Panic in Level 4

A Death in the Forest

IN 1911, A WOMAN NAMED SALLIE DOOLEY established a Japanese garden at Maymont, her estate in Richmond, Virginia. She planted bamboo, built a gazebo and a waterfall, and, according to her husband, James Dooley, a financier, “purchased the most costly evergreens from all parts of the world.” She died in 1925, leaving Maymont to the city of Richmond. It became a park, and the Japanese garden went untended. In 1951, an entomologist with the Virginia Department of Agriculture discovered a species of Asian insect known as the hemlock woolly adelgid infesting an eastern hemlock—a tree native to North America—on property near Maymont Park. The hemlock woolly adelgid is a tiny brown bug similar to an aphid; the body of an adult is covered with a protective white fluff that makes it look like a fleck of cotton. It is a parasite, and it feeds on several species of hemlock and spruce trees in Asia. This was its first known appearance in eastern North America. The suspicion was that it had come from Sallie Dooley’s languishing evergreens, though no one could be sure. Experts considered it a curiosity.

After hatching from an egg, the woolly adelgid goes through a crawler stage, when it moves around. The crawlers are almost invisible to the naked eye. They can drift in the air from tree to tree, and they can cling to the legs and feathers of migrating birds. The insect eventually settles down among the needles of a host tree. It inserts a bundle of mouthparts at the base of a needle and spends the rest of its life—a few months—sucking nutrients out of the tree. A female can lay eggs without being fertilized by a male. The offspring are clones of their mother—genetically identical to her. As it has turned out, the population of woolly adelgids in North America seems to consist entirely of female clones. Males still hatch occasionally, but they breed and live in spruce trees, and American spruces lack certain nutrients they need, so they die—a further indication that the adelgids are transplants. It hardly matters: a single female clone can generate as many as ninety thousand copies of herself in a year.

In Asia, many kinds of natural predators, especially beetles, eat the woolly adelgid, and the host trees have developed resistance to it. In North America, though, there are no natural predators of the adelgid, and eastern hemlocks have virtually no resistance to it. In coming to America, the Asian insect escaped its predators. When millions of woolly adelgids cover the branches of an eastern hemlock, it turns a dirty whitish color, as if it had been flocked with artificial snow. Many of its needles fall off. The tree puts out a new crop of needles the following spring, but the crawlers attach themselves to the new needles, the tree goes into shock, and the needles fall off again. The cycle of shock and defoliation continues until the tree dies, usually in two to six years.

There weren’t many eastern hemlocks in Richmond. The tree doesn’t occur naturally in the area, but it had been planted in some people’s yards, and specimens were scattered sparsely through the city. (Hemlocks are often trimmed into hedges.) For thirty years after its discovery near Maymont Park, the insect gradually moved around the hemlocks of Richmond, and over time many of the the hemlocks in the city lost their needles and died. However, gardeners found that if they sprayed an infested hemlock once a year with pesticides or an oil spray, the bugs would be suppressed.

In the 1980s, an entomologist with the Virginia Department of Forestry named Tim Tigner began tracking the woolly adelgid around Richmond. “We advised people not to worry about it,” Tigner said to me recently. “It didn’t seem to be doing anything.” Then, in the late eighties, Tigner learned that the insect had made its way into a natural stand of ancient hemlocks on the York River, forty miles east of the city, and he went to have a look. He got a shock: 90 percent of the hemlocks were dead. The woolly adelgid had turned the grove into a sun-bleached ruin.

BOTANISTS SOMETIMES REFER to the eastern hemlock as the redwood of the East. It is a tall, long-lived conifer with soft, flat needles and feathery foliage. It has a massive, straight trunk that rises to an impressive height, flaring into a dark, mysterious-looking crown, which is filled with all sorts of living things. The eastern hemlock’s species name is Tsuga canadensis. It occurs naturally in the Appalachian Mountains from Georgia to New Brunswick and Nova Scotia, with a range that runs westward through Michigan into Wisconsin. The tallest eastern hemlocks are somewhat more than 170 feet high, and the largest ones (measured by volume of wood) can be more than six feet in diameter. The oldest living specimens may be more than six hundred years old. Hemlocks and redwoods are extremely shade tolerant—they can grow in dark places where no other trees can survive. Both kinds of trees do especially well in moist valleys filled with temperate rain forest. It seems that few people know that there are rain forests in California. Possibly even fewer people realize that there are also rain forests in the East.

