Episode Transcript
[00:00:01] Speaker A: If deforestation in the Amazon becomes gigantic, the forest will not recover in more than 50% of the Amazon because you're going to change completely the climate. In most southern Amazon, the dry season would become six months, and there will be no way for the forest to regrow.
[00:00:24] Speaker B: That's Dr. Carlos Nobre, one of Brazil's most distinguished climate researchers and the scientist who coined the concept of the Amazon's tipping point.
He first ran those numbers back in 1988 and spent the next several decades hoping he'd gotten it wrong.
He hadn't.
The more I learned about this place, the more I realized that the Amazon is more complex than I ever imagined.
Multiple systems operating together, each one dependent on the others and breathtaking in their own right.
The atmosphere above, where invisible rivers of moisture move across the continent. The water at the surface carrying up to 20% of the world's riverine freshwater through some of the most biodiverse ecosystems on Earth. And beneath it all, an underworld of geothermal aquifers and subsurface systems that science is only beginning to map.
Together, they've taken 40 million years to build. And right now, they're all under pressure.
This episode travels through all three layers because the more we understand how these systems talk to each other, the clearer the stakes become when they start to break down, and why we need to protect them while we still can.
Welcome to episode five of Rewilding Amazonia. I'm Brooke Mitchell. Let's begin in the rainforest Forest clouds.
To understand how the tipping point works and how close we actually are, I first needed to understand the Amazon as a climate system.
And that story starts not with deforestation, but with geology.
[00:02:15] Speaker A: The Amazon is the largest tropical forest in the world. It's close to 7 million square kilometers originally and evolved over millions and millions of years, particularly since the Andes Mountains uplift that restarted about 40 million years ago and ended about 6, 7 million years ago. Because when they end, these mountains create a meteorological system that enhanced a lot rainfall.
[00:02:51] Speaker B: The Andes didn't just create a mountain range, they transformed the Amazon's destiny. Before their uplift, much of the rainforest was concentrated closer to the equator, more limited in scale. But as the Andes rose over millions of years, they reshaped atmospheric circulation across South America, creating powerful rainfall systems that expanded precipitation deeper into the continent and helped transform the Amazon into the vast forest system we know today.
[00:03:19] Speaker A: The Amazon has on average 600 to 700 trees per hectare.
And one fourth of the trees have very deep roots.
Rooting system goes to 7 to 1012 meters. But during the dry season, the forest transpires more water than during the wet season. 4 to 4.5 liters per square meter per day. The forest recycles water so well that about 45% and many other studies show between 40 and 50% really is exported out of the Amazon to the south.
[00:04:10] Speaker B: Let me make sure that lands during the driest months of the year, when it hasn't rained in weeks. The Amazon is pumping more water into the atmosphere than during the wet season.
The deep rooted trees are pulling moisture far from underground and releasing it into the air, essentially manufacturing the rainfall that keeps keeps the forest alive.
And that moisture travels far beyond the forest itself.
[00:04:37] Speaker A: We gave the name flying rivers of this water vapor. In the US it's called aerial river, but the cycle called flying rivers. The water vapor is what really induces a lot of rainfall. South of the Amazon, it's the biome. There is the tropical savannah, about 50% of the water. The rainfall in the Pantanal comes from the rivers there. Bolivia, Amazon. Also the rainfall in southern Brazil, northern Argentina, Uruguay, Paraguay. 15% of rainfall in Sao Paulo also depends on this water vapor in the southern portion, 40, 50% flying rivers, invisible
[00:05:27] Speaker B: currents of moisture carrying water from the Amazon forest to cities and farms thousands of kilometers away.
Sao Paulo, a city of 22 million people, gets a significant portion of its rainfall from a forest it can't see.
The farmers of Argentina's agricultural heartland depend on moisture that began its journey in the canopy of the Peruvian Amazon.
Water is only one part of what this system holds, though.
Over tens of millions of years, the Amazon has accumulated more than 150 billion tons of carbon stored in trunks, root systems and soil, making it one of the planet's largest terrestrial carbon stores.
