by Kent Priestley in Vol. 14 / Iss. 24 on 01/09/2008

Related topics: trees, hemlocks

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On a brittle morning last February, Will Blozan and his colleague, Jess Riddle, along with fellow arborists Jason Childs and Josh Kelley, drove west from Black Mountain to Cataloochee Valley, in the eastern part of the Great Smoky Mountains National Park. The peaks that surround the valley—Mount Sterling and Mount Guyot—were a confection of frozen fog, and the temperature hung just above zero degrees. Still, it seemed like a good morning to climb a tree.

Click on the image above to view a slideshow by Xpress writer Kent Priestley

Blozan and Riddle had spent the better part of the last two months in Cataloochee Valley, measuring Eastern hemlock trees. In early December 2006, along a feature called Big Fork Ridge, the two had discovered the first recorded hemlock exceeding 170 feet in height. The tree, which a friend of Blozan’s had named “Yughi”—Cherokee for needle—measured 171.6 feet tall. It was the first of what Blozan calls the “Holy Grail” hemlocks.

“One-seventy was the magic number,” he said later. “We never thought we’d hit it.” The days following the discovery of Yughi were flush with new records. Giants were spread along the ridge, the very biggest growing within three-and-a-half miles of each other.

Blozan and his team had returned this February morning to measure an Eastern hemlock tree they’d discovered two weeks before, growing in a place called Nellie Cove. The tree already had a name, “Usis,” the Cherokee word for antler. Blozan tossed a line 90 feet into the air, over the tree’s lowest limb. He tested the limb for holding strength and set his climbing rope. He began scaling the tree, followed a few minutes later by Childs. The majority of Usis’ trunk was a straight, massive bole, what Blozan calls a “stovepipe,” but where the crown began at roughly 150 feet above the ground, the tree devolved into a crazy mass of spires. Blozan worked his way to within 10 feet of the tree’s topmost branch and, at 160 feet above the forest floor, dropped a tape measure straight down. A shout erupted from below. Usis was 173.1 feet tall, the tallest Eastern hemlock ever recorded.

“No one ever thought we’d find one that tall,” Blozan later explained. Usis, he noted, is one of the most complex trees he’d ever climbed. “The tree is just amazingly charismatic,” he said. “People see videos of it and say ‘Damn! That’s a hemlock?’ It’s got limbs on it that are as big as whole hemlock trees get in Vermont.”

However massive, though, Usis was not faring well. A sucking insect called the hemlock woolly adelgid had found it a few years before and was systematically defoliating it. Six months after Blozan and his partners discovered the tree, Usis was dead.

A spark in dry grass

Adelgids infest the branch of a small hemlock tree along Winding Stair Branch, in Cataloochee Valley.

As pests go, the hemlock woolly adelgid might seem an unlikely character. Its young, or nymphs, are barely visible to the unaided eye. The adults are hardly bigger than an ink drop. Their strength lies in their abundance: An adult female is capable of producing several generations of offspring that can number as many as 90,000 in a year’s time. The young that emerge from the eggs, known as “crawlers,” nestle along the base of hemlock needles, where they insert thread-like mouthpieces and begin sucking. As they do, the insects draw off the tree’s moisture and nutrients. The affected leaves develop a grayish cast and turn yellow and then brown, as if scalded by a flame. Needles begin to drop. As a reactive measure, a tree will send out a flush of new leaves, but the insects continue sucking until the tree dies, usually within four to six years.

Adelgids get their “woolly” epithet from their waxy covering, which gives them the appearance of a bit of wool. In the cooler months, infested branches become covered with round, white blobs, each masking an adelgid. A heavily infested tree takes on a dirty white cast, which biologists call “flocking.”

Originally from Japan, the adelgid is thought to have been introduced to eastern North America by accident during the 1950s at Richmond, Va., in nursery stock. For years, it remained more or less in place, but by the late 1980s had spread west to the Blue Ridge, moved by the wind and unknowing humans, birds and other wildlife. By the mid-‘90s, it had destroyed the bulk of Virginia’s hemlock groves, and was moving north and south. By 1995, the adelgid had made it to North Carolina. Seven years later—much earlier than anyone expected—adelgids were discovered in the Great Smoky Mountains National Park.

