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Since early colonization of North America, new
species have been introduced at an ever increasing rate. These species have
arrived through a variety of pathways, including through the ballast of ships,
in the packing material of imported goods, and through deliberate import for
various uses. While most of these introduced species are beneficial or benign,
about 15% become invasive.
An invasive species:
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shows a tremendous capacity for reproduction and distribution throughout its
new home; and,
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also has a negative impact on environmental, economic, or public welfare
priorities.
Many introduced species do not show a propensity
to become invasive for several generations; so species we once thought were
beneficial, such as grass carp, European starlings, mute swans, and nutria have
demonstrated the characteristics of invasiveness long after their original
introduction. These and other species are proving difficult to control in their
competition against native species for food, shelter, water, or other resources
and their impacts on economic interests and human welfare. Without the disease
and predators that they contend with in their native lands, the spread of these
species can be epic in proportion and the effort to control them can reach
billions of dollars. The U.S. Fish and Wildlife Service estimates a potential
economic impact of $5 billion in the Great Lakes attributed to impacts of the
zebra mussel and attempts to mitigate those impacts. Zebra mussels have
virtually eliminated native mussels from the Great Lakes and altered the basic
food chain, threatening the availability of microscopic food for native fish.
What do we mean by native species? Generally, we
mean species of plants and animals that have evolved in the Chesapeake Bay
watershed and have developed mutually-sustaining relationships to each other over
geologic time. Certainly, some native species can become invasive when habitat
is altered and their particular needs are met on a much broader scale.
When ecologists talk about the impact of introduced species on native species and habitats, they mean that the introduced
species is reproducing and distributing itself so efficiently that it is out competing native species' use of the same habitats. Nature is in a very delicate
balance, much altered by humans, and the protection of remaining natural interactions between native species and their habitats are responsibility of
local, state, and federal agencies and all citizens.
With their highly efficient reproduction and use of new habitats, introduced invasive species can and have quickly eliminated native species from the landscape. In fact, over 45% of species
federally listed as endangered, rare, or threatened are being impacted by introduced species in the United States. On
Pacific Rim islands, Madagascar
off the coast of Africa, Australia, and Puerto Rico, introduced species are wreaking havoc on native species and severely altering their
habitats.
Introduced invasive species can include creatures such as viruses as well as large mammals and everything in between, including amphibians, reptiles,
birds, insects, plants, fish, shellfish, even
jelly fish. In Maryland, one of our primary concerns is the impacts of invasive plants on habitats that support rare, native plants and plant communities. These communities include shale barrens,
vernal pools, and peat bogs.
We are also concerned about:
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mute swans (Cygnus olor)
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nutria (Myocaster coypus)
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zebra mussels (Dreissena polymorpha)
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water chestnut (Trapa patens)
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phragmites (Phragmites australis)
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purple loosestrife (Lythrum
salicaria)
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wavyleaf basketgrass
(Oplismenus
hirtellus ssp. undulatifolius)
Also, included among species of concern are over 200 introduced species that
have viable, wild populations in the Chesapeake Bay watershed, recorded by the Smithsonian Environmental Research Center.
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Purple Loosestrife is Invading Our Wetlands
Can You Help Us Find It
and Remove It?
All of us can help to preserve and enhance opportunities for native species
to continue to thrive in Maryland and beyond. Find out what you can do to help
stop the spread of invasive species.
What YOU Can do to Help
Federal, Regional and State Support for Invasive Species Management
Message From A Former Secretary, Maryland Dept. of Natural Resources
Nutria
Economic Threats Posed by
Nutria
Read the Report
Chesapeake Marsh Restoration - Nutria Project Partnership
Mute Swan
Purple Loosestrife
Phragmites
Wavyleaf Basketgrass
Zebra Mussels
Invasive Species of Concern in Maryland
A comprehensive list of invasive species (animals, plants, insects and diseases) in managed and
natural aquatic and terrestrial habitats in Maryland, compiled by
the Maryland Invasive Species Council. This list
changes as conditions and knowledge change.
Fisheries Invasive
Species - Technical Memo No. 20
Water Chestnut
Maryland's
Ballast Water Management Regulations
Invasive and Exotic Species of North America Please
provide any comments, additions, and corrections you may have to:
Jonathan
McKnight
Associate Director, Habitat Conservation
Wildlife & Heritage Service
Maryland Dept. of Natural Resources
580 Taylor Ave., E-1
Annapolis, MD 21401
(410) 260-8539
Toll-free in Maryland:
1-877-620-8DNR, Ext. 8539
E-Mail: jmcknight@dnr.state.md.us
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