What is an Invasive plant? To answer that question we first need to define what Native, Exotic, and Invasive species are.
What is a Native Species?
What’s an Exotic Species?
What Makes an Exotic Species Invasive? (When is a Guest a Pest?)
|All organisms are native to planet Earth (until further notice) and each species of bacteria, fungi, plant, animal, and other creature has a home somewhere on this planet where it has existed and evolved for thousands of years. A native or indigenous species is one that occurs in a particular place without the help of humans, which is not always easy to determine. Species native to North America are generally recognized as those occurring on the continent prior to European settlement.
|An organism is considered exotic (alien, foreign, nonindigenous, non-native) when it has been introduced by humans to a location(s) outside its native or natural range. This designation applies to a species introduced from another continent, another ecosystem, and even another habitat within an ecosystem. European settlers brought hundreds of plants to North America from their home lands for use as food and medicine, and for ornamental, sentimental, and other purposes. introductions of exotic plants continue today and are increasing due to a large and ever-expanding human population, increased international travel and trade, and other factors.
|Many non-native species exist in apparent harmony in environments where they were introduced. For example, a relatively small number of exotic plants (e.g., corn, wheat, rice, oats) form the basis of our agricultural industry and pose little to no known threat to our natural ecosystems. The most important aspect of an alien plant is how it responds to a new environment. An invasive species is one that spreads and establishes over large areas, and persists. Invasiveness may be characterized and enhanced by robust vegetative growth, high reproductive rate, abundant seed production, high seed germination rate, and longevity. Some native plants exhibit invasive tendencies in certain situations.
How Many Plants are Invasive?
According to the Plant Conservation Alliance’s Alien Plant Working Group, about 1,050 plant species have been reported as being invasive in natural areas in the United States (see list of links). This represents an astonishing one-third or so of the exotic plant species established and self-reproducing in the wild. Some invasive species were planted intentionally for erosion control, livestock grazing, wildlife habitat enhancement, and ornamental purposes. Others have escaped from arboretums, botanical gardens, and our own backyards. Free from the complex array of natural controls present in their native lands, including herbivores, parasites, and diseases, exotic plants may experience rapid and unrestricted growth in novel environments.
Why are Invasive Plants "Bad"?
- Invasive species impact native plants, animals, and natural ecosystems by:
- Reducing native biological diversity
- Altering hydrologic conditions & flooding regimes
- Altering soil characteristics
- Altering fire intensity and frequency
- Interfering with natural succession
- Competing for native pollinators
- Repelling or poisoning native insects
- Displacing rare plant species
- Increasing predation on native birds
- Serving as reservoirs of plant pathogens
- Replacing complex communities with monocultures
- Diluting the genetic composition of native species through hybridization (source: "Weeds on Wild" NCIPC)
Invasive plants in Carrboro
For more information on the common Invasive Plants found in Carrboro check out our Presentation information and Resource Links. Carrboro strongly urges everyone to utilize native plants in your landscapes and to remove invasives when you find them. You can find information on the town's use of herbicides in the Integrated Pest Management Policy.
Some invasive plant species are very difficult to eradicate. Please contact your local NC Forest Service office for assistance with identification and eradication of invasives, and recommendations for native plant species to suit your needs. For more information on species specific invasives please visit our page with NC Forest Service leaflets.
Heather Holley, Town of Carrboro Stormwater Specialist: HHolley@CarrboroNC.gov
Laura Janway, Town of Carrboro Environmental Sustainability Coordinator: LJanway@CarrboroNC.gov