Canada.
Around eight or nine thousand years ago,
that flood dumped a big deposit of till into a massive lake.
As that lake receded,
it left behind what we now know of as the Athabasca dunes.
Then, the wind took over.
As the ice sheet pulled back,
cold air from the top rushed down
and created powerful winds that blew in a southeasterly direction.
This cool, dry air was key to slowing the growth of plants
that otherwise would have stabilized the sand with their root systems.
As the sand blew around, it didn’t just pile up into nice, floofy mounds.
Instead, it abraded any rock formations
that somehow survived being crushed by the ice.
This generated even more sand
and broke it all down into smaller and smaller bits.
Eventually, the climate warmed enough,
and the glaciers receded far enough,
that the winds shifted to a more northerly angle, where they remain today.
But by that point, there was already a lot of sand.
Today, individual dunes can rise thirty 30 meters high
and stretch for up to a kilometer and a half in length.
For a region with such unusual geology,
it might not surprise you to know
there’s a bunch of interesting life, too.
The presence of so much water
has allowed for the development of an ecosystem
that’s pretty unlike what you’d find in a desert.
There are quite a few rare forms of life found here,
and a concentration of specialist species
not found anywhere else this far north.
In fact, the Athabasca dunes
are home to ten endemic species,
which means they’re not found anywhere else on the planet.
None of them are giant worms, unfortunately.
All ten of these species are plants,
and they’ve evolved a number of adaptations
to the unusual and shifting conditions of the dunes.
Their outer protective layer,
called the cuticle, is extra tough
to withstand the constant abrasion of windborne sand.
Many grow especially quickly to help avoid being buried under a shifting dune.
And if that doesn’t work, some grow rhizomes,
which are secondary stems that sprout from the root system.
Perhaps the rarest of these species is the Athabasca Thrift.
To avoid the dunes entirely,
it makes its home on a compacted layer of pebbles
and sand called gravel pavement.
Another rare species is the Large-headed Woolly Yarrow.
It’s name sounds kind of ridiculous,
the name refers to the tiny hairs that cover its stem
and help the yarrow retain precious moisture against the relentless wind.
Another species,
called Turnor’s WIllow,
grows up to four meters tall to peek above the shifting sands.
If one of its thin, flexible branches does get buried,
it can become the start of a root system for a new,
cloned copy of the tree.
Even its seeds are well adapted --
their light weight and fine hairs
help the wind carry them to new locations.
Unlike a lot of unique environments,
the Athabasca dunes are actually pretty well protected.
They fall largely within Saskatchewan’s Athabasca Sand Dunes Provincial Park,
which is accessible only by float plane.
Of course,
distance from civilization isn’t much protection from climate change,
but so far the populations of the dunes’ most important species seem stable.
Let’s keep our fingers crossed,
because there aren’t that many lakeside, snowcapped dunefields out there.
In fact, I think there’s only one.
And now we’re going to take you from the freezing dunes of Canada
to the more conventional hot ones of the Arabian desert,
where there lives another dune-adapted species: the sand cat.
They’re the world’s only desert-dwelling cat,
and they have about the cutest cheeks we’ve ever seen,
and you can learn about them in the CuriosityStream documentary “Sand Cats,”
part of the series “Small Cats Unknown.”
And once you’re done learning about cats,
CuriosityStream has over 2400 other documentaries and nonfiction titles for you to enjoy,
including exclusive originals.
CuriosityStream is a subscription streaming service that’s available worldwide,
with content spanning science, nature, tech, lifestyle, and more.
You can get unlimited access starting at just $2.99 a month,
and for SciShow viewers,
the first 31 days are completely free
if you sign up at curiositystream.com/scishow and use the promo code ‘scishow’
during the sign-up process.
[ outro ]