On the Hunt for Unloved, Unstudied, Yet Super Important Lichen

Science
دوشنبه 29 مرداد 1397 ساعت 17:13
331
Smith sonian mag
We arrive at Cupsogue Beach, near the eastern tip of Long Island, in the foggy morning after a long drive from Manhattan. After an hour scouring the dune scrub, there is no sign of what we’re looking for. “This is the unglamorous job of trying to find something that’s rare,” says James Lendemer , a lichenologist at the New York Botanical Garden in the Bronx.
We’re searching for Cladonia submitis , more commonly known as “beach broccoli” — though “commonly known” might be generous. It’s an apparently rare lichen with a restricted range between New Jersey and Rhode Island. Cupsogue Beach, in the town of Brookhaven, is the first of three stops on our daylong trip to document where the lichen still lives.
Lendemer has devoted his life to studying these cryptic lifeforms. But even he doesn’t know if this particular lichen species is threatened. This reflects the state of lichenology as a whole. There are very few people doing basic science to figure out what species live where. Lendemer is among the few who are. Without his surveys in places like the Great Smoky Mountains and the Eastern Seaboard, we would have no idea how many lichen we are in danger of losing forever.
Lichen are fungi that live together with algae. The fungus provides nutrients and shelter, while the algae synthesizes food from sunlight. Because they are completely self-sufficient, needing nothing but sunlight and a place to anchor, they can survive in many inhospitable environments like scorched desert cliffs and barren lava fields .
Yet lichen face many of the same threats as other lifeforms: pollution, changing climate and fragmented habitats. But not only are lichen especially sensitive to change, they also suffer a public relations problem, as Lendemer is quick to explain.
“The biggest challenge is that nobody cares about [them],” he says. Add to this an overall scarcity of information and you get a rather unloved and uncared-for group of organisms.
Yet lichen are an incredibly diverse bunch. There are lichen that look like leaves or seaweed. There are lichens that look like dusty green powder, stringy bits of teased wool, or crusty vomit. There are blue lichen, yellow lichen, orange lichen and black lichen. They live on dead wood and live trees, rocks and soil, but they also have been seen on occasion to grow on rusted metal, glass and even old shoes. Lichen are found in nearly every terrestrial environment in the world and several aquatic ones as well.
Lichen aren’t just pretty to look at, they’re functional, too. They pump nutrients back into the ground and hold soil together. Many, like the map lichen Rhizocarpon geographicum , are pioneers that colonize volcanic rock, while others like the cobblestone lichen Acarospora socialis grow on harsh desert stones in the American Southwest, enriching the otherwise nutrient-poor environments. When lichen disappear, ecosystems lose all these important functions.
“And functionally that’s what’s happened now,” Lendemer says. “We’ve lost lichen all over.” Take Lobaria pulmonaria , which resembles a cluster of red oak leaves. It used to grow throughout the eastern U.S. and into the Midwest. Now it’s gone “from states like Iowa and Ohio, [and] is nearly gone in states like Pennsylvania and Maryland and West Virginia,” Lendemer wrote in an email.
What’s more, few species are filling in the ecological gap left by L. pulmonaria ’s disappearance, Jessica Allen, one of Lendemer’s colleagues, explains in an email. “In many places it has not even been physically been replaced by any lichens,” she said.
Lendemer and his doctoral student Jordan Hoffman are conducting a survey to prevent a similar fate from befalling Cladonia submitis . The species grows only in the sandy soils of dunes and pine barrens along the mid-Atlantic. “Pretty much all the habitat the species occupied is to some degree threatened,” explains Hoffman. Sea level rise and changing land use threaten to shrink and fragment these habitats, and fires that naturally sweep through these areas are projected to become more frequent and intense due to climate change.
C. submitis a unique part of the flora of New York and New Jersey, Hoffman says. Like the Tennessee coneflower, which grows in the state’s cedar glade habitats, or the California sagebrush, found exclusively in the chaparral of Southern California, the small lichen may not be the most iconic species of its region, but it contributes to the health and individuality of the ecosystem.
The baseline records that Lendemer and Hoffman are comparing against were collected over the course of around a century, explains Hoffman, and most of the sites hadn’t been revisited since. Because of this spotty data, the two scientists need to do a full field survey, revisiting as many historical sites as they can to determine to what extent the species is still present. This is what has brought us to Cupsogue Beach this morning, and what’s compelled our hours-long search through the sandy soil.
On our way back to the car, Lendemer’s laser eyes spot what may be a single tuft of C. submitis among a patch of Eastern pincushion lichen, an almost identical species. It was so small that Hoffman was hesitant to take a sample. Sure enough, in the lab the next day they discovered it was merely a fat specimen of the Eastern pincushion.
Lendemer points out a photo of C. submitis on a trailside placard. (Harrison Tasoff)
In his mid-thirties, Lendemer grew up in a rough part of North Philadelphia, near the playground where the opening fight in the television show The Fresh Prince of Bel Air was filmed. Itching for an opportunity to get out of his house, Lendemer began volunteering at the Academy of Natural Sciences when he was 12. By high school, he was able to convince the Academy’s botany curator to give him free rein in the collections.
About this time, a young botanist named David Hewitt piqued Lendemer’s interest in lichen. Having already helped organize the Academy’s fossil plant collection, Lendemer decided to locate and compile all the institution’s lichen type specimens, those representing the first sample of a species. One day, during this self-assigned project, two similar-looking samples caught his eye.
“I found one that was called one thing, and I found another that was called something different. And they were clearly the same species,” Lendemer recounts. “I figured if I was in high school and I could find that out then, you know, that’s the thing for me,” he said.
We pull into the parking lot at Pike’s Beach, a spot where our rare lichen had been found growing along the dunes back in 1936. “It’s gone,” Lendemer says after only a few minutes surveying the dunes.
