♪ ♪ ♪ M. Sanjayan: You hear a lot about carbon and carbon dioxide.

You know, carbon is actually a very common element in the universe.

The Earth does a pretty good job of balancing the carbon.

The challenge is that when too much carbon dioxide and too much methane, basically greenhouse gases, get up into the atmosphere, they heat up the planet.

And what's happening today is that because we're so good at digging up old dead bodies of fossilized plants and animals and burning it, all of that carbon gets released quite quickly into the atmosphere.

Frankly, the last time there was this much carbon dioxide in the atmosphere, the world was so warm, so hot and humid, that there were things like hippopotamus and rhinoceros running around in the Arctic.

So, humans have never actually experienced an atmosphere like this in our entire evolutionary history.

We're living essentially on a new planet, a planet that we were not evolved to deal with.

And that really is the problem.

♪ Sanjayan, voice-over: If we're going to rebalance the carbon equation, we have to find ways of restoring and protecting our natural places.

Because cutting manmade emissions through industry and fossil fuels just isn't enough on its own.

And we're running out of time.

I want to show you how there is a way through this.

♪ In the second year of this ambitious project, I am joined by journalist Ade Adepitan, an evolutionary biologist Ella Al-Shamahi, as we revisit some of the planet's most vulnerable ecosystems... Man: 2, 3.

Man: Excellent.

Sanjayan, voice-over: documenting the progress made in the last 12 months.

[Splash] ♪ From California to the Arctic... Brazil to the Maldives... Oh ho!

Sanjayan, voice-over: East Africa... Adepitan: I'm back in Kenya to find out how wildlife has been affected by the ongoing drought.

Sanjayan, voice-over: to Southeast Asia.

Al-Shamahi: I'm in Cambodia meeting locals and scientists who are saving a living fossil from the brink of extinction.

Sanjayan, voice-over: And I'll be traveling to Australia, a country on the front lines of both climate impacts and solutions.

♪ [Birds chirping] [Waves crashing] Sanjayan: One bit of good news is that people are moving away from fossil fuels to more renewable forms of energy, like hydro or solar or wind.

And that's a good thing, because, ultimately, it will draw down emissions, but there's a problem.

About 25% today of our global emissions is coming not from our burning of old carbon, fossil carbon, but our destruction of living carbon, the plants and animals that make up the world's great biodiversity.

♪ Sanjayan, voice-over: I am on the east coast of Australia to look into a pivotal type of living carbon that may be the key to slowing climate change.

♪ These sprawling seagrass meadows, mangroves, and tidal marshes are huge reservoirs of carbon and are collectively known as blue carbon.

The reason why blue carbon is getting so much interest right now is because it's really dense carbon.

It's living carbon, often doing lots of other good things like protecting coves and providing habitat for fish, but it's also so dense in carbon that, frankly, if you lose it, you'll never recover it in a human-relevant time scale.

It's essentially irrecoverable carbon that we must protect at all costs.

♪ Sanjayan, voice-over: These blue carbon ecosystems are critically important but often overlooked.

I'm joining a research team who have discovered a way of efficiently helping one of the planet's most unassuming carbon storage heroes to grow faster and wider-- seagrass.

Sanjayan: I'm out here looking for poo, not just any poo-- dugong poo.

Because in dugong poo is maybe a key to keeping seagrasses alive.

Sanjayan, voice-over: Dugongs are large marine mammals with a dolphin-like tail that inspired mermaid legends.

It's an animal I've waited my whole life to see... Wow.

OK. All right.

Woman: There are gonna be over a hundred... Sanjayan, voice-over: because the sad truth is, they've been heavily hunted all over the world.

So, if you see one, you know you're in a very special place.

But 100,000 of these massive vegetarians graze peacefully on Australia's seagrass meadows.

Dr. Samantha Tol is an ecologist who studies the relationship between seagrass health and dugong populations.

Tol: They're called a sea cow for good reason.

All they do is eat grass.

Just happens to be seagrass.

Ha ha!

Sanjayan: Large amounts of seagrass.

Up to 40 kilograms per day.

Sanjayan: 100 pounds, 100+ pounds a day.

Tol: Yes.

Sanjayan: That's amazing.

Tol: Yep.

Sanjayan, voice-over: The good news is that there's plenty of sea pasture for the dugongs here.

The world's largest plant is believed to be a seagrass grown from a single seed around 4,500 years ago.

And it blankets an area of around 77 square miles, the equivalent to an area larger than Washington, D.C. What scientists are discovering is that the secret for a seagrass meadow to thrive is in the digestive system of the dugong.

And what's so interesting about the poo as opposed to the dugong?

