On native ground

Invasion: Many scientists see the rapid proliferation of alien plant species as a deep-rooted ecological problem.

October 05, 1999|By Alice Lukens | Alice Lukens,SUN STAFF

Brenda Belensky was driving by Long Gate Shopping Center in Ellicott City the other day when she noticed a patch of purple loosestrife and got a sudden urge to tear up the plants, every last one.

Belensky, natural resources manager for the Howard County Department of Recreation and Parks, has nothing against the European imports per se. In bloom, they have pretty magenta-colored spikes that attract bees and butterflies. But when she sees a sprig of loosestrife, she thinks about each plant -- each plant! -- producing as many as 2.5 million seeds a year, primed by years of evolution to spread and multiply and crowd out native American plants. And then her mind turns to all the other foreign plants that have similar tendencies, and the enormity of the invasion in the county and around the state, and her powerlessness to stop it.

Borne by wind, water and birds, aided by human ignorance, non-native, or "exotic," plants from Europe and Asia and Africa are spreading across the landscape. And scientists like Belensky say they have neither the money nor the manpower to stop it.

"Some biologists feel that non-native invasives pose the greatest threat to the ecosystem on the planet," Belensky said. "They are disrupting the ecology, replacing the natives, competing for light and nutrients. It's kind of like somebody stealing something without you even knowing it."

Nationally, non-native species cost the economy as much as $123 billion a year, President Clinton said in February after signing an executive order directing federal agencies to expand their efforts to combat the environmental threat.

Marc Imlay, invasive exotic plants committee chairman for the Maryland Native Plant Society, said that alien plants make up 30 percent to 90 percent of the ground cover in Maryland's parks. The areas that haven't been invaded, he said, stand out for their diversity; a dozen species of rare flowers and grasses might be in one plot. He said it might be possible to control three-fourths of the invasive exotics, but it would take 10 times the present effort.

"Therefore, the news is that our future is out there pulling them, spraying them, replacing them, introducing biological controls, conducting research on better methods of control, and preventing their introduction in the first place," Imlay said.

Belensky said she feels overwhelmed by the problem on 7,000 acres of Howard County parkland. "You do what you can," she said. "It's like triage."

She is most worried about a multiflora rose invasion at the old Smith Farm in Columbia, a kudzu patch at Rockburn Branch Park in Elkridge, a flood of purple loosestrife at the Font Hill community park in Columbia, and proliferating mile-a-minute and Tartarian honeysuckle at the Middle Patuxent Environmental Area in Columbia. She also has her eye on invasive garlic mustard, autumn olive, Asiatic stilt grass, tree of heaven, spotted knapweed, and tear-thumb.

Where to start?

Even the county flower, Queen Anne's lace, is a non-native plant, she said, though not a particularly invasive one.

"I'm trying to figure out where's the best place to start and how do we budget it," she said, adding that "there's not enough money in the world" to tackle the problem. The 2-acre purple loosestrife patch at Font Hill alone, she said, would cost $2,000 to remove -- and maintaining a loosestrife-free wetland there would require more manpower than she has.

Originally from Europe, the flower came to the United States in ship ballast and was also brought over for use as a medicinal herb. If left unchecked, it will crowd out indigenous wetland plants and form plots that provide little to no habitat for native wildlife. It is classified as a noxious weed in at least 19 states, but not Maryland.

State, volunteer efforts

The state Department of Natural Resources has two major programs to stem invasive exotics: one battling water chestnuts in portions of the Bird and Sassafras rivers, the other battling phragmites, or tall grasses, on the Eastern Shore in areas that abut the Chesapeake Bay.

Volunteers work at places like Rock Creek Park, Patapsco Valley State Park, Battle Creek Cypress Swamp in Calvert County, and Ruth B. Swann Park in Charles County. Imlay said volunteers are also organizing at Sandy Point State Park in Anne Arundel County and Wheaton Regional Park in Montgomery County.

Louisa Thompson, an Ellicott City master gardener and a member of the Maryland Native Plant Society, became so concerned about the problem last spring that she decided to start a volunteer conservation stewardship program in Patapsco Valley State Park. Since April, she has organized efforts to clear exotic invasives from different parts of the park.

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