♪♪♪ SHAPIRO: I remember driving into the valley and sort of feeling like I had somehow arrived.
There is absolutely magic in that valley.
KLINE: Yosemite is natural beauty on a grand scale.
From the world's most famous vertical wall... PUTNAM: It's a kilometer deep, so it's many times taller than the Empire State Building.
KLINE: ...to the earth's largest living trees.
TOM: Over 3,000 years, think of what a giant sequoia has seen.
KLINE: This snowy range holds secrets both great and small.
And all of them are bound together by a single source of life.
It's the power of water that made life in this stone wilderness possible.
But California's climate is changing -- from flash floods to extreme drought.
How will Yosemite endure as it faces an uncertain future?
♪♪♪ [ Bird chirping ] ♪♪♪ KLINE: As the glow of pre-dawn light fills Yosemite, the forests begin to stir.
Before the moon has been properly put to bed, many who live here enjoy the early quiet when they still have the valley to themselves.
[ Birds chirping ] ♪♪♪ KLINE: This is the time to rise and take in the majesty of the High Sierra.
♪♪♪ As sunlight streams across Yosemite Valley, visitors begin to arrive.
Hang glider pilots are readying their aircraft at Glacier Point.
SHAPIRO: Watching the sun crack the horizon and light fill in the valley, it's like you can almost feel the history of the place.
KLINE: Yosemite has become a beacon for adventurers like Jeff Shapiro.
SHAPIRO: While you're setting up, the waterfalls across the valley are sort of beckoning.
It's just a place that is tangibly different than everywhere else on the planet.
That place holds magic.
Watch that wing tip on that rock.
You know, you check your gear, and you feel prepared, and you walk out to launch.
You turn the nose into the wind, and when everything is right, and the conditions feel right... Clear.
...it's 10 steps and into pure freedom.
♪♪♪ You get to fly away like a bird.
KLINE: For those brave enough to take those first few steps, the reward is breathtaking.
For this is a land of giants.
Stone monoliths far larger than any skyscraper, and trees bigger than blue whales.
This is the Sierra Nevada.
It stretches the length of California and into Nevada.
Forged by time and shaped by the power of water.
These forces carved out Yosemite's most iconic valley, gave birth to countless wild rivers, and made life in this stone wilderness possible.
SHAPIRO: I think we're not meant to fly, but we all wish we were.
To see it from the view a peregrine would see it feels pretty special.
[ Wind rushing ] [ Grunts ] Whoo!
KLINE: Yosemite owes much of its grandeur to countless waterfalls, including the tallest in North America, Yosemite Falls.
And here lies the Sierra's greatest secret.
In an otherwise dry climate, this snowy range bears the gift of water.
In winter, enough snow accumulates in these mountains to provide more than 30% of all of California's fresh water.
But as global temperatures rise, snowpack is shrinking.
To make matters worse, California is in the midst of a record-breaking drought.
And one critter may be feeling the heat more than most.
This little guy is an American pika.
Although he looks like a rodent, he's actually the smallest cousin of the rabbit.
But don't be fooled by his cuddly appearance.
Pikas are built for the cold, and they live in some of the harshest places on Earth, from the Ural Mountains of Russia to the Himalayas.
Right now, it's spring, and like the rest of the pikas in this rocky slope, he's hard at work.
♪♪♪ Pikas don't hibernate, and that means they'll need to gather and store enough food for the long, cold winter ahead.
This pika will make up to a hundred trips in a single day.
Provided they're all no more than 60 feet from home.
And for good reason.
For the little pika, danger is everywhere.
When you're the size of a potato... [ Pika chirping ] ...you're on the menu for a lot of the predators here.
At first sight of the coyote, the little pika calls to warn the others.
[ Chirping ] But as soon as the coast is clear, he's back to work.
By mid-summer, the pika's hay piles have reached enormous proportions -- so big they dwarf the little pika itself.
But this pika may be preparing for a winter that never comes.
With global temperatures on the rise and snowpack in decline, this Ice Age critter is facing an uncertain future, along with many others that call these mountains home.