So, we've always thought for a long time these animals-- they're eating the fruits, which have the seeds in them.

These fruits are small on the plant, so they can't avoid eating them.

So, we were wondering, well, you know, birds are really great at expressing seeds, and they also have been found to enhance the germination of those seeds of terrestrial plants.

So, our hypothesis was, "Well, they're still eating the plants, "so they must have gone down the route of assisting a symbiosis kind of relationship."

So, we went searching for the poo so that we could look through them so we could find those microscopic seagrass seeds.

Sanjayan, voice-over: And we don't have to look far.

Tol: There's a poo coming out right-- Oh, poo coming up?

Ha ha ha!

Oh, wow.

Over there.

That was a big one.

Sanjayan: Oh, yes!

Didn't think I'd be doing this today.

Tol: Ha ha ha!

Out there on a boat.

Beautiful day.

Collecting...feces.

That really does smell.

I'm sorry.

I mean, it's not--it doesn't smell like cow dung.

It actually smells sort of--sort of poo-ey.

Yes.

Ha ha ha!

Ughh... Sanjayan, voice-over: This might look gross, but it's in this stinky mess that we find what we're looking for.

Sanjayan: They're like little mustard seeds, aren't they?

Yeah, and because they're hard, they're able to make it through the dugong without actually getting broken down or digested.

That hard case enables them to pass through.

Sanjayan, voice-over: While trying to figure out a way of helping seagrass meadows to grow, Samantha noticed these tiny seeds are tough to sprout.

So, when we were testing the germination for these seeds, we actually noticed the ones that were taken to plant, they were starting to succumb to this kind of fungus that was growing over them, which was stopping them from being able to germinate.

We hit a poo patch.

Ha ha!

Sanjayan, voice-over: The revelation was that the seagrass seeds extracted from the dugong poo were not affected by the fungus, and they turned out to be more likely to germinate than the seeds that just fall from the plant.

And that made us question, "Oh!

"Is their stomach acid actually killing off this fungus?"

Why would that be interesting to you?

Because we're having to start looking at restoration.

If you can just take one extra step in sterilizing the seeds, and you can increase your germination by fourfold.

Seagrass seeds on their own can only move tens of meters, but when you put them in a dugong, if that dugong--it's normal hunt range 100 kilometers, that they can even go up to 650.

So, that's a lot more than tens of meters.

Yeah, so they're like a seagrass dispersal mechanism, but they're also like a fertilizing mechanism, because without the dugongs, those seeds don't germinate very well.

That's right.

Sanjayan, voice-over: Without the dugongs, the germination of seagrasses has a mere 20% success rate.

With the dugongs, that number jumps to 80, and the speed of which they grow can be up to 60% faster.

What we have here is a relationship that helps us all.

Sanjayan: We've been studying dugongs for quite a long time, and we're just starting to discover because of work that, you know, people like Sam are doing, this amazing interaction that these megaherbivores have with seagrass beds.

We can only imagine all the other interactions that are happening in ecosystems that as we lose species, we're gonna lose them and never even know what we have lost.

Sanjayan, voice-over: The race to protect keystone species is real and worldwide.

♪ In Cambodia, Ella is on the trail of a story where an iconic freshwater species was nearly made extinct by global fashion demand.

Al-Shamahi: It's great to be back in the hustle and bustle of Cambodia.

The economic boom is clear to see everywhere.

Now, don't get me wrong.

That's great for the tuk-tuk owners and the shopkeepers, but the country's natural wealth is paying a huge price.

Al-Shamahi, voice-over: The international leather trade nearly emptied Cambodia's waterways of its wild Siamese crocodiles, but today, with help, the species is making its way back.

♪ 90 minutes south of Phnom Penh is Fauna & Flora Siamese Crocodile Conservation Breeding Facility, a collaboration with the Cambodian government.

The program has been rescuing and breeding these living fossils for over 2 decades now.

Hello!

Pablo Sinovas and the team are about to return 10 captive-reared crocodiles to the wild.

Sinovas: You like to see some of the babies?

Al-Shamahi: Yes.

Definitely!

All right.

Oh, yes... Oh!

Sorry!

Would you like to-- How is this your job?

Yes!

Amazing.

Hold it so he doesn't snap.

OK. Don't bite me, please.

No biting.

I'm basically holding one of the rarest species on Earth, and I'm holding, like, the hope for it, right?

That's absolutely right, yeah.

This species was rediscovered here in Cambodia in a remote corner of the Cardamom Mountains.

Actually, local people, the indigenous people of the area, were protecting those populations because they do consider these guys to be sacred.

That was their saving grace, the fact that-- Absolutely.

the indigenous people actually regarded them as sacred.

That's right.

