Each
species in our environment – plants, animals, insects, etc.
– can be categorized as “native,” "exotic"
(or, “non-native,” “introduced,” “alien,”
“non-indigenous”…) or even a hybrid of the two. Species
also can be catergorized as “invasive.”
What
do we mean by these categories? Species that have been present
here in the northeast
USA
for thousands of years are considered “native” in this
region because of their long residence. They have been
resident here so long that other native species have adapted
to rely on them for food, shelter, and other needs. It’s
possible to learn which species lived in an area thousands of
years prior, by taking a core sample of the soil and
identifying the species of plants with remnants (i.e., pollen,
plant segments, etc.) present in that core sample.
“Exotic” species are those that arrived more recently,
having traveled from elsewhere in
North America
or even from other parts of the world. Native species have not
yet adapted to making full use of these species
Exotic,
invasive Purple loosestrife commonly occurs in
wetlands
and alongside highways.
A
species is considered “invasive” if it is very successful
at spreading through areas, via reproducing and outcompeting
other species. Both native and exotic species can be invasive.
However, it is the exotic, invasive species that are of
concern. Only a very small proportion of exotic species
becomes invasive. However, these exotic, invasive species
alter and degrade habitat for native species, reducing native
species biodiversity. Because of this, environmental stewards
attempt to control and reduce exotic, invasive species, such
as garlic mustard, carp, Japanese knotweed, and zebra mussels
to protect and restore ecosystems, habitat and native species
diversity.
NepRWA
Intern Emily traverses a wet meadow populated with exotic,
invasive Purple loosestrife.
Commonly,
what we consider to be "exotic" species here in New
England are species that were transported to
North America
since the European colonists arrived. Some of these species
were transported accidentally, while others were brought on
purpose. An example of accidental transport of an exotic,
invasive species might occur like so: Exotic plant seeds hitch
a ride on a person’s clothes when s/he is visiting another
country, then remain attached while the person travels back to
Boston, and later fall off outdoors here in Metro Boston when
the person goes for a walk. Then, the seeds grow into new
plants that reproduce. Note that this can happen in both
directions (e.g., a person visiting a similar climate
elsewhere in the world, such as in parts of China or even in
Oregon or Washington, can accidentally transport seeds from
Metro Boston, which then fall off and grow into exotic,
invasive populations there). Likewise, aquatic organisms can
flow into a ship, along with the rest of the water that the
ship takes on as ballast, while the ship is docked in a
foreign port. When the ship returns to its home port – or to
another port in another part of the world, that
life-form-filled ballast water gets dumped into the harbor to
lighten the ship for the new cargo. Now, the aquatic organisms
have another opportunity to feed and reproduce.
Some
people also purposefully transport their favorite plants and
animals from other countries and distribute these outdoors, or
propagate and sell them. Then, the species reproduce and
spread on their own.
Exotic,
invasive species are so successful because the growth of their
populations here is not controlled by the effective predators
and competitors with which they evolved in their home
territory. Although some native species may begin to feed on
the exotic species, they do not provide adequate control.
Also, some exotic species may have a growth advantage. For
example, some sprout leaves earlier in the spring than native
species, and even lose their leaves later in the fall. As a
result, the exotic species have additional time to grow, an
advantage in the competition to acquire space in which to
grow; to access nutrients, light and water; and to gain
exposure to pollinators and seed-dispersing wildlife.
What
You Can Do
Each
of us can offer native species a leg up in the competition
with exotic, invasive species:
When
walking, driving, biking or boating through areas infested
with exotic, invasive species, clean your clothing (including
shoes) and equipment before entering other areas, to avoid
spreading the seeds and plant parts elsewhere.
Wash
off your shoes and clothes after traversing an
area infested
with
exotic, invasive species. Prevent
spreading the problem.
Make
an extra effort to plant native plants in your yard, and
encourage your neighbors, friends and family to do the same.
These plants will provide habitat and food for native species. Learn
more.
Remove
and dispose of exotic, invasive plants, to prevent them from
spreading seed or re-rooting elsewhere. Learn to identify
and control exotic, invasive plants.
Projects
around the region can use your help. Contact your local
conservation group or land trust to offer your help. Help
NepRWA and the Massachusetts Department of Conservation and
Recreation to control exotic, invasive Purple loosestrife: http://neponset.org/Restoration-PLBiocontrol-VolOpps.htm.
Help DCR control exotic, invasive species. Contact DCR Natural Resources Specialist Alexandra
Echandi (617-727-4573
ext 219).
Volunteer
Beetle Rancher John participates in a Purple loosestrife
biocontrol
program in the Fowl Meadow wetlands along the Neponset River.
Two
species of Galerucella beetle
are
used to control exotic, invasive
Purple
loosestrife.
Resources
List
of exotic, invasive plants in
Massachusetts
: Massachusetts
Prohibited Plant List
List
of exotic,
invasive plants of
New England
Descriptions
and images of exotic, invasive marine
life
Identify
and control
exotic, invasive plant species
Examples
of a few exotic, invasive species found around the Neponset
River Watershed:
Garlic
mustard:
remove
& properly dispose
Japanese
knotweed:
remove
& properly dispose
Burning
bush
Japanese
barberry
November
3, 2011