[ Birds squawking ] ♪♪♪ SHAPIRO: El Cap is one of the most special places on the planet for people who love to climb.
It represents the most beautiful piece of rock that you could possibly find yourself on.
KLINE: No single vertical wall on Earth is more famous among climbers than El Capitan.
PUTNAM: It's a kilometer deep, so it's many times taller than the Empire State Building, and it displays unique geology.
KLINE: Geologist Roger Putnam and Jeff Shapiro are preparing for an ascent of El Capitan, a journey that could take them nearly a week.
SHAPIRO: [ Laughs ] The pig.
PUTNAM: The pig.
The thought of climbing El Cap to people in the early '50s or even up until it was first climbed in 1958, it seemed like the impossible.
It seemed just as remote as getting someone to the moon, because the techniques for climbing cliffs that big didn't exist.
Climbers come from all over the world to climb on El Cap, because of this particularly hard rock that can build up all those stresses and create those long, beautiful, perfect fractures.
I look at El Cap, and I see this complex history of weathering and erosion which made it look the way it does and continues to shape it to this day.
Water played a significant role in almost every part of the evolution of El Capitan and Yosemite Valley.
Water played a crucial role in actually carving out these beautiful valleys, and then glaciers polished and refined them into their iconic shapes.
El Cap was shaped within the past 1.8 million years, and the rock was formed about 100 million years ago.
That's when the dinosaurs were around.
Super common thing.
So the feature that I'm standing on is one of those exfoliation flakes.
[ Pounding ] Hear that noise?
And it puts things into perspective.
When you climb a rock that big and spend this much time around something that's this big, you feel really small.
I think about how small I am all the time.
How physically small I am and then how small I am in terms of geologic time.
♪♪♪ KLINE: Roger and Jeff set camp for the night.
This is just the first of many before they reach the summit.
SHAPIRO: You mind sleeping on the inside or outside or what?
PUTNAM: Oh, I don't care.
KLINE: It's easy to feel small in Yosemite.
It has a way of putting everything in perspective.
♪♪♪ PUTNAM: El Cap is a source of inspiration academically, mentally, physically, and it's also a source of gravitas.
KLINE: It's the last leg of Jeff and Roger's climb, but they are not quite ready to end their journey.
SHAPIRO: For me, laying on a portaledge and waking up in the morning and looking at the valley peaceful and, you know, sort of quiet in those morning hours, there's no place I'd rather be.
It's a unique place to be. It feels like it was earned.
It feels so close to civilization, but so far away, you know.
♪♪♪ PUTNAM: Yeah, buddy!
KLINE: Another arid summer unfolds, as drought persists.
Temperatures continue to rise, and forests are dying at an unprecedented rate.
Across the state, the number of dead trees has now passed 100 million.
And this sparks another problem... [ Fire crackling ] Wildfires.
[ Radio chatter ] [ Helicopter blades whirring ] [ Radio chatter ] KLINE: A century of fire suppression has created unnaturally dense stands, now filled with dead trees.
Making an already volatile situation even more explosive.
By the end of summer, this will have been one of the most damaging wildfire seasons on record.
[ Fire crackling ] ♪♪♪ Yet fire is a natural part of the ecosystem, and certain species depend upon fire for their very survival.
These black-backed woodpeckers are drawn to recently charred forests.
It's their best chance for a meal.
They'll seek out woodboring beetles in the remains of these trees.
These scorched forests are far from dead.
They are, in fact, new habitat, equally vibrant and vital.
Only recently have we begun to develop a deeper appreciation for the role fire plays in the evolution of many species, from the black-backed woodpeckers to the world's largest living trees.
♪♪♪ Sequoia National Park is home to a forest of giants.
NATE: I am so energized by these forests here.
I'm a forest nut.
And the big trees give me goose bumps every time I see them even though I've been seeing them for more than 35 years now.
KLINE: Nate Stephenson is a forest ecologist with the U.S. Geological Survey.
He has a unique understanding of the crucial part fire plays in the life cycle of giant sequoias.
NATE: So, the bark of giant sequoias is remarkably thick.