Hemlocks thrive in the temperate rain forest found in the southern Appalachian Mountains. In simple terms, a temperate rain forest is a cool forest that receives at least 80 inches of rainfall a year. Some parts of the southern Appalachians receive up to 130 inches of rainfall a year, with very little snow—more rain than in many parts of the Amazon basin. In the temperate rain forests of the southern Appalachians, hemlocks grow in moist, cool valleys and on mountain slopes, and they form dense stands in the upland valleys called coves.

Hemlocks cast deep shade, and they cover the ground with beds of needles, altering the temperature, moisture, and chemistry of the soil around them. This creates a distinctive habitat for certain animals and plants. An old-growth forest is a forest that’s survived for many centuries without being changed by logging or fire. Only small fragments of old-growth forests remain in the East. Many of them are in Great Smoky Mountains National Park, which lies along the mountainous divide between Tennessee and North Carolina. The national park covers half a million acres; about a fifth of the park has apparently never been logged. Loggers haven’t bothered to go into many coves to cut hemlocks, because the tree is practically worthless for lumber: the wood is full of knots, and often fractures when the tree falls. Some ecologists believe that the hemlock coves of the southern Appalachians contain, or until recently contained, the last examples of primeval rain forest in eastern North America—pockets of rain-forest habitat that seem to have remained unchanged for thousands of years.

In 1988, around the time Tim Tigner saw how the woolly adelgid had destroyed a grove of old hemlocks by the York River, the insect was discovered in Shenandoah National Park, in northern Virginia. It seems to have arrived there when crawlers clung to the legs and feathers of migrating birds that visit or nest in hemlock trees—the black-throated green warbler, the solitary vireo. In Shenandoah, the insect got into stands of old hemlocks packed tightly together in coves, and it multiplied with explosive speed. By 1992, most of the hemlocks in the park were infested, and three years later the majority of them were dead. Today, stands of eastern hemlock have essentially disappeared from Shenandoah National Park.

The crawlers spread rapidly northward. They moved southward only slowly, though, possibly because there were few crawlers around in the autumn when birds flew south. By 1998, many of the hemlock groves in the Delaware Water Gap National Recreation Area, which lies between Pennsylvania and New Jersey, were infested and had begun to die. From eastern Pennsylvania to Connecticut, hemlocks were being turned into skeletons. The insect got to Massachusetts. There, stands of old hemlocks were defoliated. However, a spell of intensely cold weather during the winter of 1996, when temperatures in parts of the Northeast fell to as low as twenty degrees below zero, seemed to kill many adelgids. “The hemlocks looked okay after that cold winter,” James Akerson, an ecologist with Shenandoah National Park, said. “It may have given us a false sense of hope.”

INVASIVE SPECIES OF MICROBES, plants, and animals are changing ecosystems all over the planet in a biological upheaval that may affect almost everything that lives. The cause of the upheaval is the human species. Life on the planet is being homogenized by the expanding human population and the frequent and rapid movement of people and goods, which carry invasive organisms with them. These invasives often flourish in their new ecosystems because, like the woolly adelgid, they have escaped their predators. A fungal disease called chestnut blight, from Asia, first appeared in North America in 1904. Spread by wind, rain, and birds, it killed almost every American chestnut tree. Chestnuts had once saturated vast stretches of forest in the Appalachians. They essentially vanished from the ecosystem. The term biologists use for this is “functional extinction.”

Since the 1930s, the American elm has gone almost extinct in the wild, pushed into oblivion by an invasive Asian fungus spread by an invading beetle from Europe. In the 1960s and ’70s, the balsam woolly adelgid (from northern Asia) got into the Fraser fir, a native American species growing on the higher ridges and peaks of the southern Appalachian Mountains; this parasite killed from 70 to 90 percent of the mature wild Fraser firs, making the mountains look as if they were covered with driftwood. (Today the wild Fraser firs in the Appalachians often don’t get much taller than a person before they die from adelgid infestation.) A fungal disease of unknown origin has killed off the vast majority of the wild flowering dogwoods in North America. Another disease, sudden oak death, has killed hundreds of thousands of oaks in California and may get into Eastern oaks. A European insect carrying a European fungus has lately caused a mass dying of the American beech tree, and the American beech’s future as a species in the wild is uncertain. An Asian beetle called the emerald ash borer arrived in Michigan in 2001 in packing wood from China. It is devastating to a number of species of American ash trees. Despite strong efforts to control it, the emerald ash borer keeps appearing in different places, and it seems capable of not only wiping out the ash but threatening the classic major-league baseball bat (which is commonly made of ash). Another invader, the Asian long-horned beetle, had its North American debut in Brooklyn, where it showed up in a park near warehouses that held large amounts of packing wood from China. The Asian long-horned beetle has infested tens of thousands of trees in New Jersey and Long Island, and it has shown up Sacramento. It could take out the sugar maple. In effect, the trees of North America have been hit with all sorts of Ebolas of their own.

