The Environmental Journal of Southern Appalachia

Fire, fog, floods: Scientists probe climate-change impacts in Smokies

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iiif service gmd gmd390 g3902 g3902g np000243 full pct 12.5 0 defaultMany climate-change related issues have appeared since publication of this vintage map of Great Smoky Mountains National Park. Library of Congress

Invasive insects are among the vanguard of noticeable climate changes in America’s most-visited national park

GATLINBURG — Ants scurry beneath the carpet of last year’s leaves in Great Smoky Mountains National Park. The native ants are busy spreading the seeds of violets and bloodroot, preparing a new carpet of spring wildflowers to draw thousands of visitors.

But the local insects aren’t alone under there. They have become prey to venomous Asian needle ants that also prowl the leaf litter.

These invaders dine on termites, other ants and insects, while stealing habitat from them. Unlike invasive fire ants, needle ants can live in pristine forests and build large colonies with hundreds of queens. But like fire ants, needle ants have a painful sting that can trigger an allergic reaction. 

Climate change is expected to make it easier for invasive species like needle ants to upset the delicate balance of this temperate rainforest full of rare plants and animals. That’s just one example.

A needle ant study is one of many underway in GSMNP that either reflect climate change or attempt to learn more about how it could affect the park. Research presented at a March science colloquium measures rainfall, drainage, and shifting plant and animal populations. Other scientists are creating models to understand climate change impacts in the Smokies.  

Early results reflect some of the same big-picture outcomes highlighted in new reports by the Intergovernmental Panel on Climate Change: Rising heat and extreme weather are driving species to higher latitudes and elevations, pushing many to the limits of their ability to adapt. 

This winter and spring, IPCC has been releasing reports from major working groups as part of its sixth major climate assessment. A February report projected that if global temperatures increase 2 degrees by 2100, up to 18 percent of all species on land will face a high risk of extinction. “The impacts we see today are appearing much faster, they are more disruptive and more widespread than we expected 20 years ago,” the report stated.

Foggy mountain breakdown

The biggest threat from climate change in Great Smoky Mountains National Park may be changes to precipitation, said Paul Super, science coordinator for the Appalachian Highlands Science Learning Center. Funded by the National Park Service, the program is housed in the park and approves all research projects there. Most of the research is funded through universities and grants.

Super said climate change might be shifting species from south-facing slopes to the north or limiting them to stream valleys, shrinking their populations to small refuges. 

For example, “Trout fishermen might not be able to find trout if they are being pushed up in elevation by warm temperatures below and into upstream waters tainted with acid rain,” Super said. He noted that mountain recreation activities such as trout fishing drive millions of dollars to local communities.

Those communities are also affected by changes in mountain cloud cover, which influences temperature and the rain entering stream systems needed for drinking, irrigation and recreation, Super said. Drought or flooding caused by climate change could cause significant harm outside park boundaries. Super said the park is working with several North Carolina communities to develop a flash flood warning system. 

A new model is being developed to help park managers plan for these kinds of major events, make safety decisions about when to close roads, and pinpoint where to check for damage afterward, Super said. Ana Barros, a University of Illinois professor and  emeritus professor of Duke University, expects to finish this hydrology model for all the park’s watersheds later this year. Once turned over to the park, it can be updated over time to reflect changes in vegetation and ground conditions. 

For example, Barros and her team ran simulations using the Chimney Tops fire that burned 11,000 acres within the park in 2016. The model was able to project water flow and soil moisture changes after the blaze.

The tool can also be used to project possible impacts of different climate scenarios across the park. Barros and her team have been gathering precipitation information in GSMNP for almost 15 years. “We started measuring rainfall and then quickly discovered we needed to be measuring fog,” she said. “In dry years, 50 to 75 percent of water input into the system is low clouds and fog.” That helps keep the ecosystem resilient — as long as drought isn’t accompanied by hotter weather, as it was in 2014, interfering with cloud formation. 

Jason Fridley is a biology professor at Syracuse University who studies soil moisture in GSMNP. He says the cool, cloudy ecosystem that gave the Smokies their name protects them from some of the warming effects seen in dryer mountain ranges like the Rockies. 

“But all bets are off if it starts to dry out,” he added. That could happen in response to massive disturbance of vegetation, such as a large fire. “Or there could be some kind of tipping point where the effects are so great … you get positive feedback between warming and drying,” he said. “If the vegetation changes dramatically, we could enter some new state that does not look like the Smokies. That’s what I worry most about.”

Fridley has placed soil moisture sensors at different elevations and in various forest types in the park. “One thing that really surprised me is how quickly rain effects vanish, suggesting that the frequency of rainfall is really important,” he said. “I would like to go through some climate scenarios that cut the rain frequency in half but double the amount, which is kind of the rule of thumb about what we’ll see with climate change.”

Creating a baseline

Other studies in GSMNP are gathering baseline information about plant and animal populations to use for comparison as the climate changes. 

The park hosts a National Ecological Observatory Network site through the National Science Foundation. The project includes an instrument tower near Gatlinburg as well as sampling plots throughout the North Carolina portion of the park, all collecting standardized information since 2015 about the populations of small mammals, mosquitos, ticks and vegetation, Super said. 

Scientists also track trends in specific plant and animal populations. For example, Eric Shershen, a doctoral student in ecology and evolutionary biology at the University of Tennessee, studies high-elevation mosses at places like Clingmans Dome and Mt. LeConte. He’s returning to plots sampled about 15 years ago for comparison. Shershen plans to use tiny data loggers to monitor temperature and humidity on the moss mats, with the goal of predicting how these will change in the future. 

But the majority of climate change research in GSMNP focuses more broadly on ecosystems, which affect many species at once, Super said. After all, it’s not always clear what role each plays in the ecosystem. 

For example, more than 2,000 beetle species live in the park, Super said. “Which might we really be able to do without? We don’t know,” he said. “We might discover a certain beetle was very important for controlling something that kills millions of board feet of timber from the surrounding national forest.” Another might produce an ingredient for a future life-saving drug.

Invasive impacts and diversity

Invasive species are an inreasing threat because they can reduce native plant and animal diversity. “Drier or at least warmer conditions moving into our lowest elevations would potentially open them up to new invasive species,” said Super, pointing to the recent arrival of armadillos. 

Daniel Malagon, a Clemson University doctoral student studying the needle ant invasion, has determined the Tennessee side of the park is the most vulnerable to them because of its lower elevation and milder winter weather. 

“Noticing the stark difference between the invaded forest in South Carolina and seeing it just starting in the national park got us concerned,” he said. “It’s really apparent where they have invaded: You don’t see any other ants.”

Needle ants both eat native ants and steal their habitat. This harms a native ant species responsible for dispersing seeds for one out of every three plants in GSMNP.

Starting in 2019, Malagon and his team collected hundreds of leaf litter samples from the forest floor in the park, cataloging the type and number of ants in each. They checked undisturbed woods as well as areas near visitors centers and campgrounds, where they found some needle ant supercolonies. 

“They have up to hundreds of queens per colony, so the ability of the colonies to expand is really disturbing,” Malagon said. He said he plans to request permission to try killing needle ant colonies with poisoned termites.

On the upside, Malagon’s team concluded that about 65 percent of the park has a good chance of remaining a refuge for native ants. 

Super called the Smokies “a library of resources” we still don’t fully understand, so we might not even recognize what we lose through climate change. “Keeping a healthy ecosystem with the kind of diversity that we have in the Smokies is extremely important for the long term,” he said.


 

Discover Life in America presentation by Daniel Malagon and Andrew Kanes about needle ants

 

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