AMC Outdoors, July/August 2006
Christopher Mattrick is worried. The plant ecologist for the 800,000-acre White Mountain National Forest (WMNF), Mattrick is rightly proud of the area’s diverse plant and animal populations. Certainly, a big draw for many of the forest’s six-million-plus annual visitors is the chance to see native species synonymous with New England, like the sugar maple, so brilliant in the autumn. “You travel here and think, ‘What a beautiful place, nature in its pristine glory,’ ” he says. “Many people think it’s a primeval woodland and it is, to a great degree, just that.” But the question that keeps the scientist up at night is just how long will it stay this way?
Mattricks’s main concern is invasive species: the hundreds of non-native insects, earthworms, and plants that are threatening the forest’s natural biodiversity. “We are on the cusp of invasion,” he says. “I can see a trend moving in that direction.” In fact, what’s bugging Mattrick is that he’s done more than simply observe the influx of exotic plants originally from faraway places-like Japanese knotweed and the Norway maple; he’s also helped chronicle it. And the news isn’t good.
Since 2001 scientists from the WMNF and the New England Wildflower Society have been inventorying invasive plants within the forest’s borders, as well as in adjoining areas. What they’ve found, says Mattrick, are about 2,000 infestations, most of them occurring in the disturbed areas that are prime breeding ground for all types of invasivesÑtrailheads, road edges, and power line corridors. Mattrick’s personal estimate is that the actual number of cases is 20 times greater.
The WMNF is hardly the only place struggling with the impact of proliferating invasive species. Across much of New England, and the rest of the country, native plants and animals are literally fighting for their lives against species originally specific to Asia, Europe, and other parts of the world. Spurred by globalization and the easy international movement of people and products-the New Zealand mudsnail recently discovered in the Great Lakes is believed to have been imported via ships’ ballast water-invasives, once introduced to a new ecosystem, lack natural predators. Because of this, they flourish.
While there are plenty of non-native species or “aliens” that enter new ecosystems with little impact, invasives also can have a devastating effect. The chestnut blight, caused by an Asian fungus, essentially wiped out the American chestnut, a tree that had been both an important part of the ecosystem and the economy. Dutch Elm disease, West Nile virus, and Hoof-and-Mouth disease are other high-profile examples of havoc that can be wreaked when invasives aren’t controlled.
The changes to the landscape are unmistakable. In Virginia, for example, The Nature Conservancy’s Brad Kreps says, “You could potentially, 10 to 15 years from now, be walking through a monoculture of garlic mustard.” Kreps, who works at the 7,000-acre Warm Springs Mountain Preserve and directs the conservancy’s Allegheny Highlands Program, adds, “If it’s left unchecked, it will spread-and it will out-compete natives for light and moisture.”
According to The Nature Conservancy, invasives are at least partly responsible for the decline of nearly half of the threatened and endangered species in the U.S. By the organization’s calculations, only habitat loss poses a bigger threat to endangered plants and animals.
Species On The March
A few years ago Nicky Pizzo, AMC’s senior interpretive naturalist at Pinkham Notch, took her workshop participants down to Glen, N.H., to show them a cattail marsh that had always been full of songbirds. She was shocked when she arrived. No cattails. No songbirds. “It was completely and totally taken over by Japanese knotweed. Within just two summers this plant completely out-competed all the native plants that grow there and now it’s the only thing there,” she says.
Diverse, thriving ecosystems of native species are being replaced by invasives all across the Northeast. And while the culprits, either plant or insect, vary their impacts, they share certain patterns. Perhaps the most disturbing are the ripple effects the dominance of an invasive can have on other species. The black and pale swallowwort, an aggressively growing New England vine that can flourish in sun or shade, grows to six feet tall as it entwines and chokes milkweeds.
Bad for the milkweed, of course, but as Cynthia Boettner, a coordinator with the New England Invasive Plant Group at the Silvio O. Conte National Fish and Wildlife Refuge, explains, the emergence of swallowwort (also known as “dog-strangling vine”) might be worse news for monarch butterflies, who mistake the plant for the milkweed on which they traditionally lay their eggs. “Confused monarchs sometimes lay their eggs on the swallowwort, and larvae that hatch from those eggs just die. They can’t survive on the swallowwort,” she says. “We fear this is a sink for the monarch population.”
Unfortunately, examples abound all over the Northeast. Pizzo describes glossy buckthorn, a dense shrub that often outgrows native trees and wildflowers. It strangles native plants, but it also can hurt birds. “It produces bright berries and because they are out-competing the other plants, sometimes they are the only option there for food,” says Pizzo. “Glossy buckthorn, because it branches very low, causes the birds to nest low and their nests are easily predated by other wildlife.”
Farther south, the tiny hemlock woolly adelgid is rapidly ravaging hemlocks, particularly in the southern Appalachians. A native of Asia, hemlock woolly adelgids can be easily spread, either by the wind, birds, or by human transport of infected trees. The insects, which look like tiny, fuzzy white dots, feed off the sap at the base of the needles, cutting off important nutrients. Typically, once a hemlock is infested with the woolly adelgids it will die within five years. And the impact the disappearance of the hemlocks could have is nothing short of dramatic. Their thick foliage keeps mountain streams cool, which is vital for trout, salamanders, and many aquatic insects. Hemlocks are also key nesting places for birds like wood thrush and warblers.
Next: Gearing Up for the Fight >>
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