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Supertrees: Meet the Amazonian giant that helps the rainforest make its own rain

The Brazil nut tree plays a critical role in the global climate and weather across South America. Deforestation is putting it all at risk.

Researcher Delano Campos scales an 80-meter tower at the Amazon Tall Tower Observatory to collect air samples and maintain instruments.
Victor Moriyama for Vox
Umair Irfan is a correspondent at Vox writing about climate change, Covid-19, and energy policy. Irfan is also a regular contributor to the radio program Science Friday. Prior to Vox, he was a reporter for ClimateWire at E&E News.

UATUMÃ SUSTAINABLE DEVELOPMENT RESERVE, Brazil — The white mist is thick and creamy, and it envelops me as I plod up the steep stairs of the exposed steel tower. In this swirling fog, it’s hard to tell how high I am and how much further I have left to go.

Wearing a climbing harness that’s a little too snug and secured by a cable that looks a little too thin, I unclip my carabiner from the railing and attach it to the next one up. The diamond plate flexes under my weight as I move toward the next set of steps. I can’t see the ground, but I can see that the gaps between steps on the stairs are wide enough for my boot to easily slip between them.

I have inadvertently ended up at the front of our little group, far ahead of everyone else who set out on this climb. The scientist guiding us suggested we get to the top of the tower by sunrise, which meant waking up at 4 am and scaling the structure in the dim light of early morning. Alone in the clouds, I pause at a landing marked “200 meters,” feeling the whole tower sway in the wind. It’s silent and still, save for a breeze roiling wisps of fog between the steel braces of the tower.

A top-down view of an orange metal network of bars and steps of the tower, shrouded in mist.
The thick mist of early morning makes it impossible to see very far during the climb up the Amazon Tall Tower Observatory (ATTO). The steps are narrower and farther apart than they appear.
The reporter is seen with helmets and safety equipment at the top of the Amazon Tall Tower Observatory.
I was the first to arrive at the top of the tower, joined about 30 minutes later by the rest of the group. The fog was still thick more than 1,000 feet up, and the tower noticeably swayed in the wind.
Umair Irfan/Vox

I am here in the jungle, a half-day’s journey by pickup truck and boat from the nearest major city, two-thirds of the way up the Amazon Tall Tower Observatory, the tallest structure in South America, to experience a force that defines the Amazon rainforest as we know it.

The hundreds of billions of trees, spread over the 2.1 million square miles of forest below, channel a colossal volume of water into the air every day. Alongside that water, they emit an elixir of chemicals that react to form particles, inducing that moisture to fall back out of the sky.

The rainforest, amazingly, makes about half of its own rain.

In the early morning hours, a huge upward torrent of fog emanates from the treetops, spreading so thick that it’s impossible to see more than a few feet in any direction. This moisture rises into the sky and condenses as it cools, forming clouds (scientists call this the evapotranspiration process). When it meets dust and particles, it forms drops that create rainfall.

View from the top of the Amazon Tall Tower Observatory
The heat from the rising sun leads the fog to thin out, showing just how high up we are on the tower.
A view of the Amazon Tall Tower Observatory from another research tower.
The Amazon Tall Tower Observatory is one of the tallest structures in South America and a valuable tool for studying the rainforest.

It’s a vital mechanism for keeping the Amazon’s vine-draped greenery lush. The downpours top up the aquifers that slake the thirst of tens of millions of people in Brazil’s cities and irrigate the farmlands that feed them, even those thousands of miles away and far from the rainforest itself. In some parts of the jungle, the rain is so regular that locals plan their days around it, scheduling breaks and short naps during afternoon rainstorms before returning to work once the skies clear.

The daily churn of rainfall and evaporation has a cooling effect on the region and can influence rainfall patterns as far away as the United States. And as its rain-drenched vegetation grows, the Amazon inhales and stores a gargantuan volume of carbon, an effect that ripples throughout the global climate system.

The Amazon rainforest has been described as the lungs, the sweat glands, and the heart of the planet, but these metaphors are inadequate. The Amazon is not an organ, but an organism unto itself, sprawling beyond the sum of its parts. Nothing else compares to what the Amazon rainforest does for itself, the region, and the rest of the planet.

The rainforest isn’t one community as much as it is a mosaic of different communities. Sections like this one are dense, dark, and lush, while others are more sparse and sunny.
Victor Moriyama for Vox

Yet a soccer-field-sized area of the Amazon rainforest is cleared every 60 seconds due to logging for timber, or clearing space for cattle ranching, soy farming, and mining. As the forest loses trees, it loses its rhythm: rain, evaporation, transpiration, condensation, rain.

