What is an invasive species?
Invasive species are plants or animals that cause damage to the ecosystems they inhabit. These species are typically introduced to natural areas and water bodies, intentionally or unintentionally, by people. Once in the wild, invasive species grow and spread out of control. As these species spread, they displace native plants and animals, alter critical ecosystem processes, and degrade wildlife habitat. Invasive species are typically not native to the places they invade. Non-native or exotic species can become invasive because outside of their native range because they don’t have predators, pathogens, or other natural/evolutionary forces to keep their populations in check. Invasive species are not undesirable simply because they are non-native or exotic. Rather, it is the negative ecological and economic consequences of invasive species that make them a conservation concern. The above photo is garlic mustard (Alliaria petiolata), an invasive woodland herb. (Photo Source: David Cappaert, Michigan State University, Bugwood.org)
Characteristics of invasive species
Invasive species are characterized by high rates of reproduction and dispersal. Invasive plants are typically prolific seed producers, and tend to spread vegetatively, regularly sending up new shoots from roots and rhizomes (underground stems). Phragmites or common reed (photo left) is an invasive wetland grass which produces an abundance of seed and also spreads through an extensive system of roots and rhizomes. (Photo source: John M. Randall, The Nature Conservancy)
Invasive species are habitat generalists, meaning that they are tolerant of a wide range of environmental/habitat conditions. Invasive plants tend to do especially well in areas that have been disturbed by humans.
Many invasive plant species have a longer growing season than native species. They can leaf out earlier in the spring and go dormant later in the fall, giving them competitive advantage over other species. Japanese honeysuckle (photo right) is a broad-leaved evergreen vine that covers and strangles native shrubs and trees. It will continue to grow through the winter months while native trees and shrubs stand dormant. (Photo source: Jil M. Swearingen, USDI National Park Service, Bugwood.org)
Controlling invasive species
To help protect biodiversity and preserve the health and integrity of our remaining natural ecosystems, it is often necessary to control invasive species. Invasive species management has become integral to the practice of ecological restoration and nature conservation.
There are four standard methods for controlling invasive species: mechanical, chemical, cultural, and biological. In the case of invasive plants, mechanical methods include pulling, cutting, mowing, or burning. Chemical control involves the use of pesticide. Biological control involves the introduction of a predator, pathogen, insect, or herbivore that feeds on the invasive species to keep the size of the population of that species in check. Cultural control involves the modification of human behavior to prevent the introduction and spread of invasive species. For example, choosing not to use invasive plants in one’s garden can help prevent the introduction and spread of invasive species. Preventing the introduction of invasive species is the most effective method of control.
FOR takes an integrated approach to invasive species management. Integrated pest management is an economical and environmentally-sensitive approach to managing weeds and pests. The methods of controlling the weed or pest are determined based on a thorough understanding of the ecology and lifecycle of the pest, the costs involved, as well as careful consideration about the hazards to people, property, and the environment. If you are interested in helping control invasive species at FOR, click here.
Or click here for our 2009 Weed Warriors schedule
Click the download link below for more information about specific invasive plants found in the Rappahannock watershed.