Scientists counting carbon in Amazon rainforests
The machete-wielding scientists ventured into the Amazon, hacking through dense jungle as the mid-morning temperature soared past 38C.
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.
It's vandalism in the name of science.
About 90 km 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 left intact and releasing it when 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.
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, which sprawls across more than six million square kilometres 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. His team looks 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. When trees are chopped 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 UN 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 C by 2100, according to nonprofit consortium Climate Action Tracker, far surpassing the 1.5- to two-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.
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 providing financial support and several scientists to Sanquetta's team.
There are scientists measuring forest carbon on nearly every continent. Aside from Sanquetta's team, 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.
No one team could hope to sample enough of the vast rainforest for an exact count of carbon harboured by the Amazon. It's also a moving target; the rainforest varies from tangled jungle to more open, riverine spaces, and 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. Preliminary findings indicate planting a mix of Amazon species is more effective in sequestering carbon than allowing the area to regrow naturally.
Findings also suggest there's 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. A replanted hectare of forest after 10 years holds about 44 tonnes. Soy farms hold an average of only two tonnes.