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| Invasive
Plants |
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With
the increase in world travel and trade the opportunity for certain
aggressive species to spread themselves throughout the globe has
dramatically increased. There is no longer any true biological
separation of the continents. We are creating a sort of biological
Pangaea – the ancient "super continent" that scientists
believe once included all of the land on Earth.
What
is happening worldwide is an increase in certain problem species
on many continents. These aggressive species may be the stimulus
for a new wave of evolution – hybridizing with native species
on each of the continents – potentially creating a somewhat
homogenized world flora.
In
the past invasive species have often been thought of only in
terms
of their economic threat – their effect on agriculture,
ranching and industry. This is where most of the effort to
control plant pests has been focused.The ecological threat
to our natural communities, however, is equal to the economic
threat posed by these species. Today we are at a turning point:
many
government
agencies, private conservation organizations and even such
powerful political lobbies such as the National Rifle Association
and
Ducks Unlimited are taking notice of the effects of invasives
on natural communities and undertaking efforts to stop this
invasion. What follows are a series of thoughts and facts on
invasive species
as a group. This list is not complete nor is it comprehensive,
but it can make you aware of some of the most important facts
regarding invasives. CLICK on the links below to learn more.
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| WHAT
IS AN INVASIVE PLANT SPECIES? |
- Native
Plant – a
species that reached its location without
assistance from humans.
- Exotic
species – a
non-native plant or animal introduced into a new location
by human activity, either intentionally or by accident.
- Invasive
species – a
non-native (adventitious) species that is capable of
moving aggressively into a habitat and monopolizing resources
such as light, nutrients, water,
and space
to the detriment of other species.
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| HOW
DO INVASIVE SPECIES GET HERE? |
- Horticultural
activity is responsible for about 60% of invasive species
introductions (arboretums, botanic gardens,
gardeners).
- Conservation
activities (Soil Conservation Service, Department of Agriculture)
introduced about 30% of invasive plants, mostly for screening,
windbreak, and erosion control, but also to supply food
and cover
for wildlife.
- Accidental introductions
make up the remaining 10%. For example, purple loosestrife
was first brought to the U.S. in the hold of a ship via
ballast water, then later introduced for horticultural
purposes).
- Some species
may be native to certain regions of North America
where they are not invasive, but arrive in new regions through
assisted range expansion or transportation
to other parts of the country for ornamental purposes,
where they can become invasive (black locust, for
example).
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| WHY
ARE WE CONCERNED? |
- According to
the North Carolina Botanical Gardens "Biota of North America"
study, at least 4,000 species of non-native plants occur
outside
cultivation in the United States. Most of these escaped
species cause few problems, but 79 species cost
the U.S. economy more than 97 billion dollars annually in lost crops,
failed recovery efforts for endangered species, and control
efforts.
- Invasive species
have contributed to the decline of 42% of U.S. endangered
and threatened species, and for 18% of U.S. endangered
or threatened species, invasives are the main cause of
their
decline.
- Invasive species
compete directly with native species for moisture, sunlight,
nutrients, and space. Additionally, some studies suggest
that the fruit produced by invasives may not be as nutritious
for local wildlife, requiring them to eat more frequently.
Fruits and seeds of invasive species are the "junk
food"
of the natural world.
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| WHY
ARE INVASIVE SPECIES SO SUCCESSFUL? |
- Most
species have predators in their natural range that
keep their population numbers in check. When new species
are introduced, however, they come
without their natural predators.
- Most
invasive species produce copious amounts of seed. This
seed is often bird- or wind-dispersed, allowing it to cover
great distances in a short period of time.
- Some
invasives have aggressive root systems that can spread
long distances from a single plant. These root systems
often grow so densely that they smother the root systems
of surrounding vegetation.
- Some
species produce chemicals in their leaves or root systems
which inhibit the growth of other plants around them.
- Most
invasives cast extremely dense shade beneath which native
vegetation can not survive.
- Most
invasives thrive on disturbed soil, such as that around
newly developed land, or along highways.
- As our region
becomes more fragmented, through development, local habitats
become more vulnerable to invasives.
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| WHAT
CAN WE DO? |
- Many private
organizations and government agencies are beginning to
look at this very serious environmental
problem, seeking solutions. It
appears that areas with intact, highly diverse, or complex
systems are more resistant to invasion and dominance by
exotic
species, so increased protection of areas of natural diversity
is one way to defend against species loss to invasives.
- The first step
is to prevent any additional, potentially invasive introductions,
because once they gain a foothold they are costly and time-consuming
to control.
- Monitoring and
early detection of new infestations is imperative. Invasive
species outbreaks are most easily controlled when they
are small and the plants are young.
- If we can not
achieve total control or eradication, we must learn to
manage invasive species populations to restrict size and
spread, and
prevent them from establishing new populations.
- Finally we must
take an active role in returning our native vegetation
to areas where invasive species have been eradicated. Removing
invasives without restoring our native flora only opens
the site up for re-colonization by the invading force.
- In addition to
supporting organizations that are trying to understand
and control invasives, individuals can consider landscaping
with native plants, and inform others of the problem.
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Resources & Links
Publications:
NEWFS staff and volunteers, as well as a number of other
agencies, have produced publications and articles on invasive
plant species. To view some of these online, visit the links below.
[Note: most
of these documents are presented in Adobe Acrobat (PDF) format.
Many of them are large files that may take a long time to download.
For these, we recommend a high-speed internet connection (cable,
DSL). You may wish to download the files to your own computer
for faster viewing in future. SEE BELOW for
more information on how to open documents in Adobe Acrobat.]
Websites:
- Invasive
Plant Atlas of New England (IPANE)
The Invasive Plant Atlas of New England is a web accessible atlas of
invasive plant species for the New England area, with a concentration
on the state of Connecticut. The site contains information and descriptions
for nearly 100 plants suspected of being invasive in New England. Information
on distribution, synonomy, identification, and biology is provided. CLICK
HERE for more information. A specimen database may also be viewed.
- Links to
State Invasive Groups
These sites contain the most up-to-date information on invasive species
legislation and/or lists for each of the states listed.
- These additional
sites have good information on invasives identification and
control. You may have to search further on their
sites to find this information.
- Websites
with many other links to sites containing information on
invasive species:
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| * NOTE: To view Acrobat files, you will need to have installed
the free Adobe Acrobat reader which can be downloaded at the Adobe site. CLICK
HERE to visit Adobe download page. If you have any difficulty downloading
this document, please contact webmaster@newfs.org |
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