(birds tweeting) - [Catherine] Mono Lake isn't a place that you necessarily hear about all the time, but when you get here and you realize how special this place is...

The tufa, the shrimp and the flies that live in the lake and the millions of birds that are attracted to it, you're gonna discover something you haven't seen before.

- [Geoff] Mono Lake's twice the size of San Francisco.

In this high desert area, it's twice as salty as the ocean.

It's got a pH of 10.

There's probably 3, 4 trillion brine shrimp living in the lake, size of a thumbnail.

And so places like Mono Lake are really refuges for wildlife.

- [Ryan] The saline lakes are existentially threatened on planet Earth.

If the lake was gone, then ecosystem collapses.

Mono Lake would be a toxic dust bowl.

- [Narrator] Many of the big sailing lakes of the Americas are on the brink of collapse due to climate change and water diversions.

The story of Mono Lake is about how we save them.

(bright music) - [Ryan] I've been coming to Mono Lake my whole life.

My parents were the first State Park Rangers here.

- Well, how was breakfast today?

- It was good.

Yeah, good coffee.

(both laugh) We used to dress up for the 4th of July as the, I was the alkali fly, and my brother was the brine shrimp, and my mom was in the tufa tower costume, and so I've been involved with Mono Lake for a while.

(engine revving) - Bye.

- [Ryan] We're right on the flank of the Sierra Nevada Mountains, where it's kind of smashing into the Great Basin Desert and you have lots of snow falling in the Sierra, and it's melting and it's coming down into the Mono Basin, which is this closed basin where the water comes in and it can't leave.

Water evaporates out, but all the minerals stay there.

So that's why it has become so salty.

- We know that Mono Lake is at least 760,000 years old because of some volcanic sediment from an eruption that happened at that time that we were able to see in the center of the lake, on the island.

Some people believe it may be millions of years old.

- [Ryan] Mono Lake in particular has these tufa towers that are these limestone rocks that are made when the salt water mixes with the fresh water.

- They're fossilized springs, they form under the lake and they're a sign of where the lake used to be.

One of the signs is this ice age tufa that's up here far from today's lake, that formed underneath the waters of a much higher ice age lake in a wetter time.

(soft music) Fresh water comes up from the bottom of the lake.

If there's some calcium in the fresh water, will mix with the unusual water chemistry of Mono Lake itself to form a calcium carbonate like a limestone.

That will collect and collect and grow and grow following the flow of water up from the bottom and create these really enchanting and interesting tufa towers.

- [Ryan] They're also really important for the ecology of the lake.

Algae grows on the tufa towers and the shrimp and flies eat it.

The flies scuba dive in a little air bubble down to the rocks, and they lay their eggs and to go through their life stages on the tufa rocks.

The ospreys also like to nest on the tufa towers because they provide like a little island for them to nest on.

- The Mono Lake doesn't have any fish.

It's too salty and too alkaline.

And although they are fish eaters, they don't mind a longer commute to the creeks and lakes nearby to catch fish to then bring back to their nests on Mono Lake.

- Mono Lake's striking because the ecosystem is pretty simple.

- [Catherine] There are trillions of brine shrimp in the lake and probably trillions of alkali flies as well along the shore.

- That sounds, kind of maybe not appealing, but they're a really lovely and wonderful fly that that hangs out on the shore and they don't like to land on people, which is great news.

- [Catherine] And then those things provide food for millions of migratory birds that visit Mono Lake every year.

- [Geoff] It's a vital spot for them.

If Mono Lake disappeared, they really wouldn't have the food resources they need to be able to make that journey from Canada all the way to South America.

- The main work I'm doing here at Mono Lake is researching phalaropes.

Phalaropes are a very small shorebird.

They arrive here around the start of July.

The phalaropes will swim around and twirl around in a circle to create a little vortex that brings the larvae and the pupa up to the surface.

They're going to eat like crazy for several weeks and then they're gonna fly nonstop all the way to South America from here, which is about three to 4,000 miles.

They form these really amazing flocks.

Sometimes you see thousands and thousands of them flying around and making these murmurations where they're turning really fast and putting on a big show.

And then when you have them in your hand, they're just like, how do you possibly exist?

You're so little and light, and how are you gonna fly thousands of miles now?

(bright music) There's a lot of indications that the saline lakes that the phalaropes depend on are really in big trouble because of climate change, but also because they almost uniformly have water diversions happening from them.

- In 1941, the city of Los Angeles Department of Water and Power started diverting the creeks that feed Mono Lake and so the lake dropped dramatically.

- Its level went down, down, down, ultimately losing half of its volume.

There's a bunch of problems that come from that.

One is the lake just gets saltier and saltier 'cause it has less water in it.

We wouldn't have migratory birds coming here, there wouldn't be a food resource for them.

We'd have massive dust storms from the exposed lake bed.

- And that dust has really really fine particulates and it's actually shown that those are really, particularly bad for human health.

If Mono Lake was a toxic dust bowl 'cause the lake was gone, then this wouldn't be a very pleasant place to visit.

- So I've heard about Mono Lake and I joined the Mono Lake Committee when I was in fifth grade.

What really struck me as a kid was how unfair it seemed.

Los Angeles was taking all of the water from the streams and that just really seemed like something that needed to be fixed.

- Ultimately, Mono Lake was saved in 1994 when the State Water Board made the decision to have the water go back to the lake.

And it is one of the best protected, if not the best protected saline lake in the world because it has dedicated water right.

- We've got challenges at Mono Lake, it's still too low.

We're not at a healthy level.

In fact, we're 10 years overdue at getting the lake up to the required management level, which would be 10 feet higher right here at the top of this pole.

- As we've seen, the climate's changing, we're getting less snow, there's less water going around, we need to have that buffer.

So I'm optimistic that that's gonna happen because so many people are so dedicated to protecting Mono Lake.

- [Geoff] There's a lot of magic to Mono Lake.

It recruits its own advocates and its own people to speak for it and work for it.

Even my daughter is doing science research here in the Mono Basin about glaciers and how climate change is changing the environment here as we work to protect Mono Lake at the same time.

- Something that recently I've realized is that Mono Lake, it's an intergenerational project to protect it.

It's really wonderful and amazing to have the continuity of having had my parents dedicate their lives to Mono Lake, to to be working here too and to be able to be part of this story.

- There's no, did anybody retrieve it?

- Mono Lake is the story of hope.

Mono Lake is still here, Mono Lake is thriving compared to some other places in the world.

- We're all realizing that protecting the phalaropes is not just about Mono Lake, it's about protecting all these places and how they all work together to support these little birds.

- Mono Lake would be gone by now if people hadn't invested in protecting this place.

It gives you hope to see that we've made progress and it gives you motivation to tackle the challenges that are ahead.

(mellow music)