When a parasite moves to a new habitat, it can find new hosts through a process called the trans-species jump. Often the new host has no resistance; the host and the parasite haven’t had time to adjust to each other through natural selection. (It is frequently not in the best interest of a parasite to kill its host quickly.) One example is the human immunodeficiency virus, HIV. It appears to have once lived in chimpanzees, though it doesn’t make them sick—the chimp’s immune system is well acquainted with the virus and has learned how to deal with it. In Africa, at various times and places in the twentieth century, HIV made trans-species jumps into humans—probably through hunters who killed and butchered chimps, and so were exposed to infected chimp blood. Once the virus had escaped the chimpanzee’s immune system, it amplified itself freely in its new hosts.

Another example of an invasive species is the Ebola virus. Ebola is a parasite with a known tendency to make trans-species jumps into new hosts. Ebola lives naturally in some unknown type of host in central Africa—possibly a bat, possibly a wingless fly that lives on a bat, or quite possibly some other creature. Ebola probably doesn’t make its natural host very sick. Ebola makes primates incredibly sick. This means that primates are not the original host of Ebola.

Outbreaks of Ebola in humans tend to burn out fairly quickly, but Ebola is a far more serious matter for gorillas. In recent years, roughly a third of the gorillas in protected areas in central and west Africa have died from Ebola virus. The virus is spreading unchecked in the gorilla population of central and western Africa, and it kills around 90 percent of the gorillas it infects. No one knows how Ebola has been getting into gorillas; possibly some disturbance in the ecosystem has put the animals into contact with the unknown host of Ebola.

I sometimes wonder if the unknown natural host of Ebola is itself an invasive species—some sort of rodent or insect, perhaps—that’s moving into disturbed habitats in the African rain forest. If so, this might explain why Ebola seems to be jumping into gorillas more frequently these days. Ebola’s host might be moving into new niches that have opened up in a rain forest that’s being changed by logging and human invasion. The Ebola host might be bringing itself and its parasite—Ebola—into close contact with gorillas. The World Conservation Union recently put the western gorilla on its critically endangered list; the Ebola virus, together with poaching, could push the western gorilla to extinction in the wild (some gorillas would persist in captivity). In other words, what happened to the American chestnut could also happen to the western gorilla: functional extinction due to a species-jumping parasite.

Global climate change has become entangled with the problem of invasive species. A warmer climate could allow some invaders to spread farther, while causing native organisms to go extinct in their traditional habitats and making room for invaders. The earth’s biosphere can be thought of as a sort of palace. The continents are rooms in the palace; islands are smaller rooms. Each room has its own decor and unique inhabitants; many of the rooms have been sealed off for millions of years. Now the doors in the palace have been flung open, and the walls are coming down.

Global climate change may be helping the hemlock adelgids spread both north and south. Winters in the north are becoming steadily warmer, and the insects are not likely to be hit as often with deep cold. Summers in the southern Appalachians have lately become drier and hotter, and drought stress makes infested hemlocks far more susceptible to parasites. Climate change may also mean that the adelgids will be more active when birds are flying south. Recently, the woolly adelgid has turned up in Ohio, Michigan, Vermont, New Hampshire, and Maine—approaching the northern limits of the hemlock range. Wherever it goes, it seems to get into every hemlock. It kills saplings before they can produce seeds, and so, in every place it arrives, it stops the hemlock species from reproducing. Many experts have concluded that the insect could kill nearly all the eastern hemlocks; if so, the species would essentially disappear from the wild.

ON DECEMBER 3, 2001, an arborist named Will Blozan discovered woolly adelgids on the branches of a wild hemlock in the Ellicott Rock Wilderness, on the Blue Ridge in South Carolina, near the extreme southern end of the hemlock range. No one had expected to see the insect this far south so soon. “It was a spear through the heart,” Blozan told me. He phoned Rusty Rhea, an entomologist and the forest-health specialist for the Forest Service in Asheville, North Carolina. Rhea was surprised. He sent out a bulletin to all rangers in the area warning them to look for adelgids. Within two weeks, Rhea was getting reports. The insect had gone all over the mountains.

