The machete-wielding scientists ventured into the Amazon, hacking through dense jungle as the mid-morning temperature soared past 100 degrees Fahrenheit (38 C). Soaked in sweat, the small group of men and women sawed and tore trees limb from limb. They drilled into the soil and sprayed paint across tree trunks. This is vandalism in the name of science.
Amazon rainforest
Jungle Lab
Sweat-soaked researchers obtained samples of trees, other vegetation and soil in the Amazon rainforest in November, seeking to learn how much carbon the area contains. It’s one step toward curbing climate change.
In the trees about 90 km (55 miles) from Rondônia state capital Porto Velho, the Brazilian researchers are seeking to learn how much carbon can be stored in different parts of the world’s largest rainforest, helping to remove emissions from the atmosphere that foment climate change.
“It’s important because we are losing forests globally,” said Carlos Roberto Sanquetta, a forestry engineering professor at the Federal University of Paraná in Brazil. “We need to understand what is the role that forests play,” both in absorbing carbon when they are left intact and releasing it when they are destroyed.
Sanquetta led the weeklong research expedition in November, overseeing a team including a botanist, agronomist, biologist and several other forestry engineers to take myriad samples of vegetation - living and dead - for analysis.
It’s rigorous and elaborate work, often in humid and insect-infested conditions, involving chainsaws, spades, corkscrews and calipers.
“These are not white-coat scientists just lecturing people,” Raoni Rajão, who specializes in environmental management at the Federal University of Minas Gerais and is not involved with Sanquetta’s team. “These are hardworking people that get their hands dirty.”
Holistic approach
The Brazilian team is just one contingent among hundreds of researchers seeking to measure carbon in the complex and environmentally crucial Amazon rainforest ecosystem, which sprawls across more than six million square kilometers in nine countries.
Some research seeks only to quantify carbon in trees, but Sanquetta says his team’s approach is holistic, measuring carbon in underbrush, soil and decomposing plant matter as well. In addition, his team is looking beyond primary forest, examining reforested areas to shed new light on how much carbon they hold - information key to incentivizing restoration efforts.
Carbon dioxide (CO2) is the most prevalent of the greenhouse gases, which lock heat into the earth’s atmosphere. Trees soak up carbon dioxide from the atmosphere and store it as carbon, one of the cheapest and easiest ways to absorb greenhouse gas.
The process also works in reverse, however. When trees are chopped down or burned - often to make way for farms or cow pastures - the wood releases CO2 back into the atmosphere.
“Every time there is deforestation, it’s a loss, an emission of greenhouse gas,” said Sanquetta, who is a member of the U.N. Intergovernmental Panel on Climate Change, the world’s top climate science authority.
At current emission rates, global temperatures are expected to rise about 2.9 degrees Celsius by 2100, according to nonprofit consortium Climate Action Tracker, far surpassing the 1.5- to 2-degree limit needed to avert catastrophic changes to the planet. Climate change raises sea levels, intensifies natural disasters and can spur the mass migration of refugees.
Deforestation in the Amazon has accelerated during the administration of Jair Bolsonaro, the right-wing president of Brazil. Since he took office in 2019, at least 825 million tonnes of CO2 have been released from the Brazilian Amazon deforestation.
That’s more than emitted by all U.S. passenger cars in a year.
In a statement, the office of Brazilian Vice President Hamilton Mourão, who leads the government’s Amazon policy, said the rise in deforestation predated the current administration and that the government has been working around the clock to thwart destructive mining and lumber trafficking.
“We have not achieved the desired degree of success, but it could have been worse,” the statement said.
Meticulous measurements
Key to understanding and addressing the climate threat is bringing more precision to carbon measurements in receding forests.
“Everyone wants this information,” said Alexis Bastos, project coordinator of the nonprofit Rioterra Study Center, a Brazilian organization that provides financial support and several scientists to Sanquetta’s team.
Getting information from the trees
Sanquetta and his team collected samples from plots 10 meters long by 20 meters wide, meticulously analyzing, marking and documenting everything that was there. Below is the step-by-step work in one of those sample areas of the Amazon rainforest.
1x1m samples
20m
10m
Plants sampling
Within the plotted area, trees and plants with a circumference less than 15 cm are estimated by sampling areas of 1 square meter.
50cm samples
20m
10m
Ground litter sampling
Smaller plots of 50x50cm are defined to collect samples of ground debris.
Trees
Tree inventory
Trees with a circumference over 15 cm within the area are measured, identified and tagged.
Sampling line
Necromass sampling
A line through the middle of the plot is traced; any dead plant of over 2cm width crossing the line is measured and classified.
Soil test
Soil compaction
The ground is punctured in five places on the plot with a tool that measures resistance in order to estimate the density of the soil.
Carbon samples
Fertility samples
Soil samples
Just outside the plot area, soil samples are taken from one location at four different depths to measure carbon levels, while two additional samples to measure soil fertility are taken from separate locations.
Matching tree
Tree autopsy
Scientists determine the most prevalent species on the plot and then select one species nearby that matches those in the plot. This “representative” tree is cut down; parts that are too heavy, like the stump, are weighed on-site with leaves and smaller parts sent for laboratory analysis.
Incinerated tree
Lab measurement
In the lab, the wet sample weight is taken. They are dried and then weighed again. Finally, the samples are incinerated to measure the remaining carbon.
Today there are scientists measuring forest carbon on nearly every continent.
Aside from Sanquetta’s team, for instance, the Amazon Forest Inventory Network with its more than 200 partner scientists is trying to standardize carbon and other measurements, garnering huge amounts of data to “quantify” the forest.
