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Invasives threaten N.Y.'s natural order - 28 September, 2009
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Michael Risinit
The Journal News
Lower Hudson edition
mrisinit@lohud.com
In the 1997 movie "Men in Black," the characters played by Will Smith and Tommy Lee Jones work for an agency monitoring and managing alien activity on Earth. Their charges include a host of not-of-this-world creatures: worms that make a nice cup of coffee, large insects that drink sugar water and human-looking individuals blinking two sets of eyelids.
Of course, in the real world those don't exist (as far as we know, anyway). But other interlopers do, such as swallow-wort, zebra mussels, Chinese mitten crabs and northern snakeheads. They are among some 4,000 or so species in the United States that are both non-native (alien) and damaging to their new digs. Be they animal, plant or pathogen, such beings are called invasive species.
As a threat, invasives have been judged second only to habitat loss when it comes to a region's biodiversity - the abundance and variety of living things. Northern snakeheads, originally from China, can wipe out native fish populations. Chinese mitten crabs can be bad news for the Hudson River's blue crabs, and their burrowing can destabilize stream banks and earthen dams. Swallow-wort, imported from Europe, is a menace to monarchs. The butterflies are fooled into laying eggs on a plant that cannot support their offspring.
There's no official list yet of the dozens of invasive species calling New York home. But there's a definition. An invasive species is "non-native to the ecosystem under consideration, whose introduction causes or is likely to cause economic or environmental harm or harm to human health," according to the Final Report of the New York State Invasive Species Task Force. That harm "must significantly outweigh any benefits," the 2005 report said.
Government and private organizations are trying to eradicate or control the ones here - mile-a-minute vine, golden nematode - and keep others at bay.
The plants, insects, diseases and fish that shouldn't be here, but are, can be the stuff of bad dreams. Ed McGowan, a science director for the Palisades Interstate Park Commission, is part of a Lower Hudson Valley coalition addressing the threat of invasive species. Where others "see greenery, scenery," he sees trouble for the region's natural order.
"I should (have nightmares), but I don't remember my dreams," McGowan said on a recent, thunderstorm-threatened afternoon.
One of his current battles is with mile-a-minute weed, a kudzu-like vine capable of growing more than 20 feet in a year. It forms dense mats, chokes out native vegetation and can kill trees. The plant, a native of eastern Asia, was accidentally introduced in the 1930s when it hitchhiked with nursery stock. His weapon? Goats.
Two goats, on loan from the Glynwood Center in Philipstown, spent much of their summer on Stony Point's Iona Island, a former military complex now part of Bear Mountain State Park. The vine with triangular leaves and barbs wasn't their first choice to munch on, McGowan said, "but they got to it eventually."
"It involves a lot of management. You need fences. You need to be concerned about coyotes in this area (who could decide to dine on the goats)," McGowan said as an osprey flapped above the nearby Hudson River.
The pair were charged with eating the plant into submission, which the goats did until they were relocated to another enclosure. That happened every 12 days. The goats left their former pens as smooth as putting greens, McGowan said. But shortly afterward, the areas were again lush with mile-a-minute.
Sheep, instead, were on duty at Ward Pound Ridge Reservation in Cross River. There, they were shepherded among several plots every three days. Their periodic return seems to keep mile-a-minute vine in check, compared to the goats' eat-it-and-leave-it approach.
Their reappearance, said Gary Kleppel, an Albany University, SUNY, professor, and his graduate student, Caroline Girard, mimics the behavior of deer and other plant-eating animals that would intermittently pass by and dine. Native grass was starting to sprout in once mile-a-minute-only territory.
"These two plants are in a desperate battle for dominance," said Kleppel, director of the school's Biodiversity Conservation Program. "If you take its (mile-a-minute) edge away, look what happens."
Not all non-native species are invasive. Corn, for example, was developed in Mexico and Central America and brought to this country by Indians. It needs human cultivation to survive. But animals and plants have been jumping borders and countries since humans first wandered the globe. Explorers and early settlers carried some invasive species to the New World, such as various earthworms and rats. Globalization and more international trade, though, have increased the invasion rate.
Emerald ash borers, a beetle whose larvae can wipe out ash trees, probably arrived in the United States on wood crates and pallets aboard cargo ships or airplanes coming from its native Asia. It was found this year in western New York.
The round goby, a fish native to the Black and Caspian seas, competes with and preys on native fish. It has been found near Buffalo and Rochester, most likely descended from those that hitched a ride in ships' ballast water and were discharged into the Great Lakes.
"It's hard not to answer 'all of them,' " said Steve Sanford, director of the state's Office of Invasive Species Coordination, when asked which invader he worries about most.
His office is to send a report to the state Legislature by January listing New York's invasive species and how to deal with them.
"More and more, society is realizing all the harm that comes from invasive species," he said. "When it upsets the balance, usually the system functions to a certain degree, but certain things are going to be lost. It depends on how much you value biodiversity."
Along with reshuffling nature, those invading plants and animals carry a financial impact. The annual cost of invasive species to the U.S. economy is about $138 billion, according to the federal government, including agricultural losses, infrastructure damage and management costs. Zebra mussels - small mollusks originally from Russia - alone account for about $270 million in economic damage in North America, said Dave Strayer of the Cary Institute of Ecosystem Studies in Millbrook in Dutchess County. He characterized the figure as an underestimate.
He and his colleagues have been studying zebra mussels in the Hudson River since their appearance in 1991. The thumb-size shellfish can clog water pipes and power-plant intakes.
"Zebra mussels came into the river and turned it upside down. In the last few years, we've seen evidence that parts of the river are coming back," Strayer said.
The mussels upset the river's food chain by sucking out much of the phytoplankton - the tiny plant life - upon which other river creatures depend. Recently, Strayer and fellow scientists have found fewer older and bigger zebra mussels in the river, leaving them to wonder what's causing the change. While the future of zebra mussels in the Hudson plays out, he said, the average person's concern should be about invasive species in general. More needs to be done to focus attention on the issue, Strayer said.
"Let's stop it. Let's do better," he said. "We've been very slow in coming around to controlling invasive species. But we're not taking this problem seriously enough."
Learn more:
For more information about invasive species, visit the New York Invasive Species Clearinghouse at nyis.info or the U.S. Fish and Wildlife Service's site at fws.gov/invasives/index.html.
To learn more about the Cary Institute of Ecosystem Studies and its invasive species work, including zebra mussels, go to www.ecostudies.org/IES_invasive_species.html.
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