The hunters were stalking their prey on a wooded path in Patapsco Valley State Park south of Baltimore, peering closely into the underbrush. But they weren't looking for animals.
The group of amateur naturalists was on a search-and-destroy mission for exotic plants that have invaded Maryland and are killing off native life. The problem of invasive species is drawing increased attention as globalization has brought more international trade, which has led to more seed-hopping from continent to continent.
Esther Quinn, a high school teacher from Catonsville participating in the plant hunt yesterday, pointed to a vine with razor-sharp pins prickling from its stem and lime-hued triangular leaves. It was a Devil's Tear Thumb - a plant from Asia that grows so fast it earned the nickname of "Mile a Minute."
"Evil little vines, evil," Quinn muttered.
It's not that they're evil, said Chris Brooks, the park ranger leading an educational tour yesterday called "Bad, Bad Plants" in the state park in Halethorpe. It's that a small percentage of non-native plants proliferate when they're transplanted into an area where they have no natural checks on their growth.
They outcompete local plants, steal all the sunlight and smother everything else, said Brooks. Because they're not part of the normal diet of local animals and insects, their monopolies can be deadly, he said.
The effort by state park workers and volunteers to rip out the invaders isn't a matter of xenophobia, Brooks said. It's an attempt to maintain the balance of life that allows insects to live in plants to which they're adapted, which allows birds and other native animals to eat the insects and have enough food to survive.
"We like seeing deer, chipmunks and other animals in our parks. But deer cannot digest bamboo leaves, for example," Brooks told the half-dozen local residents who joined him in an hourlong trek through the park. "We want the native plants, because they're easier for the native animals to eat."
Over the past four years, the Maryland Department of Natural Resources and local governments across the state have stepped up efforts to identify and kill the worst invasive plants, said Kerrie Kyde, invasive plant specialist for the state wildlife agency.
Nationally, about 5,000 exotic plants and animals are believed to be causing serious enough problems that they're classified as invasive. That's only perhaps 1 percent of species that have been transplanted here from Asia, Europe and elsewhere, according to experts.
