Scientists study whether elevated carbon dioxide levels such as those found at Rincón de la Vieja might help or hurt tropical environments globally.
Along with two teams of scientists, Deering is pursuing not potential volcanic drama but something imperceptibly gradual — carbon dioxide seeping invisibly from cracks in the volcano’s foundation and exposing the surrounding environment. The question is whether that elevated exposure is a positive, a negative or neither — and what it might mean for the fate of tropical forests globally.
The stability of the world’s climate depends in part on these areas.
While many climate scientists believe that tropical forests will begin to absorb progressively less CO2, other research suggests that higher concentrations of the gas could actually protect them, an idea dubbed carbon fertilization.
In Costa Rica’s natural laboratory, a dense, steamy tangle in the country’s northwest corner, the teams hope to get closer to the answer. The issue is “one of the biggest uncertainties in climate projections of the fate of the planet,” says NASA scientist Josh Fisher, the ecologist leading the trek. He believes the study “could be a game changer.”
If extra carbon dioxide revs up Rincón de La Vieja’s jungle, the teams should find bigger trees, more carbon-dense species or some combination where gas levels are particularly high. One group is working on the volcano’s wetter north side and the other on its drier south side, to better assess and then compare two different ecosystems.
Graduate student Jacob Bonessi inputs data after measuring carbon dioxide levels around Rincón de la Vieja. (Dado Galdieri / Hilaea Media) |
Another NASA scientist had been the first one to propose studying carbon fertilization on a tropical volcano’s shoulders. Several years earlier, Florian Schwandner had helped the Philippines set up a successful network for detecting early symptoms of eruptions of 8,000-foot Mount Mayon, with sensors to track the flow of carbon dioxide from faults in its foundation. (One telltale sign of an oncoming eruption is when that flow suddenly increases.)
At the space agency’s Jet Propulsion Lab in California, the volcanologist hoped satellite-based measurements of carbon dioxide releases would provide early warnings around the world. His research group was filled with ecologists and frequent discussion of trees’ carbon sink, although nobody knew how to forecast the sink’s future.
A certain kind of experiment often came up in conversation: spraying extra carbon dioxide into a forest parcel to study how trees respond. Such carbon-enhancement trials had been run often in the United States and in other temperate regions and had shown that extra carbon dioxide sometimes increased forest growth.
The studies’ relevance for tropical forests was uncertain, but the huge logistical costs of trying to replicate them in remote equatorial areas had been prohibitive.
An alternative solution dawned on Schwandner in 2016. The constant low-level discharges of carbon dioxide from volcanoes might bathe surrounding forests in enough gas to run an enhancement experiment “for free.” He emailed Fisher, proposing a “compellingly crazy carbon fertilization idea.” Four years later, with funding from NASA, it was finally a go.
Schwandner, Fisher, and several other scientists and graduate students recruited for the project spent months scouring geological studies and satellite images of Costa Rica, hunting for faults and vents where the 6,286-foot-tall Rincón de la Vieja might be exhaling CO2 onto its rainforest carpet. They pinpointed 16 likely regions.
Stewing in CO2
Deep in the jungle, Deering’s team has doubled back, retracing their steps along the river bed and away from the canyon walls. They soon discover a trail near the spot he pointed out. Their local guide, a botanist, says a tapir probably made it foraging for fruit and leaves.
Deering and graduate student Jacob Bonessi are taking dozens of CO2 measurements daily. They stop not far from a pile of fresh tapir dung. Deering tightly clamps the metal chamber he carries onto a patch of damp jungle soil. An umbilical cord of hoses channels soil exhalations into the apparatus on his back. Buzzing over bird calls, a pump inside the case draws the gas into an instrument that computes the concentration of carbon dioxide wafting up from the ground.
The pair gaze for a few minutes at the forest’s emerald palms and twined strangler figs. A troop of howler monkeys can be heard in the distance.
Bonessi checks the reading, displayed on a tablet linked by Bluetooth to the electronics on Deering’s back.
“What you got?” asks Deering. “One point one four six,” Bonessi answers. “Big time!”
Deering whoops his enthusiasm. The number is one of the highest they’ve seen.
Volcanologist Chad Deering walks through the tropical rainforest with a gas-testing kit. (Dado Galdieri /Hilaea Media) |
The team — traveling only with small backpacks stuffed with lunch, gear for measuring trees and bug repellent — heads to another targeted destination a few minutes uphill. Fisher dons a pair of snake-resistant chaps after a close call with a rattlesnake. Fina Soper, an ecologist and professor at McGill University, wears a custom neckerchief to protect against mosquitoes and ticks. “Badass Biogeochemists,” it reads.
At each stop, they record the diameter of all trees bigger than a sapling inside a plot the shape and size of a soccer pitch’s center circle. Soper struggles one afternoon with an uncooperative tape measure, a special forester’s rule purchased just for this trip. She loops the metal ribbon around a trunk as broad and true as a Greek temple’s column. But the band won’t retract.
“It figures that I’d break the most low-tech device I’ve used in my life,” she mutters, tugging on loops of the snarled steel.
Fisher hopes to vastly ramp up their observations, if this initial expedition pans out, with return trips using one of the most advanced drones flown by NASA. Meanwhile, they painstakingly probe Rincón de la Vieja’s secrets. Ten days of slashing and slogging will yield the diameters of 952 trees between the two groups of scientists. Back home, they’ll calculate the mass of carbon stored in the wood of each plot using standard formulas.
“It’s good,” Fisher says halfway through the expedition. “Everyone’s healthy. Everyone’s happy. Equipment is working.” But as he well knows, a technical problem could upend the good fortune at any time. And then, he adds with a laugh, “We’ll all be fighting with each other. And everything will go to hell.”
Clouds of gases and vapor from the Rincón de la Vieja volcano rise in the surrounding tropical forest in Costa Rica. (Dado Galdieri / Hilaea Media) |
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