[Crocodile squeaking] What caused the decline of these animals?

The demand for their skins for the leather trade, and as a result, they disappear from 99% of their former range.

Oh, my God.

So, basically, these poor creatures were about to become extinct because of handbags and belts.

Yeah, basically.

Al-Shamahi, voice-over: Thankfully, the demand for crocodile leather has declined globally, reducing pressure on wild species of crocodiles in Cambodia, but Pablo is focused on just one species-- the Siamese.

Al-Shamahi: How many crocodiles have you actually released into the wild?

We've released 140 crocodiles so far.

And how many are in the wild?

In Cambodia is an estimated 300 crocodiles left in the wild.

So, you are responsible for half the crocodiles in the wild in Cambodia.

So, every crocodile counts.

[Latch snaps] [Men shouting indistinctly] Al-Shamahi, voice-over: These top predators were virtually lost from Cambodia before scientists really knew they were here.

We've been given a second chance to not mess it up.

Oh, my gosh!

Al-Shamahi, voice-over: Each animal being introduced to the wild is fitted with a tracking device that will allow the team to monitor them.

♪ We are heading deep into the Cardamom Mountains rainforest.

[Birds chirping] Once released, these crocodiles will be protected by the community that live here and in return, their presence will hopefully safeguard the [indistinct] ecosystem and the people that call it home.

Mr. Chan is from the indigenous Cham community.

To them, the Siamese crocodiles are sacred and must be protected.

[Chan speaking native language] ♪ Al-Shamahi, voice-over: Mr. Sam Han, a researcher for Fauna & Flora, joined Mr. Chan in his crocodile conservation efforts.

and the Cambodian Crocodile Conservation Project was formed.

[Han speaking native language] So, how important is it for you to be working with local communities?

Al-Shamahi, voice-over: The time has finally come for these crocodiles to take their rightful place in the forest.

♪ Al-Shamahi: These are literally her very, very last few seconds before she's released into the wild, before she's free.

It's kind of epic, right?

Good luck, guys.

Yeah.

♪ Free!

Yeah.

Al-Shamahi: Whoo!

Amazing!

Well done!

Where's the hand?

Look at his face!

He's just beaming!

Oh, my God.

What is your hope for this crocodile and all the other crocodiles?

Uh, my hope is that she will start producing lots of eggs and then that will help boost the populations.

The ultimate goal would be to have a population that is viable in the long term.

We're aiming for 10,000 crocodiles in Cambodia.

It's an ambitious target, but we are on our way.

Al-Shamahi, voice-over: Although we are just beginning to learn about Siamese crocodiles, scientists believe they are important to keeping the balance in this ecosystem.

Sanjayan, voice-over: Back in Australia, the benefit the dugongs bring to their habitat is a key part of the carbon equation.

One of the reasons seagrasses are so good at absorbing carbon is that here in the tropics, they grow fast.

Sanjayan: How much carbon is there in tropical seagrasses like the ones you find around here?

So, with this meadow being at 12,000 hectares, it equates to about 13,000 to 19,000 megatons of carbon sequestered per hectare per year.

Sanjayan: Hectare by hectare, how does it compare without the habitats?

About 3 times more carbon sequestration power than the [indistinct] rainforest per hectare.

Sanjayan, voice-over: Carbon sequestration is the process of carbon dioxide from the atmosphere and storing it.

Sanjayan: And you think dugongs are playing a role in keeping those-- that carbon sequestration healthy?

Yes, I do.

Without the dugongs, we know that not only do they disperse the seeds which helps create genetic diversity, they actually keep that turnover rate within the meadow, which makes sure that the species are actively looting their leaves, they're actively regrowing, they're keeping diversity within the meadow.

And all of those things lead to a stronger, resilient meadow, and the more resilient it is, the likely it's gonna stay and do its sequestration job.

Yeah, yeah.

So, like, dugongs are like basically carbon sequestration machines.

Yeah!

Sanjayan, voice-over: It seems that flattery does pay off.

I'm finally graced with a glimpse of these mythical creatures.

Oh, oh!

Oh, look!

2!

2 of them!

Yep!

Is it 2, or is it 1?

Just really-- right here, guys!

Tol: Yeah.

Ha ha ha!

Look at that!

Ahh!

And their tail.

Ha ha ha!

Ha ha ha!

Ha ha!

You got to see 'em!

Thank you.

♪ That's a special moment.

I mean, actually-- actually to see a dugong, you know, in the wild like this...

I've wanted to do this all my life.

They don't stay on the surface very long, so it's just a glimpse and then they're gone.

But they are here, so I'm sure we'll see more.

There, there, there!

There are 2 of them!

Oh, 3!

