They’re Sizing Up Earth’s Lungs. It Takes Tape Measures and Tree Climbing.

AMACAYACU NATIONAL PARK, Colombia — With the help of a small rope tied around his ankles, Eugenio Sánchez, lithe at age 50, shimmied himself all the way up a towering tree like a human inchworm, his chest heaving from the exertion, just to pick a few leaves.

The leaves, found only on the highest branches, would help the scientists waiting below identify the species. And that, along with the tree’s exact size (or at least as close as one can approximate a tree’s size) would tell them something very important: how much carbon it contained.

The team, wearing gumboots caked with mud, were at the beginning of a monthslong process of painstakingly measuring pretty much every woody plant growing on this patch of Amazon rainforest in Colombia, one by one — a census of all 125,000 individual plants with a trunk size at least 1 centimeter in diameter.

It is part of a new, multimillion-dollar effort in dozens of patches of forest across the world that’s aimed at figuring out, to an unprecedented degree of precision, the extent to which forests perform an epic service to humanity by capturing and locking away huge amounts of carbon dioxide, the main planet-warming greenhouse gas.

The Amazon is vast. Nearly 10 Texases would fit in it. Amid that emerald expanse, this infinitesimal patch, less than a tenth of a square mile, is a stand-in for the larger whole. As a representative sample of the northwestern part of the Amazon, it contains around 1,200 species of woody plants, from gigantic kapok trees to tightly coiled liana vines — all of that in the space of six or seven New York City blocks.

With measuring tape and magnifying glasses, the scientists and their helpers traipsed over slippery snarls of roots and pushed through dense undergrowth. Fallen carcasses of giant matamatá and ojé trees became makeshift gangplanks across swampy whorls of muddy detritus.

For most of the year, in fact, this parcel of forest is flooded and accessible only by canoe. It is crawling with scorpions, tarantulas and chiggers that burrow into skin.

One might ask, all that trouble just to put a tape measure around a tree?

At a global scale, this kind of hand-gathered data may fill a major gap in our understanding of forests. Last year, the Bezos Earth Fund put $12 million toward creating at least 30 of these sites across the world, mostly in the tropics. The effort is spearheaded by the Smithsonian Tropical Research Institute, or STRI, which pioneered the calculation of forest biomass decades ago. They hope to one day have 100 of these sites.

More accurate carbon accounting, these groups say, will strengthen the fledgling efforts to put a realistic trading price on carbon dioxide emissions as a way of creating financial incentives to discourage deforestation and to pollute less. This data could also improve the complex models that scientists use when trying to understand global warming.

Along the way, the team in Colombia has also discovered previously uncataloged and rare species. And for some local Indigenous people, like Sánchez, there’s employment that draws on generations of inherited wisdom.

Information so granular as to almost feel intimate, in other words, is a hefty tool to fight global warming and ecosystem loss. How do you save the forest if you don’t know how it’s changing? How do you mend a relationship if you don’t know your partner’s needs?

“We have always said that the forest is our roof,” said Lauris Sangama, 48, a Tikuna Indigenous woman who carried a caliper and an electronic tablet for data gathering and whose village of 186 people is enveloped by the national park, Amacayacu, where the census is taking place. “Now that I understand carbon and all of that, I know the forest is even more important than we ever imagined.”

The data gathered at sites like these will be married with data from satellites that peer down from space and categorize trees based on characteristics that are visible from above. But most satellites can’t reliably penetrate the forest’s thick canopy.

“You can only get truly accurate carbon measurements by combining satellite data with ground-truthing,” said Laura Duncanson, a remote sensing expert at the University of Maryland. “Like, I’m talking tree-hugging.”

Tropical forest and other land absorbs one-third of all the world’s planet-warming carbon dioxide emissions. The Amazon, despite its immensity, is actually particularly fragile. This year, fires in the Brazilian Amazon hit a 14-year high. The whole region was bathed in smoke as the team did its work recently.

Scientists have been warning for years that the Amazon is nearing a tipping point where it shifts from capturing carbon dioxide to being a net emitter of it. As it shrinks, it becomes less able to pull water from the ocean and sustain its lushness (which, in a climate-system way of thinking, is also its ability to store carbon).

These trends are driving a wide array of efforts to protect or expand forested land.

These can include carbon offsets, essentially credits representing investment in projects that avoid, reduce or store emissions, which individuals or companies can buy to compensate for their own greenhouse gases; or reforestation bonds, a type of tradable security designed to give investors a higher financial return when the money is used to plant trees that can extract more carbon out of the atmosphere.