Release that carbon into the atmosphere and the consequences ripple across every climate system on Earth.
In 1988, a different question started to consume Carlos.
Not what does the Amazon do? But what happens if we push it too far?
[00:06:29] Speaker A: So I decided to ask a scientific question that I asked if the deforestation in the Amazon becomes gigantic, the forest will not recover in more than 50% of the Amazon because you're going to change completely the climate. In most southern Amazon, the dry season would become six months and there will be no way for the forest to regrow.
[00:06:55] Speaker B: Over the following decades, he kept refining the answer and eventually he reached a number.
If deforestation exceeds 20% of the Amazon, combined with global warming exceeding 1.5 degrees Celsius, the system tips. And now long term atmospheric monitoring towers planted across the Amazon, part of a massive Experiment Carlos Hupp, launched in 1999, are measuring it in real time.
The southern Amazon's dry season is lengthening. Rainfall is declining and trees are dying at higher rates.
And then there's carbon.
[00:07:32] Speaker A: In 1990s, the Amazon was removing more than 1.5 billion tons of, of carbon dioxide from the atmosphere. Now it's removing much less, 300 million. And that area, the forest degradation of the forest. The dry season becomes warmer, drier, longer. The forest has become a carbon source
[00:07:57] Speaker B: in its most deforested regions. In the eastern and southeastern Amazon, the forest has already crossed that line, shifting from carbon sink to carbon source.
The system that spent millions of years pulling carbon out of the atmosphere is now in those places, putting it back in.
And Carlos is unambiguous about what happens to the rest of the Amazon if we don't change course, Even if we
[00:08:22] Speaker A: really don't reduce emissions, and if we fail completely into zero deforestation, we are going to reach a tipping point in the Amazon by 2040, but no longer than 2050.
And if we really cross the tipping point of the Amazon, then by 2017, 28 to 2100, we are going to lose about 70% of the Amazon forests. We are going to Release up to 2100 more than 250 billion tons of carbon dioxide. We're going to lose the largest biodiversity. We are going to reduce a lot of this water vapor transport to the south, the flying rivers, the Pantanal, will disappear. So this is an ecocide, an ecological suicide.
[00:09:20] Speaker B: An ecological suicide.
What a powerful statement at the end of our conversation.
Carlos isn't describing something happening to the Amazon from the outside. He's describing a system that, pushed past a certain point, begins to dismantle itself.
The tipping point is not inevitable, though. The pathway out exists near zero deforestation, a dramatic reduction in global emissions, and active restoration.
The window is narrow and closing, but we haven't crossed it yet.
That distinction is everything.
Which means the future of the Amazon depends on whether we understand what we're protecting and whether we're willing to listen to what the system is already telling us.
The Amazon's rivers and its charismatic inhabitants have something to say about that.
The Amazon basin carries roughly 15 to 20% of the world's riverine freshwater discharge, not just in the main river, but across thousands of tributaries, floodplains, lakes and wetlands, connecting ecosystems and communities across an area so vast that managing it requires international coordination on a massive scale.
And unlike the atmosphere above or the geology below, this water world has a living ambassador to understand what's happening underneath the water's surface.
I spoke with Maria Jimena Varrama, a veterinarian, National Geographic explorer and scientist with the Omacha foundation in Colombia. Her studies focus on one of the region's most iconic animals, the pink river dolphin.
[00:11:03] Speaker C: The river dolphins for me are like a Pokemon. Are like, are so, so crazy to exist because they are pink and are in the middle of the river and you can see the forest in the landscape. They are so strong animals, so resilient.
They start to be in a freshwater ecosystem like 5 billions of years ago. They adapt themselves and evolution with this freshwater ecosystem.
[00:11:36] Speaker B: Five million years while the Amazon was being shaped by the forces Carlos described the these animals were evolving alongside the river system and developing adaptations that exist nowhere else in the dolphin family.
[00:11:50] Speaker C: They developed some things like increase the size of their meadow for try to echolocalize better because in the water in the Amazon you can see anything.