Ha ha ha ha!

Look at them, right there!

Ha ha!

Sanjayan, voice-over: A major threat to this ecosystem is the increase in ferocity of tropical storms triggered by our warming planet.

[Rumbling, thunder] They can rip the plants from the seabed with devastating impact on dugong populations and in turn are unable to regenerate without the animals they feed.

In Greenland, scientists are racing to understand how the shaggy survivors of the Ice Age are being affected by our current climate change before it's too late.

To figure this ecosystem out, a team of scientists led by Niels Martin Schmidt are on a mission to sedate a female muskox to collect data and implant a sensor.

Schmidt: So, there's a group of muskoxen at the small hill out there called [indistinct], and that's where we very often catch muskoxen.

Sanjayan, voice-over: Muskoxen are the largest herbivores here, playing a key role in the health of the tundra.

They graze on small productive pastures and then empty their bowels on drier areas.

Thus, their movement transports nutrients uphill, expanding plot communities.

Not only that, their grazing could make the tundra more efficient at taking carbon from the atmosphere.

[Walkie-talkie beeps] Sanjayan: Carbon capture is very much influenced by animal grazing.

For every time an animal walks into an area and start to graze, the plant will respond by regrowing, so that would increase the uptake of carbon.

Sanjayan, voice-over: Sadly, here their population is currently in decline, so, Niels' research is focused on females and their young.

In order for the team to get up close, the animal must be sedated.

[Click] The dart is in the female.

The cow is down.

Sanjayan, voice-over: She may look like a cow, but she's more closely related to sheep and goats.

You happy to grab her?

I'll just see how I... Yep, I have her.

[Indistinct] We've got her!

Don't let her aspirate.

Sanjayan, voice-over: It's a race against time to collect as much data as possible.

216.

Is she [indistinct]?

Doesn't matter.

Sanjayan, voice-over: The muskoxen gene pool is tiny, making them highly vulnerable to new diseases.

In Arctic Canada, the muskoxen have experienced serious decline, losing 50% of their population in a decade.

With warmer temperatures, diseases are moving north, exposing those animals to new pathogens against which they are less resilient.

Schmidt, voice-over: What we basically can do is to understand the full extent of the role the muskoxen play in an ecosystem, and it's not just climate impacting muskoxen.

It's all [indistinct].

57 minutes, yeah.

Sanjayan, voice-over: The final job is to insert a vaginal implant transmitter.

Man: [Indistinct] is inserting this vaginal transmitter that will give a signal once she gives birth, if she gives birth.

Sanjayan, voice-over: With this clever gadget, the scientists will know exactly where and when a newborn arrives.

What we're gonna do now is gonna get some medication that's gonna reverse the anesthetic.

Super.

Aw, look there.

[Laughter] Sanjayan, voice-over: The impact of our warming planet is not only expanding the reach of diseases in the Arctic, but causing the collapse of ecosystems in other parts of the world.

In 2015, 40 million mangrove trees shriveled up and died of thirst in Australia due to climate change, the worst such event in recorded history.

[Birds chirping] Today, the country is stepping up its efforts to protect, restore, and plant mangroves.

They can hold up to 5 times more carbon than a tropical rainforest, making it the hardest-working blue carbon ecosystem on Earth.

The forest I'm exploring has a heavy load to process.

At its epicenter is Cairns International Airport.

And it just goes to show that we can live in and with really productive natural systems.

Sanjayan: I can hear huge jets taking off because the airport is just there.

[Jet roaring] And yet here, it's just an absolute Eden.

Crabs and snails, spiders and mudskippers.

When you look at how black this mud is, you know, you know it's chock-full of carbon... [Splashes water] and that's what we're here for.

♪ Sanjayan, voice-over: Wetland ecologist Dr. Fernanda Adame is part of a team working to quantify the value of the environmental services this mangrove forest provides.

Why are you trying to verify how much carbon there is here?

It's important to know how much carbon is in the forest but also how much would you gain if you restore them or how much would you lose if you, you know, deforest them.

The idea is that, um, Australia is trying to reduce its emissions partly by improving the natural assets like how using natural vegetation, especially mangroves, seagrasses in removing carbon from the atmosphere and also storing them for long periods of time.

Yeah.

So, that's a small component, but it's a very important one-- Yeah.

because it will be one of the only strategies that's not just about carbon, but it has-- delivers a lot of co-benefits besides carbon.

Sanjayan, voice-over: This gnarly forest does 4 amazing things.

It sucks up and stores masses of atmospheric carbon.

It creates unique habitats for animals and plants.

Removes toxic nitrates from rivers and runoff before it reaches the Great Barrier Reef.

And it shields the coast and the airport from erosion.

