Environmental police are moving today to poison a menacing colony of snakehead fish in an otherwise tranquil Crofton pond. Even if the predatory fish are wiped out, a larger struggle against invasive species will be far from won.
Maryland faces uphill battles with dozens of destructive alien organisms.
Multiflora rose, tree of heaven, Vietnamese stiltgrass, mile-a-minute, purple loosestrife, gypsy moths and garlic mustard might not seem as exciting as an air-breathing, ground-traveling fish that can grow to the size of a golf bag, but experts say they are changing the face of Maryland's landscape as they crowd out native wildlife.
On the ecologically fragile Chesapeake Bay, the oyster fishery has been dangerously depleted, in part by a parasitic disease called MSX that arrived in the region with Asian oysters in the 1950s.
Meanwhile, nutria, large rodents brought from South America decades ago to support the fur industry, are eating their way through the vast marsh that provides food and shelter for tens of thousands of waterfowl at the Blackwater National Wildlife Refuge.
Elsewhere around the bay, natural resource experts are struggling to limit damage caused by alien species as diverse as mute swans, phragmites and water chestnuts.
More trouble appears to be on the way by trains, boats and planes that carry countless containers across the nation and around the world into Maryland every day. State environmental officials are worried about 17 "red alert" species that are not established here but could hammer the state soon.
Among them are zebra mussels, which clog water pipes and boat engines; Asian longhorned beetles from China, which might wipe out forests; red imported fire ants, which pack an extraordinarily painful sting; spiny water fleas, which starve small fish and others up the food chain; giant salvinia plants, which congest lakes and ponds; and plum pox, a virus that can ruin peach orchards.
"It's a monumental challenge," said Glenn Therres, associate director of the Wildlife and Heritage Service at the state Department of Natural Resources.
In February, representatives of state, federal and nonprofit groups working together as the Maryland Invasive Species Council released an updated list of 75 invasive species of concern.
Some are regulated by state or federal law, while others are not regulated but made the list because biologists and natural resource managers recognize their negative environmental and economic effects.
Fast growers
Many non-native plants live peacefully in Maryland, including most of the area's food crops and popular garden plants. But some have proved aggressive, taking over parks, forests, yards and roadsides with their quick growth, efficient reproduction and ability to choke out other plants.
They displace native plants and leave little food or habitat for insects, birds and animals further up the food chain - including endangered species.
Invasive plants might also increase erosion, add to pollution in waterways and increase fire dangers as they replace less flammable undergrowth.
In a phenomenon she compares with the supernatural powers in the movie The Sixth Sense, Ellen Nibali, a University of Maryland horticulture consultant, sees unwelcome plant species destroying local foliage where other people observe green leaves and assume nothing is amiss.
"Once you are aware of it ... it's pretty amazing," Nibali said. "It sneaks up on you. ... In some areas, it is reaching a critical mass."
Foreign animals, fish and insects are also causing big trouble. They might have no natural predators here and might consume food sources, eat their way through valuable forests and disturb habitats.
Then there is an indirect impact when people can't enjoy parks and natural areas that might have cost millions of dollars to create.
Nationally, the economic loss from these invaders is estimated at $100 billion a year.
No one knows how much is invested in fighting back.
Maryland spent $1.8 million battling invasive species in 2000, according to the Maryland council. But many other agencies, nonprofit groups and individuals are spending untold millions more to attack invasives, from backyard gardens to large wildlife refuges.
Farmers are forced to spend time and money in efforts to keep invasive weeds from harming their crops, while fishing, cattle and timber industries take steps to limit economic harm from invasives.
A drop in the bucket
Examples such as the $4 million in state and federal money spent over two years to study nutria in Maryland, or the $10 million New York spent annually to reduce the number of sea lampreys in the Great Lakes, are a drop in the bucket, say environmentalists.
Marc Imlay, vice president of the Maryland Native Plant Society, said his and other groups support a bill in Congress seeking $900 million in federal matching funds for efforts across the country.
Although state and federal agencies have plans in place to fight several specific species, Therres said a broader approach is needed.
Agriculture agents are stationed at ports, examining incoming products. But modern containers are packed too tightly for each to be inspected thoroughly. As commerce has increased sharply, the problem has intensified, said Bill Gimpel, chief of plant protection and weed management for the Maryland Department of Agriculture.