[ Tree thuds ] And it's very fibrous, and it's fire resistant.
So when you have that much thickness there, some of it might burn off during a fire, but there is enough left over to protect the tree.
Fire has been burning at the base of giant sequoias probably for millions of years, and this is one of the sequoia's responses to that.
To take advantage of the fire in one sense and then to protect itself from fire.
KLINE: Giant sequoias are the largest trees on Earth.
They can grow for more than 3,000 years.
But without fire, they cannot reproduce.
NATE: The giant sequoias really are born of fire.
Fire gives them three things they need for regeneration.
The first one is, it punches a hole in the forest.
That allows there to be more light and more water for the sequoia seedlings.
The second thing it does is it heats the cones up in the mature sequoia trees without harming the trees.
And those cones open up.
♪♪♪ And there's a rain of seeds on the ground.
And the final thing it's done is it cleared away all the leaves that have built up.
Because sequoia seeds need to hit bare mineral soil before they can germinate and survive well.
♪♪♪ Then the winter storms come in and bury them in a blanket of snow.
And then when the spring comes, they have the ideal conditions.
It's warmer. It's really wet, and those seeds will take off and become seedlings.
♪♪♪ KLINE: From their birth among the ashes, these seedlings have become the groves we see today... ...with trees nearly 300 feet tall.
NATE: Over 3,000 years, think of what a giant sequoia has seen.
How many times did Native Americans sit at the base, have lunch, look up, and marvel at the crown of the sequoia?
And now we're doing it again today.
It's humans just living their lives under these trees for millennia.
♪♪♪ [ Birds chirping ] KLINE: These ancient groves provide a home for a diversity of wildlife... ...that often goes unnoticed.
A family of yellow-bellied marmots has taken up residence at the base of this giant sequoia.
These little guys are spring pups, and they're just beginning to explore their world.
Cautiously at first.
They are part of an extended family of a dozen individuals or maybe more.
And right now, they're sticking close to their brothers and sisters.
While some adults are keeping a watchful eye, the rest are fattening up for winter.
During the summer, marmots eat at a frenzied pace.
[ Birds chirping ] They can spend nine months of the year hibernating, so storing up enough fat is vital.
And some marmots will have doubled their body weight by the end of summer.
The little ones don't seem to have the same urgency to fill up as their parents do, but they'll need to learn quick.
Without enough fat reserves, they won't make it through the winter.
Before they really get started, their mealtime is cut short.
Something is coming.
It's a black bear.
[ Bear growls ] A marmot sounds the alarm to alert the colony.
[ Marmot chirping ] But the bear pays little attention to the marmots.
Fattening up on these fresh fir shoots is a far easier way to prepare for the coming winter.
Here wildlife can live out their lives relatively undisturbed.
And this is no accident.
Yosemite, along with Sequoia and Kings Canyon National Parks, are the Sierra's greatest sanctuaries... ...protecting critical habitat and restoring species once thought lost.
Peregrine falcons, long absent from these mountains, have returned home to nest once again on the cliffsides of the Sierra.
[ Falcons keening ] ♪♪♪ And they are not alone.
One of the Sierra's greatest icons is staging its return.
♪♪♪ [ Device beeping ] No animal embodies the wildness of this range more than the Sierra Nevada bighorn sheep.
John Muir called them 'the bravest of all Sierra Mountaineers.'
FEW: People talk about them being icons of wilderness.
They sit out lightning storms on alpine ridges.
Yosemite is full of steep, craggy, rocky landscapes, and that's exactly where bighorn sheep thrive.
KLINE: This makes the job of the Sierra Bighorn Sheep Recovery Program a constant challenge.
Today, Alex Few and Tom Stephenson are in the Eastern Sierra, trying to determine just how many sheep are in this vast range.
FEW: There were once about 10,000 Sierra bighorn, and they're one distinct subspecies of bighorn of three found in North America.
KLINE: Bighorns rely on the strength of the herd to survive.
From the time they're born, they have less than 48 hours to keep up with mom and the rest of the herd across these jagged cliffs.
[ Wind howling ] Life in these mountains can be a test of extremes.