Will Blozan is a tall man in his thirties with dark blue eyes that can take on a guarded look, and he has a laconic way of speaking. Blozan has wide shoulders and powerful-looking hands, but his hands move with a sensitive, precise quality—they’re the hands of a professional tree climber. He is the co-owner of a tree-care company called Appalachian Arborists, based in Asheville. (Arborists, who used to be known as tree surgeons, get around in trees using ropes.) He is also the president of the Eastern Native Tree Society, a small organization dedicated to discovering giant trees in the East. Since 1993, he had been spending his spare time exploring patches of old-growth forest in the Appalachians from New Hampshire to Georgia. Will Blozan became well known among tree biologists for having discovered and measured many of the tallest and largest trees in eastern North America. He often found them while he was bushwhacking through remote valleys in the southern Appalachians; he got into places that may not have had human visitors in years or decades.

In the Great Smokies in summer, the heat can be Amazonian. The land can slope sixty degrees, and in many places the undergrowth consists of a mesh of rhododendrons. “It’s total suckage in there,” Blozan said. “‘Rhodo wrestling’ may be the appropriate term for movement in the Smokies.”

When he found a big tree, he would get an estimate of its height using a laser device. Later, he would climb to the top, using ropes, and would send a measuring tape down along the trunk—this is the only way to determine the height of a tree to the nearest inch.

As he explored around, measuring tall trees, Blozan spent a lot of time around the southeastern tip of Great Smoky Mountains National Park, in a place called the Cataloochee Valley. It is a rain-forest wilderness, “well known for making you wet,” Blozan said. The Cataloochee Valley is centered on a rumpled drainage dissected by hundreds of small upland coves and divided by ridges and mountains. A few hiking trails wander through the Cataloochee, but many parts of it are very difficult to enter.

Blozan eventually discovered that the Cataloochee Valley has the highest average tree height—more than 160 feet—of any watershed in eastern North America. The Cataloochee contains more than 80 percent of the world’s tallest eastern hemlocks. It also contains the world’s largest yellow poplar and four of the world’s tallest white pines, including the tallest tree in eastern North America, a white pine that Blozan discovered in 1995 and named the Boogerman Pine. In January 2007, he found what turned out to be the world’s tallest eastern hemlock, growing in a cove in the Cataloochee. He and Jason Childs, another arborist, climbed it and measured it with a tape, and got 173.1 feet. Blozan named the world’s tallest hemlock Usis, which is the Cherokee word for “antler.” “The Cataloochee is the epicenter of the eastern hemlock species,” Blozan said. “The valley has the largest and best groves of eastern hemlock in the world.” In effect, the Cataloochee Valley is the Notre Dame cathedral of the eastern forests.

By the summer of 2002, the woolly adelgid had been found in the Cataloochee. Few national parks have a forester on the staff, but the Great Smoky park does: Kristine Johnson. Kris Johnson is a slender woman in her fifties with a calm manner. Since 1990, she has been managing the park’s efforts to beat back exotic invaders. “We currently have about a thousand sites in the park where exotic plants have gotten in, and we’re dealing with ninety different species of invading organisms,” Johnson told me—everything from Japanese stiltgrass to princess trees and fire ants. “We knew that sooner or later we would have the woolly adelgid. People around here have a saying: ‘All the trouble comes from the North.’ But we were still surprised by how quickly it got here.”

The parasite may have been carried to North Carolina by people. In the summer of 2001, state nursery inspectors began finding infested hemlocks in nurseries in western North Carolina. The contaminated hemlocks had been imported into the state from areas where the bug was a problem. North Carolina inspectors ordered the nurseries to destroy their infested hemlocks. This was a money-losing deal for a business. “A speculation is that less-than-scrupulous nursery owners were unloading infested material on their customers,” Kris Johnson said.

Now that the insect had arrived in the Great Smokies, what weapons were available to combat it? And how many hemlocks would need to be defended? It was clear that large numbers of hemlocks grew in Great Smoky Mountains National Park, but it wasn’t immediately obvious, even to Kris Johnson, roughly how many there might be. She and her colleagues estimated, finally, that there might be 300,000 to 400,000 large hemlocks in the national park, not counting smaller, younger trees. Most of the hemlocks were tucked away in wilderness valleys, far from roads or trails.