“Some people were doing bird surveys in the park to get a preinfestation assessment,” Blozan recounted. “So they were out surveying birds and doing plots and suddenly were like, ‘Oh crap. It’s here.’ They’d found it.”

The Great Smoky Mountains National Park might be as close to adelgid heaven as any place on earth. Nowhere in the Eastern hemlock’s range is the climate so congenial. Winters are mild; summers are humid and relatively cool. And nowhere is the adelgid’s host tree so abundant. The cathedral groves of hemlock in the park were a virtual “salad bar” for the parasite, Blozan said. “Of all the places on earth, this is the food trough. There’s an absolutely huge amount of food—huge trees, close together, and plenty of birds and other wildlife and storms to move the adelgid around.”

It follows, he said, that the pest has “exploded” in the park, “like a spark hitting a nice field of dry grass.”

“What is this tree doing?”

Arborist Will Blozan measures the hemlock named Yonaguska.

Blozan traces his affinity for the hemlock to an experience he had more than a decade ago, while living in Gatlinburg, Tenn., near the park’s western boundary. At the time, he was renting a cabin whose back deck bordered a stream. On the stream’s banks were hemlocks, some of them nearly 200 years old. One of the trees, a stunted, crooked one, caught Blozan’s eye one day as he gazed out at the forest from the deck.

“It was just kind of twisting its way over the water and going everywhere,” he said. “And I was watching it as it swayed in the breeze, wondering what is this tree doing? Does it want to get tall? Is it happy where it is?” Just then, as Blozan was lost in reverie, a nearby beech tree shed one of its hulking, gray limbs. The limb fell and shattered the hemlock to bits. In a single moment, a tree that had emerged from the soil about the time of the Civil Warƒ was gone. And Blozan wondered, “Is this tree trying to tell me something? Since that time I’ve thought, well maybe I have to speak for these trees.”

Blozan began studying the hemlock in 1993, while he was working as a forestry technician in the park. In 1998, he started his business, Appalachian Arborists, with partners Brian Hinshaw and Michael Davie. By 2003 he was using every chance he had to visit the park’s hemlock groves, driving over to climb them and take their measurements. In 2005, he gave the project a name: Tsuga Search. It would be done under the aegis of the Eastern Native Tree Society, a nonprofit research organization whose acronym, ENTS, corresponds with the breed of giant, walking trees featured in J.R.R. Tolkien’s novels.

Given the speed with which the adelgid was moving through the Appalachian forest, there wasn’t time to work toward generating the money needed for the study, so Blozan decided to fund the project himself, through his company. To date, he estimates he’s spent $100,000 on the effort. The National Park Service has also given him a $25,000 matching-funds grant.

Blozan has made a career of climbing trees, but hemlocks, he said, pose a special challenge. Their tops are full of broken and dead limbs, each of which needs to be cleared off before the tree can be safely scaled. Old-growth trees, especially, are full of debris and accumulated dirt. An easy climb can take as little as two hours. A hard one can take as long as six hours, a full-day’s work. “They just don’t cooperate,” he said.

Valley of the Giants

Blozan takes notes on Yonaguska.

A few weeks before Christmas, I set off for the Cataloochee Valley with Blozan. He wanted to get more precise measurements of a hemlock named Yonaguska, for a Cherokee chief who resisted the tribe’s removal to the West in the 19th century. We drove into the valley and parked along a paved road. Blozan threw together a small backpack of equipment, took a moment to consult a map and then walked into the woods ahead of me.

