Understanding the Problem
Understanding the problem
Frequently Asked Questions
What are Invasive Exotic Plants?
Where do they come from?
How do they get here?
How do they behave in their native lands?
Doesn't the addition of a non-native species
increase biodiversity?
Plants move around naturally –
Isn't their arrival part of a natural cycle?
Why should we care?
What You Can Do
People have been moving plants around Earth’s continents
for centuries. Plants have long been valued for their use
as food, shelter, medicine and ornamentation and have been
widely introduced to new areas intentionally so that we may
take advantage of the many benefits they offer. Additional
plant species have made their way to new places accidentally
in the ballast of ships, on machinery, and through various
other avenues of transport.
In most cases, exotic plants are not a threat to natural
communities and do not interfere with our use and enjoyment
of natural resources. Most introduced plant species have remained
an asset in our yards, gardens, agricultural lands and developed
areas. Among the many thousands of species intentionally introduced,
a few have aggressive growth habits that result in their invasion
into wild, unmanaged areas such as wetlands and woodlands.
Once established, these invasive exotic plants can significantly
disrupt habitats.
As a result, the plants can run rampant, out-competing native
plants for space, sunlight, and nutrients. Native plants keep
an ecosystem healthy and stable and are generally more beneficial
to wildlife populations.
Infestations of exotic plants may also interfere with navigation,
recreation, power generation, water suppy, production on agricultural
and range lands, and create public health and safely hazards.
The direct monetary cost of trying to control and alleviate
the negative effects of these plant pests are enormous, running
into hundreds of millions of dollars annually in the United
States.
Frequently Asked Questions
What are Invasive Exotic Plants?
Invasive exotic plants are non-native plants that invade and
alter both natural and managed areas. When invasive, exotic
plants reach new areas where they are free from their natural
predators they persist and proliferate to the detriment of
native plants and animals. It’s important to remember
that not all non-native plants are invasive and not all invasive
plants are non-native.
Where do they come from?
Most invasive plants come from other continents and countries,
but some, like the black locust (Robinia pseudacica)
are native to other regions of the United States.
How do they get here?
Accidental Importation: Some plants arrive accidentally
in air or water cargo. Purple loosestrife is thought to have
arrived in North America by seeds stuck to livestock. Boaters
can carry bits of Eurasian milfoil on their boat from one
lake to another and hikers can move garlic mustard seeds along
trails on their boots and clothes.
Agricultural Operations: Some of Vermont’s most
important agricultural crops, such as red clover, are exotic
plants. Plants like reed canary grass, however, are invasive
exotics that were brought to the US as hay for livestock.
Conservation Plantings: Conservation organizations
have also been responsible for the spread of some exotic plant
species. Bush honeysuckles were once planted in restoration
projects because ecologists believed them to be good habitat
and food for wildlife. Research now suggests that honeysuckle
berries are nutritionally deficient for wildlife and predation
increases on bird’s nests built in honeysuckles.
Aquarium Trade: Many of Vermont’s worst aquatic
invasive exotic plants were once prevalent in the aquarium
trade. Aquaculturalists who improperly dispose of their aquarium
plants into rivers, lakes and streams can inadvertently release
invasive plants into our waters.
Ornamental Plant Trade: Horticulturalists and gardeners
alike take delight in finding rare, new plants to display
in their gardens. Very few of these exotic plants move and
invade outside of their landscaped setting, but the few that
do cause great harm to our natural world.
How do they behave in their native
lands?
In their native habitats these species are often found in
small, well-behaved populations. This is because they occur
with other organisms, such as other plants, insects and diseases,
that keep the plant’s population in balance. When humans
import these plants from their native environment we do not
bring along all the other organisms that keep the plant’s
populations in check in the new area.
Doesn’t the addition of a
non-native species increase biodiversity?
Yes – if you are only concerned with the number of species
in the short term. Invasive exotic plants will become a “new”
species in an area but may also decrease the number of native
species found there as well. Purple loosestrife, now common
in many Vermont wetlands will, out-compete rare, native wetland
plants that are only found in Vermont or northern New England.
Local biodiversity may increase at the first arrival of these
plants but then plummet once the invasive exotics replace
the native plants. When this happens, global biodiversity
will decrease at the loss of the rare plant.
Plants move around naturally –
Isn’t thier arrival part of a natural cycle?
It is true that plants' populations will expand or contract
in their native ranges
as local climates change. This movement usually occurs slowly,
over periods of thousands of years. plants and animals will
also have time to adapt and change. We are concerned about
the invasions that humans have caused. When we bring non-native
plants, quickly and in large numbers, from far away geographic
areas the result is the decrease of our own native biodiversity
which does not have time to adapt to these rapid changes.
Why should we care?
Following habitat destruction, invasive species are the second
leading cause biodiversity loss around the world. Forty-two
percent of threatened and endangered plants and animals in
the United States are directly harmed by the presence of invasive
organisms. International, federal, state and municipal governments
spend billions of dollars each year to control and rectify
the harm caused by invasive plants.
What You Can Do
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