of mountain ecosystems. They offer critical habitat for birds. As many as 90 species can be found in hemlock forests. A few, mostly songbirds, seem particularly associated with hemlocks: the black-throated green warbler, the Blackburnian warbler and the Acadian flycatcher. Some warblers nest nowhere else. Hemlocks do best in moist ground and, while they are found from swamps to ridges, they are especially common along streams where they play a major role in stream ecology, helping to soften temperature extremes, creating structure in stream courses, offering a rich breeding ground for the invertebrates that fish feed on. In a study the U.S. Geological Service did for the National Park Service, researchers found: Hemlock-dominated watersheds supported more aquatic invertebrate (insect) species than streams draining hardwood forests. Fifteen aquatic insect species were strongly associated with hemlock and three species were found only in hemlock streams. Brook trout were two and a half times as likely to occur in hemlock streams as in hardwood streams, and were twice as abundant in hemlock streams. So if there are brook trout in your favorite mountain stream, thank a tree--most likely a hemlock. In all, according to some experts, hemlock forests are home to upwards of 120 vertebrate species as well. Hemlocks are a favored browse species for white-tailed deer, a dietary preference that can inhibit hemlock regeneration as deer nip off new growth.
How Does the Adelgid Spread and Kill? Winds can carry the pest. So can migratory birds, mammals and humans. Another source apparently is infected nursery stock. And the pest itself is prolific. All hemlock woolly adelgids are females and continue the cycle asexually. The annual increase in numbers is startling: one adelgid can lay up to 300 eggs and that will produce as many as 90,000 new adelgids in a single year. Generations of the pest inhabit the same tree. The hemlock woolly adelgid attaches itself to the base of hemlock needles and feeds on starch. That slows the growth of needles and causes them to drop, which in turn deprives the tree of nutrients. The crown thins and branches die back. Infected trees die in a surprisingly short time--5 to 10 years, some researchers say, as few as 3 to 5 years according to others.
Dire Comparisons…and Some Hope The disappearance of hemlocks promises both aesthetic and potentially devastating environmental consequences. Some analysts are comparing it to the chestnut blight, a fungus that struck in the early part of the last century and by 1940 wiped from the landscape an estimated 3.5 billion chestnut trees. The loss transformed the forests of the Southern Appalachians and the hemlock woolly adelgid is on a path to wreak a similar transformation. But forest science is much advanced since the chestnut blight struck and researchers from a variety of state and federal
agencies and universities are aggressively at work to stop the spread of the adelgid. Prospects range from pesticides, which are practical on individual trees or in small stands but are likely not much use in deep forests, to biological methods that could well work in the backcountry. In particular, two nonnative beetles that prey on adelgids--and only on adelgids--show promise.
Adelgids and the Nantahala-Pisgah Forest Plans As the research continues, though, hemlocks will continue to die. The question is what will replace them. To a surprisingly large degree, that is a matter of human choice: what do we want our forests to look like--to be and do--in the wake of the loss of hemlocks. Forest ecologists doubt that there is another single coniferous species that is ideally suited to replace the hemlock and its role in ecosystem health in western North Carolina. A likelier option is some combination of conifers chosen fairly deliberately to fill the void. Absent some such action, hardwoods are likely to claim the vacuum. These matters of choice are very much the province of the revised forest plans for the Nantahala and Pisgah National Forests.
Off-Road Vehicles: A Forest Service Chief ’s Prophetic Words Conservationists remember with considerable fondness the tenure of Mike Dombeck as Chief of the U.S. Forest Service. Among other things, Dombeck presided over the development of the Roadless Area Conservation Rule of 2001, a policy that aimed to maintain intact the remaining 60 or so million roadless acres on our national forests. In a series of speeches delivered after he left his agency post, Dombeck outlined what he termed the top 10 threats to the national forest system. “I believe off-road vehicle or all-terrain vehicle use will be the public land issue of the decade,” said the former Forest Service Chief. “We have more people going more places on public land more often, with more kinds of all-terrain vehicles than ever before. Many people want to go anywhere anytime with anything regardless of the impact on the land, water, vegetation or wildlife.” Dombeck predicted that bringing “support, order and agreement” to the use of such all-terrain vehicles (ATVs) and off-road vehicles (ORVs) on public land will be tough enough to make the “spotted owl issue look easy.” Reading Dombeck’s comments, it is difficult not to conclude that ATV-related problems will be coming soon to a national forest near you, if they aren’t already there…and they probably are. Numbers of off-road-vehicle (ORV) users in the U.S. have multiplied, rising to 36 million in 2000 compared to 5 million 30 years earlier. Some sources put the number of ATVs in North Carolina’s Mountain Treasures
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