Exotic Species

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Exotic Species
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Whats the Problem?

• Zebra mussel--expected to cause extinction of 90
  species of mussel in Miss Basin alone within 50
  yrs. It reduces food and oxygen for native
  fauna it also causes 100 million annually in
  damage to water pipes and filtration systems, and
  in control costs.
• Brown tree snake--wiped out 9 of Guams 18 native
  bird species, 17 species of vertebrates, causes
  200-300 power outages/yr, numerous bites of
  children, etc.

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Whats the Problem?

• Melaleuca tree --destroyed 600,000 hectares of
  Florida wetland, airborne secretions poisonous to
  humans, almost impossible to eradicate
• Cane toad
• Rats -- more than 80 of worlds major islands
  have invasive rats, causing declines in native
  bird populations and disease

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Emerald ash borer
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Costs

• Economic
• Tourism
• Agriculture/fishing
• Control/damage
• Trade
• Biodiversity
• Loss of diversity
• Pain
• Diseases
• Viruses
• Allergies
• Fire ant bites
• Ecosystem
• disruption

Rats (Rattus rattus and R. norvegicus) and house
mice (Mus musculus) On farms (particularly
poultry farms) mice and rats are numerous and
destructive the total on-farm rodent population
is estimated as over 1 billion. It is estimated
that there is about 1 rat/person in the U.S in
homes and other domestic dwellings, for a total
of about 250 million. Conservative estimates are
that each of these rodents causes about 15 in
damages per year. Therefore, 1,000,000,000 mice
and rats on farms 250,000,000 rats in homes and
other buildings 1.25 billion rodents X 15
18,750,000,000 in damage costs
alone. http//alic.arid.arizona.edu/invasive/sub7/
p3.shtml
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Whats the Problem?

• Approximately 50,000 non-native species are
  estimated to have been introduced into the U.S.
• Invasive species are estimated to cost about
  138 billion in environmental damage and losses
  each year.?
• Non-native plants are invading about 1.7 million
  acres of U.S. wildlife habitat each year.
• Yellow starthistle, an invasive plant, now
  dominates almost 10 million acres of once
  productive grazing land in northern
  California.??Approximately 65 of the crop losses
  attributed to plant pathogens (primarily fungi),
  or 21 billion, is attributed to non-native
  species.

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Causes?

• Increased globalization, trade, transportation,
  etc.

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• In response to the threat from introduced
  species, biologists are issuing dire warnings.
  E.O. Wilson speaks of introduced species as the
  stealth destroyers of the American environment
  (McDonald 1999 A15). Another ecologist worries
  that invasive species are likely to rise
  progressively to the most widespread and dominant
  proportion of terrestrial biota (Di Castri 1991
  448). Many other biologists speak of exotic
  species, introduced by humans, as biological
  pollution (McKnight 1993). KSF

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Executive Order 13112

• On Feb 3, 1999, Executive Order 13112 was signed
  establishing the National Invasive Species
  Council. The Executive Order requires that a
  Council of Departments dealing with invasive
  species be created.
• By the authority vested in me prevent the
  introduction of invasive species and provide for
  their control and to minimize the economic,
  ecological, and human health impacts that
  invasive species cause, it is ordered as
  follows
• "Alien species" means, with respect to a
  particular ecosystem, any species, including its
  seeds, eggs, spores, or other biological material
  capable of propagating that species, that is not
  native to that ecosystem.
• (f) "Invasive species" means an alien species
  whose introduction does or is likely to cause
  economic or environmental harm or harm to human
  health.(g) "Native species" means, with respect
  to a particular ecosystem, a species that, other
  than as a result of an introduction, historically
  occurred or currently occurs in that ecosystem.

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• Invasive Species Executive Order directing
  federal agencies to begin what Agriculture
  Secretary Dan Glickman called a unified, all-out
  battle against the spread of alien species in
  the United States. Praising the order, Interior
  Secretary Bruce Babbitt observed, There are a
  lot of global bioinvasive hitchhikers, and now is
  the time to take action. The costs to habitat and
  the economy are racing out of control.

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Human introduction

• Saltcedar tamarisk--introduced by human beings,
  escaped to Southwest desert, where it is
  outcompeting native plants with harmful effects.
  But tamarisk has since speciated. The new
  species has never existed anywhere else in the
  world.
• Finches, armadillos, indirect introduction

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Evolutionary criterion

• But what determines the area?
• Also, determining the exact moment of speciation
  is impossible.

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Historical Range

• Again, problems of identifying range spatially
  and temporally.

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Degradation

• Devine invasive harmful non-natives

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Degradation

• But what is harm to an ecosystem, and how much
  makes it invasive?

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Community Membership

• But community model in ecology is suspect
• Ecosystems are constantly changing
• Seems to presuppose a natural harmonious
  distribution of species in any given ecosystem
• Todays exotics may be tomorrows natives

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Moriaty and Woods

• None of the above criteria are necessary or
  sufficient to identify an exotic species.
• Exotic species is a cluster concept

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Are Exotic Species Bad?

• Do non-native species typically adversely affect
  biodiversity, ecological health, etc.?
• Sagoff biology doesnt answer this question.
• Sagoff like the immigration issue, the topic is
  complex. Some non-natives help, some do not and
  some natives help, and some do not.

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