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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. Gearing Up For The Fight As invasives continue their march, Cynthia Boettner has a daunting job. Boettner is part of a team whose task is to protect the biodiversity of the Silvio O. Conte National Fish and Wildlife Refuge, which encompasses 7.2 million acres in four states along the Connecticut River, most of it privately owned. Many of these landowners are not be actively involved and invasives are abundant. Resources, however, are finite. The team picks their fights. “Rather than trying to battle those species that are already widespread, knowing that it’s so labor intensive and costly, we’re putting a lot of effort towards a few species we can actually keep from becoming problems,” she says. At the top of the list is water chestnut, a plant that forms a thick canopy over slow-moving water as it grows, and, among other problems, blocks the sunlight from submerged plants. In this war, land managers also need to choose their method of warfare. They can pull by hand or machine, use herbicides, or attempt biological control. For Boettner, most of the time, getting volunteers to jump in a canoe and go out pulling water chestnut is effective. “It’s easy to grab a hold of and pull out, and because it’s large you can see progress quickly,” she says. “And this particular species is an annual, so if you can prevent that plant from producing seeds it’s dead, and it doesn’t cause any problems the next year.” Indeed, the water chestnut problem in the Chesapeake Bay is under control thanks to similar ongoing work. However, some plants, like Japanese knotweed, are extremely difficult to fully extricate from the ground. “You can cut it and remove it but ... the roots are deep and they spread really fast,” says Katie Holden, assistant administrator in the department of planning and land management for the town of Concord, Mass. “If you leave any, even a small fragment, then that would regenerate.” Also, ironically, pulling or cutting some plants, like the seemingly omnipresent purple loosestrife, when they are seeding can actually help spread the plant.
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Garlic Mustard. Photo by Randy Westbrooks.