His pace was punishing. Every 20 feet or so he would disappear, obscured by the flapping leaves of rhododendron. And they weren’t garden-variety rhododendron, either; these were old-growth bruisers with a knack for making pulp of shins and arms. At one point I plunged chest-deep into a thicket of the evergreen plant known as dog-hobble. I fought my way out, panting, and found Blozan a few steps ahead of me, coolly gazing into his laser rangefinder, measuring the height of a nearby tree.

We worked up the side of a steep, narrow cove divided by a stream called Winding Stair Branch. Every few minutes, Blozan would pause to take additional readings with his rangefinder. At length we passed through an especially dense grove of rhododendron and found ourselves at the base of a huge hemlock. We’d arrived at Yonaguska.

Blozan discovered the tree in 1997. The next year he climbed it in an attempt to see if it was as tall as a hemlock named Tsali, which grew a little way down Winding Stair Branch. It wasn’t, but its bulk was nevertheless impressive. Yonaguska is huge, with a base that flares into several massive, moss-covered buttresses, and a dark, deeply furrowed trunk that presses against the sky.

Hemlocks are not the only big trees that grow in Cataloochee. For the most part, the coves that enfold the valley never felt the bite of the ax. Name a species of Eastern tree, and chances are good that its largest example grows there: the tallest known white pine, the tallest white oak, the tallest black and yellow birches, the largest Northern red oak, the largest tulip-poplar, the largest cucumber magnolia and the largest yellow buckeye. With good reason, Blozan calls the 10-mile Cataloochee Valley “the Valley of the Giants.”

For each hemlock studied, Blozan and his Tsuga Search partners have marked off a 25-meter circular plot around the tree, identifying and measuring all the vegetation within that area. Over they past two years, they’ve filled five field notebooks with data, each listing the size and other particulars of several hundred trees. For each tree measured precisely in the Tsuga Search project, Blozan said a dozen to 100 have been “roughed out” using the laser rangefinder.

Never a fast-growing tree, in Cataloochee’s north-facing coves, the hemlock is the model of patience. Where a deciduous tree like the tulip-poplar might attain a volume of 1,600 cubic feet in the span of 200 years, a hemlock will take twice that long to reach the same size. But the hemlock has an advantage: It is shade-tolerant, and can grow in the understory of much larger trees, biding its time. The oldest hemlock yet found in Cataloochee, a slight specimen with a diameter of a little more than two feet, is 450 years old—a seedling when Queen Elizabeth I assumed England’s throne. Some of Cataloochee’s biggest hemlocks could well be that old—or older—but their heartwood tends to be rotten, making it impossible to remove an accurate sample from them.

Before the start of Tsuga Search, the world-record hemlock was 168.9 feet tall, also measured by Blozan, in 1998. Since the study began, 70 trees taller than 160 feet have been found, 57 of them in Cataloochee.

Nearby, perhaps 20 feet from Yonaguska, was another big hemlock, whose green top-growth was visible from the ground. I asked Blozan how it had managed to survive. “It’s right by the water,” he said. “It has a huge canopy; plenty of vigor. It’s busting back out again, but I’m sure at this point that every single needle is occupied with adelgids. To save a tree that big would be monumental effort at this stage. And it probably wouldn’t be successful, because chemicals just don’t act fast enough.”

Blozan and Riddle came across Yonaguska in February 1998, when the park was gripped in a major drought. When they found the tree, its top was still lush and ferny. But it died the next year, presumably from drought stress. Blozan at least considers it a dignified death, compared to succumbing to adelgids.

In the woods nearby, a wren chided us. Somewhere in the distance, a woodpecker gave out a mad, laughing call. I rapped on Yonaguska’s trunk with my knuckles. It made a hollow thonk. Blozan admonished me, in a half-serious way. “Don’t knock this tree down before I measure it,” he said.

Fighting back

The adelgid is only the most recent threat to the Appalachian forests. Beech-bark disease, a fungal affliction carried south by bark beetles, has already swept through the Smokies, rupturing its host trees’ bark and girdling their vascular tissue. The disease kills bigger trees first.