Oil spray—the treatment that helps smaller trees in urban yards—wouldn’t work in wilderness areas, where hundreds of thousands of large hemlocks would need to be drenched every year. There were two other promising options, though. Scientists at the University of Tennessee, funded in part by a private group, Friends of the Smokies, started a small lab for breeding a kind of lady beetle native to Japan that eats woolly adelgids. It was hoped that the beetles, released into the wild, would eat lots of adelgids, cutting down their numbers and eventually getting their population reduced to the point where hemlocks could survive the infestation.

Rusty Rhea, of the Forest Service, pushed the beetle strategy forward, and researchers began releasing the beetles. The lady beetles were tiny—the size of a sesame seed—and they initially cost about two and half dollars each; a cup of them cost thousands of dollars. When they were released at test sites, they had no measurable effect. But in 2007 (after years of test releases), a test in Banner Elk, North Carolina, in which different species of adelgid-eating beetles had been released over several years, had promising results. One type of beetle, from the Pacific Northwest, got established at the site and was eating adelgids, and the hemlocks there were looking better. Even so, there remained questions about whether and how quickly such results could be achieved on a large scale—if enough beetles could be bred and released and would multiply fast enough to save the hemlock forests that were dying or were under immediate threat. The beetles might work in the long run, but by then it might be too late for most hemlocks.

There was also an insecticide treatment, a chemical called imidacloprid, which is made by Bayer. Imidacloprid had to be mixed with water and injected into the soil around the root system of a hemlock. The chemical slowly moved into the foliage. When the adelgids sucked it into their bodies, they died. Imidacloprid is an artificial kind of nicotine. (Tobacco plants produce nicotine as a natural insecticide.) The injections were labor-intensive, but there was no good alternative: if imidacloprid was sprayed from the air, it would wipe out beneficial insects and wouldn’t kill many adelgids—the insect’s woolly coat sheds water.

The chemical had some advantages: it didn’t migrate much through soil, so it would not be likely to spread widely into the environment, and it degraded quickly in sunlight. However, it was a toxic compound that could kill many grubs in the soil near the tree, as well as other insects feeding on the tree. It did not seem to affect vertebrates—frogs, salamanders, birds.

“I wouldn’t want to see chemical treatment be the only way to save hemlocks, but nothing else is ready right now,” Blozan said. “Either you get some invertebrate kill around the treatment site or you get an ecosystem collapse—that’s the choice.”

As soon as adelgids were found in the park, the Forest Service and Bayer began seeking Environmental Protection Agency permission to use the chemical in wild forests (it had already been approved for ornamental and landscape settings). The park treated ten old-growth hemlocks, as a test. Will Blozan’s company, Appalachian Arborists, was hired to climb the trees and take samples of the foliage, to see how the chemical was moving through the tree. It can take a year or two for the benefits to become noticeable; some trees die anyway. “After treatment, the hemlock can look completely dead, but sometimes it will come back, and in three years it’ll be vigorous,” Blozan said. The ones that lived would need to be retreated every few years. The hemlocks would be like AIDS patients: they would never be free of the disease, though some might survive indefinitely on drugs. “What you get is a forest on life support,” Blozan said. “But at least it can be kept alive while we hope for a cure.”

Getting funding to fight the insect in the Great Smoky Mountains park was a byzantine process. The National Park Service, Kristine Johnson’s employer, ran the park, but the Forest Service had responsibility for controlling pests in federal forests, including the national parks. The Forest Service is in the Department of Agriculture, while the National Park Service is in the Department of the Interior. Funding for insect control competes with other Forest Service needs, such as fighting forest fires. And the Forest Service appears to concentrate its pest-control efforts on trees that have commercial value—it had spent more than $100 million trying to get the emerald ash borer contained—and hemlocks aren’t worth money.

Great Smoky Mountains National Park is the most-visited national park in the United States. More than nine million people pass through the park and experience its sights each year—that’s more than twice the number of people who visit Grand Canyon National Park annually. Now the primeval rain-forest habitats of the Great Smoky national park were under grave threat. In 2003, Kristine Johnson asked for and got about $40,000 from the Forest Service to save the hemlocks in the Great Smoky Mountains park. In the next few years, the Forest Service spent about $15 million on research into ways to control the adelgid, but it spent very little to actually deploy the weapons that were available. By 2007, direct Forest Service funding for the park to fight the bugs was only $250,000 a year, with private donations increasing the total somewhat.

“The government is so damned slow,” Blozan said. “Very little was done in the first two to three years.”

