Definition: Invasive plants are introduced species that become aggressive when moved without their natural competition to a new environment. Kudzu is an example of a plant from Asia deliberately introduced to solve land problems in the '30s. Plants native to the United States can also become aggressive when moved to another region. Black locust is such an example.
Noxious Weeds: Plants designated as noxious weeds include invasive plants that compromise agriculture, harm humans, or degrade natural areas. Most States have a unique state noxious weed list to fit their needs. There is no national noxious weed list. Only a Federal Weed Seed list exists to minimize the transfer of certain weed seed of agricultural concern.
What's the Problem? Invasive plants impact our nation environmentally as well as economically at a cost of $23 billion annually according to a recent Cornell study. Invasive plants spread into another 4600 acres daily. This is not natural evolution; rather changes ramped up by increased global mobility. These changes are caused by human decisions. We must decide to make better choices with the future in mind.
What Are the Impacts of Invasive Plants?
* Contaminate or outcompete crops.
* Decrease forage value of rangeland and pastures.
* Displace valuable wildlife habitat.
* Eliminate waterfowl migration stops.
* Reduce property values and ability to acquire loans.
* Alter ground water reserves
* Change the aesthetics of the landscape.
* Degrade our natural heritage and educational value
* Threaten biodiversity and research value.
* Increase fire threats
* Compromise roadside visibility and safety.
* Attract wildlife to roadside
* Add to cost of roadside maintenance.
What Are the Sources of Invasive Plants?
1. Unintentional introductions via movement of products, packing materials, etc.
2. Erosion controls include plants like: kudzu, reed canary grass, Bermuda grass, crownvetch, and birdsfoot trefoil
3. Plantings of fast-growing windbreaks and hedge rows: autumn olive, privet, honeysuckles, buckthorns, and multiflora rose have impacted natural areas.
4. Unwitting ornamental introductionsÉ. Norway maple, Russian olive, barberries, etc.
5. Accidental movement by wildlife...garlic mustard, purple loosestrife, and most berried plants via birds.
6. Importation of topsoils to a project increases ragweeds, thistles, and sweet clovers,.
7. Ill-timed maintenance disturbances like blading, mowing, ditch dredging, bare-grounding increase weeds like kochia, foxtails, thistles, and milkweeds.
8. Use of forage mulches that have not been certified weed-free increase invasives.
9. Adjacent agriculture practices increase bindweed, many thistles, leafy spurge, knapweeds, and cheatgrass.
10. Bare ground spraying increases kochia, mullein, and more.
11. Commercial wildflower seed mixes often include invasive Dames rocket, oxeye daisy, and Queen Anne's Lace, etc.
12. Erosion control mixes often include aggressive sweet clovers, alfalfa, smooth brome, trefoil, perennial rye, etc. (photo on right)
13. Movement of construction equipment from a weedy site to a non weedy site.
14. Everyday vehicle air disturbances move seeds.
15. Tourists pick weedy plants or capture seeds in pant cuffs.
What Can Vegetation Managers Do? Note Pg. 19 for best management practices (BMPs).
Ten Invasives To Watch: Those causing huge consequences and moving quickly across the landscape include: kudzu, Canada thistle or thistles in general, knapweeds, leafy spurge, purple loosestrife, salt cedar, yellow star thistle, Russian olive/autumn olive, giant phragmites, and black locust. Other plants are climbing the charts and moving across the country: Ailanthus, common buckthorn, bush honeysuckles, pampas grass, Johnson grass, multiflora rose, garlic mustard, Siberian elm, privets, Japanese barberry, butterfly bush, crownvetch, cogongrass, reed canary grass, Japanese stilt grass, English ivy, and oriental bittersweet. Although some are unique to one region, all are capable of adapting to more regions as kudzu as proven from coast to coast.
Executive Order 13112: Signed in February of 1999, this Executive Order aimed at invasive species, asked all agencies to cooperate and communicate in a war on weeds. A National Invasive Species Council (NISC) was formed as a result. It is a watchdog and coordinating group advised by the best weed experts in the United States. It released a national management plan to assist each State in statewide management planning. Many States are forming their own State Councils or Associations. They will serve as liaisons between the NISC and their own State issues.
The FHWA sent guidance on EO 13112 to the field in the fall of 1999. The FHWA encouraged:
1. State DOTs to inventory roadside vegetation before developing plans.
2. no DOT project will be funded by FHWA if planting known invasives on it.
3. State projects will incorporate an invasives analysis in each NEPA process
4. States join interagency partnerships as in state councils and/or MOUs
5. increased funding of maintenance efforts, research, and training
How To Incorporate EO13112 Into NEPA Process:
What: During alignment studies, map invasive plant problems.
When: During predesign, preferably before rights-of-way have been purchased to allow for: a) not buying infested lands that will be costly to use, and b) consider an alternative.
How: Inspect project site and adjacent lands to map existing plants. Management recommendations and mapping should be part of the Environmental Impact Statement.
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This page last modified on August 4, 2004