[ Thunder rumbling ] Flash floods and lightning storms one day can be followed by months or even years of bone-dry conditions.
Yet the Sierra bighorns were undaunted by these extremes.
That would all change with a single event.
The discovery of gold in the mid-1800's put the Sierra Nevada on the map.
And thousands of settlers began to move west.
[ Sheep bleating ] With them came millions of domestic sheep.
But these sheep would prove to be the bighorns' Kryptonite.
With no resistance to the diseases they carried, bighorn populations would plummet, disappearing entirely from Yosemite's high country.
By the 1990s, only 100 bighorns were scattered across the Sierra.
TOM: There became a tremendous amount of concern about the potential for the population to go extinct, and recovery efforts were undertaken.
KLINE: Their goal -- to restore Sierra bighorns to their former range.
FEW: Bighorn sheep are really slow to colonize new habitat, so we have to help them get there.
KLINE: Bighorns are placed in large metal transport crates and flown into the heart of Yosemite's high country.
As simple as it seems, this moment is the culmination of years of preparation for Alex and her crew.
While some are eager for their new freedom, others are more hesitant.
FEW: When we opened the gate, I felt this overwhelming sense of pride and hope.
KLINE: Thanks to these recovery efforts, there are now 600 sheep in the Sierra Nevada.
For the first time in a century, bighorns have reclaimed their rightful place in Yosemite's high country.
This is just one more step in returning Yosemite's wilderness to the wild things that once called it home.
♪♪♪ As the drought stretches through summer with no relief in sight, these continued arid days are threatening another icon of the Sierra.
NATE: What has really pushed this drought into new terrain for severity is the increased temperature.
KLINE: Temperatures rising from climate change have amplified the drought's effects.
NATE: It increases the evaporative power of the atmosphere.
So the atmosphere is pulling more water out of the plants than it would normally.
With that, we are seeing things happen in giant sequoias that have never been reported before.
KLINE: Sequoias are losing foliage at an unprecedented rate, in some cases more than half the tree.
In order to better understand the impact, researcher Anthony Ambrose and his team need to look high up in the canopy of these giants.
♪♪♪ AMBROSE: We're going to collect some leaf samples from the top of the tree and the base of the crown to measure the water status of the tree and to get a better idea of how stressed they are.
KLINE: The tree acts as a timeline stretching back thousands of years, and the further up you go, the closer you get to the effects of today.
The team continuously monitors these sequoias to determine how they are faring as their most crucial resource, water, is in diminishing supply.
AMBROSE: These trees we've measured use between 500 and 800 gallons of water a single day in the summertime.
Which is just a phenomenal amount of water.
That all gets supplied by the snowmelt here in the Sierra Nevada.
The snowpack is a really, really important water source for the giant sequoia forest.
We put the leaf end in this chamber here and pressurize it slowly, and as soon as the water comes up onto the surface, we record how much pressure it took to push the water out.
So the measurements that we've been getting so far over the last couple weeks is indicating that they are definitely at stress levels greater then we've ever measured in giant sequoias before.
This is the first time that I've ever been climbing in these trees and actually observed anything that's noticeable stress.
So it is kind of upsetting in a way.
But I take some comfort in the fact, knowing that these are really tough trees.
They're really resilient, and they've dealt with droughts and fires and other really extreme conditions in the past.
With temperatures continuing to increase, they may reach some tipping point.
And that's what we're trying to learn.
At what point is it too much for them to recover?
KLINE: As summer comes to a close, cool autumn breezes bring relief to a parched Yosemite Valley.
In the high country, it's the beginning of the rut -- mating season for bighorn sheep.
These young rams are assessing each other's strengths and weaknesses.
Male bighorn sheep live in a highly competitive world.
These competitions are a way of establishing dominance.
Their ranking may ultimately determine who gets to breed.
It's an enormous expenditure of energy, but it's the price of admission if this young ram hopes to mate.
In the Eastern Sierra, fall colors unfold with a dusting of snow -- a promising sign in an otherwise dry autumn.
Water has become an increasingly scarce commodity.
