Originally aired during the week of August 28, 2000
You've seen them. You've admired them. Perhaps you've even planted them. But now they are displacing native species of plants at an alarming rate throughout the Connecticut River watershed. We're talking about "exotic invasive" plants and some of the names on the list might surprise you. For instance, some species of honeysuckle - like the Japanese and murrow varieties - are now more common than native types. Botanists identify about 3000 plant species in New England. Of these, about 1000 are considered "exotic" - they were imported (intentionally or accidentally) from Asia or Europe. Of this group, about 90 plants are considered pests, because they tend to grow very quickly and crowd out native flora. For instance, the native cattail is being choked out of many local marshes by purple loosestrife, a plant from Asia.
We can point to many non-native plants that have fit very nicely into the New England landscape without destroying native plants. Introduction of a non-native species can be considered part of its natural evolutionary spread. But we also know some of these plants can create a lot of havoc with native flora. Exotic invasives grow fast and can quickly cover a landscape. And they can disturb wildlife habitat. (For instance, some birds can't nest in the fields of purple loosestrife that are displacing the native cattail). More research is needed to help us understand changes in the ecosystem caused by exotic invasive plants. You can learn about other invasive species at a new exhibit now on display at Montshire. Montshire is an interpretive center for the Silvio O. Conte Wildlife Refuge, which is developing strategies for monitoring and controlling invasive plants.
Of about 1000 species of non-native pants growing in New England, only about 90 are considered "problem plants." These plants make many fruits and seeds, spread easily, and grow very quickly, crowding out native plants. Some of these so-called "exotic invasives" have gotten a boost from well-meaning gardeners. Goutweed, a leafy perennial native to Europe that makes hardy ground cover, is very hard to get rid of once it is established. The plant is now spreading into floodplain forests with seeds dispersed by water run-off. These forests are home to special communities of native plants, some of them quite fragile. Over the years, many of these forests have been converted to agriculture or altered by damming. Disturbed every spring by high water, goutweed and other invasive can overwhelm native plants in the remaining floodplain forest habitat.
You don't have to look hard to see evidence of exotic non-native plants gaining ground in the Connecticut River region. In many places, broad fields of purple loosetrife dominate areas that used to be populated by cattails. Exotic invasives crowd out native plants, and scientists are worried that decline in the health of native species may lead to less biodiversity. That is, fewer species of plants may lead to a more fragile habitat for other creatures. For example, several lakes and ponds in our region are threatened by Eurasian milfoil. The speedy growth of milfoil threatens native water plants and also cuts down on the amount of sunlight reaching the pond bottom. Submerged plants, fish and other aquatic life, may be affected. Addressing the threat to natural diversity posed by invasive plant species is a key priority of the Silvio O. Conte Wildlife Refuge.
Some exotic species of plants grow so quickly they crowd out and destroy native plants. One reason for the success of these "exotic invasives:" they left their natural predator back in their country of origin. Scientists have done controlled studies importing insects that feed on invasive plants like purple loosestrife. The process of using the plant's natural enemies against it is called bio-control. These "purple-plant eaters" seem to do a good job reducing purple loosestrife in limited areas. The release of the insects was approved after rigorous testing, to insure they did not feed on crops or native plants. At Montshire, you can see a new exhibit that features profiles of several plants on the "least-wanted" list. Montshire is an interpretive center for the Silvio O. Conte National Fish and Wildlife Refuge, which is developing strategies for monitoring and controlling invasive plants.
