Saving Vulnerable Giants

Sukee Bennett joins researchers who sniff the air among California’s redwoods to gauge how they will fare in a warmer climate. Illustrated by Katherine Rudebusch and Phillip Krzeminski.

Evening fog rose from the Pacific Ocean. It flowed over the hilly shoreline and into California’s Big Basin Redwoods State Park, where a team of four scientists gathered under the planet’s tallest trees.

The team divvied up flasks for collecting air particles from the shoreline, forest and nearby grassland to run an unprecedented study on fog and the coast redwoods it embraces. They mentally prepared to stay up all night, knowing a $1.75 million National Science Foundation grant rode on their study’s success.

Elliott Campbell, an environmental engineer at UC Merced, drove 30 miles every hour between the seashore and grassland that surrounds Big Basin. At both locations, he and a student bounded out of Campbell’s car, held flasks up to the night sky and captured wisps of air. Then they sealed their samples, raced back in the opposite direction and did the same thing all over again.

Mary Whelan, a UC Merced ecologist, camped out with a student in the heart of Big Basin’s forest. Huddled within Whelan’s car—they hadn’t brought a tent—the partners minded their beakers, which collected air particles outside. The two played rummy with cards cut out of scrap paper to stay awake.

For the four scientists, the thrilling all-nighter in the spring of 2015 was an effort to gather samples of airborne carbonyl sulfide, a cousin of carbon dioxide that’s less bountiful and “chubbier in size,” Campbell says. Volcanoes and deep-sea vents emit the gas when they erupt. Carbonyl sulfide produced underwater rises out of the sea with fog. Campbell’s team hopes to show that the amount of the gas in fog can reveal how climate change affects forests.

Graphic: Phillip Krzeminski

Healthy trees take in carbonyl sulfide when they consume fog during photosynthesis. So, the gas typically is more abundant along the coastline where it’s produced than in the forests to which it flows. But when trees are sick, they don’t absorb fog or the vitamins it holds, and carbonyl sulfide levels don’t decrease as dramatically. By studying the air and its load of carbonyl sulfide gas—rather than the trees themselves—Campbell and his team are assessing the health of all the redwoods in one area simultaneously.

It’s a novel approach, because biologists usually study select trees and the prickly needles they carry. “The problem is,” Campbell explains, “there’s a lot of leaves and a lot of trees out there to measure.”

Redwoods are a bellwether for climate change in California.

By exploring the foggy air surrounding redwoods instead, scientists can find clues about the interaction between entire forests and the atmosphere. Campbell’s team hopes to use these clues to educate the public about climate change in an effort to save California’s giant trees.

“They’re not just an iconic part of the state experience. They are a bellwether for climate change in California,” says California Secretary of Natural Resources John Laird. He adds that this study—which Campbell has named The Summen Project, after the Ohlone word for redwood—“is going to help us understand the changing health of the redwoods and possibly tell us the steps we can take to protect them.”

Laser power

Many of Northern California’s coast redwoods are growing faster than they used to, says UC Berkeley ecologist Anthony Ambrose, who has studied the trees for 20 years. But more than 100 miles south of Big Basin, along the rugged Big Sur coastline, the trees are struggling. Core samples show that their tree rings are closer together, illustrating that the trees don’t grow as steadily as their siblings up north.

Campbell wants to figure out why. A native of Santa Cruz, he’s excited to study coast redwoods, but prefers to examine entire ecosystems rather than singular trees. He believes the secret to doing so is locked in the air’s unique chemical composition where redwoods dwell.

To study the air’s chemicals, Campbell is using a tool called a laser spectrometer, which analyzes the chemicals in air captured in flasks. The spectrometer has helped Campbell’s team draw a link between carbonyl sulfide consumption and redwood photosynthesis, which scientists have never done before.

The first time Campbell worked with a laser spectrometer, he was a graduate student at the University of Iowa. “It was a cold winter,” he says, grasping the mug of chai he carries. “Then some friends of mine in an air pollution lab invited me to come on a field trip to Veracruz, Mexico. It was a no-brainer, right?”

