Estimating%20Extinction%20Risk%20(the%20IUCN%20criteria)

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Estimating Extinction Risk(the IUCN criteria)

• Fish 458 Lecture 24

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Identifying Species at Risk of Extinction The
IUCN Framework

• The IUCN Red List characterizes all species
  (plants and animals) into various categories of
  risk of extinction.
• The same framework is applied to all organisms
  irrespective of their biology and exploitation
  history (implies a need to scale biological
  quantities e.g. by generation time).

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Goals for IUCN Listing

• Provide scientifically-based information on the
  status of species at the global level.
• Draw attention to the magnitude and importance of
  threatened biodiversity.
• Influence national and international policy and
  decision makers.
• Provide information to guide actions to conserve
  biological diversity.

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Summary Statistics

• Threatened Species (of those evaluated)
• Total (41 3155723 of 9474)
• Mammalia (57 113087 of 2133)
• Aves (56 1183 3 of 2123)
• Elasmobranchii (41 390 of 95)
• Number of threatened species by country
• USA (998 131 fishes)
• Australia (524 44 fishes)

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A History of the Listing Process

• Qualitative until 1994.
• 1994 First quantitative framework (used for the
  1996 Red List).
• 2000 Revision to the 1994 framework.

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Basic framework (2000 model)
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The threatened categories

• Critically Endangered (considered to be facing
  an extremely high risk of extinction in the
  wild).
• Endangered (considered to be facing a very high
  risk of extinction in the wild).
• Vulnerable (considered to be facing a high risk
  of extinction in the wild).

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The criteria

1. Reduction in population size
2. Small geographic range
3. Small population size and declining
4. Very small population size
5. Quantitative estimate of extinction risk

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The basic structure
Criteria CR EN VU
A Value Value Value
B Value Value Value
C Value Value Value
D Value Value Value
E Value Value Value
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How to use the system

• Rank the species against each of the criteria
  (note that there are separate thresholds for each
  criterion / category of risk).
• Set the final category to the highest level of
  risk.
• This process has been computerized (RAMAS).

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The A criterion (mature individuals)

• Direct observation.
• An index of abundance.
• Decline in the area of occupancy, extent of
  occurrence / quality of habitat.
• Actual or potential levels of exploitation
• Effects of introduced taxa, pollutants, etc.

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The A Criterion (past reductions)

• Observed, estimated, inferred or suspected
  reduction over 10 years or three generations of
• 90, 70,50 and causes ceased, understood and
  reversible
• 80, 50, 30 and causes not ceased, not
  understood, or may not be reversible

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The A criterion (future reductions)

• Projected reduction over any 10 year or three
  generation period of 80, 50, 30.
• Can include the past and future.
• Reduction may not have ceased, not be understood,
  or may not be reversible.

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Defining Space in the System

• Extent of occurrence area contained within the
  shortest continuous boundary which encompasses
  the present occurrence of a taxon.
• Extent of occupancy smallest area essential at
  any stage to the survival of the population
  (e.g. breeding area).

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Criterion B (Geographic range)

• Extent of occurrence less than 100km², 5000km²,
  20000km² and two of
• Severely fragmented or at a single location (CR)
  / no more than 5 locations (EN) / no more than 10
  locations (VU)
• Continuing decline
• Extreme fluctuations
• Extent of occupancy less than 10km², 500km²,
  2000km² and two sub-criteria.

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Criterion C(Small size and declining)

• Population size less than 250,5000,10000 and
  either
• Continuing decline at least 25 within three
  years or one generation, 20 within five years or
  two generations, 10 within 10 years or three
  generations
• Continuing decline and
• No subpopulation larger than 50, 250, 1000
  individuals
• At least 90, 95, 100 of individuals in one
  subpopulation
• Extreme fluctuations.

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Criterion D(Very small population size)

• Critically endangered 50 mature individuals.
• Endangered 250 mature individuals.
• Vulnerable 1000 mature individuals OR very
  restricted area of occupancy (lt20km²) or number
  of locations (5 or less).

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Criterion E(Quantitative analysis)

• Probability of extinction in the wild is at least
  
• 50 within 10 years or three generations (CR).
• 20 within 20 years or five generations (EN).
• 10 within 100 years (VU).

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Overview of Success

• Very widely used internationally.
• Does not require much data.
• Generally easy to understand and apply.
• Can be applied across a wide range of taxa (e.g.
  insects to trees).

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Problems with the Framework-I

• Specifying thresholds
• The thresholds are only roughly comparable.
• The original intent was for the thresholds to be
  consistent with the E criterion but this has
  changed over time.
• The thresholds for the A criterion in particular
  (and the use of inferred / suspected
  declines) have been controversial (e.g. listing
  of Atlantic cod).

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Problems with the Framework-II

• Fishes!
• 1996 Red List The quantitative criterion
  (A1abd) for the threatened categories may not be
  appropriate for assessing the risk of extinction
  for some species, particularly those with high
  reproductive potential, fast growth and broad
  geographic ranges. Many of these species have
  high potential for population maintenance under
  high levels of mortality, and such species might
  form the basis for fisheries

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Problems with the Framework-III

• The decline criterion.
• Managed species.
• Long-lived species (three generations can be
  several thousand years for some trees).
• Should criteria E over-rule?
• The criteria are broad brush and should not
  overrule more sophisticated analyses. Many fish
  species would have being threatened or endangered
  at some time.
• How to incorporate precaution.
• No use of ecological knowledge.

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Areas of Disagreement

• African elephants
• Some fish species (cod)
• Marine turtles (Flatback, Olive Ridley, Green)
• Crocodiles.
• Note all are species subject to harvest.

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Readings

• IUCN Web site www.iucn.org
• Mace and Lande (1991) Conservation Biology
  5148-157.
• Mace et al. (1992) Species 1916-22.
• Mace and Stuart (1994) Species 22 13-24