A Liking for Lichens

After nearly 100 years of study, the consensus by the 21st century was that the lichens of the Smokies were a known quantity. Biologists estimated that the 463 species that had been documented in Great Smoky Mountains National Park represented at least 90% of the total number of lichen species in the park.

Erin Tripp and James Lendemer were not so sure. On a trip to a nearby state park in 2005, they had made several discoveries, leading them to suspect Great Smoky Mountains also harbored many unknown lichens. Tripp, a botanist from the University of Colorado, had set up a 1-hectare plot in the eastern part of the park to monitor ecological changes in the hardwood forest, and they decided to start looking for lichens there.

The first day they examined the plot the following summer, they identified 110 species of lichens, including 36 that had not previously been found in the park. An additional 11 lichens they collected within the forest plot turned out, after further examination, to be new to science. That same day, Lendemer, a renowned lichenologist at the New York Botanical Garden, hiked a couple of miles up a nearby trail and added several more new-to-science lichen species to the park’s list. The two friends were exuberant.

“You keep encountering things that you hadn’t encountered before,” said Lendemer, whose passion for lichens dates to his high school days. “That’s what I live for.”

Every summer for the next decade, Tripp and Lendemer came back to Great Smoky Mountains to look for more lichens, organisms that Tripp describes as fungi and algae sandwiches. Through their work — including a field guide to the park’s lichen species to be published this spring — the duo hopes to introduce both scientists and park visitors to lichens’ diversity. But one of the main goals of their research is to help staff protect the many rare species of lichens found in the park. And the first step to preserving them is to know where they are. Armed with that information, park managers can take additional steps to protect trees, rocks and soils that are host to unique lichen populations.

“It’s one of the fundamental building blocks of the ecosystem.”

The inventory can also help scientists monitor the impact of climate change on lichens. Warming temperatures have favored tree pests, which have decimated trees such as eastern hemlocks that provide lichen habitat, said Jessica Allen, a lichenologist at the Atlanta Botanical Garden. According to Allen’s models, the Smokies’ high-elevation lichens are particularly threatened, but she needs accurate lichen distribution data to make reliable predictions. “Now we have this incredible baseline,” Allen said. “We’re set up to watch what’s going to happen there.”

Lichens come in a variety of colors, from olive gray to rust orange, and range from crusty to leafy to shrubby in appearance. The fungi provide much of the lichens’ structure, and the algae or cyanobacteria supply food through photosynthesis. Lichens don’t have roots, but they can attach themselves to almost anything. Most are found on rocks, tree trunks or dead branches, but they can also cling to tombstones, abandoned cars and farming equipment. Some can live thousands of years, and they can grow in extreme conditions, thriving in arctic climates and withstanding long periods of drought. Lichens have even survived exposure in space on the outside of the International Space Station.

According to some estimates, lichens cover 6% of the surface of the Earth, but while they live pretty much everywhere, they receive relatively little attention. Conservation plans typically focus on megafauna and routinely ignore lichen species, Tripp said. Lichenologists have identified scores of rare species — at Great Smoky Mountains, for example, nearly a quarter of the lichen species are known from a single occurrence. Yet, only two lichen species are listed under the Endangered Species Act across the entire United States. “There should be hundreds of species,” Tripp said. “Hundreds!”

Lichenologists note that the symbiotic organisms perform crucial ecological roles. They serve as a food source for flying squirrels in the Appalachians, pronghorn in the West and tree snails in the Everglades, said David Lamfrom, NPCA’s regional director for the Southeast and a wildlife biologist. Green salamanders use lichens as camouflage to hide from predators, some bats roost almost exclusively in lichens, and birds collect lichens with antibacterial properties as nesting material, he said. “It’s one of the fundamental building blocks of the ecosystem,” he said. “It’s food, it’s shelter and it’s medicine.”

Humans have also benefited from lichens in various ways. Dyes made from Scottish lichens color the wool used to make Harris tweed, tea made with old man’s beard lichens is believed by some to provide various health benefits, and some Native American tribes have eaten specific lichen species (some other species are poisonous). Allen once enjoyed a dinner prepared by a Chinese lichenologist that included lichen salad, soup and pancakes. “The best are breaded and deep-fried,” she said.

One of the lichens’ most valuable attributes for humans is the organisms’ sensitivity to air pollution. When sulfur concentrations increase, some lichen species change color or die off, so monitoring lichen populations can help scientists track air quality. Allen said pollution had nearly extirpated all lichens from New York City by the 1930s. “With increased air regulations, we see these species come back,” she said.

Susan Sachs, the chief of Great Smoky Mountains’ education branch, said the park had “tremendous issues with air quality” in the 1990s and early 2000s, and Sachs has taught groups of middle school and high school students how to use lichens as a monitoring tool. Sachs also has used her position to tell people about Tripp and Lendemer’s research and introduce visitors to microscopic fauna such as rotifers, nematodes and tardigrades that use lichens as habitat. “It’s really fun to watch people discover this hidden world,” she said.

So exactly how big is that world? Over the decade that Tripp and Lendemer studied the park, they examined nearly 50 1-hectare plots covering a variety of habitats, and they picked up other specimens while hiking for a total of about 6,000 lichens collected during their fieldwork. In addition, they looked at more than 11,700 specimens from existing collections under a microscope. After walking at least 2,000 miles and devoting personal funds and countless hours to the effort, they identified a total of 920 lichen species — a record for a national park — including eight that occur nowhere else in the world and one that had been presumed to be extinct.

“I don’t think either of us thought we would double the park checklist,” Tripp said.

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Discovering a host of new species offers some side benefits. Over the course of his career, Lendemer has made a point of naming lichen species after women. (He and Allen are behind lichens honoring Dolly Parton and Oprah Winfrey, for example.) At Great Smoky Mountains, Tripp and Lendemer wanted to recognize park scientists and educators, who are crucial to the development of science yet rarely receive the credit they deserve. They named five of the lichen species they discovered after park staff members who supported and promoted their research. One of the new lichens, Lecanora sachsiana, whose common name is Susan’s Sacs (for its sacs of spores), is a whitish lichen so nondescript that even when Lendemer was pointing at it, Sachs had trouble seeing it. Still, she is thrilled with the honor. “It bears my name, so of course, I love it,” she said. “It’s not showy. It’s got its own beauty.”