In the state of Veracruz, carbonyl sulfide is plentiful because of nearby volcanic activity. By using flasks and lasers to measure carbonyl sulfide at various nearby locations, Campbell and his friends discovered the gas was less abundant in the air where plants dwelled. The plants ate carbonyl sulfide—just as they eat carbon dioxide—when they photosynthesized.

Graphic: Sukee Bennett

Campbell was inspired by the trip and the precision with which he could measure carbonyl sulfide. He moved from Iowa to UC Merced, where he began mapping ebbs and flows of the gas across the planet. Then in 2015, the University of California opened the new  Institute for the Study of Ecological and Evolutionary Climate Impacts (ISEECI) under the direction of UC Santa Cruz ecologist Barry Sinervo. The institute was looking for climate change–based research ideas—and because of his time in Veracruz, Campbell had one.

Environmental engineers had never used laser spectrometers to study forests, and neither had ecologists, Campbell says. But he thought they should try. His confidence was infectious; soon enough, Campbell had support from ISEECI and was rallying a team of ecologists, engineers, oceanographers, chemists and social scientists to help.

“We have a plan. Let’s do this!” he told them. “He is just so optimistic,” Whelan says.

Previous redwood studies, such as those conducted by Ambrose and his mentor, famed UC Berkeley redwood ecologist  Todd Dawson, focused on carbon dioxide. Plants eat that gas, turn it into sugar, and spit out oxygen. As humans pump out carbon dioxide—cars, planes, freighters, factories and farms all release it—trees and other plants do their best to clean it up. In fact, they devour about one-quarter of all the carbon dioxide we emit. “They’re scrubbing the atmosphere,” Campbell says. Dawson and his team study carbon dioxide concentrations within trees’ needles to detect how healthy the tree is. If a redwood is storing a lot of the gas, it’s photosynthesizing and growing.

But measuring carbon dioxide to study tree health poses some problems, Campbell says. He describes this method, which focuses on individual leaves and branches, as putting a box over one section of a single tree. “When you put a box over some leaves, it’s a very controlled system,” he says. Scientists obtain a specific measure of carbon dioxide from one tree, which tells them whether that tree is healthy or sick. But every redwood is different. Measuring carbon dioxide only in select trees makes it hard to tell how the forest is faring overall.

By measuring carbonyl sulfide, Campbell looks at the atmosphere around numerous trees rather than a single redwood. “We’re putting a box over the whole forest,” he says.

No rain checks

When Campbell and his team pulled that all-nighter in May 2015 to run their first study, they hypothesized that the air hovering around the sea and grassland would have higher concentrations of carbonyl sulfide than the air in the heart of Big Basin’s forest. Fog would pour out of the ocean and flow into the woodlands, where redwoods would take it in and absorb carbonyl sulfide in the process, they believed. After collecting air samples from the beach, forest and grassland, the team needed to test the samples to see whether their hypothesis was correct.

At Stanford’s Carnegie Institution for Science, Whelan used a laser spectrometer to analyze the 48 capsules of air that she, Campbell, and the two students had collected across the three sites. The results confirmed the team’s hypothesis. While the seashore and grassland had similar levels of carbonyl sulfide, there were 39 to 51 fewer molecules of the gas for every trillion molecules of air in Big Basin than on the seashore—suggesting that concentrations of airborne carbonyl sulfide are linked to redwood photosynthesis. The National Science Foundation awarded the team $1.75 million to continue its research based on these results.

With the fragility of Big Sur’s redwoods in mind, Campbell and Whelan decided to head there next. Campbell rented a 4-wheel drive, since his Prius would not have survived the pernicious path—a narrow dirt corridor on a cliff face—to the field site. It was September 2015, and autumn rains had begun falling, though it was dry on the afternoon the team set out.