Then, just as the insects appeared in the Great Smokies, Charles Taylor, a Republican North Carolina congressman who was the chairman of the appropriations subcommittee in charge of the national parks, began seeking $600 million from Congress to build a highway across Great Smoky Mountains National Park. The park was next to Congressman Taylor’s district. Because the terrain in the Great Smokies was so rugged, the road would need to include three bridges, each likely to be longer than the Brooklyn Bridge—pork spanning a wilderness. Congressman Taylor argued that local residents would need to use the road and that it would bring jobs to his district. Environmentalists called it “the road to nowhere.” The road went places in Congress, which appropriated $16 million to develop plans for it. This slug of funding tended to squeeze out other congressional appropriations for Great Smoky Mountains National Park. And none of the road money could be used for controlling the insects. In 1988, when Yellowstone National Park was devastated by forest fires, the federal government spent more than $100 million trying to put the fires out.

At any rate, the staff of Great Smoky Mountains National Park did what they could with the money they had. In 2003 and 2004, park employees treated hemlocks near public areas with imidacloprid—trees in campgrounds and along roads but not those deeper in the woods. The next year, the chemical was approved by the EPA for use in forests, and Kris Johnson and her colleagues designated special zones, called “hemlock conservation areas,” where every hemlock would be treated. Will Blozan’s company, Appalachian Arborists, won a contract and put a crew of five to work, while another crew, of eight, went to work under a park forester named Tom Remaley. The conservation areas totaled two square miles; Great Smoky park covers eight hundred square miles.

The biggest problem was carrying the water needed to mix with the chemical. The crews collected water from creeks in jugs, put the jugs in backpacks, and rhodo-wrestled their way up the mountainsides. A crew could treat between a hundred and four hundred hemlocks a day. At that pace, saving all the hemlocks in the national park was simply not possible. (Bayer later came up with a sort of a pill containing imidacloprid that could be tucked among the roots of a hemlock. The pill doesn’t require water. As this is being written, the pill is being tested. If it works, crews carrying backpacks full of pills might be able to treat thousands of hemlock trees a day.)

In no other park were officials making the kind of effort that Great Smoky officials were. “Many other parks are ‘monitoring the decline,’ as I would put it, while they’re implementing control in high-public-use areas,” Johnson said. “I could put a hundred people to work treating hemlocks.”

The woolly adelgid had not yet arrived in Cook Forest State Park, in northwestern Pennsylvania, which contained some of the richest old-growth eastern hemlock forest. “These parks should have a plan ready, and at the first sign of adelgids they should execute their plan,” James Åkerson, the Shenandoah ecologist, said. A few million dollars—and a pill that works—would probably save the remaining fragments of old-growth hemlock forests. It wasn’t clear that the government cared to spend the money, though.

While the parks were waiting for Washington, Appalachian Arborists was hired to treat hemlocks on private property using the soil-injection method. The Reverend Billy Graham had thousands of sick hemlocks at his religious training center near Black Mountain, North Carolina; Will Blozan saved them. “If you don’t treat the tree, it will die,” Blozan said, “and then you’ll have to spend two or three thousand dollars having it removed.” He also began treating another species, the Carolina hemlock. A very rare tree, the Carolina hemlock occupies a narrow range, primarily in North and South Carolina, where it grows on dry, rocky outcrops, on the lips of gorges and clinging to cliffs. There were thought to be about 520 Carolina hemlocks in South Carolina. At last count, there were exactly twelve of them known to be in Georgia. The Carolina hemlock looks like something out of a Chinese painting. It’s a gnarled, wind-blasted thing with a mushroom-shaped top and downsweeping limbs flowing into space. Some of the smaller ones can be half a thousand years old. “The Carolina hemlocks are almost-beyond-words beautiful,” Blozan said.

The state of South Carolina hired Blozan and his partners to try to save the state’s 520 Carolina hemlocks, and the men treated nearly every specimen, often while rappelling down a cliff. Most of the Carolina hemlocks across the border in North Carolina were on national forest land, however, and were not being treated.

ONE DAY IN AUGUST, I drove into the Cataloochee Valley with Will Blozan to see what had happened. In the back of his jeep were backpacks full of ropes and tree-climbing gear. We followed a dirt road that switchbacked down into the valley. It was a lush place, lined with meadows at the bottom, rising into ridges and coves blanketed with forest. The forest was streaked with gray areas, as if smoke filled it. We parked in a meadow and put on our packs. It was a hot day, and clouds were piling over the mountains. Blozan looked around. “The truth is, I despise hiking,” he said. “I don’t do it unless there’s a tree to climb somewhere on the hike.” He wrapped a green bandanna around his head. We followed a trail that led into the woods along a creek called Rough Fork, crossing bridges made of single logs.

