Washington Post - Daniel Grossman
Scientists
study whether elevated carbon dioxide levels such as those found at
Rincón de la Vieja might help or hurt tropical environments globally.
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Steam and hot gases rise from the crater of Rincón de la Vieja, an active volcano in Costa Rica. Two scientific teams are measuring the carbon dioxide that seeps from cracks in the volcano’s foundation to determine its impact on the surrounding tropical forest. (Dado Galdieri / Hilaea Media)
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Chad
Deering trudges up a dry river channel on the north side of Rincón de
la Vieja, one of Costa Rica’s active volcanoes. He wears a baseball cap
emblazoned with the phrase Semper Fi, a token of his tour of duty with
the Marines, and lugs a peculiar apparatus, part of a sensitive
gas-testing kit, that looks more like a metal mixing bowl. The bedrock
here is smooth lava, a lifeless tear in the rainforest that blankets
Rincón de la Vieja’s flanks.
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.
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TOP: Ecologist Josh Fisher, left, and graduate students Nel Rodriguez Sepulveda and Katie Nelson traverse one of Rincón de la Vieja's slopes. BOTTOM LEFT: Graduate students Nel Rodriguez Sepulveda, left, and Katie Nelson walk near the volcano. They and other researchers are measuring carbon dioxide levels around Rincón de la Vieja. BOTTOM RIGHT: A scientist gauges the airflow in the tropical forest surrounding the volcano. (Dado Galdieri / Hilaea Media)
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Every year, tropical
forests soak up more than 2 billion tons of carbon dioxide, a
substantial share of what’s emitted by power plants, industrial
smokestacks and vehicle exhaust pipes. Yet how increasing temperatures
and decreasing rainfall will affect them long term remains unclear.
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.
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Graduate student Jacob Bonessi inputs data after measuring carbon dioxide levels around Rincón de la Vieja. (Dado Galdieri / Hilaea Media)
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A crazy idea
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.
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From the tropical forest in the shadow of Rincón de la Vieja, clouds obscure the volcano. While many climate scientists believe that such forests will begin to absorb progressively less CO2 because of climate change, other research suggests that higher concentrations of the gas could actually protect them, an idea dubbed carbon fertilization. (Dado Galdieri / Hilaea Media)
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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.
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Volcanologist Chad Deering walks through the tropical rainforest with a gas-testing kit. (Dado Galdieri /Hilaea Media)
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All
over the planet, soil exudes carbon dioxide. It’s a waste product that
microbes and subterranean fauna churn out while generating energy from
oxygen and nutrients. But what the scientists have detected is well
above the background level seeping from the soil here. This is the type
of spot, infused with extra carbon dioxide from the volcano’s fractured
rock, they were looking for. The trees here are stewing in it.
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.
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LEFT: Fiona Soper, a McGill University biology professor, walks amid thick vegetation while assessing the plant species near Rincón de la Vieja. RIGHT: Ecologist Fiona Soper uses snake gaiters. Rattlesnakes are plentiful in the Rincón de la Vieja National Park. (Dado Galdieri / Hilaea Media)
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By gathering detailed observations from many sites —
each exposed to a unique combination of influences — she and the others
are trying to account or control for the factors that influence tree
heft. They’ll then tease out the effect of each factor, especially the
one that concerns them most: greater carbon dioxide.
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.”
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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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