Iguana Specialist Group Main Page

Main
  ISG Home

Action Plan
 Contents
 Donors
 Supporting Groups
 Publishing Information
 Foreword
 Acknowledgements
 Executive Summary
 List of Contributors
 References
 Appendix 1
 Appendix 2

Chapter One:
 Conservation Strategy

Chapter Two:
  Taxonomic Accounts

Chapter Three:
  Action Plan

Appendix 2. Criteria for IUCN Red List Threat Categories (1994)

Critically Endangered (CR)

A taxon is Critically Endangered when it is facing an extremely high risk of extinction in the wild in the immediate future, as defined by any of the following criteria:

  1. Population reduction in the form of either of the following:
    1. An observed, estimated, inferred, or suspected reduction of at least 80% over the last 10 years or three generations, whichever is longer, based on any of the following:
      1. direct observation
      2. an index of abundance appropriate for the taxon
      3. a decline in area of occupancy, extent of occurrence, and/or quality of habitat
      4. actual or potential levels of exploitation
      5. the effects of introduced taxa, hybridization, pathogens, pollutants, competitors, or parasites.
    2. A reduction of at least 80%, projected or suspected to be met within the next 10 years or three generations, whichever is longer, based on any of (b), (c), (d), or (e) above.

  2. Extent of occurrence estimated to be less than 100km2 or area of occupancy estimated to be less than 10km2, and estimates indicating any two of the following:
    1. Severely fragmented or known to exist at no more than one location.
    2. Continuing decline, observed, inferred, or projected, in any of the following:
      1. extent of occurrence
      2. area of occupancy
      3. area, extent, and/or quality of habitat
      4. number of locations or subpopulations
      5. number of mature individuals.
    3. Extreme fluctuations in any of the following:
      1. extent of occurrence
      2. area of occupancy
      3. number of locations or subpopulations
      4. number of mature individuals.

  3. Population estimated to number less than 250 mature individuals and either:
    1. An estimated continuing decline of at least 25% within three years or one generation, whichever is longer, or
    2. A continuing decline, observed, inferred, or projected, in numbers of mature individuals and population structure in the forms of either:
      1. severely fragmented (i.e., no subpopulation estimated to contain more than 50 mature individuals)
      2. all individuals are in a single subpopulation.

  4. Population estimated to number less than 50 mature individuals.

  5. Quantitative analysis showing the probability of extinction in the wild is at least 50% within 10 years or three generations, whichever is longer.

Endangered (EN)

A taxon is Endangered when it is not Critically Endangered, but is facing a very high risk of extinction in the wild in the near future, as defined by any of the following criteria:

  1. Population reduction in the form of either of the following:
    1. An observed, estimated, inferred, or suspected reduction of at least 50% over the last 10 years or three generations, whichever is longer, based on any of the following:
      1. direct observation
      2. an index of abundance appropriate for the taxon
      3. a decline in area of occupancy, extent of occurrence, and/or quality of habitat
      4. actual or potential levels of exploitation
      5. the effects of introduced taxa, hybridization, pathogens, pollutants, competitors, or parasites.
    2. A reduction of at least 50%, projected or suspected to be met within the next 10 years or three generations, whichever is longer, based on any of (b), (c), (d), or (e) above.

  2. Extent of occurrence estimated to be less than 5,000km2 or area of occupancy estimated to be less than 500 km2, and estimates indicating any two of the following:
    1. Severely fragmented or known to exist at no more than five locations.
    2. Continuing decline, observed, inferred, or projected, in any of the following:
      1. extent of occurrence
      2. area of occupancy
      3. area, extent, and/or quality of habitat
      4. number of locations or subpopulations
      5. number of mature individuals.
    3. Extreme fluctuations in any of the following:
      1. extent of occurrence
      2. area of occupancy
      3. number of locations or subpopulations
      4. number of mature individuals.

  3. Population estimated to number less than 2,500 mature individuals and either:
    1. An estimated continuing decline of at least 20% within five years or two generations, whichever is longer, or
    2. A continuing decline, observed, inferred, or projected, in numbers of mature individuals and population structure in the forms of either:
      1. severely fragmented (i.e., no subpopulation estimated to contain more than 250 mature individuals)
      2. all individuals are in a single subpopulation.

  4. Population estimated to number less than 250 mature individuals.

  5. Quantitative analysis showing the probability of extinction in the wild is at least 20% within 20 years or five generations, whichever is longer.

Vulnerable (VU)

A taxon is Vulnerable when it is not Critically Endangered or Endangered but is facing a high risk of extinction in the wild in the medium-term future, as defined by any of the following criteria:

  1. Population reduction in the form of either of the following:
    1. An observed, estimated, inferred, or suspected reduction of at least 20% over the last 10 years or three generations, whichever is longer, based on any of the following:
      1. direct observation
      2. an index of abundance appropriate for the taxon
      3. a decline in area of occupancy, extent of occurrence, and/or quality of habitat
      4. actual or potential levels of exploitation
      5. the effects of introduced taxa, hybridization, pathogens, pollutants, competitors, or parasites.
    2. A reduction of at least 20%, projected or suspected to be met within the next ten years or three generations, whichever is longer, based on any of (b), (c), (d), or (e) above.

  2. Extent of occurrence estimated to be less than 20,000km2 or area of occupancy estimated to be less than 2,000km2, and estimates indicating any two of the following:
    1. Severely fragmented or known to exist at no more than ten locations.
    2. Continuing decline, observed, inferred, or projected, in any of the following:
      1. extent of occurrence
      2. area of occupancy
      3. area, extent, and/or quality of habitat
      4. number of locations or subpopulations
      5. number of mature individuals.
    3. Extreme fluctuations in any of the following:
      1. extent of occurrence
      2. area of occupancy
      3. number of locations or subpopulations
      4. number of mature individuals.

  3. Population estimated to number less than 10,000 mature individuals and either:
    1. An estimated continuing decline of at least 10% within 10 years or three generations, whichever is longer,

      or

    2. A continuing decline, observed, inferred, or projected, in numbers of mature individuals and population structure in the forms of either:
      1. severely fragmented (i.e., no subpopulation estimated to contain more than 1,000 mature individuals)
      2. all individuals are in a single subpopulation.

  4. Population very small or restricted in the form of either of the following:
    1. Population estimated to number less than 1,000 mature individuals.
    2. Population is characterized by an acute restriction in its area of occupancy (typically less than 100 km2) or in the number of locations (typically less than five). Such a taxon would thus be prone to the effects of human activities (or stochastic events whose impact is increased by human activities) within a very short period of time in an unforeseeable future, and is thus capable of becoming Critically Endangered or even extinct in a very short period.

  5. Quantitative analysis showing the probability of extinction in the wild is at least 10% within 100 years or five generations, whichever is longer.
Iguana Specialist Group