[ Birds chirping ] And places where water persists are now critically important.
Despite autumn's light snowfall, bone-dry conditions continue to plague the Sierra.
[ Woodpecker tapping ] But now, as winter approaches, a storm front is building.
[ Thunder rumbles ] Cool wind sweeps across the valley, extinguishing the heat.
And for the first time in far too long, the air is heavy with moisture.
[ Thunder rumbling ] ♪♪♪ As temperatures drop, the chill in the high country gives way to the first big snow of the season.
♪♪♪ After a long hiatus, winter has returned to Yosemite.
Waterfalls collect icicles along their edges.
And streams become a thick slurry of snow and ice.
Lakes freeze under a blanket of fresh snow.
[ Coyote yipping ] Life in the valley seems to pause as winter takes hold.
♪♪♪ Yosemite takes on a fairy-tale quality that seems both benevolent and menacing.
♪♪♪ Animals waste no time preparing for a winter that is suddenly upon them.
Deer forage for what little remains.
And squirrels harvest the last of the pine nuts before they are buried by the quickly falling snow.
[ Coyotes yipping ] A pair of coyotes tiptoes through fresh snowdrifts, searching for voles.
It takes skill to catch something you can't see.
And patience not to let your food know you're coming.
[ Snow crunches ] [ Vole chirping ] [ Vole chirping ] But if you stick with it, the reward is well worth it.
'Cause at the end of the day, in Yosemite Valley, it's every coyote for himself.
A pika takes advantage of a break in the snowfall to gather up a few remaining twigs.
He joins the ranks of the few brave enough to endure winter in the high country.
Hopefully, his hay piles will be enough to see him through the frigid months ahead.
♪♪♪ For the Sierra Nevada, this year's snowfall may be a tiny drop in the bucket.
But its impact on those working to protect these groves cannot be overstated.
NATE: It's been pretty dry, and the trees have looked pretty stressed, and I'm looking forward to leaving that behind.
It just feels full of life here again.
♪♪♪ AMBROSE: It's been several years since we've had a good snowpack here in the Sierras, and it's just so beautiful.
And the trees are gonna be loving this, for sure.
KLINE: The research team returns to the Giant Forest, a forest that continues to surprise them.
NATE: I've gotten what for me seems like an epiphany.
We've always known that sequoia groves are wetter spots on the landscape than the rest of the forest.
It also seems to me now that even during droughts, they have a more reliable water supply.
So not only do they have more, it just stays more even through time.
And that really drives home what a magical spot sequoias grow in.
KLINE: Outside these groves, firs, pines, and cedars have been dying in numbers never seen before.
But the trees within these groves are thriving.
AMBROSE: Now that we have kind of a baseline during the severe drought, we'd like to continue that into the future and monitor how they respond to changing climatic conditions over time.
Okay, the height here is 4.30 meters.
KLINE: The health of these giants indicates a hidden supply of water, somewhere below the surface.
And as temperatures continue to rise in the coming years, countless species may endure in the shadow of these giants.
♪♪♪ As night falls on Yosemite, the moon bathes the valley in an unearthly light.
[ Coyote yipping ] Frigid winds chase away the remaining visitors.
[ Coyote yips ] With each passing storm, winter pulses like a beating heart.
♪♪♪ [ Coyote yips ] Snow gathers and melts away again.
Rivers rise and carry water down into the valley.
There are few wild rivers left in the Sierra Nevada, but there are still wild stretches of river to run.
Kayakers are drawn to this stretch of Cherry Creek, not simply to test their grit, but to connect with nature in its purest liquid form.
♪♪♪ While snowmelt has reignited these wild rivers, at their source, high up in the peaks of the Sierra, John Dittli and Todd Calfee are trying to determine what effect this year's snowfall has had on the region.
They're on a snow survey expedition for the California Cooperative Snow Survey Program.
It's one of the longest continuous records of snowfall in the United States.
DITTLI: Last year, it was the driest year on record.
We did a 12-day snow survey.
There was almost no snow to even measure.
Home sweet home!
CALFEE: All right.
