The questions and answers below provide information on invasive plants that threaten the Southern Appalachian region.
To answer that question, let's talk about invasive species in general for just a moment. Because of growing concern for the damage caused by invasive species of all types, a Presidential Executive Order was signed in 1999 "to prevent the introduction of invasive species and provide for their control and to minimize the economic, ecological, and human health impacts that invasive species cause..." The Order defines an "invasive species" as any species that is alien to the ecosystem under consideration and whose introduction causes or is likely to cause economic or environmental harm or harm to human health. So, an invasive plant is one that has been introduced into an environment where it did not evolve, and thus has no natural enemies to limit its reproduction and spread. And its spread causes harm--both economic and environmental.
Humans are primarily responsible for the introduction of invasive plants, either accidently or intentionally. Accidental introduction occurs when they are inadvertently brought in as crop seeds, soil used as ballast, or in various imported plant materials. They can then spread into the wild.
Some invasive plant introductions have been intentional. European settlers brought plants with them to the "new world." They were used for food, landscaping, erosion control, or ornamentation. Some of these plant introductions were beneficial. For instance, almost all U.S. crop plants (corn, wheat, rice) are non-native. But, many introduced non-native plants were not so beneficial, and have caused major economic losses in addition to harming the environment. Once introduced, they are able to dominate because they may reproduce and spread prolifically, out-compete native species for resources, and have no natural predators.
Because they can displace native plants, reduce habitat suitability for native animals, spoil pastures for livestock, block forest regrowth, and clog rivers. Invasive species have the ability to crowd out native species and those that depend on them for food, shelter, and habitat. Some have brought about changes in habitat by accelerating fire cycles, altering soil fertility, and drying up water supplies. This impact of invasive plants on biodiversity is a major concern.
Already over 34 billion dollars is spent annually on controlling invasive species. Granted, much of this amount is used to control agricultural weeds, but that still leaves millions of dollars spent on controlling invasive plants. And, the problems associated with the spread of invasive plants are likely to become more severe due to population growth, the rapid movement of people, the alteration of the environment, and the increase in the trade of goods and materials among nations.
The Southern Appalachian Region, consisting of parts of seven states--Alabama, Georgia, Kentucky, North Carolina, South Carolina, Tennessee, and Virginia--is known worldwide for its exceptional variety of plants and animals. However, the balance and diversity of this mountain environment will decline as invasive plants continue to spread, impacting all the species that live here. For instance, the National Park Service (NPS) considers invasive plants one of the most serious threats facing national parks today. Estimates indicate that invasive plants infest 4,600 new acres of federal land each day. They can cause irreparable damage to natural resources, and efforts to control their spread are expensive and not always effective. Our own Great Smoky Mountains National Park is severely impacted. In all, more than 380 different kinds of nonnative plants live in the Park, and the NPS is actively controlling 50 of the most invasive. Their efforts are focusing on the prevention of new introductions, the eradication of present threats, and the restoration of native plants. In addition, they hope to increase public awareness of the damage that invasive plants can cause.
Problem plants vary from region to region. However, non-native invasive species do exhibit a number of characteristics, which include:
As plant expert Ketzel Levine points out, "...you know all too well when a plant's too good to be true. If it flowers fast and makes tons of seeds... tolerates drought, flood, sun and shade... sends out runners the minute you turn your back and shows up all over the yard... Give it up."