IUCN 2001 Red List Categories (Version 3.1)

(Note: These criteria were also used for ratings assessed in 2002 and 2003; for Red List Categories from previous years, see 1960's, 1970's, 1980's, 1994, 1996, 2000)

2001 Categories:

  • EX - Extinct. A species is Extinct when there is no reasonable doubt that the last individual has died. A species is presumed Extinct when exhaustive surveys in known and/or expected habitat, at appropriate times (diurnal, seasonal, annual), throughout its historic range have failed to record an individual. Surveys should be over a time frame appropriate to the species's life cycle and life form.
  • EW - Extinct in the Wild. A species is Extinct in the Wild when it is known only to survive in cultivation, in captivity or as a naturalized population (or populations) well outside the past range. A species is presumed Extinct in the Wild when exhaustive surveys in known and/or expected habitat, at appropriate times (diurnal, seasonal, annual), throughout its historic range have failed to record an individual. Surveys should be over a time frame appropriate to the species's life cycle and life form.
  • CR - Critically Endangered. A species is Critically Endangered when the best available evidence indicates that it meets any of the criteria A to E for Critically Endangered (see Section V), and it is therefore considered to be facing an extremely high risk of extinction in the wild.
  • EN - Endangered. A species is Endangered when the best available evidence indicates that it meets any of the criteria A to E for Endangered (see Section V), and it is therefore considered to be facing a very high risk of extinction in the wild.
  • VU - Vulnerable. A species is Vulnerable when the best available evidence indicates that it meets any of the criteria A to E for Vulnerable (see Section V), and it is therefore considered to be facing a high risk of extinction in the wild.
  • NT - Near Threatened. A species is Near Threatened when it has been evaluated against the criteria but does not qualify for Critically Endangered, Endangered or Vulnerable now, but is close to qualifying for or is likely to qualify for a threatened category in the near future.
  • LC - Least Concern. A species is Least Concern when it has been evaluated against the criteria and does not qualify for Critically Endangered, Endangered, Vulnerable or Near Threatened. Widespread and abundant taxa are included in this category.
  • DD - Data Deficient. A species is Data Deficient when there is inadequate information to make a direct, or indirect, assessment of its risk of extinction based on its distribution and/or population status. A species in this category may be well studied, and its biology well known, but appropriate data on abundance and/or distribution are lacking. Data Deficient is therefore not a category of threat. Listing of taxa in this category indicates that more information is required and acknowledges the possibility that future research will show that threatened classification is appropriate. It is important to make positive use of whatever data are available. In many cases great care should be exercised in choosing between DD and a threatened status. If the range of a species is suspected to be relatively circumscribed, and a considerable period of time has elapsed since the last record of the species, threatened status may well be justified.
  • NE - Not Evaluated. A species is Not Evaluated when it is has not yet been evaluated against the criteria.

Criteria for Critically Endangered, Endangered and Vulnerable:

Critically Endangered - A species is Critically Endangered when the best available evidence indicates that it meets any of the following criteria (A to E), and it is therefore considered to be facing an extremely high risk of extinction in the wild:

A. Reduction in population size based on any of the following:

  • 1. An observed, estimated, inferred or suspected population size reduction of greater than or equal to 90% over the last 10 years or three generations, whichever is the longer, where the causes of the reduction are clearly reversible AND understood AND ceased, based on (and specifying) any of the following:
    • (a) direct observation
    • (b) an index of abundance appropriate to the species
    • (c) a decline in area of occupancy, extent of occurrence and/or quality of habitat
    • (d) actual or potential levels of exploitation  
    • (e) the effects of introduced taxa, hybridization, pathogens, pollutants, competitors or parasites.
  • 2. An observed, estimated, inferred or suspected population size reduction of greater than or equal to 80% over the last 10 years or three generations, whichever is the longer, where the reduction or its causes may not have ceased OR may not be understood OR may not be reversible, based on (and specifying) any of (a) to (e) under A1.
  • 3. A population size reduction of greater than or equal to 80%, projected or suspected to be met within the next 10 years or three generations, whichever is the longer (up to a maximum of 100 years), based on (and specifying) any of (b) to (e) under A1.
  • 4. An observed, estimated, inferred, projected or suspected population size reduction of greater than or equal to  80% over any 10 year or three generation period, whichever is longer (up to a maximum of 100 years in the future), where the time period must include both the past and the future, and where the reduction or its causes may not have ceased OR may not be understood OR may not be reversible, based on (and specifying) any of (a) to (e) under A1.