There is already a market for instruments like these worth almost $1 trillion. But for them to be priced to work properly, better data is needed on precisely how much carbon different forests hold.

“Bad data can equal junk credits,” said Khaled Diab at Carbon Market Watch, a nonprofit organization. “That problem is incredibly difficult to solve.”

Doubts about this data are one of the reasons that last year, the carbon offset market shrank for the first time in seven years.

Those problems, while at the heart of the tree census in Amacayacu, barely dented the ardor of the team carrying it out.

Álvaro Duque, 59, a professor at Colombia’s National University who is leading the census, has a resounding, expressive voice. As he and his colleagues hiked from a remote research station even deeper into the forest toward the census plot, it was hard not to imagine that any nearby wildlife heard them from miles away and fled.

“The air in the forest understory is filled with compounds that make us feel relaxed,” he said excitedly. “Can’t you feel it?”

The only thing that would muffle their voices was mambe, a fine, matcha-green powder made from a mixture of coca and yarumo leaves that is widely enjoyed locally. To partake of its slight stimulating effects, you pack it by the spoonful in your cheek, allow your saliva to seep into it, and then let it slowly leach into your system.

With cheeks packed, it is difficult to speak. Eventually, though, the words pour forth. Everyone competed to tell stories of snake bites, helicopter rescues and 50-mile walks through the forest to play soccer.

“It makes you speak from the heart,” Duque said.

Duque is also animated by having received funding for this research project. The Bezos grant is the kind of money that researchers in Colombia, or Cameroon, or Cambodia rarely expect to get.

“In this country, we’ve got four botanists for the entire Amazon,” said Andrés Barona, 45, who works for Instituto Sinchi, a government research body focused on the rainforest. Barona is a walking encyclopedia who can tell you the family, genus and species of nearly every plant he sees. Still, he said, “we have species we don’t know even know which family of tree they belong to here.”

The census sites chosen by STRI are particularly biodiverse. Locations with the most different kinds of trees are the most useful in training the remote-sensing algorithms used by satellites to scan vast stretches of the jungle.

The biodiversity of Amacayacu is breathtaking.

According to Duque, there are an average of about 250 tree species per acre. Tiny saplings, their baby leaves still bright red. Knee-height adolescents, their survival still uncertain. Then those reaching chest height, perhaps a centimeter in diameter, crossing the threshold for inclusion in the census.

Some will shoot 100 feet into the canopy, providing new branches where squirrel monkeys and white-throated toucans can make their societies.

When not in the forest conducting the tree census, many of the team members sleep in a spartan research center, built on stilts in the woods. There, one evening, over a peg of rum, Duque recounted what the forest had given him.

“This,” he said, waving his arm around at the cornucopia, “saved me.”

Like many of his colleagues, he came up during dark years in Colombia, marred by bloody wars against druglords and Marxist guerrillas. He was raised by a young, single mother. But an abiding interest in trees since childhood provided a constant.

Today, he uses his position to lift others up.

Sangama, for one. She is the only transgender person in Palmeras, her village, a cultural handicap she described with candor. Nevertheless, she was elected as the village’s vice curaca, or chief.

Recently in Palmeras, having commuted back home in a boat, she cooked plantains over coals. She lives with her boyfriend, nearly 30 years her junior, and a woman he recently had a child with. And she has been Duque’s most reliable tree-measurer for nearly 20 years, a position of stability that helped her to transition.

“In our community, being trans is seen as something horrible, something that shouldn’t exist,” she said. “But by doing science, I prove I have a role — that there’s no distinction between a man’s and a woman’s work.”

Work of this kind sheds light on dynamics in the Amazon that are far from obvious.

For instance, new studies posit that despite the arboreal biodiversity, about half of the region’s carbon is contained in just 2% or so of its species. And those species, typically enormous hardwood trees, may be the most susceptible to climate change (and illegal logging).

It would logically follow that the most effective steps to take would focus on protecting those trees. But it takes this kind of research to know that. “The dark age of tropical data scarcity might be ending,” said Duncanson.

With the data collection well underway, Duque and Barona carried their bags toward the river where a boat would take them back into the air-conditioned world. The sky was acrid with smoke from fires both near and distant. It was devoid of storm clouds, billowing upward to the edge of the stratosphere, ready to rake the forest with rain. None had fallen in 16 days.

This article originally appeared in The New York Times .