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Invasive Plants. Monica Vernon Ecol 474. What is an Invasive Plant?. An invasive plant species is defined as one that has or is likely to spread and develop self-sustaining populations, and become dominant or disruptive.

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Invasive Plants

Monica Vernon

Ecol 474

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What is an Invasive Plant?

  • An invasive plant species is defined as one that has or is likely to spread and develop self-sustaining populations, and become dominant or disruptive.

  • Invasive plants interfere with ecosystem function and are a serious threat to biodiversity and productivity in different habitats.

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Also Known As

  • Invasive plants are also known by names such as weeds, and include adjectives such as alien, noxious, exotic, transient, or foreign, to name just a few

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Why Does it Matter?

  • Invasive plants are second only to habitat loss and degradation in endangering native plant species. They are also the second most serious threat to biodiversity in all ecosystems.

  • Negative effects of the invasive plants can be seen in many factors including competition for resources, hybridization, introduced or increased nitrogen fixation, and increased sedimentation among other things.

  • Invasive weeds in wetland areas cause problems for water resource managers, can inhibit drainage and interfere with intended uses for a body of water, and also provide a habitat for vectors of diseases. A recent estimate on the cost of invasive plants was put at $35 billion a year.

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  • Plants original uses were medicinal and agricultural, but over time with society acquiring more disposable wealth, they also became a hobby with ornamental gardening and experimentation. Experimental gardens, commercial nurseries, and international trade of plants and seeds flourished

  • Today’s interest in horticulture and plant exploration is one of the pathways of invasive plant introduction and spread. The United States has encountered various problems for over a century due to invasive plants, largely because of ornamental use or intentional introduction

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How are They Being Spread?

  • The Internet

  • Rarely differentiates between the plants that are invasive and those which are not.

  • Every aquatic plant that was listed on the federal or state noxious weed list was found on the internet. Because many are pretty and easy to grow there are problems with them being sold.

  • Easy access to the internet has increased the spread of invasive species. Species may now repeatedly, on larger scales than ever, be introduced to new areas

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How are they Being Spread?

  • Botanical Gardens and Arboreta’s

  • Usually more knowledgeable and have greater lengths of time in observation of plant behavior, issues still arise such as invasive species being mistaken for non-invasive and problems with a period known as lag time.

  • One may believe a new plant safe and noninvasive due to the fact it was observed for a period of time without displaying characteristics of an invasive plant, but many invasive plants do not begin to invade for many years. Lag time for many species has still not been determined. A few reasons for this is the fact some of the invasive plants only become invasive after changes in environment, genetic changes within the plant, or introduction of pollinator.

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How are They Being Spread?

  • Many Hobbyists/Nurseries usually don’t have the knowledge to recognize invasive species. Even those who have some knowledge of invasive species very often misidentify an invasive species for one they think to be safe.

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What Can Be Done?

  • The results of a recent study brought two main issues to the forefront. The first issue is that people need to know what exactly is invasive. Many stated if they knew about the invasiveness of a plant they would not be involved with a purchase. The second big issue that arose from the study was that the best way to inform and educate most people as to what plants are invasive would be to place a label on the plants in the nurseries

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What Has Been Done?

  • Environmental and economic damage continue to rise because of invasive plants. Though the United States government has made laws against importation of species listed in the Federal Noxious Weed Act (White 2001), there are still very few restrictions on importation of plants. We do not have screening for invasive plants before introduction, though Australia and New Zealand have already implemented such regulations (Hoddle 2001). Though President Clinton signed an executive order for an Invasive Species Council to be developed, little has still been done to reduce the harm invasive plants have caused previously or will cause in the future. Controlling the distribution of invasive plants has also been hindered because of the threat of conflict with international trade agreements (White 2001).

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What To Do:

  • If all groups involved work together to pool resources and stand up as a unified front, there will be a better chance for action. A national plan is needed that includes development of regulations, education programs, plant lists, and plant labeling (White 2001). A national plan, if implemented, will take much gathering of information, analysis, and cooperation between all involved. There must be effort to also locate and prosecute those who intentionally grow, sell, or distribute invasive plants (Kay 2001).

  • The best thing we can do as a country to prevent further damage is to start educating our citizens of the dangers of aquatic plants and their effects on ecosystems around the world.

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  • Hoddle, Mark S. “Restoring Balance: Using Exotic Species to Control Invasive Exotic Species”. Conservation Biology 18.1. (2004). 17 Septmber 2006

    <http://www.balckwell-synergy .com /links /doi/10.1111/j.15231739.2004.00249.x/pdf>

  • Kay, Stratford H., Steve Hoyle. “Mail Order, the Internet, and Invasive Aquatic Weeds.” J. Aquat. Plant Manage. 39:88-91 (2001). 14 September 2006


  • MacIssac, Hugh J., Robert J. Colautti. “ A Neutral Terminology to Define ‘Invasive’ Species”. Diversity and Distributions 10, 135-141.(2004) 17 September 2006

  • White, Peter, Sarah Hayden Reichard. “Horticulture as a Pathway of Invasive Plant Introductions in the United States”. BioScience 51.2(2001). 17 Septmber 2006>