For the past decade, Dr. Adame has been researching how this living barrier between plant and sea acts like a gigantic kidney-- cleansing water of toxins.

Sanjayan: What happens if there is too much nitrogen in these mangroves?

Adame: Um, I guess it's like eating too much cake.

You start growing too much.

OK.

But then the trees grow, a lot, but then the roots they don't keep up.

So, what happens when you have like a big storm or you have a drought, then the trees fall down and they die.

So, you get lots of above-ground growth-- Yes.

which looks, great, but they're not stable, they're not strong.

Yeah, they're not stable.

Yes.

Sanjayan, voice-over: Nitrogen is one of the main pollutants coming from agricultural runoff.

If left unfiltered, it goes on to contaminate the sea and kills coral.

Adame: So, they basically clean it from excess fertilizers or excess nitrogen pollution coming from urban developments.

So, they're very good at that.

If we didn't have this mangrove forest, the impact would be felt on the Great Barrier Reef.

Exactly.

Yes.

All the nitrogen, and it could be tons and tons of nitrogen that's going through here, the trees are taking it, there's bacteria turning into air, and then when you go the other side of the mangroves, the water comes out much cleaner.

Right.

Sanjayan, voice-over: New carbon ecosystems like this are saving the Great Barrier Reef, less than 20 miles away from being poisoned by industrial pollution.

And now more than ever, corals need all the help it can get.

With climate change, sea temperatures are rising, and experts are predicting that coral could cease to become reproductive.

That would mean that eventually coral reefs would disappear altogether, a devastating situation especially for island nations like the Maldives.

The coral act as a shield from rising sea levels and storm erosions.

But help is coming.

And exciting breakthrough by acoustics expert Professor Steve Simpson and his pioneering team at Bristol University in the UK is unraveling underwater communications and discovering that listening to the heartbeat of the reef might be the key to healing it.

Simpson: This is a prototype.

What we're gonna be doing here is to be spreading our underwater ears out with a hydrophone in each end.

And these hydrophones are listening in different directions.

And then with a 4-track recorder and some wet headphones, we're gonna be able to snorkel and actually listen live to the reef.

I've never done that before, so it's really exciting to see what a reef sounds like as we swim over it.

Sanjayan, voice-over: Jess Hodge, a marine ecologist researching coral restoration, helps drag Steve's giant ears through the reef so they'll be able to listen live to what Steve calls "the ocean's orchestra."

[Clicking] The first time I've ever heard a reef like that.

That is amazing!

It's a really fresh insight into the reef.

We see bright, colorful fish.

We see colorful corals.

But what we don't connect with so well is the soundscape.

Our ears don't work underwater.

But with acoustic recorders, we realize that the soundscape is absolutely full of life.

And that soundscape is the sound of biodiversity.

[Crackling and popping] Sanjayan, voice-over: Those eerie crackles and pops have a functional purpose that Steve is only just identifying, and it's a game changer.

An experiment devised by Josh Pysanczyn, a coral researcher at Bristol University, revealed for the very first time that lava coral the baby building blocks of all reefs around the world respond to specific sound frequencies.

Not only is this mindblowing, but the lab work shows that corals move towards the sound of a healthy reef and use fish voices as cues to sink to the bottom and set up home.

Now Steve wants to know which fish on the reefs can help guide baby coral down through the ocean.

Simpson: So, what we're gonna be doing today is actually putting 4 hydrophones out on a reef in a square about 2 meters apart.

So, that starts to spread out our sensory system over a wider area.

Then in the middle of the square, we're gonna put a 360-degree camera, so when we listen back to the soundscape, and we hear a sound coming from the left, we can turn the screen and see which species made that sound.

[Clicking and popping] Sanjayan, voice-over: They spend the afternoon positioning recording devices and leaving them there for 2 days.

Historically, coral reefs have bounced back from extreme weather and temperature events, but as these events become more severe and more frequent, there'll be no recovery time between the blows.

This is likely to be the case for 99% of the world's reefs.

Coral is going to need our help.

What these scientists are discovering might just be the lifeline needed to speed up coral restoration.

Simpson: It's been really exciting starting to unpack these recordings.

Um, so, this is totally new to science.

So, if we watch the video, we're looking for a fish arriving... and producing the sound.

[Clicking and popping] That's--that's the regal angelfish-- Yeah, exactly.

And I don't think anybody's recorded a regal angelfish before.

[Giggling] Yeah, we can assign each different fish species was there with their audio.

Exactly.

So, this really is a kind of pioneering adventure into the soundscapes of coral reefs.

Sanjayan, voice-over: These new discoveries have huge potential for the coral restoration work beginning here.

