Human Impacts-Introduced Species

What Are They?

• 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 Now-Over

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

• Herbicides• Some insects will eat it• Rust fungus attacks it• Some animals will graze on it