Post on 13-Dec-2015
transcript
Invasive Species!
I. Invasive Species
A. Most species introductions are actually beneficial to humans – we depend heavily on introduced species for food, shelter, medicine, and aesthetic enjoyment.
B. Introduced species such as corn, wheat, rice, cattle, poultry, and other livestock provide more than 98% of the US food supply.
I. Invasive Species
C. Some definitions:1. Native species – A plant or animal naturally
found in a region – it has naturally adapted to the soils and climate of a region over millions of years.
2. Introduced species – A plant or animal not native to an area. Often introduced species will die in an area without extra water, nutrition, fertilizers, ect.
I. Invasive Species
3. Invasive Species – A species likely to cause economic or environmental harm.
a)Invasive species grow/reproduce in an “out of control” manor – they have no natural predators, competitors, parasites, or pathogens to help control their numbers in a new environment.
b)They often reduce or wipe out populations of native species.
I. Invasive Species
D. In the US, there are an estimated 7,100 harmful invasive species. Some of them were introduced accidentally – whoops! And some were introduced purposely to control pests or erosion.
II. Case Study 1 – The fire ant
A. Fire ants were introduced accidentally – in the 1930s, Argentinean fire ants arrived on shipments of lumber and coffee to the port of Mobile, Alabama.
B. Since the 1930s they have spread aggressively by land and water through the south (they can float).
II. Case Study 1 – The fire ant
C. When they arrive in an area, they kill off 90% of the native ant population, and kill deer fawns, birds, livestock, pets, and at least 80 people who are allergic to their venom.
D. Fire ants cause an estimated $68,000 damage an HOUR to crops and phone/power lines.
E. Fire ants have no natural predators and also have become genetically resistant to pesticides.
III. Case Study II - Kudzu
A. Kudzu, sometimes called the plant that ate the south, was introduced deliberately in the 1930s from Japan to help control soil erosion in the southeastern US.
B. Kudzu grows over a foot a day, and is estimated to cover 150,000 acres a year.
C. Kudzu engulfs and kills trees and vegetation, and is very hard to eradicate.
IV. Case Study 3 – The Zebra Mussel
A. In 1986, the larvae of the zebra mussel arrived in ballast water discharged from a European ship near Detroit, Michigan.
B. The thumbnail-sized mollusk reproduces rapidly and has no natural enemies in the great lakes.
C. They have displaced other mussel species and depleted the food supply of other native species.
IV. Case Study 3 – The Zebra Mussel
D. Zebra Mussels have also clogged irrigation pipes, shut down water intake pipes for power plants and city water supplies, and fouled beaches.
E. Currently the mussels cost both the US and Canada about $16,000 per hour in damages.
V. Controlling Invasives
A. Biological Control (or biocontrol) – Another organism is introduced to control/kill invasives
B. Control means not complete eradication, but reducing species to economically or environmentally manageable levels
C. Have had some success in controlling some invasives – insects and weeds have seen the most success.
V. Controlling Invasives
D. Often introduced biocontrol organisms will feed on native species when the invasives have been eradicated, or sometimes if they find the native species more tasty.
E. As biocontrol science has become better, scientists look for organisms that eat only the target organism.
F. Case Study 4 – The Cane Toad
G. Biocontrol gone bad! Released in Australia in 1935 to control cane beetles in sugar fields. 3,000 were released and now there are several million in northern Australia.
H. Venomous toads found in Central and portions of South America. Rather than eating these insects, they pretty much ate everything else (they are generalists).
I. Their numbers stay controlled in their native habitat, but have grown out of control in Australia because they have no natural predators and abundant food – they eat pretty much everything, including pet food if left outside.
J. Their toxin is secreted from their skin, and causes death to small predators and pets. Some humans have died from eating toads or their eggs.
Cane Toad Video
http://video.nationalgeographic.com/video/player/animals/amphibians-animals/frogs-and-toads/toad_cane.html