Great Smoky Mountains

Long before the Great Smokies became a national park, its mountains peeked out among clouds of haze. The Cherokee called the mountains “Shaconage”: the place of the blue smoke.

The iconic clouds in the park – on the border of North Carolina and Tennessee – are as important to the Great Smoky Mountains National Park as glaciers are to Glacier National Park and Joshua trees are to Joshua Tree National Park. The blanket of haze is part of the draw for the Smokies’ 11.4 million visitors in 2018, almost twice the number at the Grand Canyon.

The haze is more than a sight to see: High rainfall totals and summertime humidity foster plant growth, making the region a biodiversity hotspot. The Smokies are home to 30 species of salamanders, earning the park the title of salamander capital of the world.

Moisture from the haze may also be protecting the ecosystem from the changing climate. But as the climate continues to warm, the nature of the Smokies’ cloud cover may change.

Ana Barros, a professor of civil and environmental engineering at Duke University, said rising temperatures could, in theory, decrease cloud cover, threatening key habitats for creatures such as salamanders. And Jason Fridley, a biologist at Syracuse University, warned in an interview that if the region sees a decline in precipitation on mountain peaks, “that might be catastrophic.” So scientists are working to understand the park’s clouds before they change forever.

Inside a cloud forest

On a recent June day in the park near the North Carolina and Tennessee border, white wispy clouds hung at eye-level. They were torn away from the overhead blanket of clouds like you might pull apart cotton candy.

Smoky Mountains
In a cloud forest in the Great Smokies, tiny water droplets create a haze. (Photo credit: Brooke Bauman)

Along the roads going down the mountain, clouds rolled through the landscape and descended into the forests below. Every twist and turn gave way to a new view of the fog as it crept up, swallowing trees whole. Visitors pulled off the road at overlooks to admire the shape-shifting clouds.

The minuscule water droplets that make up the clouds can create an immersive experience.

“When you’re looking at them coming, you know, they just look like a little bit of smoke,” Barros said in an interview. “Nothing much is going on. And then within a few minutes, it starts getting a little bit, you know, darker – less visibility – and within an hour, you’re dripping, literally dripping wet. And yet you didn’t feel any raindrops hitting you.”

Cloud forests in Smokies – the high-elevation ecosystems immersed in the clouds – differ from western mountain ranges. The mountains of the American West are typically wettest at the bottom and dry and rocky at the top. But in the Great Smokies, the mountains are generally most moist at the top because the highest elevations are immersed in low-hanging clouds.

Trees are both the beneficiaries and the creators of the passing clouds. They capture moisture from the air as droplets condense on the leaves and fall to the roots. But trees also help form the haze. They release gases that transform into solid particles when they’re exposed to oxygen. Water droplets in the air – blown up from the Gulf of Mexico and the Atlantic – condense on these particles and form clouds.

In 2004, Barros came back from a trip studying rainfall in the Himalayas and was looking for a new project. She became intrigued by the cloud forests in the southern Appalachians but noticed there wasn’t much data on rainfall in the region.

Opportunities arose when disaster struck. A series of hurricanes destroyed part of I-40 along Pigeon River in 2004 along the North Carolina and Tennessee border, forcing the highway to close two of its four lanes for several months. In hopes of characterizing patterns in southern Appalachian precipitation, NASA funded a study.

From 2007 to 2009, Barros and a team of researchers installed a network of 32 rain gauges in the region that straddles North Carolina and Tennessee, in open areas where the gauges can collect moisture directly from the sky.

The gauges resemble fat canister rockets and stand on metal poles. Rain enters a wide funnel on the top, then travels through mesh that keeps out particulate matter. A bucket below tips over when full. A data logger counts how many tips occur, enabling researchers to measure how much rain has fallen.

Curious visitors

Douglas Miller, a professor of atmospheric sciences at UNC-Asheville, helped Barros install the gauges. He manages a team of undergraduate students who monitor the rain gauge network and protect it from an array of culprits. Ants and wasps like to nest under the gauges, especially during particularly rainy periods. But Miller and his students have faced even bigger problems.

“The other thing that we have learned is that bears are very curious,” Miller said in an interview.

Bears have attempted to investigate the rain gauges, with enough force to jostle the gauges in the blocks of cement that they sit in.

Curious bear
A bear visits a rain gauge on Big Cataloochee Mountain. (Image: Courtesy of Douglas Miller)

Miller’s team collects data from the loggers, then sends it to Barros for quality control and analysis. As the initial data came in, Barros noticed something odd. The researchers had gathered data from two different types of measuring instruments that were side-by-side in the same plot. Sometimes when the instruments that count raindrops collected a high number of drops, the rain gauges that measure the amount of liquid rainfall in the same area didn’t register any precipitation.

Why would one instrument show practically zero rainfall, while another standing next to it showed a lot? Barros realized the answer must be that raindrops in the Smokies’ cloud forests are tiny – too small to register in a traditional rain gauge. They’re also plentiful: Barros found that moisture from low-level cloud cover accounts for about 40 to 60 percent of the region’s rainfall.

Creatures at risk

That cloud cover could help protect the park as the climate changes – at least in the short term.

“It’s like trying to heat a wet rag versus a dry one,” said Fridley, the biologist at Syracuse University. “So if you think about the southern Appalachia as having a wet blanket over the tops of the mountains, that might at least for right now be keeping them relatively cool.”

But changing rainfall patterns or warming temperatures could decrease cloud cover. “If the tops start drying out, that might be catastrophic,” Fridley said.

Barros said rising temperatures will reduce cloud cover and allow more shortwave radiation from the sun to further warm the region. It’s a vicious feedback loop: The additional warming will decrease cloud cover even more. But Barros said the degree of the impact is uncertain.

The potential dangers are particularly daunting for the park’s enormous diversity of living creatures, such as the red-cheeked salamander, which is a terrestrial species native to the park.

Salamander
Red-cheeked salamanders must stay moist to breathe through their skin, which leaves them susceptible to the changing climate. (Photo credit: Fredlyfish4 / Wikipedia)

Red-cheeked salamanders are a key part of the food web because they can eat land-bound insects and worms that aquatic salamanders can’t reach. They also don’t have lungs so they breathe through their skin. They must remain moist, so warming temperatures and the potential decline of cloud cover are threats.

In theory, species living at low elevations might seek refuge at cooler, higher elevations as temperatures rise. But the reality may be more complex.

The National Park Service recently provided funding to Barros and Fridley to study how climate change will shape ecosystems in the Great Smokies. The scientists’ model should provide better predictions of how species will react to a changing climate, which could help them preserve the park’s biodiversity.

“We should be able to get an idea of where the habitat will remain that these high elevation organisms need so that we’ll know where the refugia might be for something like the red-cheeked salamander,” said Paul Super, research coordinator in the Smoky Mountains park, in a recent interview.

The red-cheeked salamander is just one example of the dangers the Great Smoky Mountains face as the climate changes. Many questions about the park’s future remain, particularly because changes to key ecosystems like spruce-fir forests will be gradual.

“With sea-level rise, you see it fairly quickly. With glaciers melting away, you’re seeing it fairly quickly,” Super said. “Things are going to be really radically changed by the time our spruce-fir forests change into something else.”

So Super said it’s critical to monitor conditions in the park: “If you start taking a complex ecosystem and start pulling at it, pulling things off, the whole thing will change in ways that you may not fully have predicted.”

AUTHOR
Brooke Bauman is an intern at YCC and a student at UNC-Chapel Hill studying environmental science, geography, and journalism.

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