VOA标准英语2011--Non-Native Weed Threatens Northwest Clam

（单词翻译）

Non-Native Weed Threatens Northwest Clams²

The usual story of invasive species goes something like this: an exotic plant or critter hitches³ a ride on some incoming cargo⁴, alarm bells go off and an eradication⁵ campaign starts.
But now, Japanese eelgrass, a non-native seaweed showing up along America's West Coast, breaks that mold.
Willapa Bay produces more shellfish for American tables than any other inlet on the West Coast. Brian Sheldon's family has been growing clams and oysters⁶ on the tide flats here for three generations.
"These little holes here are all clams. I call this my college fund bed," he says. "I tell my kids, you go out and work that bed, because that's how you're going to college."
But, Sheldon jokes, the way things are going that's shaping up to be an inexpensive state school rather than a plush private college.
His clam¹ beds should be bare sand but Sheldon's acreage is being overrun by a green sea grass that really belongs on the other side of the Pacific.
"In the summer, this piece of ground here will be completely covered with grass," he says. "It kinds of sits in there and holds the heat in there in the bed and it makes the clams watery⁷ and weaker."
Sheldon calls it an infestation⁸ that has reached devastating⁹ proportions. Several neighboring companies have simply abandoned some of their clam beds.
"Our yields are down 40 to 50 percent, you know."
Marine¹⁰ biologists believe the Asian eelgrass was most likely brought to Washington State decades ago in shipments of oysters from Japan. The plant is also called Japonica or dwarf¹¹ eelgrass. It has spread north to British Columbia and south along the Oregon coast into California.
Shellfish growers want Japanese eelgrass declared a noxious¹² weed so they can spray herbicide or mow¹³ the invader¹⁴ down. California has already done so. To the growers, it seems obvious that Washington and its neighbors should do so as well. The sea grass is not native. It's causing a nuisance and there are control methods that work.
But not so fast, argue some marine scientists, state agencies and conservationists.
"In most areas of the world, these plants are highly protected. So in my mind, the ledger¹⁵ needs more examination," says Sandy Wyllie-Echeverria, a marine biologist with the University of Washington. "There are areas where Japonica has been shown to be a valuable resource and there are other areas where it is quite mixed."
In the Northwest, he says waterfowl like to eat the sea grass. A suite¹⁶ of smaller creatures probably lives and feeds in the vegetation. The eelgrass might also stabilize¹⁷ eroding¹⁸ beaches.
The Sierra Club also opposes eradication of the accidental colonist¹⁹, even though it's non-native.
"For two reasons; one, it is fish habitat. But more importantly, in their efforts to eradicate²⁰ Japanese eelgrass, there is a very high probability they could be eradicating²¹ native eelgrass," says the Sierra Club's Laura Hendricks. "That is something that would have a major impact on recovery of our fish species and the birds."
Caught in the middle is the Washington State Noxious Weed Control Board, which floats a possible compromise - list Japanese eelgrass as a noxious weed but only on commercial shellfish beds.
"It might not be the end-all, be-all solution that either side is looking for but what it does do is allow us to acknowledge it is a problem in one area, but it is not considered a problem in the other areas," says Alison Halpern, director of the panel.
Halpern's gotten some positive feedback, but not everyone's on board yet. Shellfish growers say it's a good start, but worry the plan could require them to fight the non-native sea grass into perpetuity.