Some invasive species were brought to the United States because people believed that they were attractive or useful additions to gardens and parks. Later, their dark sides were revealed, sometimes after they were loosed on the ecosystem through carelessness or the discarding of unwanted pets or potted plants.
The Maryland Agriculture Department checks nurseries and landscaping companies to be sure they are not spreading invasive plants. But Gimpel noted that he has just five people to examine 10,000 acres of nursery stock, so "we're spread pretty thin."
The state Department of Transportation recently joined the fight against invasives, targeting the fast-growing tree of heaven in the open spaces for which the department is responsible.
Volunteers pitch in
Parks and other natural areas, where Imlay said 30 percent to 90 percent of the land is covered by invasives, are on the front line in the effort to preserve native plants and animals. But it is a difficult job.
"You would have to have a monumental staff" to deal with all of the invasive species in a park, said Mark Raab, superintendent of the natural resources division of the Howard County Department of Recreation and Parks. His department is in the early stages of assessing the extent to which open spaces have been invaded.
Locally, volunteers have proved important - and cost-effective - in battling invasive plants. Small groups of concerned residents pull exotic plants regularly at Greenbelt National Park, Chapman Forest and Ruth Swann Park in Charles County, Brookside Gardens in Wheaton, Myrtle Point Park in St. Mary's County, Middle Patuxent Environmental Area in Howard County and other places around the state.
In a wooded area of her back yard in Howard County's West Friendship neighborhood, Nibali has taken responsibility for a small piece of the struggle. Using a weed cutter and her hands, she is removing multiflora rose and oriental bittersweet while preserving native Virginia creeper vines and encouraging new growth of native dogwood and oak trees.
After three years, about half of the area is open ground covered in beneficial leaf mold and dotted with trees, while the rest remains a tangle of unwanted bushes and vines. Nibali hopes native ferns and shrubs will move into the cleared areas, though they face extra pressure from deer that are eager to eat native vegetation.
"It's doable," she said. With education, "people can identify and remove invasive species."
But, for an extended effort such as hers, she said, "forever and ever, I'm going to have to watch these woods."
An inventory of alien species
The following is a sampling of some of the exotic invasives that threaten Maryland:
Gypsy moth (Lymantria dispar):Devastating to North American forests, the gypsy moth originated in Europe and Asia but was brought to the United States by a researcher hoping to breed it with other moths. It eats foliage from hundreds of North American plant species, particularly oaks and aspen.
Zebra mussel (Dreissena polymorpha): Native to Eastern Europe, zebra mussels reproduce readily, grow rapidly and travel easily by clinging to boats, trailers and water recreation equipment. They cling to surfaces underwater in clusters, clogging water pipes and boat engines.
Nutria (Myocastor coypus): Introduced from South America for the fur trade, this rat-like creature has a long tail and orange teeth. Large numbers have taken over wetlands, eating vegetation down to the roots and increasing erosion.
Water chestnut (Trapa natans): This aquatic plant from Eurasia has a rosette of floating leaves. Competitive and fast-growing, it fills up streams and lakes from top to bottom, making them impenetrable and blocking out light.
Mile-a-minute (Polygonum perfoliatum) Also called devil's tear-thumb, this trailing vine has light green triangular leaves and small turquoise berries. Native to Asia, it grows very rapidly - up to 25 feet a year - and smothers other plants.
Purple loosestrife (Lythrum salicaria): This European perennial has distinctive purple flower stalks. It is very difficult to remove or contain because one plant produces over 1 million seeds, and it can regenerate from roots or stem pieces.
Tree of heaven (Alianthus altissima): A rapidly growing tree native to China, the tree of heaven has smooth stems, pale gray bark and a strong odor. It can overrun other plants, creating a thicket, and its roots are aggressive enough to damage sewers and foundations.
Japanese/Vietnamese stiltgrass (Microstegium vimineum): This rapidly encroaching grass forms dense mats that displace native plants along creeks, floodplains, roadsides and fields. Native to Asia, it is lime green with silvery hairs down the middle of the blade.
Multiflora rose (Rosa multiflora): Originally desired to contain soil erosion and provide cover for wildlife, multiflora rose is a dense, spreading shrub that takes over open spaces. Native to Japan, it has thorns and white flowers and can reach 15 feet tall.
Phragmites (Phragmites australis): A wetland grass also called common reed, this plant produces thick colonies and pushes out other plants while providing little food or shelter for wildlife.