Invasive Species Tips

Spotted Knapweed (Centaurea biebersteinii)

The United States alone is estimated to hold approximately 200,000 different species of plants, animals, and microbes. However, since early colonization, over 500 native species have gone extinct, and many more have decreased to "vulnerable" population levels. The Nature Conservancy and the National Heritage Network took an inventory of 20,000 native-species, of which one-third were found to be at risk of extinction. Why? Invasive species such as Spotted Knapweed (Centaurea biebersteinii) certainly play a leading role.

An estimated 39% of all extinctions since 1600 have been due entirely to the introduction of exotic or invasive species. Though at first the introduction of new species may logically increase biodiversity, these non-natives who lack predators out-compete the native species for food, water, nutrients, and light.

The Spotted Knapweed is indigenous to Eurasia, and was introduced to the United States in the late 1800s. It was transported unintentionally as a containment of alfalfa and from soil used as ship ballast. It has since infested all of the United States (except Alaska), and has been reported "invasive" in the red-marked states. (see map)

The plant aggressively attacks pastures, dry meadows, flood plains, rangeland, and most other dry and sandy sites. It grows in the early spring, where it out-competes native plants for water and nutrients. Furthermore, grazing animals typically avoid eating spotted knapweed in favor of the native plants which heightens the weed's advantage. The plant produces seeds that remain viable for years, and are often transported by livestock, humans, vehicles, and contaminated hay.

Spotted Knapweed has many negative environmental and economic impacts, deeming its eradication extremely important. Small infestations can be controlled by hand pulling, though the taproot and crown must be fully removed. Long-term grazing by sheep and goats can reduce Spotted Knapweed's spread, and biological controls are often used for larger infestations. One study shows that biological controls in Montana have reduced Spotted Knapweeds seed production by at least 40%.

The fact remains, however, that preventing the spread of Spotted Knapweed is far more cost-effective than reacting to its infestations, and individuals can take make a difference! Reducing traffic through infested areas, cleaning footwear/backpacks etc. after hiking, using weed-free hay, and not grazing livestock in infested areas are all methods to reduce seed spread.

Text and Photo Sources:
www.nps.gov/plants/alient/fact/cebil.htm

www.invasive.org/eastern/biocontrol/13Knapweed.html

Kudzu (Pueraria lobata)

Kudzu was purposefully introduced from Japan in 1876 to curtail soil erosion and provide feed for livestock.  However, the plant now occupies 7 million acres and is often referred to as “the plant that ate the South.”  Other appropriate nicknames include “mile-a-minute vine” and “foot-a-night vine,” and the latter is no exaggeration.  The plant literally swallows forests, preventing other plants and trees from getting proper sunlight.  Once established, Kudzu grows at a rate of nearly 60 feet per season, translating into an astonishing 12 inches per day.

Invasive plants such as Kudzu are the primary culprit for causing species extinction and the resulting decrease in biodiversity.  Because of biodiversity’s vast aesthetic, ecological, agricultural, medicinal, and invaluable importance, it is critical that these invaders be eradicated.

Due to its sheer volume, getting rid of Kudzu is no easy task.  Consistent, close mowing may be effective, but the kudzu root-crown must be cut to immediately thwart its growth.  The entire root system does not need to be destroyed.

The crown is a fibrous knob of tissue that forms from underground vine nodes.  Vines exclusively grow from these crowns, and if any portion of the crown remains in tact, the plant has the potential to grow back.  In fact, kudzu is often spread during the eradication process because soil embedded with healthy crowns is often transported to a new location where the crowns then spawn new vines.

Public lands in our nation are being overtaken by invasive non-native species such as Kudzu at a rate of 4,600 acres a day.  Get involved in the nation-wide effort to eradicate invasive species on National Public Lands Day 2007!

Text Sources:
Wright, Richard T.  “Environmental Science”
and Wikipedia.org “Kudzu” http://en.wikipedia.org/wiki/Kudzu
Photo Source: Wikipedia.org “Kudzu” http://en.wikipedia.org/wiki/Kudzu

Garlic Mustard ( Alliaria petiolata )

In a normal, healthy ecosystem, there is a checks and balance system that prevents rapid overgrowth by any one species.  However, at the rate of nearly 4,600 acres a day, many public lands in our nation are being overtaken by invasive or non-native species, often originally enabled and introduced by human activity.  Alliaria petiolata or Garlic Mustard is a prime example.

Garlic Mustard was first introduced to the United States via Long Island, NY in the 1860s.  European settlers most likely brought the weed overseas for food, or medicinal purposes.  Since its introduction, the weed has spread from eastern Canada, south to Virginia and west to Kansas and Nebraska, bullying native species along the way stealing nutrients, light, moisture, soil, and space.  Spring beauty, Wild ginger, Dutchman’s breeches, Bloodroot, Hepatica, and Trilliums are all examples of native species that are struggling to compete with Garlic Mustard for these resources.  Additionally, White tailed deer prefer munching on native plants rather than Garlic Mustard, leaving no proper predator to curb the weeds’ exponential growth.  Instead, the deer help eliminate Garlic Mustard’s few competitors.

The tale of Garlic Mustard is not uncommon, and many ecosystems are in danger of being overrun with often irreversible environmental damage, as well as significant economic damage.  It is estimated that invasive weeds cost the United States 32 billion dollars annually through water contamination, soil loss, and decreased land values—to name a few.  This, coupled with the invaluable loss in biodiversity has constituted a state of biological emergency, according to Bureau of Land Management.   

There are many ways for citizens to get involved in the battle against invasive species.  Visit local public land managers and offer to volunteer.  Manpower is often the missing link!  Become familiar with the invasive species that affect your area and the techniques used in their eradication.   

If you are battling a light infestation of Garlic Mustard, hand removal can be effective.  Preferably when the ground is moist, pull the plant slowly to extract the main root that is deep in the soil.  For larger infestations, cutting the Garlic Mustard to ground level will help prevent seed spread.  With both methods, be sure to remove the pulled/cut plants from the area to prevent re-infestation.

This year, National Public Lands Day is dedicated to the eradication of these alien species.  Join us on September 29 to help mitigate the ill-effects of invasive species in your area!

Text Sources: BLM- newsletter – 4,600 acres a day http://www.nps.gov/plants/alien/fact/alpe1.htm
and Earth Gauge- Awareness Week- Economic
Photo Source: BLM- newsletter- 4,600 acres a day