Without these towering giants and the soil beneath them acting like a gargantuan reservoir of carbon, fewer heat-trapping gases will be absorbed and the process will eventually reverse. The carbon in the forest will enter the atmosphere, accelerating the planet’s warming.

The Brazilian Amazon this year has suffered an alarming spike in deforestation and forest fires that environmental activists blame on lax law enforcement and tacit approval from Brazil’s right-wing government. Scientists say there are seldom natural fires in the rainforest; almost all are ignited by humans.

These losses sparked international outrage. “Our house is burning. Literally,” wrote French President Emmanuel Macron on Twitter in August. “It is an international crisis.”

Smokes rises from forest fires in Altamira, Pará state in Brazil, in the Amazon basin, on August 27, 2019.
Joao Laet/AFP/Getty Images

But Brazilian President Jair Bolsonaro was defiant, arguing at the United Nations General Assembly that the Brazilian Amazon belongs to Brazil and that international alarm over its destruction is a threat to the country’s sovereignty.

Eventually, Bolsonaro deployed the military to fight the fires and declared a moratorium on new blazes. But the losses the Amazon has experienced are already having consequences. The dry season is getting longer, and scientists are finding imprints of deforestation in the record droughts seen in major cities like São Paulo, some 1,500 miles away.

A scenario even more alarming lies ahead. About 17 percent of the Amazon has been lost since 1970, and if deforestation reaches around 25 percent, scientists warn that the Amazon may not create enough of its own rain to sustain itself. The ecosystem could enter an irreversible cascade of collapse and degrade from tropical rainforest into savanna, a process known as a dieback.

In 20 to 30 years, the Amazon could reach a tipping point of 25 percent deforestation. This would begin an irreversible collapse, eventually turning the world’s largest rainforest into dry savanna.
Amanda Northrop/Vox

This prospect has added urgency to research conducted atop this swaying steel tower. Scientists here are racing to understand all of the complicated ways in which the Amazon rainforest interacts with the world around it — before it’s lost. But to truly appreciate the breathtaking power of the rainforest, it helps to start with a single tree.

The towering Brazil nut tree is a microcosm of how the rainforest makes its own rain

The Amazon rainforest is home to nearly a quarter of the planet’s terrestrial biodiversity, and its waters have more fish species than any other river system. More than 100,000 invertebrate species, 378 reptile species, 400 amphibian species, 427 mammal species, 1,300 bird species, 3,000 kinds of fish, and 40,000 types of plants live in this magnificent ecosystem.

Life here has yielded novel scientific insights and produced lifesaving medicines. New species and benefits are still being discovered. There are even tribes of indigenous people that, to this day, have eluded contact with the outside world.

Amid this splendor, the trees in the rainforest stand out.

One example is the iconic Brazil nut tree, Bertholletia excelsa, also known as Para nut. It’s not as massive as the sinuous, sprawling kapok tree, nor as precious to loggers as the chocolate-colored mahogany. But Bertholletia excelsa is one of the most powerful tree species in the jungle. It’s the only member of its genus and it thrives deep in the jungle, surrounded by billions of other trees, drenched by the near-daily downpours it helps create.

A Brazil nut tree, Bertholletia excelsa, in the Amazon rainforest.
This Brazil nut tree near the banks of the Uatamã River rises high above the canopy in the Amazon rainforest.
Umair Irfan/Vox

Humans are still learning how to grow Bertholletia in plantations, so almost all of the world’s crop of Brazil nuts comes from wild trees. It’s just a tiny example of how the Amazon’s expansive, interlocking ecosystem can be impossible to replicate.

En route to the Amazon Tall Tower Observatory, or ATTO, I spotted one of the trees from a boat on the Uatamã River, a tributary of the Amazon River. Its crown of wavy oval leaves towered over its neighbors along the riverbank. After we unloaded our gear from the boats, I walked along a dirt path up to the tree.

Standing at its roots, the tree’s nearly 6-foot-wide trunk filled my view and eclipsed the smaller trees around it. The ground was spongy with leaf litter and damp from the rain. Even mid-afternoon, the hottest time of the day, the thick, looming canopy cast a cool shadow. Vines draped down the sides of its gray bark; highways of leafcutter ants scurried over its roots. A screaming piha bird called out with its resounding three-tone chirp.

From the soil to the sky, every layer of the Amazon rainforest pulsates with life. And every day, this Bertholletia bridges the two, channeling more than 260 gallons of water into the air daily.

