Human Impacts-Introduced
Species
What Are They?
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Species humans bring to a new ecosystem
Can be intentional or unintentional
New ecosystem is probably not ready
New species can dominate in ecosystem
lacking natural predators
• Outcompete native species in their niche
Stink Bugs
• 1988-Introduced to US from East Asia in
shipping crates
• First seen in Allentown
• Pest Insect
• Produce Large Populations
• Resistant to Pesticides
Stinkbugs (cont’d)
• Outcompete native insects who do not resist
pesticides
• Feed on crops such as cotton, corn, soybeans,
and shrubs
• No natural predators
• Release unpleasant odor when threatened
Zebra Mussels
• Native to streams in South Russia
• First seen in North America in Great Lakes in
1988
• Have natural enemies in Europe, but not
North America
• Invasive in North America, Great Britain,
Spain, Ireland, and Sweden
Zebra Mussels (cont’d)
• Introduced to North America by ocean-going
ships
• Since introduction, have spread far
• Cost to manage in Great Lakes is over $500000
per year
• Outcompete native animals for food
• Can suffocate other clams and mussels
• Possible source for deadly avian botulism
Kudzu
• Introduced to US from Japan in 1876 in
Centennial Exposition in Philadelphia
• Introduced to Southeast shortly thereafter
• Marketed as ornamental plant, cow feed, and
to prevent oil erosion
• When left unattended, it spread quickly and
became a weed
• Covers 7400000 acres in the US
Kudzu (cont’d)
• Native to China where colder climate controls
it
• Controlled in US through mechanical,
biological, and chemical methods
• Mechanical: Cutting it back, which is time
consuming
• Biological: Bacterial blights and insects
• Chemical: Herbicides and soil solarization
Cane Toad
• Originated in Central and South America
• Introduced to Caribbean islands, Pacific
islands, and Australia
• Australia was particularly susceptible due to
its distinct, isolated, ecosystems
• Introduced to Australia to control cane beetle;
failed
• Spread rapidly: 1935-about 100 toads NowOver 200 million
Cane Toads (cont’d)
• Australian predators cannot handle toxin
produced by toad
• Some predators try to eat them, resulting in
less biodiversity for the predator species
• Outcompete native species for food
Cane Toad Control Methods
• Physically trapping them
• Unfortunately, may trap wrong species
• Toxins from adults can be used to lure
tadpoles
Yellow Star Thistle
• Native to Mediterranean basin where it has
herbivore enemies and coevolved with other
plants
• Introduced to California after the Gold Rush
• Thrived due to Mediterranean Climate
• Human activity helped to distribute plant (i.e.
mowing, land grading, soil disturbance)
• 5 million acres of it just in California
• Does not have many predators in US
Yellow Star Thistle Control Methods
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Herbicides
Some insects will eat it
Rust fungus attacks it
Some animals will graze on it