DITTLI: This could very well be a prolonged dry period of 30 years, of 100 years.
It's happened before, and it's gonna happen again.
KLINE: The current drought may be simply a preview of the future -- a hotter, drier California.
DITTLI: 69% of average.
CALFEE: Oh, yeah, not good, but it's better than it has been the last few years.
DITTLI: It's going to be more and more important to know exactly how much water is in the Sierra Nevada.
It's California's biggest reservoir.
We drive a tube into the snow, pull that up, and weigh it.
And when we weigh that, we're actually weighing the amount of water in the snowpack.
55, 48, 56.
KLINE: While an improvement over recent years, the water content is still far below normal.
DITTLI: I'm fortunate enough, I guess, to have lived in the Sierra now, to be here for the heaviest winter on record and the lightest winter on record.
It makes you really realize that there really is no such thing as normal.
KLINE: Season by season, these dramatic shifts in weather will become the new normal.
But over the long term, snowpack will continue to decline.
Even now, snow cover varies greatly across the range.
♪♪♪ Some talus fields have received little or no snow at all -- crucial insulation for the pika's tiny home.
Yet these rocky slopes may have insulating properties of their own.
[ Pika chirping ] Persistent ice beneath the talus fields keeps the pika cool in summer, while the sun warms the stones in winter, helping to keep the pika's home at a steady temperature even as the climate warms.
From their humble origins 10,000 feet up, these small flakes of snow have far-reaching influence.
Snowmelt feeds wetlands more than 70 miles away.
Marshes flood, welcoming tens of thousands of migratory visitors.
Sand hill cranes and snow geese overwinter here, before beginning their long journey north.
[ Birds squawking ] Wetlands like these once covered vast areas of California's Central Valley.
But today only small pockets remain, and these have become critical habitats.
[ Birds squawking ] At dawn, one of California's greatest spectacles unfolds as snow geese take to the sky in the thousands.
[ Geese honking ] ♪♪♪ Days in Yosemite are warming, but before it disappears for the season, winter is about to take one last curtain call.
Crowds of photographers are beginning to gather along the banks of the Merced River.
Each of them is hoping to capture a single frame of magic.
MAN: I got here around 5:30 in the morning, had breakfast, and I've been here since 8:30 in the morning.
So... [ Laughs ] It's been a long day. [ Laughs ] MAN #2: It only happens once a year, but with the drought, it hasn't happened up here with this intensity for five years.
MAN #3: I tried last year, but there wasn't enough water to light up the falls, so trying again this year.
WOMAN: This is our second time -- third -- and this is the first time we're actually probably going to get the shot.
MAN #4: This is my sixth attempt to get this picture.
WOMAN: And so it's sort of like the photographers' chase.
It's something we all talk about -- chasing after the shot.
MAN #5: There are so many things that can happen to make it not work, like it doesn't rain or it's cloudy, so to have it be just rained, just snowed, it's fairly clear skies.
This is the kind of thing you just can't pass up as a photographer.
If you're close enough that you can get here, you just have to go.
KLINE: The phenomenon happens just as the sun begins to set.
WOMAN #2: The sun makes the water glow like a ribbon of red-orange fire.
KLINE: The effect only lasts about 10 minutes, and as the sun begins to illuminate Horsetail Fall, cameras are at the ready.
[ Camera shutters clicking ] ♪♪♪ ♪♪♪ [ Cheering, whooping ] [ Applause ] MAN #4: I think Yosemite Valley looks like God took his finger and carved out a little path so we could have a good time.
And in my opinion, you don't have to be a particularly religious person to feel inspired here.
It's just an amazing place.
♪♪♪ KLINE: Another season in Yosemite has come to pass.
The forests are reborn with new and wondrous life.
Fluorescent red snow plants erupt from the ground and spring begins again.
From forests of giants... ...to the tiniest of creatures... [ Pike chirps ] ...all of them bound together by a single source of life.
It's the power of water that is the heart and soul of this most magical range of light.
♪♪♪ ♪♪♪ ♪♪♪ ♪♪♪ ♪♪♪ ♪♪♪