Exotic Species and Biodiversity

Exotic Species- "any species, including its seeds, eggs, spores, or other biological material capable of propagating that species, that is not native to that habitat." (U.S. Fish and Wildlife and Wildlife Services)

Invasive Species- "an alien species whose introduction does or is likely to cause economic or environmental harm or harm to human health" or "a species that is not-native to the ecosystem under consideration and whose introduction causes or is likely to cause economic or environmental harm or harm to human health" (Invasive Species Advisitory Commitee - (ISAC) Executive Order 13112)
Useful link: http://www.fws.gov/invasives/faq.html

1. How are introduced exotic species a threat to biodiversity?
  • Once population of exotic species spreads it's very difficult to get rid of them
    • An exotic species population isn't reversible, and can keep spreading
  • Cause the endangering of native species
    • Eat food sources that they would eat so not enough food is left
    • Steal habitats so not enough spaces for all the native species to live
    • Sometimes eat native species
    • Competition for niche
    • 1,880 species in US 49% are endangered because of invades species.
  • Greater threat than pollution, harvest, and disease combined to environment
    • Messing with key ecosystem processes/ chemically and physically changing the environment / economically
    • $137 billion spent/ hurting economy
    • o Have to spend lots of money on fixing the damage the exotic speeches have caused
    • Chemical control and supplies

2. What happens if the exotic species can't find a niche?
  • Survival isn't possible if an exotic species can't find a purpose/ niche
  • Competing with native species for the same niche
  • No two species can share the name niche
  • The more competition there is the more the new specie will struggle for survival

3. If it is a threat to our environment, why are exotic species still being imported into the U.S.?
4. How does an exotic species arrive in its environment?
• Humans play a role in this, and the proportion of increased humans has gone up with the number of exotic species
• Unintentional release: Species that are released without the intention of them creating a population like the aquarium species (red piranha), and the accidental escape of plants. 1. Fisherman dump bait that didn’t come from the same water, like crayfish. 2. Shipping activities with ocean going vectors (one of the main factors.) The ships take ballasts of water for stability for another area of water, and then can dump up to 1 million liters in strange water. The invasion happens when ballasts are taken from different ports, and if the species can survive in the new conditions a population can grow. An example of this would be the spiny water flea. 3. Canals. Canals have watersheds connecting them, and organisms use these to cross canals. The sea lamprey entered the great lakes from the Atlantic ocean through canals
• Intentional release: Exotic species released intentionally in an environment. 1. Humans want to increase the value of fisheries so they imported rainbow trout. 3. Exotic species are placed to try to eliminate other non useful/ annoying species. 3. Animal vectors. Sometimes birds transport the most exotic species, they can either be carried directly or digested by the birds.

Are all exotic species invasive species?

No. Exotic species are species that are non-native to an area, but invasive species are harmful to the environment. (See definitions at top of page)

Why are invasive species bad? For whom?

Invasive species have many large impacts to human health, natural resources, and the environment.

Issues Include:
  • Human Health
    • Respiratory infections (West Nile Virus)
    • Poisonous plants
  • Natural Resources
    • declines in wildlife habitat and timber availability
    • soil becomes unstable
    • can eliminate resources
  • Environment Harm
    • Native species
      • Invasive species can eat and destroy their populations
      • Invasive species can spread diseases amongst the native species

What happens to the native species?

  • It is difficult to know exactly when an invasion occurs, because usually they aren’t noticed until after it has happened
  • Must examine invaded and non invaded sites in order to see how they are affected
Where are exotic species located?
George Laycock, The Importation of Animals: The Unforeseen Consequences.
  • Grass Carp Invasion:
    • At first, they were welcomed: seen as a possible sport fish
    • Within 2 years the carp was in 38 states: rooted in the mud, was not a food or a sport fish
    • Brought to the U.S. to keep the waters free of weeds
  • Hawaiian Islands:
    • Sugar cane became infested with cane rats: imported mongoose and house sparrows to kill the rats
  • Florida:
    • Piranha: worries that they will actually become established
    • Blue Talapia: imported for weed control, now crowds bass and bluegills’ habitats
  • Peacock fish: from South America, seen as a sport fish: little is known about their effect on the native species
Can they benefit the ecosystem?
How do humans help species thrive and survive?
(U.S. Fish and Wildlife and Wildlife Services), George Laycock, The Importation of Animals: The Unforeseen Consequences.

  • Humans release the species into the wild
  • They think it’s a good idea: sport fish, help the environment
  • Difference between intentional and unintentional introductions
    • Intentional introduction: released into the wild on purpose or escape where they then unexpectedly become an invasive species problem
    • Unintentional introduction: exotic species arriving here accidentally, without our knowledge