Steve plans to play these recordings of healthy reefs back out into the ocean using underwater speakers... essentially tricking billions of baby coral into setting up home on dead and degraded reefs.

♪ Coral reefs and blue carbon ecosystems depend on each other, much like humans and the natural world.

In Australia, the aboriginal culture knows this more than most.

The Yirrganydji people are the traditional landowners of this particular mangrove forest.

Their connection spans over tens of thousands of years, and to this day, it still brings the community together.

I'm joining the Dawul Wuru Aboriginal Corporation and the Yirrganydji Land and Sea Rangers as they work with the Cairns International Airport to protect and monitor the mangroves.

This land was where we know our people used to camp.

so it is a very important part of the country to the Yirrganydji people, and we as [indistinct] get to work and look after country, but it's even more special when we get to work with people that want to look after country with us.

A lot of people have made Cairns home now, and it's become all our responsibilities, not just the [indistinct] or the landowners.

It's our responsibility to look after country.

And beach cleanups and drain cleanups are all part of that.

So... welcome to country.

[People talking indistinctly] You do this full-time?

Yeah, full-time.

Sanjayan, voice-over: Ashlyn Skeene has an ancestral connection with this land.

She volunteers as a ranger with the group, honoring her inherited responsibility to the mangroves in the hope it'll inspire others.

My mother, she always says to me she loves the smell of mangroves in the mud because it makes her feel at home.

And as a kid, I always picked it up and said, "When I smell mud, I think of home and I think of my mother."

Oh, that's a very sweet story.

Yes.

[Waves crashing] Definitely is the younger generation that have to pick up where everyone [indistinct].

Yeah.

And we are definitely the future, for sure.

Sanjayan, voice-over: Beach cleanups have been a regular activity over the past 7 years, resulting in positive, visible change.

Skeene: When we first started coming out here, we were collecting tons of rubbish.

and now when we come back, most of the time, it's just very general cleaning-- tiny little bags.

It's--it's really good.

It's been maintained really well.

These are a guaranteed find every time.

Every time.

Man: Flipflops.

[Laughter] You find shoes often.

Not in fashion.

Not even a pair.

Skeene: I feel like individuals have an impact, um, whether they're small or whether they're large.

It's still an impact, and I think if you've got lots of individuals doing very little things, that--that can make a big difference.

Sanjayan, voice-over: While the Yirrganydji are still waiting for their rights to this area to be granted, Brian and the Rangers continue to care for this land with dedication, which I think is extraordinary.

We acknowledge, and our partners acknowledge, that we've got connections to this country, so we just continue to do what we do.

If we wait for the title, um, too many of our elders will slowly pass away.

And we've got a responsibility to--to the country right now.

And we've got to be out there now.

So, you feel your responsibility to the land to country, as you call it, outweighs the struggle for title and-- Yeah.

Well, we belong to this country.

We've got to look after it.

We've got young people that are wanting to know and wanting to be part of caring for country now.

They want to be part of managing.

They know we've got a responsibility.

They can't wait till they're 30.

Sanjayan, voice-over: The urgency that the Yirrganydji people feel to protect this ecosystem from pollution and our rapidly changing planet is also found in the Arctic.

[Wind howling] Here, extreme weather events could be behind the decline in muskoxen populations at least around Zackenberg Research Station The data collected by Niels and his team reveals that in extreme snow years, all of the pregnant muskoxen lose their babies when the climate is too wet and newborns can perish as they're not yet waterproof.

Documenting whether the collared muskoxen actually give birth after a long winter is hard, but for Niels, this would be the holy grail.

And with super-advanced camera collars, he's one step closer.

Schmidt: We have some special female collars that we will deploy for the first time.

This is the camera collars that will-- in addition to position, acceleration, it'll take pictures once per hour.

And that will hopefully give us some nice footage of newborn calves.

Sanjayan, voice-over: They will be Niels' eyes and ears... [Man on walkie-talkie] allowing the researchers to monitor the females... [Click] even in the dark depths of the Arctic winter, when there's no light and no scientists around.

Ohh!

Ugh!

Over here, we have an audio locker that will for the next 6 weeks continuously record every sound.

This can be used to validate their behaviors.

We hope to get 21 collars on this season, and that will be 10 on bulls and 11 on cows.

Schmidt; Organisms adapt to life under extreme conditions.

That could be the Arctic.

That could be Australia.

but if you then add extreme events, say, heatwaves in Australia, say, extreme amounts of snow in the Arctic, you may actually push these species beyond their limit.

Sanjayan, voice-over: The natural world plays a critical role in our planet's health.

If ecosystems are to remain resilient, then preserving biodiversity is vital.