The team wanted to find out if Big Sur’s redwoods were consuming less carbonyl sulfide than their northern cousins—a sign that the Big Sur trees might be unwell, and therefore taking in less fog. Campbell and Whelan met Cameron Williams, a seasoned tree climber in Dawson’s lab who had volunteered to give them a hand. Standing at the base of the most regal redwood in the Landels-Hill Big Creek Reserve, 50 miles south of Monterey, Williams shot a dart from a crossbow, hitched the dart to a high branch and began climbing the tree. He fastened thick coils of tubing around the tree’s branches. The coils collected air and pumped it into Campbell’s flasks on the forest floor.

In the evening, Williams bid Campbell and Whelan farewell. The pair planned to camp out all night—when redwoods are busiest drinking fog—as the coils collected air from atop the trees. But after the sun descended, it started to pour. Afraid of becoming stranded, Campbell and Whelan were forced to abandon their equipment and evacuate.

“The road was almost like a slurry,” Campbell says, his eyes wide. “We were trying to drive down in the 4X4 and it was sliding in the mud with no railing,” Whelan adds, describing the dirt artery between the research site and the main road. At one point, Campbell asked Whelan if she could walk alongside the car—“because if he went into the ravine,” Whelan says, “I’d be able to get help.”

Campbell returned for the samples a few days later. When he tested them, he found that carbonyl sulfide concentrations in Big Creek were comparable to those in Big Basin. It meant redwoods in Big Creek were absorbing air as readily as their northern siblings.

But Campbell is still worried. The results of his two research trials prove that concentrations of carbonyl sulfide in the air are linked to redwood photosynthesis. He’ll need many more days of data sampling, however, to compare the overall health of Big Creek and Big Basin’s forests.

Big Sur is home to the southernmost population of coast redwoods in the country. Because of the region’s climate, its trees are bound to suffer, Campbell believes. “It’s already as hot and dry as they can tolerate,” he says. If redwoods become stressed, they’re less likely to photosynthesize and take in carbonyl sulfide in the process.

If Big Sur’s trees disappeared, the redwood range would shrink, and so would their billions of carbon-collecting leaves. Other tree species, which lack the density of leaves that coast redwoods have, would struggle to take their place. The local climate could begin to warm at a faster rate.

Even at the current rate of warming, California’s coast redwoods might be better off farther north, where temperatures are cooler. But the trees don’t have legs to move. Researchers are faced with a conundrum: They can carry seedlings northward, but in an effort to save redwoods, they’d displace species like Douglas fir “and upset the Oregonians,” Campbell chuckles. Scientists agree the better option is to learn more about the fragile relationship among climate, fog and forests, he says.

A future with giants

Within the next year, Campbell will publish the results from his nights of data collection in the Journal of Biogeosciences. He and his team have many more hours of analysis to do. They had planned to continue their Big Sur research this spring, but the winter’s unprecedented rainfall made the Landels-Hill Big Creek Reserve nearly inaccessible until at least fall 2017.

When the roads are cleared, Campbell and his team will fasten air samplers to redwoods, which will stay in the forest and measure carbonyl sulfide for three years. Campbell will share his findings with Stanford social scientists Nicole Ardoin and  Lauren Oakes, who will use the data to develop surveys and educate park visitors about the effects of climate change on the colossal trees.

“Elliott had a vision,” Oakes says. “He wanted the Summen Project to be interdisciplinary.”

Oakes, who is interested in how environmental changes affect the public, believes the Summen Project’s findings could inspire park visitors to take a greater stand against climate change. People are most likely to protect things they care about, she explains. And people love redwoods.

After all, they’re the world’s tallest trees. They can live more than 20 human lifetimes, and they’ve elegantly risen out of Earth’s soil for 65 million years. But redwoods are not invincible. “I have a redwood in my front yard in Santa Cruz. It seems to grow by itself—and it somehow planted itself there—yet it depends on fog,” says Secretary Laird. “We know redwood trees have depended on things in the past climate that might not be the same now. But we don’t fully understand the implications and what we can do.”

One thing is clear, however. Today, the coast redwood’s greatest threat—and its greatest hope—stands on two legs.

© 2017 Sukee Bennett / UC Santa Cruz Science Communication Program