And more problems could be on the way. Sudden oak death, a fungus that shares a genus with the blight that caused the Irish potato famine, is so far restricted to the West Coast but occasionally rides east on nursery stock, prompting quarantines.

New insect pests are afoot and moving south, as well, including the Asian longhorned beetle or starry-night-sky beetle, a native of China whose grubs are so big and voracious that their feeding makes an audible grinding sound in the affected trees. And there is the emerald ash-borer, an exotic beetle that was found in Ontario in 2002. The borer has already spread as far south as western Pennsylvania, leaving an estimated two million dead ash trees in its wake and putting the future of the wooden baseball bat into question. Every packing crate, plant and cardboard box from overseas or across the continent, it would seem, holds the possibility of arboreal catastrophe.

Climate change may be the wildcard in this formula, with the power to hasten or slow the demise of the forest, at least as we’ve known it. Some have theorized that global warming is abetting the adelgid’s spread, with a decades-long warming trend playing out in a lower mortality rate for the insect and a consequent higher death rate of its prey species.

But the example haunting Blozan is that of the American chestnut, which was felled in the early 20th century by an imported fungus. The disease, which raises blisters around a tree’s stem and girdles it, was first noticed on American chestnut trees in the Bronx Zoo in 1904. Its airborne spread is believed to have left billions dead chestnuts in its wake during the following decades. The disease was keenly felt in Appalachia, where some scientists believe nearly one in three trees may have been an American chestnut before the blight arrived, a vital source of food (or “mast”) for wildlife, wood for construction and bark for tanneries. Now, all that remains of the chestnut in most of its former range is the occasional root-sprout.

Details about the American chestnut—its size, its extent—are lost to us, said Blozan, a fact that is a major impetus for Tsuga Search. “With species that we’ve already lost, like the American chestnut, we don’t know how tall it could get or how much wood they could get. And we can never, ever get that information again. It’s gone. So there’s this big blank in the history books. There’s speculation about how tall it could get, but no one ever detailed it. I didn’t want that to be the fate of the hemlock.”

For its part, the National Park Service has made “a very aggressive” effort to combat the adelgid, said Tom Remaley, the Great Smoky National Park’s hemlock woolly adelgid program coordinator. Last year alone, the park spent three-quarters of a million dollars on adelgid control, and has annually renewing funds in its budget dedicated to combating the pest. (Blozan’s company has so far been awarded two contracts for adelgid control in the park, Remaley said.)

A pesticide made of synthetic nicotine and applied to the soil is a proven treatment. Thus far in the Great Smoky Mountains National Park, Remaley said, more than 75,000 acres of hemlock have been treated. Roughly 300,000 beetles that prey on adelgids have been released in the park. Some of the tallest surviving trees were treated with pesticide last year, but the year’s exceptionally severe drought meant that the chemicals, which depend on rainfall to be drawn up by a tree’s roots and into its branches and foliage, remained in the ground.

“We’ve lost essentially a year of treatment because of the drought,” Blozan said. “A lot of the trees we treated died. And a lot more will die.”

That didn’t need to be the case, he insists. “More money could be going into resource management rather than, say, mowing the grass in the park,” he said. “For every time the park service mows the grass along the road they probably could save 10 acres or more of old-growth hemlock forest, using the same funding. So where are your priorities, people?”

The park service’s standing orders make an imperative of preservation, but Blozan said the lack of forethought that has gone into saving the big hemlocks puts that goal in question. “They wanted to preserve this forever,” he said. “But it’s not happening. And that’s what blows my mind—the park was formed for the forest, to preserve the trees. And yet it won’t adequately fund their treatment.”

Remaley, though, countered that the park is spending “multiple millions of dollars” on the problem. “You could say, ‘Yes, we could do more,’” he said. “We say that, too. We’d like to have more money. But you do what you can do. You beg for as much money from as many sources as you can find.” Remaley mentioned that in addition to its outlay for pesticides and beneficial insects, Great Smokies now has a full-time crew of seven employees working on the adelgid problem.