In Australia, the rangers survey the biodiversity around Cairns Airport.

To date, they've identified 12 threatened species in the area.

Sanjayan: Every few meters, we seem like we're into a different species of mangroves, different species of tree composition, and then these little patches of rainforest.

It's--it's quite diverse.

Singleton: That's why it's really important to keep these ecosystems healthy because we know those species are endangered.

Sanjayan, voice-over: I started this Australian journey in the desert, where to keep that fragile ecosystem healthy, the community is waging war on cats and camels.

Here, the enemy is smaller but equally dangerous.

So, that is the famous Australian cane toad.

And this guy, as innocuous as he looks, has decimated wildlife here in Australia, but also on other islands.

Initially introduced to deal with a beetle that was, you know, eating up cane fields-- that's why they call them cane toads-- but obviously, didn't really fancy the beetles, but fancied pretty much everything else.

And anything that can fit into this giant, wide mouth, it'll eat.

So, baby birds, eggs, insects, uh, little animals, little marsupials, this little guy is big trouble.

Sanjayan, voice-over: Trouble that needs to be minimized.

Normally, if found in nature reserves, rangers euthanize the toads to reduce their impact on other species.

In my lifetime, we've destroyed half the world's mangrove forests.

The degradation of our coastal ecosystems could be releasing up to 1 billion tons of carbon dioxide into the atmosphere each year.

While growing new mangroves could also be a part of the long-term solution, we must do what we can to protect the mature carbon-rich mangroves we have left.

Global wetlands matter if we're going to limit the temperature of our planet.

Blue carbon ecosystems are not the only ones under pressure.

In Cambodia, Ella is learning about the plight of Southeast Asia's greatest river system that has been drained of its sand.

Al-Shamahi: I'm in Phnom Penh to meet Brian Eyler.

Brian has spent the last 20 years researching and engaging with local communities from China to Vietnam to protect the Mekong River.

Eyler: The river's a mighty system that provides for tens of millions of people.

Al-Shamahi: Sand mining is probably not something that many of us have given much thought to.

But after water, sand is the most exploited resource in the world.

So, this is what we're talking about--sand mining.

This has actually got 2 pumps.

And actually, if you look around, you can see there's some boats that are barely above the water level 'cause they're so filled with sand.

Al-Shamahi, voice-over: Around the world, we use 50 billion tons of sand and gravel a year, enough to build a colossal wall to encircle the planet.

It's the key ingredient of cement and concrete.

So, all of our cities and roads are built of it.

All of this sand comes from nature, and nature, as it turns out, needs it back.

Eyler: 8 years ago, none of these tall buildings were here, and they're all built from sand taken out of the river.

And they're being built at a very rapid pace.

[Tapping] We're extracting sand from the Mekong 7 times faster than it's replenishing.

So, this pace can't keep up.

Rivers know how much sand and sediment they need.

When you take it out, they're gonna look for more.

So, when that happens, the river takes sand and sediment from its banks.

Riverbanks are collapsing, homes are falling into the river as well.

So, we're paying the price for this.

Al-Shamahi, voice-over: The impact of sand mining is being felt hundreds of miles away.

Historically, the flat parts of this river sends water surging into one of the world's largest freshwater fisheries-- the Tonle Sap Lake, capable of providing half a million tons of fresh fish a year.

By taking sand out of the bottom, the river level drops, so it's going to take much more energy and water to cast that water up into the Tonle Sap, which feeds the fishery which then feeds the people of Cambodia.

Al-Shamahi, voice-over: If sand mining continues unchecked, the impact on the system could be the final straw for the Tonle Sap.

If it collapses, Cambodia's main source of protein and possibly the livelihoods of tens of millions of people throughout Southeast Asia may also cease to exist.

Al-Shamahi: Are there solutions that will solve this?

There are ways to bring this breakdown that's happening here under control.

Al-Shamahi, voice-over: Researchers from Newcastle University have been using scanning technology to track changes on the riverbed over time.

These dots are craters.

Correct.

10 years ago-- Oh, my God!

you see these beautiful sand dunes, you know, like you would see along the ocean, except they're under the river.

And now they're gone.

Al-Shamahi, voice-over: Where towering dunes once stood, now gigantic craters 8 meters deep and 17 meters wide scar the riverbed.

Al-Shamahi: This is so alarming.

It's just a completely different surface.

But also, this technology allows us to measure how much sand is being removed.

But now that we can see it, it's possible to bring transparency and accountability and... in a way to make this more sustainable.

So, data which is quite depressing, you're saying could actually be part of the solution.

From here, there's progress.

Al-Shamahi, voice-over: With the undeniable evidence, scientists can bring pressure to bear on governments to act.