Of course, Bertholletia is not alone. It stands alongside more than 390 billion trees in the Amazon, belonging to an estimated total of 16,000 tree species throughout the rainforest, of which 6,727 species have been described, many of which can also gush hundreds of gallons into the air daily.

The sun crests over this verdant ocean every morning, and as the light hits the leaves, the rainforest takes its first steamy breath of the day. All of this moisture feeds into a massive body of water floating above its canopy, constantly fed by evapotranspiration and dispatching rain throughout the forest. In a way, the mightiest rivers in the Amazon flow through the sky.

Mist rises above trees in the Amazon rainforest.
The morning mist as seen from ATTO shows just how much moisture moves up from the rainforest.
Umair Irfan/Vox

Scientists are still learning about all the ways the Amazon rainforest is linked to the rest of the planet

From Manaus, Brazil — the capital of Amazonas state — the journey to the Amazon Tall Tower Observatory starts with a three-hour car ride across highways and dirt roads, followed by a two-hour boat ride, capped with a bouncy 30 minutes on a jungle road in a pickup truck.

Researchers from Brazil and Germany teamed up in 2009 to select a site and build this tower to study the rainforest with minimal human influence, where diesel exhaust and road dust wouldn’t interfere with measurements of pollen, carbon, and volatile organic compounds. They also wanted to make sure the roads they built to support the research station couldn’t be easily used for illegal logging and poaching.

“If you create a street [all the way to the research site], people are going to cut down the rainforest,” warned Stefan Wolff, a meteorologist at the Max Planck Institute for Chemistry who is studying the exchange of gases between rainforest and atmosphere. The tedious trip, across the river and dirt roads, that scientists and supply crews make to ATTO three times per week, serves as a barrier to miscreants.

The amenities at the research station are austere. The main camp is just a corrugated-roof mess hall and a bunk, where about two dozen people — scientists, staffers, maintenance workers, cooks — all sleep in hammocks just a couple of feet apart from one another. There is running water and a nearby generator that provides electricity, but internet is brought in via satellite, and much of its bandwidth is reserved for scientists transmitting data to research centers in Brazil and Germany.

The logistics are all in support of an effort to measure and monitor the rainforest in its most pristine state. The key questions the scientists are trying to answer here are how the rainforest influences the world around it and how the world, in turn, influences the rainforest. It’s part of a truly global system, the scale of which is difficult to comprehend.

Scientist Cybelli Barbosa at her research station near the Amazon Tall Tower Observatory.
Researcher Cybelli Barbosa collects data at her station near ATTO. Her research will help produce better regional rainfall forecasts and improve global climate models.

It begins 3,000 miles away in the Sahara Desert, where dust crosses the Atlantic on trade winds and lands in the rainforest, nourishing the Amazonian soil. The dust whipped up in the Bodélé Depression in Chad, an ancient lake bed, contains phosphorus that is vital for plants.

Without this movement of dust — about 22,000 tons of it per year — the forest would be starved of important minerals, and the specific makeup of trees, shrubs, and ferns would change. That would, in turn, alter how much water is evaporated and how much carbon is absorbed, creating an altogether different ecosystem.

The Amazon rainforest currently absorbs about 2 billion metric tons of carbon each year, roughly 5 percent of the world’s annual emissions. Within its biomass, it holds about a decade’s worth of human-produced greenhouse gas emissions.

At the same time, the Amazon generates far-reaching effects of its own. The movement of moisture from the rainforest influences patterns of rainfall across much of South America, and signs are emerging that deforestation is worsening droughts around the continent.

A NASA model of cloud formation over South America
This NASA weather simulation shows how rain clouds are constantly bubbling up over the Amazon and moving across the continent.

But scientists were long in the dark about just how all these local, regional, and international links to the rainforest came together.

In 2012, scientists here constructed an 80-meter steel tower outfitted with instruments to measure rain, carbon dioxide, volatile organic compounds, and aerosols going into and coming out of the Amazon rainforest. It was a start, but they soon realized they needed to cover more areas, which meant getting higher above the forest.

It helps to think of the tower as a wide-angle camera lens. If you mount the instruments close to the treetops in the canopy, you pick up only the movement of gases from the trees immediately below. Move the sensors higher, and you can monitor a wider region.

In 2015, the team inaugurated a 325-meter-tall orange and white steel tower, stayed with guy-wires, sending steel, scaffolding, and construction equipment by boat and dirt roads to this part of the jungle.