So the ecolocalization is so much better than the other species of of cetaceans because they need to see where is the fish, where is the trees in the water, where is the boats. So they had like radar in their mind. So it's incredible.
They can move their head, the river dolphins can move this tail because they need to. Inside the food forest, the water can change their level more than 20 meters. So the ecosystems are changing all the time and they need to adapt to this change.
[00:12:48] Speaker B: A landscape that completely transforms twice a year from open beach to fully submerged forest and back again. And these Dolphins have spent 5 million years learning to navigate both versions.
Their bodies are an archive of everything this river system has ever demanded of them.
You might be wondering what makes a pink dolphin. Well, pink.
[00:13:11] Speaker C: They are not all the time pink. They become pink with the exercise, with the movement, because all the capillaries around the body start to give a lot of blood. But some dolphins are pink all the time. Depends on the phenotype of each single dolphin. Like us. Sometimes some people are are rush all the time, but not all.
[00:13:35] Speaker B: Through a health assessment program running across Brazil and Colombia, Jimena's team captures individual dolphins for no more than 20 minutes. Taking blood samples and tissue samples, running ultrasounds, testing for parasites and infectious disease and returning the dolphins back to the river.
The data they're collecting is new for this species and what it's showing is that the river is sick.
[00:14:00] Speaker C: The dolphins like a mirror or what happened around them. So if we have found high levels of mercury, that means the people who eat the same fish of the dolphins had high levels of Mercury. If we found some antimicrobial resistance, that means the people around these dolphins don't use both these antibiotics and they are in the river. So they are a mirror of what happened. And we try to use these dolphins for work with the public health, for work with different governments, different institutions to show what happened in the river and not just protect the dolphins, not just protect the river and protect the people who depends on that.
[00:14:46] Speaker B: That framing the dolphin as a mirror reoriented my understanding of her work.
The health assessments are more than a conservation tool. They're a diagnostic report on everything the river touches. The fish, the communities, the water itself.
And the reports coming back are deeply troubling.
The biggest red flag, Jimena told me, is mercury.
[00:15:10] Speaker C: The red flag, the bigger red flag is the mercury contamination.
This is a very toxic element for the body and can bioaccumulate biomagnetic in the ecosystem. It's like a silent enemy because you eat mercury and don't show signs in this moment.
The mercury accumulate, accumulate, accumulate and years after can show what's happening. We found in different dolphins levels other than 35 milligrams per kilogram of mercury.
And the limit of permits of this mercury is 0.5 milligrams per kilogram. So we are set the concentrations in a very huge part is incredible. So if this happened with the dolphins, it's happened with the people.
[00:16:11] Speaker B: 70 times the permitted limit in animals sharing their food source of with the communities living alongside these rivers.
The source isn't a mystery.
Illegal gold mining releases mercury directly into river systems where it enters the food chain and works its way up.
The same criminal economy running through almost every crisis in this series is poisoning the water at its source.
Mercury is the loudest signal, but the dolphins are carrying others.
[00:16:41] Speaker C: We found two different antimicrobial resistance. We found Klepsiella, we found E. Coli, we found different bacterias with a lot of resistance to normal antibiotics. That means the people around don't use correctly these antibiotics. We have in Colombia, the problem, a lot of the people, all the people can buy some antibiotics with any recipe. So it's so easy to find antibiotics and use how they want.
And that is what happens in the
[00:17:19] Speaker B: river and beyond the antibiotic resistant bacteria in the bloodstream of river dolphins. Jimena's team has found evidence of a parasite causing large papillomas in the reproductive systems of female dolphins.
A parasite they believe may be crossing from domestic cattle into wild dolphins for the first time.
The full picture isn't clear yet, but the pattern is The Amazon's rivers are absorbing everything happening on land around them and the dolphins are registering it all.
The question is whether anyone is listening. And on that front, Jimenez coalition has been making sure the answer is yes.
In 2023, 11 of the 14 countries where river dolphins are found signed a declaration committing to their conservation, including China, where related freshwater dolphin species live.
