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Editor’s note: This article is part 1 of the five-part in-depth series Fraught Forests from Carolina Public Press, which examines the challenges of climate change for Western North Carolina’s mountain forests.

Unusual periods of drought, with heightened risk for wildfires, damage the health of Blue Ridge Mountain forests in Western North Carolina. At the opposite extreme, intense rainfall events cause erosion, landslides, flooding and other damage to forests and surrounding areas. 

When these erratic cycles follow one another with greater frequency and intensity, along with extreme swings in hot and cold temperatures, the forest ecology experiences a destabilizing whipsaw effect. 

Humans trying to manage these vast forests, whether on private or public lands, face an unprecedented challenge as climate change promotes such chaos. Plant and animal species that reside and rely on the forests, including increasing numbers of human residents, experience the disruption of these unpredictable weather events in the forests.

More subtle, but also insidious, average daytime maximum temperatures and nighttime minimum temperatures continue rising well above the levels seen a few decades ago, shifting the habitable zone for key species that have lived in the forests for thousands of years, while opening the door to invasive species that threaten the woodland region’s continued existence.

Scientists, forest managers and environmental advocates are all trying to get a handle on what’s at risk in the Western North Carolina forests due to climate change and other factors, as well as what they can do about it.   

How much trees drink makes a difference, especially at the highest elevations and ridge tops of the Southern Appalachians. When it rains, trees absorb water through roots, where they store and transport moisture via a complex network of tissue, releasing water vapor into the atmosphere from needles or the surface of leaves.

But what happens to a tree’s appetite during periods of drought in what has typically been one of the Southeast’s soggiest ecosystems? 

The answer is that ridge-top forests are particularly greedy drinkers when it’s dry, according to three N.C. State University researchers in the Department of Forestry and Environmental Resources — doctoral student and lead researcher Katie McQuillan, and faculty co-authors Katherine Martin and Mirela Tulbure, who recently published their results in the journal Landscape Ecology.

Using satellite imagery to examine how forest water use changed over time in the Blue Ridge ecoregion, they discovered that high-elevation and ridge-top forests capitalize on first access to precipitation. 

Ridge crests and the highest elevations of the state’s western forests are just two of many microclimates and forest ecosystems altered by climate change. A warmer climate, experts predict, will likely bring greater weather variability with potentially high rainfall events interrupted by longer dry spells.

The impact on forests, however, is not solely an ecological problem. An ecosystem stressed by a more extreme climate will reshape how people live near forests, how they recreate and how they interact with the species that inhabit the woodscape of Western North Carolina.

“One of the factors that influence how much water a forest uses is how hot it is outside,” McQuillan told Carolina Public Press. “So, when it’s hotter, the forest needs more water to continue to be happy and productive.”

Tree species accustomed to cooler conditions that are capable of guzzling water at a high rate “don’t care how much water is available; they’re going to continue using as much as they need until it runs out,” she said.

The fallout may be less water available to run downstream and quench the thirst of lower-elevation forests, aquatic biodiversity and potentially exacerbate the effects on downstream communities that rely on a steady flow of water to drink, for recreation, energy or agriculture.

If trees devour more water when it’s parched, “it’s a signal that they’re stressed,” Martin said. This will expose communities at the edge of the forest to the fallout of erratic weather events.

Look back no further than Aug. 17, 2021, when the remnants of Tropical Storm Fred, which had formed over the Gulf of Mexico, settled over the high ridges of Haywood County, unleashing 14 inches of rain in 12 hours. 

Cruso, a small unincorporated community on the East Fork of the Pigeon River, was hardest hit.