Big hemlocks, hundreds of years old, appeared. Sunlight seemed to blister its way through them. They were between 50 and 80 percent defoliated, but the national park crews had treated them, and many seemed to be alive, for now. “That one’s looking better,” Blozan noted, squinting at a hemlock that seemed half dead to me. He said that he had a map of the Cataloochee in his mind, with individual trees in it. “I’ve been all over these mountains. Even if I haven’t seen a tree in ten years, I still know exactly where to find it in a crowd of trees,” he said. “I’ve often wondered what a proctologist who’s passionate about his work thinks when he sees a crowd of people.”

He cut away from the trail, and we began bushwhacking up a slope. Here the trees were small, and patches of grass grew among them: the slope had been a cow pasture eighty years earlier. The slope ended on the knee of a ridge covered with rhododendrons. We followed the ridge upward, climbing steadily higher.

The trees got very big, and the forest seemed to get a lot darker. We had passed the edge of the old pasture and entered something like virgin American forest, a stretch of woods that had apparently never been logged. There were massive hardwoods—big yellow poplars, hickory trees, ash trees, mixed with an occasional sick-looking or dead hemlock. The ground was covered with all sorts of plants and shrubs—very high biodiversity, and the plants were all natives. No invading plants here. In various places there were woodland violets, early yellow violets, partridgeberry, masses of doghobble, wild lettuce, a lily called twisted rosy stalk, doll’s-eyes, and Dutchman’s-pipe. There was a brownish plant called squawroot that lives on rotting vegetation; bears eat squawroot in early spring after they come out of hibernation, and it purges their digestive systems.

The invaders were tiny or invisible to the naked eye. We passed hard, blackened stalks of wood: the remains of flowering dogwoods that had died a decade earlier from the invading dogwood fungus. Here and there stood rotting beech trunks and dead standing hulks called snags. The beech trees had gone almost extinct in this part of the Cataloochee within the previous five years. One small beech tree was still alive, its bark dotted with flecks of white fungus. This was the European beech fungus spread by a European insect. The beech tree was still alive, but it was doomed, and it was the last of its kind visible in that part of the forest. Here and there lay huge, moundlike, rotting cylinders of wood: the fallen trunks of American chestnuts, which had most likely died during the 1930s and ’40s, killed by the chestnut blight fungus, which drifted through in the air. Seventy years after dying, they still hadn’t rotted away. The forest was a palimpsest, telling stories of loss and change.

As we went along, I found myself rhodo-wrestling. The rhododendrons won, and Blozan moved ahead. He seemed to slip through them without much effort.

Higher up, we crossed the ridge and looked down into a cove. It was drained by a creek named Jim Branch. As we moved downslope into the cove, sunlight began to flood the area, and the air grew hot and ovenlike. Around and above us extended ghosts, hemlocks that had been treated too late and were dead or mostly beyond saving. The ground was covered with surging plants, coming up in the light, including masses of stinging nettles. I couldn’t see any adelgids; the parasites had died with their host. The air was filled with clouds of gray branches, like giant floating dust bunnies.

We stopped under a tall hemlock that glowed with green, a survivor in the cove. “This may be the healthiest hemlock in the park,” Blozan said. It was known as Jim Branch No. 10, and it was 150 feet tall. One of the ten experimental trees that the park had treated in 2003, it had been treated again in 2005.

Blozan pulled the end of a climbing rope out of his pack and tied it to a cord he’d left strung in the tree. He used the cord to pull the rope into the tree, and he anchored the rope, making it safe for climbing. When you climb a tree, you begin by climbing up a rope into the crown of the tree. This is because most trees don’t have branches near the ground that can be climbed on. The hemlock’s lowest branch was about sixty feet above the ground.

Blozan put on a helmet and a tree-climbing harness and began ascending along the rope, using rope ascenders—mechanical devices that grab a rope and enable a person to climb up the rope without slipping down it.

I put on my helmet and harness and waited, watching Blozan. He got into the branches and kept moving upward until I could barely see him. Then I started ascending the rope, using ascenders.