“Of course Will’s opinion is that we should be out there spending any and everything we can,” said Rusty Rhea, an entomologist with the Forest Health Protection office of the U.S. Forest Service in Asheville. “You know, Will’s a friend of mine, but that’s just not a sustainable philosophy. You can’t spend thousands and thousands of dollars to keep trees scattered all over the place alive for a few years. Sooner or later, people are going to start asking ‘So why are we doing this?’”

To mourn a species

The Eastern hemlock serves a unique ecological role. A 2001 study found that as many as 30 species of birds rely on the trees for shelter and feeding opportunities. As much as 84 percent of wood thrush nests are built in young hemlocks. Several species of warblers depend on hemlocks for nesting cover. Certain species of beetles, ants and moths depend on stable hemlock forests. Hemlock bark provides a growing medium for lichens, some species of which remove atmospheric nitrogen from the air and convert it into a soluble form, which travels to the forest floor and provides a valuable fertilizer for surrounding vegetation.

In his article, “A Death in the Forest,” in the Dec. 10, 2007, issue of The New Yorker, Richard Preston repeated the belief, common among forest ecologists, that the Eastern hemlock is headed for a “functional extinction.” In other words, the species may survive—with or without human intervention—but its role in the forest will be so diminished as to be negligible, like the occasional American chestnut sprout that manages to ripen a nut or two before it succumbs to blight.

So what faces the Eastern hemlock is a managed future. The tree will only develop a resistance to the adelgid over many generations, if it manages to at all. “The genetic diversity of hemlock is just not that broad” to allow that to happen, said Rhea.

And while research is ongoing to determine whether predatory insects may consume enough adelgids to create a balance and give the hemlock a chance of survival, the tree’s best hope for now may lie in the routine application of pesticides, an expensive and limited strategy.

Even the park service’s Remaley conceded that the hemlocks may be consigned to a sort of exhibitory role in years to come. A portion of the park’s 1,600-acre conservation area for the tree is in areas accessible to a majority of visitors, Remaley explained, “so we can preserve these areas as a kind of outdoor museum piece.”

Other populations of Eastern hemlock have yet to be invaded by the adelgid. An outlier forest of hemlocks grows near Chattanooga, Tenn. within the Savage Gulf State Natural Recreation Area. The site contains some of the tallest hemlocks outside of the Southern Appalachians, trees that range to more than 150 feet tall. Blozan said he planned to travel there this winter to volunteer his time to help create a management plan for the trees, a recipe for their survival.

At Cataloochee, the situation is less hopeful. Of the 30 superlative Eastern hemlock trees Blozan and his study partners chose to concentrate on for the project—the 15 tallest and 15 largest—22 have already died. Of the eight remaining trees, Blozan believes that only four have the necessary vigor to survive the adelgid. I asked him how, given how badly things had gone for Cataloochee’s big hemlocks, he’d managed to not fall into a deep depression.

“I’m not sure that I haven’t,” he replied.

Blozan needed to take the measurements of one more tree before we left the company of Yonaguska. I walked down the hill a bit and stood next to the subject tree while Blozan went up the ridge to sight it with the laser. I picked a broken hemlock branch off the ground and waved it along the tree’s trunk to give him a point of reference. Blozan was out of sight, obscured by rhododendron. Apparently, he was still mulling the question of mental health.

“It’s like a guy I used to work with always said,” he called out. “‘You’ve got to laugh to keep from crying.’”

A moment passed and Blozan had his reading. The tree, its top infested with adelgids, was a solid 160-footer, the 70th measured to date.

Blozan made his way down the ridge and stepped over the giant trunk of a fallen hemlock that had still been alive in 1997, when he and Riddle first surveyed the cove along Winding Stair Branch. Its surface was slick with moss and covered in tiny rhododendron seedlings and strands of spider web, jeweled with dew. It seemed to be melting away.

“I don’t know how to mourn a species,” he said as he gathered up his tools. “I haven’t figured that one out yet. I guess I’ll need to eventually.”