That same year, the Ramsar Convention, the international treaty governing wetlands, passed a resolution formally recognizing river dolphins as sentinels of aquatic ecosystems.
[00:18:26] Speaker C: We achievement the last year a resolution for river dolphins, like sentinels of the aquatic coastal systems in Ramsar sites. So this is so important because the river dolphins, of course, are not in all the Ramsar sites, but is like image, like umbrella, like sentinel of the aquatic ecosystem and can show the importance of using one species for conserve the different Ramsar sites. So it's incredible.
[00:18:56] Speaker B: And when I asked Tamina what keeps her going back onto the river in the heat for another capture, her answer came without hesitation.
[00:19:05] Speaker C: The first image to come to my mind is the dolphin. Like you see the dolphin and it's still there, still being strong, still being resilient with all of the treats they have around them, but still there. They give me hope, they give me like propose to still doing that, but the people who start to work with them, the people who change a little bit their mind and start to be with interest, with a different approach to the dolphins, to the process, to the environmental things that give me hope.
Look the child when we have some workshops in the schools talking about this, talking about the conservation, and look, the different eyes of the children with all of the hope, give me hope.
[00:20:01] Speaker B: The dolphins are still there, navigating the flooded forests, reading the river with their extraordinary sonar and carrying in their blood the full story of everything the Amazon's water touches.
But there is one more layer to this system, one that few of us ever think about.
And to understand it, I called Andres Ruzo.
Andres is a geothermal scientist, conservationist and National Geographic explorer, currently completing his PhD at Southern Methodist University.
He grew up moving between Peru, Nicaragua and the United States. And his entry point into the Amazon was through the heat of the earth itself and what it has to do with the forest above.
[00:20:50] Speaker D: When I think of the Amazon, I ultimately think of, frankly, the greatest celebration of life on our planet. This is one of the most interconnected systems anywhere. And it is absolutely wild how every detail just magically, beautifully interconnects. So when we're talking about the Amazon, what we're talking about is the Amazon basin, right? This is a water Biome, if you will. This is the kingdom of water, but it also has a well in the air component, right? People have talked about the, the floating river, right? The, the clouds, the, the river system in quotes, that is floating through the air that creates the rains that gives the Amazon rainforest that very title. But then also there's another side under the surface, and that's where the aquifers, the geothermal aquifers come in. And everything in that whole three, those three worlds coming together and they interplay and they interact with each other. Every drop of water has a fingerprint, isotopes, elements inside those waters. And it gives you details about how some of this interplay works and how they connect to each other. And that is, is the real basis of anything you want to study in the Amazon.
[00:22:05] Speaker B: Andres has spent years trying to understand how these layers connect. The tool he uses is water itself, specifically, the chemical fingerprints carried inside individual water molecules that reveal where they've been, what systems they've passed through, and how the surface world and the deep earth are talking to each other.
The Amazon, in his understanding, is not a forest sitting on top of geology.
It is a conversation between three systems that has been running for millions of years.
That understanding became concrete for Andres through a story that starts with a legend his grandfather used to tell him. As a boy in Lima,
[00:22:47] Speaker D: my grandfather used to tell me this crazy story about the Spanish conquest of Peru. One of the details included a river that boiled. It's the legend of Paititi. Paititi, El Dorado in Spanish, is a lost city of gold hidden deep in the Arizona. The Spaniards and the Inca, they've been fighting for 40 years. The Inca are finally conquered, and new waves of wannabe conquistadors come into Peru looking for gold and glory. And the Inca, out of vengeance, tell them, oh, okay, okay.
Go to the Amazon. You want gold.
To the east, in the land of the plant, there is an entire city made entirely of gold. And the few that return come back with these horrifying stories.
Giant spiders as big as your hand that eat birds. Snakes that can swallow a man whole. Fierce warriors with poison arrows that'll kill you and a nick. Powerful shamans with spells that drive you mad.
And one of the details was of a reefer that boiled.
