Invasive Species

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Invasive Species
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What is an Invasive Species?

• A species that has been introduced or is not
  native to an environment
• Invasive species are generally harmful to the
  local habitat or native species
• Unwanted pest
• Not all non-native organisms are invasive

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More Examples of Invasive Species

• Grey squirrel
• American beaver
• Cane toad

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Different Routes of Invasion

• Most invasions are due to human activities
• Plant or pet trade
• Commercial shipping
• Tourism
• and many other routes

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Quiz What Characteristics Make A Good Invader?
?

• Rapid reproduction
• Fast growth
• High dispersal
• Tolerant to many different conditions
• Able to live off many different foods
• Used by humans

?
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The Impact of Invasive Species

• Ecological
• Reduce native biodiversity
• Direct predation on local species
• Spread of disease
• Upset balance of local ecosystem

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The Impact of Invasive Species

• Economical
• Very expensive - agricultural pests cause
  millions of dollars of damage every year!
• Very expensive to eradicate invasive species

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Controlling Invasive Species

• Controlling invasive species once they have
  become established is difficult.
• Control is also usually very expensive!
• There are four main ways that invasive species
  are controlled
• Physical control
• Chemical control
• Biological control
• Prevention

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Physical Control of Invasive Species

• Controlling plants
• Mechanical excavation, strimming, etc.
• Removal of plants by hand
• Installation of growth barriers
• Controlling animals
• Culling
• Trapping and hunting
• Putting up barriers or fences

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Chemical Control of Invasive Species

• Chemical control involves applying poison to
  eliminate invasive species
• E.g. Eradication of rats on Henderson Island
• Use rodenticide (rat poison)
• Insecticides pesticides
• to control insect pests
• Herbicides (weed-killer)
• to control plants

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Biological Control of Invasive Species

• Uses a living organism to control invasive
  species
• This organism may eat the invasive species or
  cause it to become diseased
• Biological control agents must be carefully
  assessed before release to ensure the control
  species will not become invasive itself

Seven-spot ladybird
Harlequin ladybird
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Preventing Invasive Species

• Prevention is better than cure!
• Preventing invasive species
• from being introduced
• somewhere in the first place,
• or preventing them from
• spreading if they do arrive,
• is the key to avoiding
• long-term harm to ecosystems

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Barrow Island Case Study

• Barrow Island is a small
• island off the NW coast
• of Australia that is home
• to many species that
• have become rare or
• extinct on the Australian mainland

• This is partly due to a rigorous Quarantine
  
• Management System (QMS) operated by Chevron,
• which prevents invasive species from becoming
• established on the island