As we walk back to the car, he explains that the endless tracts of houses in the Hamptons didn’t exist back in the 1930s. “This is the main reason why it probably declined,” he says.
The housing developments don’t just disturb lichen and other species in their immediate area; disturbing the land has effects that radiate outward and can last for centuries.
Pioneer species colonize land that has been flooded, burned, or otherwise wiped out. But they’re eventually succeeded by other life forms more adapted to live in the now-renewed environment.
A region matures as successive waves of species roll in from more established areas nearby and opportunistic pioneers move on to newly disturbed land. A healthy ecosystem, therefore, will have patches of land at different levels of succession.
But human activity affects large tracts of land all at once, reducing the size and number of mature habitats. Without these refuges providing a steady source of old-growth species, those species will eventually disappear, even if suitable habitat returns.
“Once you lose an old-growth forest you will lose that for many centuries,” says Hoffman, the doctoral student.
Lendemer’s basic survey work is helping lichenologists learn more about what lichen species tend to live in an area, and gives a baseline for future scientists to track changes in lichen populations.
Kerry Knudsen , a fellow lichenologist, provides some perspective. “Once you have a good idea of what’s there, then you can start to understand what is threatened or endangered,” says Knudsen, who splits his time between University of California Riverside and The University of Life Sciences in Prague, the Czech Republic. Right now there are only two lichen listed as threatened or endangered by the U.S. government. Compare that to the 942 plants and 1,447 animals on the Endangered Species List.
Lendemer’s work may someday change this as he adds prodigious amounts of data to our collective knowledge about the organisms. “There [are] somewhere between 10 or 20 people that are doing fairly intensive collecting, but nobody is doing it at the level James is doing it,” says Knudsen. In the last 13 years, Lendemer has coauthored descriptions of 127 new species and corrected many more misidentifications, by his own estimates.
Given his role at the New York Botanical Garden —which boasts the second largest plant and fungus collection in the world — Lendemer is well positioned to have a large impact on his field.
“And he will,” says Knudsen. “He’s already the best lichenologist in North America in my opinion.”
Others think so too. Lendemer offers his expertise to government agencies and environmental groups working on conservation, helping them identify areas of high biodiversity or ecological importance for conservation, according to Gary Kauffman, a plant ecologist with the U.S. Forest Service.
One of Lendemer’s surveys uncovered a holdout of rare Mount Sterling Script Lichen — a species Lendemer helped discover — in the wilderness of Pisgah National Forest, in eastern North Carolina, says Kauffman. The lichen was known from only seven small pockets in the upper reaches of Great Smoky Mountains National Park, just over the border in Tennessee. Without this basic fieldwork, there’s no way for scientists to craft management strategies.
On the car ride to our third site the conversation turned to Lendemer and Hoffman’s recent field trip to North Carolina. The two had joined a biologist from the forest service to search for lichen in the Nanthala National Forest. On this trail was one known occurrence of Japewiella dollypartoniana , a species Lendemer had named after the actress and musician Dolly Parton, in honor of her Appalachian roots and to recognize her philanthropy in the area.
“Being the excitable nerds we are, we decided that it would be an excellent idea to get pictures of Dolly Parton’s lichen with pictures of Dolly Parton,” says Hoffman. So, prepared with print-outs of Dolly, the three set off to find J. dollypartoniana , as well as the other lichens they were looking for.
They spotted some of the small, crustose lichen on a slender tree halfway up the trail and immediately began posing for celebrity pictures with it, when a family of hikers appeared. The biologists explained themselves as well as how the lichen got its name, and its significance in the ecosystem.
“Initially, they chuckled and walked a while down the trail,” says Hoffman. “But before long, they actually came back! They asked us if THEY could pose with Dolly and her lichen!” It turns out the hikers were big fans of Parton. It was a short interaction, but the hikers’ interest in the lichen warmed the scientists’ hearts.
The elusive C. submitis at last. (Harrison Tasoff)
Lendemer and Hoffman are hopeful as we pull up to the trailhead at Dwarf Pine Plains, a few miles from the beach in the village of Westhampton. And their hope turns out to be well-founded: After only a few minutes, the sandy pine barrens reward us with three clumps of Cladonia submitis . Hoffman eagerly samples the lichen as Lendemer sets off to find more.
After 30 minutes Lendemer returns, announcing that he had found what he called an “embarrassment of lichen.”
“Clearly there’s a crap-ton [of C. submitis ] in this vicinity,” Lendemer says, as Hoffman and I survey the area. “And a crap-ton is a technical amount,” he jokes. “It’s defined as more than 1,000 individuals.”
They take samples and photos, and celebrate their good fortune. “I don’t think I’ve ever seen that much of it in one place!” Lendemer exclaims on the way home. Despite the challenges they face, it’s a relief to know there are still areas where lichen can thrive.
Since our outing, Lendemer and Hoffman discovered that C. submitis is actually quite abundant where it occurs. However, despite the wealth of lichen at Dwarf Pine Plains, the species has disappeared from many sites from earlier in the historical record.
“A lot of these historical sites, where the species once was, [have] now become backyards, parking lots, restaurants, and other types of residential or commercial areas,” Hoffman explains in an email. This means that the sheer number of individuals per site is probably not the best indicator of how the species will perform or cope with the threats that it faces, he says.
Lendemer and Hoffman will contribute their work to the International Union for Conservation of Nature, which compiles the Red List of Threatened Species. The IUCN is just wrapping up their assessment of C. submitis , and Hoffman says that the data they collected supports the case for ranking the species as endangered.
“We have plenty of reasons to suspect it could be threatened,” Hoffman says. “And it would be a shame to see something disappear from our backyard just because we didn’t have enough data to spot its decline.”
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