[00:23:46] Speaker B: The story stayed with him.
Years later, while mapping Peru's geothermal energy potential for his PhD, Andres came across data points in the Amazon that made him wonder if the legend could be real.
Every scientist he asked told him no. Boiling rivers only exist next to volcanoes. And the central Peruvian Amazon is 700 km from the nearest active volcanic city center. One senior geologist told him flatly not to ask stupid questions.
Then he mentioned it to his aunt at a family dinner in Lima.
[00:24:21] Speaker D: And then she looks at me and she's just like, the boiling river does exist. It's real.
I've been there. And I'm looking at her like, you're crazy. And then she's like, yeah, I swam in that river. And I'm like, yeah, no, I definitely know you're crazy, right? You swam in a boiling river. You crazy. I said, like too much peaceful sour for you, you know, like you're cut off. Genuinely, I thought she was messing around with me. She's got a great sense of humor. I love her to death. She used to do indigenous rights work, had made friends with the wife of this powerful shaman that guarded over the area, and they had been invited to visit.
[00:24:54] Speaker B: Four months after that dinner, Andres and his aunt tried to reach the shaman by every channel they could find, but nothing.
Eventually his aunt made the call. They needed to stop waiting and just go. The next morning they were on a plane at 5am to the central Amazon. Then three hours by truck, an hour by motorized canoe, then another hour on foot through the jungle led by one of the shaman's apprentices.
[00:25:19] Speaker D: And then we get to the top of this big hill, hot day, carrying the packs, you know, we're all breathing heavily, right?
We sit down for a break in the background. I remember hearing this like it sounded kind of like an ocean wave that was just constantly crashing. I asked the shaman's apprentice, what is that? And he just kind of smiles and he points down towards the valley below us and he goes, that's the river. And I'm like, what? So I look down and I see between the trees and these are massive trees. I see these wisps of I thought was smoke. And he says, go. So I bowled down this hill, run through this community and suddenly I'm just like, stop at the clearing. And I'm face to face with basically everything my aunt had said was going to be 60 foot walls of green, right? Like 20 meter walls of green, these beautiful massive trees. And in between that there's this river on either side. It's flanked by these ivory colored beautiful stones. And the water itself was this almost transparent turquoise.
There was a thin layer of mist just kind of dancing in the breeze there. It was definitely as wide, if not wider than a two lane road. It was going on for definitely at least 200 meters, just like they said. And all I could Think of was that's a lot of steam. I run down to the edge and I remember taking that first breath in that hot, thick moisture air going into your nose, into down your throat and into your lungs and like really feeling that heat. I wasn't prepared for that. It was kind of like when you breathe inside of a sauna. Imagine walking into a sauna, not thinking twice and just boom. It burns everything, right? And then I take that temperature measurement and I was looking at, it was just under 90 degrees C.
So it was about, it was about 87 degrees Celsius, which is about 180, 889 degrees Fahrenheit. Over 700 kilometers, over 430 miles away from the nearest active volcanic center.
[00:27:20] Speaker B: Water burns human skin at 47 degrees Celsius. This river was running at nearly twice that and science had no record of it.
What followed was a years long effort to understand what the Boiling river is and to protect it.
Andres met the shaman who had guarded the site for decades, a man who became a close friend and mentor.
The shaman gave Andres his blessing to study the river with one condition.
[00:27:51] Speaker D: And his response was, yes, of course I give you my blessing to study this river, but I ask you in turn to help us bring it to the world responsibly.
We can no longer conceal, to protect. And even then he was painfully aware that not only was his culture facing cultural degradation, right? Globalization is advancing, but also the jungle is disappearing and continues to disappear. I have dedicated at this point like a third of my adult life, if not more to this project from that moment on. And we continue fighting for it and frankly, like, well, not going to stop until it's protected.
[00:28:34] Speaker B: Today, the Boiling river has nearly 200 collaborators working on it from research institutions around the world. And what they found could transform science.
[00:28:46] Speaker D: This is the hottest naturally occurring microecosystem in all of the Amazon.