The tall tower holds up tubes that suck in air from the top and pump it to a laboratory housed in a shipping container at its base. The instruments there — like chromatographs and spectrometers — measure the churn of gases, moisture, aerosols, and particles above the tops of the trees that link this forest to the global climate system. Scientists can even identify the source of some particles by testing the DNA they find.

However, these tools remain vulnerable to the peculiarities of the jungle, like torrential rainfall and defecating birds. I watched a pair of scientists remove a bee infestation from a box of electronics on top of another 80-meter tower at the site, delicately scraping away the hive and capturing the queen in a plastic bottle.

Researcher Layon Demarchi works on top of the 80-meter tower near the main tower at ATTO.
Researchers at ATTO have to contend with large temperature swings and torrential rainfall. Botanist Layon Demarchi captures a queen bee from a hive that has taken up residence in one of the instruments.

But at the top of the main tower, one doesn’t need sophisticated devices to sense the immense scale of the rainforest’s influence on the weather. It’s playing out right before me.

The sun is rising over the horizon. Breaks appear in the fog, the mist condenses into discrete clouds, and the forest starts to peek through. Heated clouds begin to rise straight up as winds at different altitudes shuffle the puffy white cotton balls past each other like overlapping highways. The tower sways as the wind picks up.

Clouds soon start pouring out fine shrouds of rain. A few minutes later, mist begins to rise from the trees again. The scene plays out thousands of times a day over the Amazon, recycling moisture over and over until it reaches the ocean.

The scientists at ATTO are also tracking this cycling of moisture on much smaller scales. Back on the ground, some of the researchers are zooming in on individual trees, and sometimes, down to their leaves.

Around sections of the camp, researchers have placed baskets that capture falling leaves, seeds, and sticks to track the biological productivity of diverse biomes of the rainforest, like the low-lying campina. It’s a part of the forest with poor, sandy soil and a high water table that stunts the growth of plants, but shelters a large variety of epiphytes like orchids. The campina stands in contrast to other parts of the forest with imposing, fast-growing trees that quickly blot out the light above and thin out the vegetation below.

Scientists examine leaves collected from trees in the Amazon rainforest.
From huge swaths of rainforest down to individual leaves on trees, scientists are learning about how the ecosystem sustains itself and how these effects ripple across the globe.

Layon Demarchi, a botanist at the National Institute of Amazonian Research (INPA), measured the growth of tree trunks in a 50-by-50-meter section of the campina with a micrometer, tracking how they change with rainfall patterns. “It’s a little island in the forest,” Demarchi says. The Amazon rainforest isn’t one big ecosystem as much as it is dozens of unique biomes stitched together, he explained, each with its distinct library of life, but working together to spread moisture and nutrients that sustain the rainforest as a whole.

There are other experiments scattered throughout the research station. Behind the bunk, a laser cloud-measuring instrument is pointed upward to the skies monitoring their volume and composition. Laboratories in shipping containers track the opening and closing of stomata, the pores on the leaves of various trees, studying how they release moisture and take in carbon dioxide.

The stomata emit volatile organic compounds like isoprenes, which react in the air to form particles, explains Cybelli Barbosa, a postdoctoral fellow at the Max Planck Institute for Chemistry who frequently conducts her work with a machete at her side. Those particles then serve as nucleation points, allowing moisture to condense and form droplets. Rain in the rainforest isn’t just an accident of the weather; Bertholletia, like millions of other trees in the Amazon, induces rainfall.

The findings at ATTO will eventually feed into global climate models that will help us understand the changes we’re making and what the future holds for life as we know it.

“Our work can very practically be used to make policy decisions,” Wolff says. “As we are performing long-term measurements of various meteorological parameters, we directly see the differences in those variables from season to season, year to year.”

But the baseline for the forest is rapidly changing.

Scientist Layon Demarchi measures the growth of a tree in the Amazon rainforest.
Botanist Layon Demarchi measures the growth of a tree in the Amazon rainforest. Tracking how vegetation responds to changes in temperature and rainfall is critical to understanding the Amazon’s role in the global climate system.

Preserving the Amazon benefits the whole world, but there’s immense pressure on the ground to exploit it

About an hour’s boat ride downriver from ATTO is the village of Maracarana, home to about 300 people. Maracarana was settled in the 1970s as this part of the forest was cut away to make room for ranching cattle. But in 2004, the Brazilian government established the area as part of the Uatumã Sustainable Development Reserve. It’s a forest protection system that attempts to combine conservation with sustainable forest uses by local traditional communities. The designation created legal protections for more than 1 million acres of this section of the rainforest and punishments for those who would destroy it.