The challenge is “there’s differences in species across the Amazon. In Peru in the southwest versus Guyana in the northeast, there’s virtually no species overlap at all, so it’s completely different plants in exactly the same climate,” said Oliver Phillips, the network’s coordinator and a tropical ecologist at the United Kingdom’s University of Leeds.
The network’s partners use precise parameters to capture the major carbon reservoirs, including in dead plant matter and soil. For instance, if a tree is on the border of a plot, it should be measured only if more than 50% of its roots are in the plot.
No one team could hope to sample enough of the vast rainforest for an exact count of carbon harbored by the Amazon. It’s also a moving target: The Amazon rainforest, which varies from tangled jungle to more open, riverine spaces, is constantly shifting, as more trees are chopped down while restoration efforts are accelerating.
Sanquetta’s team began its current line of research in 2016, relying on support from Rioterra, which itself received funding from Petróleo Brasileiro SA (Petrobras), the Brazilian state-owned oil firm. At the time, Rioterra was replanting destroyed areas of rainforest, and wanted to know how much carbon was being sequestered. Petrobras told Reuters in a statement that it had been working for years to honor its “social responsibility” commitments, which among other things meant supplying energy while “overcoming sustainability challenges.”
Each weeklong expedition costs about 200,000 reais (more than $37,000 dollars). Sanquetta said his project has not received any money from Petrobras directly.
When the Petrobras funding dried up, Rioterra found support from the Amazon Fund, backed by the governments of Brazil, Norway and Germany.
Preliminary findings indicate that planting a mix of Amazon species is more effective in sequestering carbon than allowing the area to regrow naturally.
But findings also suggest there is no substitute for leaving forests untouched: A hectare of virgin Rondônia forest holds an average 176 tonnes of carbon, according to Sanquetta’s analysis of Brazilian Science Ministry data. By comparison, a replanted hectare of forest after 10 years holds about 44 tonnes, and soy farms hold an average of only 2 tonnes.
Carbon keepers
Below are estimates of carbon storage by hectare in Rondonia state, according to the Federal University of Paraná (UFPR) and Brazilian Science Ministry data.
SOY FIELD
100m
100m
2 tonnes
COW PASTURE
5 tonnes
REPLANTED SECONDARY AMAZON FOREST
(10 years regrowth)
44 tonnes
NATIVE AMAZON PRIMARY FOREST
176 tonnes
Or the equivalent weight of 44 Asian elephants
SOY FIELD
100m
100m
2 tonnes
COW PASTURE
5 tonnes
REPLANTED SECONDARY AMAZON FOREST
(10 years regrowth)
44 tonnes
NATIVE AMAZON PRIMARY FOREST
176 tonnes
Or the equivalent weight of 44 Asian elephants
SOY FIELD
100m
100m
2 tonnes
COW PASTURE
5 tonnes
REPLANTED SECONDARY AMAZON FOREST
(10 years regrowth)
44 tonnes
NATIVE AMAZON PRIMARY FOREST
176 tonnes
Or the equivalent weight of 44 Asian elephants
SOY FIELD
COW PASTURE
100m
100m
2 tonnes
5 tonnes
REPLANTED SECONDARY AMAZON FOREST
(10 years regrowth)
NATIVE AMAZON PRIMARY FOREST
44 tonnes
176 tonnes
Or the equivalent weight of 44 Asian elephants
SOY FIELD
COW PASTURE
100m
100m
2 tonnes
5 tonnes
NATIVE AMAZON PRIMARY FOREST
REPLANTED SECONDARY AMAZON FOREST
(10 years regrowth)
44 tonnes
176 tonnes
Or the equivalent weight of 44 Asian elephants
Healing the planet
Out in the jungle,Sanquetta’s team members swatted away swarming, stingless bees, while they dissected a 10-by-20-meter plot that’s been growing back naturally for almost 10 years, abandoned by a farmer.
The team counted 19 trees with trunks measuring at least 15-centimeters in circumference, a threshold above which trees generally hold significantly more carbon. Edilson Consuello de Oliveira, a 64-year-old botanist from neighboring Acre state, wrapped a tape measure around one of them.
“Bellucia!” he called out, identifying Bellucia grossularioides, a fruit-bearing tree that is one of the fastest to regrow. He rattled off the measurements, while another scientist scribbled them down.
A biologist nailed number markers into tree trunks. Meanwhile, a few in the group were hewing into a tree with a chainsaw, having selected it for “autopsy.” The shorn trunk was cut into pieces, the leaves stripped and bagged, and the stump dug up and weighed on a hanging scale strung from branches above.
“It’s destructive, but we only do it for a few trees,” said Sanquetta.
Another group drove a motorized, 3-foot (1 meter) metal corkscrew into the ground and pulled up dirt from four different depths. Others measured the width of decomposing plants with calipers and raked up ground debris.
The samples were taken back to the lab, where the team dried and weighed them, before incinerating them in a dry combustion chamber that allows them to measure how much carbon is contained.
The team measured 20 plots during a week’s work in November. The final goal is 100 plots by later this year.
The work offers “a way to measure the health of the planet,” Rajão said, but also “how quickly the planet could be healed.”
Reporting by
Jake Spring
Graphics by
Marco Hernandez
Sources
Federal University of Paraná (UFPR) Biofix laboratory.
Ministry of Science, Technology and Innovation of Brazil.
Brazil’s National Institute for Space Research (Inpe).
Edited by
Simon Scarr, Katy Daigle and Julie Marquis