It is a perfect window as to what a post climate change impacted Amazonia might look like. Because depending on where you are in the Boiling Rivers valley, the subsurface temperatures might be 10 degrees C hotter than background temperatures. And it's already hit steady state and it's already jungle. So how's that impacting plants? There's another group looking at ants and insects, fish specialists, bird specialists, all sorts of people trying to understand this area. If we understand, we'll know the baseline. If we know the baseline, we can make sure we keep to it as much as possible, especially in the face of human impact.
[00:29:32] Speaker B: What's living in those thermal waters? It turns out may have implications that reach far beyond the Amazon.
[00:29:40] Speaker D: People don't realize it, but all of modern biotech, all of it, and all of modern medicine associated with that biotech and all of those advances are linked to geothermal systems and extremophile ecosystems.
If you look at any modern biotech, CRISPR and PCR are basically the, you know, one, two, punch. They are the baseline for everything you're going to do. Pcr, the polymerase chain reaction, is your genetic copy machine. We got PCR because we protected Yellowstone, because we protected the mushroom hot springs, which allowed for Thomas Frog to come study the mushroom hot springs. The Amazon is one of the most biodiverse places on earth. The western Amazon in Peru is a mega biodiverse region. So within a mega biodiverse region, we have extremophile ecosystems. There's a lot there.
[00:30:30] Speaker B: We protected a hot spring in Wyoming and it gave us the molecular tool that underpins modern medicine.
The Boiling river sits at the intersection of the world's greatest biodiversity and an extreme geothermal ecosystem that we're just beginning to study.
And what it might yield is an exciting mystery.
The potential it holds is immense and an urgent argument to protect the site.
Near the end of our conversation, Andres told me about an evening he spent with a shaman by the river and had asked about El Dorado, the city of gold.
[00:31:06] Speaker D: Big smile just crept across his face and he looks at me, gives a little face and goes, you mean you missed it?
I was like, what do you mean I missed it? He's like, his eyes kind of glance around and he's like, you missed it. It's here, it does exist. And it all clicked. So when the Inca said, go to the east, to the land of the plants, you'll find an entire city made entirely of gold.
The play on words is life.
Gold can be either the tears or the sweat of the sun, depending on your tradition, can be seen as a sacred thing representing life itself. To the east, in the land of the planet, there is a city of life.
You will be walking on interlaced tree roots. You will be walking through great halls of columns of massive trees. There will be a canopy over your head that is the vaulted ceiling of the jungle.
You tell me that that's not a city of life. The conquistadors were so focused on the gold, on the short term monetary asset, that they missed that beautiful jungle that was in front of them.
[00:32:16] Speaker B: The conquistadors walked through a city of life and saw only a jungle.
Hundreds of years later, the question Andres has been asking. And the question this series has been circling this whole time is if we are still making the same mistake.
Whether we are so focused on what can be extracted from the Amazon and that we keep missing what it is.
Three systems working together for 40 million years. Flying rivers above, sentinels in the water. And a geothermal world beneath the forest floor whose depths we have barely touched.
And what gives Andres hope?
[00:32:53] Speaker D: What's beautiful about nature? You give nature a chance and it will come back. Life will find a way. It will make it and it will adapt and it will evolve. We just need to keep those cycles in balance. We need to protect that. The jungle can grow back. Without that, there is no future.
So what are your options? Right.
Charge the windmill.
[00:33:17] Speaker B: When I started working on this series, I viewed the Amazon as mostly a rainforest, a vital and irreplaceable one, but a forest nonetheless.
What Carlos, Jimena and Andre show me is that I was seeing only one layer of an ancient and interconnected web of life with systems so deeply interwoven together that disrupting any one of them puts the others at risk.
And yet, at every level, there are people paying close attention and working in their own ways to hold the Amazon together.
In the next episode, we meet the people who have been standing up against the destruction of the Amazon.
And in some cases, have paid the highest price for doing so.
This is rewilding Amazonia. I'm Brooke Mitchell. See you in episode six.