Sixty feet above the ground, with Blozan climbing above me, I stopped and stood on a branch. (I was still attached to the rope, so that I couldn’t fall.) Then I opened a bag and took out a complicated rig of ropes called a motion lanyard. The motion lanyard, also called a double-ended lanyard or a spider lanyard, is the principal tool used by some climbers for ascending to the tops of extremely tall trees, including hemlocks and redwoods. Here I will call it the spider lanyard.

The spider lanyard works much like Spider-Man’s silk. You dangle in the air from the spider lanyard, which is attached to branches over your head. While your weight is suspended on the lanyard, you move upward by flinging alternating ends of it over branches overhead, getting it attached to successively higher branches. With a certain technique, using certain sliding knots, you can raise your body upward through the air, suspended on the rope, without touching the tree, or you can lower yourself, or you can hang motionless in midair on the spider lanyard, with your feet and hands touching nothing. More often, though, you hang on it with your feet lightly braced against the tree, for balance. Your life depends on the spider lanyard. If it is incorrectly attached, it can fail or a branch can break, and you will fall to the ground. A skilled tree climber can move from point to point in a tree while suspended entirely on ropes, not touching the tree with any part of his or her body.

Blozan was climbing rapidly above me, moving from branch to branch.

The tree was filled with a spicy tang, the scent of green hemlock, and it was covered with living things. There were rare dark-brown lichens called cyanolichens, which fix nitrogen straight from the air. They fertilize the canopy of old forests. There were beard lichens, horn lichens, shield lichens, and one called ragbag, which looks like rags in a bag. There were small hummocks of aerial moss, spiderwebs, insects associated with hemlock habitat. There were mites, living in patches of moss and soil on the tree, many of which had probably never been classified by biologists. The hemlock forest consists in large part of an aerial region that remains a mystery, even as it is being swept into oblivion by Mrs. Dooley’s bug.

We stopped and rested at 130 feet. Blozan was standing on a small limb. “When these trees die, the nearby streams turn brown,” he said. “The water gets full of tannic acid. As long as I’ve been coming here, these streams were crystal clear. Now they look like they’re coming out of a bog.” Many insects and fish that live in hemlock streams, such as the stone fly and the brook trout, are also threatened by sunlight and heat pouring into stream environments that were once shady and cool.

Blozan loosened his rope and climbed straight to the top. I followed him, moving more slowly. We spent a while lolling in the top of the tree. A bird landed near my face. It looked at me, hopped toward me, and let out a string of territorial cries. It was a red-breasted nuthatch, a species that feeds in hemlocks. Birds don’t always seem to recognize a human in the top of a tree. Whatever this bird thought I was, it didn’t seem to like having me there. A ruby-throated humming-bird began hovering around us, seemingly attracted to my red shirt. It throbbed off into the distance.

From the top of Jim Branch No. 10, we could see that the forest canopy was a ruin. The crowns of the dead trees were still encrusted with living material—a hemlock rain-forest canopy without the hemlocks. It was a scaffold of lichens and other organisms. The trees that harbored them had died so recently and so suddenly that they were all carrying on, for the moment, as if nothing had happened.

WHEN IT BECAME APPARENT that the eastern hemlock might nearly cease to exist, Blozan and his partners founded the Tsuga Search Project, an effort to identify and measure the world’s tallest and largest eastern hemlocks before they were gone. They spent more than $100,000 of their own money on it. Brian Hinshaw, one of the partners, told me, “We just want to try to understand what we once had in these hemlocks.” In the Cataloochee Valley, Blozan walked into groves where he found what had been among the world’s tallest hemlocks. They were already dead, but he and his partners climbed the skeletons and measured them anyway. “The data are for someone someday,” he said. In October 2007, Blozan and one of his partners, Jason Childs, went into a cove in the Cataloochee to check on the health of the world’s tallest hemlock, Usis. Blozan had treated Usis with the chemical, and they wanted to see how it was doing. It was dead.

Three flagship species of migrating birds make their nests in hemlocks: the Blackburnian warbler, the black-throated green warbler, and the solitary vireo. In spring, they arrive in the Cataloochee before leaves come out on hardwoods; the evergreen hemlocks offer them cover, food, and a place to nest. No one knows what will happen to them when they arrive in the spring. Many other birds feed in hemlocks or nest in them, including the Acadian flycatcher, the Louisiana waterthrush, the winter wren, and the red-breasted nuthatch. The flying squirrel lives in hemlocks, and it feeds on fungi around their roots; the flying squirrel seemed to have gone into a decline. When an old hemlock falls, a world passes away. As for the Cataloochee Valley, most of the eastern hemlocks there were dead.