Residents were given cash to stop cutting down the forest but were still allowed to reap its bounties, provided they did so in a way that allowed it to regenerate. Claudomiro Dos Santos Gomes, 52, works in Maracarana as a farmer and volunteer conservationist. He explains that people in the village now grow manioc, corn, beans, and watermelon on the cleared pastureland. From the forest, they harvest Brazil nuts, acai berries, and andiroba oil, a popular ingredient in incense and organic cosmetics. The government also helps the people in the village take their products to market in major cities like Manaus. The area’s clear and calm waters have made it a popular destination for sport fishers, too.

Claudomiro Dos Santos harvests coconuts near his home in the village of Maracarana in the Uatumã Sustainable Development Reserve.
Maracarana locals like Claudomiro Dos Santos Gomes are working on ways to live sustainably alongside the rainforest, such as by harvesting coconuts and other fruit.

Nomadic indigenous groups who once roamed the reserve taught the newer arrivals about the cures and remedies of the rainforest, according to Dos Santos Gomes, and there are many more benefits that have yet to be discovered.

“It’s more lucrative right now to preserve the forest,” Dos Santos Gomes says.

But he notes that there are more than a dozen villages along the Uatumã River in this rainforest reserve, and not all of them are good stewards. There is little oversight or monitoring, so in many villages, people end up taking conservation money from the government to preserve the rainforest while also taking bribes from illegal loggers.

And in Maracarana, the residents in this area still need to power their homes, charge their phones, build health clinics, and send their children to school, which means they need to trade for resources from the outside. If people stop buying the crops from them, or if the demand for rainforest products surges, the pressure to clear the forest or overexploit it will grow.

With the Amazon seeming far-off and remote — even for most Brazilians — its value as a global store for carbon, a generator of rainfall, and a regional air conditioner is abstract and easy to take for granted. And it’s even more difficult to get other countries to step in when almost two-thirds of it is contained within the borders of just one country.

Brazil’s election of far-right President Bolsonaro has sparked a new surge of deforestation. His administration has made no secret of its desire to sell off the wood, land, and mining rights to the forests, as well as to roll back protections for the indigenous people who live there. His administration has scoffed at the idea of the rainforest as a global asset.

“It is a fallacy to say that the Amazon is the heritage of humankind, and a misconception, as confirmed by scientists, to say that our Amazonian forests are the lungs of the world,” Bolsonaro told the UN in September. “Using these fallacies, certain countries, instead of helping, followed the media’s lies and behaved in a disrespectful manner and with a colonialist spirit. They even called into question that which we hold as the most sacred value: our own sovereignty.”

The accelerating pace of disruption has sparked bloody confrontations with indigenous groups that want to preserve the forest and their way of life. And for the planet as a whole, time is rapidly running out for humanity to drastically cut its greenhouse gas emissions to limit this century’s warming to 1.5 degrees Celsius, the more ambitious target of the Paris agreement.

View of a burnt area of forest in Altamira, Pará state, Brazil, in the Amazon basin, on August 27, 2019.
Joao Laet/AFP/Getty Images

The Amazon rainforest is one of the most important barriers against unchecked warming and intensifying drought cycles in Brazil and beyond. But scientists are concerned that deforestation and fire are pushing the Amazon too close to an irreversible cycle of collapse. And evidence shows that the rainforest’s capacity to absorb carbon is already declining.

“We believe that negative synergies between deforestation, climate change, and widespread use of fire indicate a tipping point for the Amazon system to flip to non-forest ecosystems in eastern, southern, and central Amazonia at 20-25% deforestation,” Carlos Nobre and Thomas Lovejoy wrote in a 2018 editorial in the journal Science Advances.

In another editorial published Friday, they argue the tipping point has arrived. “At current or higher deforestation rates and continued global warming (and increasing vulnerability of the Amazon forest to fires), the tipping point may be crossed irreversibly in the range of 15 to 30 years,” Nobre told Vox.

Researchers at the Amazon Tall Tower Observatory study the both the forest and the trees.
Climbing towers and trees, scientists at ATTO are building a better understanding of how the Amazon rainforest benefits the world.

That’s not much time at all. If scientists can get their message out about how trees like Bertholletia benefit people across the Earth — even those who may never taste its nut or stand in its shade — they may help secure the future of the rainforest.

Victor Moriyama is a Brazilian documentary photographer with a focus on public security and violence, indigenous communities, environmental conflicts, and deforestation.

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