Al-Shamahi: Standing here, the scale of this just feels completely and utterly overwhelming, but at the same time, you heard what Brian said.

The solutions are all there.

They're there!

And, so, I'm also leaving this boat with a sense of surprising hope, which I think we should all be clinging to.

[Birds chirping] Sanjayan, voice-over: Freshwater systems form a small faction of our planet but play a disproportionately large role in the global carbon cycle.

They act as a busy transit system moving carbon from inland streams and rivers to the ocean.

And the sediments they carry play a critical role in the efficiency of mangrove ecosystems.

Here at Cairns Airport, corporate action along with indigenous and scientific knowledge have formed an exceptional collaboration.

Together, they're just beginning to understand how important sediments are to the mangrove's role as a blue carbon ecosystem.

[Tires squealing] Lucy Friend is the airport's Environmental Manager.

They're taking carbon core samples to figure out how much of it is hidden underground.

Man: Here.

Take it down?

OK, go for it.

[Pounding] Man: Don't fall.

Friend: A lot of the carbon's in the mud.

Yeah.

So, all of the leaves and everything that's accumulated over time will get stored in the mud.

[Pounding] Woman: Uh, it's about... Sanjayan: Why is the airport interested in this?

I think part of it is because we have so much mangroves, but half of the airport land holdings is natural area, so-- Yeah.

half of it is this-- it's 350 hectares.

So, we want to look at quantifying the value of those areas.

So, a big part of that is a cultural value and we look at the biodiversity value as well.

These mangroves protect our infrastructure, and we're in a really vulnerable spot.

So, that's important.

But the other part is that airports are carbon-heavy industries.

We do have a lot of planes, a lot of fuel use.

Yeah.

And we know that-- that mangroves are really important ecosystems for storing carbon for a long period of time.

Yes.

So, we wanted to research how much carbon so we can quantify that.

Are you potentially thinking of using some of the restoration here as offsets... in terms of reducing your overall carbon load?

Yeah.

We've always had commitments to cause no harm.

Every corporation has those commitments, but we wanted to put-- Very few of them actually do it.

We wanted to put some meaning behind it.

We know that we have emissions.

You know, we're moving towards renewable energy and offsetting as much as we can.

Sanjayan, voice-over: Forests like these build up deep deposits of organic matter called peat.

Samples like this can potentially reveal... Sanjayan: Wow.

hundreds of years of trapped carbon.

Sanjayan: So, you get a 1.5 meter tube like this, you're talking, you know, several hundred years of sampling.

Friend: Well, it really depends on how much sediment is coming down those rivers and how much the mud is building up in those ecosystems.

Um, that's why we're kind of doing this research to look at, um, new sediment rates as well.

So, in addition to the coring, we're also putting down markers and looking at how quickly the mud will build.

And that will give us an indication of how old it is and how long it's been building for.

Oh, right, right, right.

Then you can get a better understanding of the rate of accumulation of all this... blue carbon.

We'll then be able to quantify the stocks of carbon here and also the annual draw-down rate, so the sequestration rate.

[Waves crashing] Sanjayan, voice-over: Australia is considered a global blue carbon hotspot, holding as much as 12% of the world's carbon.

We need that carbon to stay where it is, safely stored away to protect us all.

Our oceans store an astonishing 50 times more carbon than the atmosphere and about 20 times more carbon than every plant and plot of soil on land combined.

We have an opportunity to do things properly.

We have the inherent wisdom, the science, and we have the technology to understand when things are going wrong and why.

Now we need the money and the political muscle to implement what needs to be done.

Sanjayan: Yeah, we came to Australia because this continent is a the epicenter of climate change, not climate change in some distant future but right now.

And after spending time in the desert and after spending time on this coast, you know, I've really come away with 2 thoughts.

[Flames crackling] So, when you're in the desert, and you're watching these indigenous communities using ancient fire practices to keep the land diverse and vibrant, endangered species present and keeping catastrophic fires away, they're just doing what they've always done.

The consequence of that is maintaining a habitable planet, not just for them and their livelihoods, but for all of us!

And then you come out here and you start looking at the carbon density of seagrass beds and mangroves, you find out that they're really chock-full of carbon.

If we can actually replicate the restoration of the most carbon-dense ecosystem on Earth at scale, that actually will change the thermostat of the planet.

It just makes me think about these interactions between animals, between biodiversity, and how some of those interactions play such a crucial role in terms of regulating our climate.

There are lots of answers that are rooted in indigenous wisdom and answers that are rooted in modern, cutting-edge science.

Put the two together, maybe there's a path forward.

♪ Changing Planet Season 2 is available on Amazon Prime Video.

♪ ♪ ♪