B. Geographic range in the form of either B1 (extent of occurrence) OR B2 (area of occupancy) OR both:

  • 1. Extent of occurrence estimated to be less than 100 kmē, and estimates indicating at least two of a-c:
    • a. Severely fragmented or known to exist at only a single location.
    • b. Continuing decline, observed, inferred or projected, in any of the following:
      • (i) extent of occurrence     
      • (ii) area of occupancy     
      • (iii) area, extent and/or quality of habitat    
      • (iv) number of locations or subpopulations     
      • (v) number of mature individuals.
    • c. Extreme fluctuations in any of the following:
      • (i) extent of occurrence     
      • (ii) area of occupancy     
      • (iii) number of locations or subpopulations     
      • (iv) number of mature individuals.
  • 2. Area of occupancy estimated to be less than 10 kmē, and estimates indicating at least two of a-c:
    • a. Severely fragmented or known to exist at only a single location.
    • b. Continuing decline, observed, inferred or projected, in any of the following:
      • (i) extent of occurrence     
      • (ii) area of occupancy     
      • (iii) area, extent and/or quality of habitat     
      • (iv) number of locations or subpopulations     
      • (v) number of mature individuals.
    • c. Extreme fluctuations in any of the following:     
      • (i) extent of occurrence     
      • (ii) area of occupancy     
      • (iii) number of locations or subpopulations     
      • (iv) number of mature individuals.

C. Population size estimated to number fewer than 250 mature individuals and either:

  • 1. An estimated continuing decline of at least 25% within three years or one generation, whichever is longer, (up to a maximum of 100 years in the future) OR 
  • 2. A continuing decline, observed, projected, or inferred, in numbers of mature individuals AND at least one of the following (a-b):
    • (a) Population structure in the form of one of the following:     
      • (i) no subpopulation estimated to contain more than 50 mature individuals, OR     
      • (ii) at least 90% of mature individuals in one subpopulation. 
    • (b) Extreme fluctuations in number of mature individuals.

D. Population size estimated to number fewer than 50 mature individuals.

E. Quantitative analysis showing the probability of extinction in the wild is at least 50% within 10 years or three generations, whichever is the longer (up to a maximum of 100 years).

Endangered  

A species is Endangered when the best available evidence indicates that it meets any of the following criteria (A to E), and it is therefore considered to be facing a very high risk of extinction in the wild:

A. Reduction in population size based on any of the following: 

  • 1. An observed, estimated, inferred or suspected population size reduction of greater than or equal to 70% over the last 10 years or three generations, whichever is the longer, where the causes of the reduction are clearly reversible AND understood AND ceased, based on (and specifying) any of the following:
    • (a) direct observation   
    • (b) an index of abundance appropriate to the species   
    • (c) a decline in area of occupancy, extent of occurrence and/or quality of habitat   
    • (d) actual or potential levels of exploitation   
    • (e) the effects of introduced taxa, hybridization, pathogens, pollutants, competitors or parasites.
  • 2. An observed, estimated, inferred or suspected population size reduction of greater than or equal to 50% over the last 10 years or three generations, whichever is the longer, where the reduction or its causes may not have ceased OR may not be understood OR may not be reversible, based on (and specifying) any of (a) to (e) under A1.
  • 3. A population size reduction of greater than or equal to 50%, projected or suspected to be met within the next 10 years or three generations, whichever is the longer (up to a maximum of 100 years), based on (and specifying) any of (b) to (e) under A1.
  • 4. An observed, estimated, inferred, projected or suspected population size reduction of greater than or equal to 50% over any 10 year or three generation period, whichever is longer (up to a maximum of 100 years in the future), where the time period must include both the past and the future, and where the reduction or its causes may not have ceased OR may not be understood OR may not be reversible, based on (and specifying) any of (a) to (e) under A1.

B. Geographic range in the form of either B1 (extent of occurrence) OR B2 (area of occupancy) OR both: 

  • 1. Extent of occurrence estimated to be less than 5000 kmē, and estimates indicating at least two of a-c: 
    • a. Severely fragmented or known to exist at no more than five locations.
    • b. Continuing decline, observed, inferred or projected, in any of the following:
      • (i) extent of occurrence     
      • (ii) area of occupancy     
      • (iii) area, extent and/or quality of habitat     
      • (iv) number of locations or subpopulations     
      • (v) number of mature individuals.
    • c. Extreme fluctuations in any of the following:
      • (i) extent of occurrence     
      • (ii) area of occupancy     
      • (iii) number of locations or subpopulations     
      • (iv) number of mature individuals. 
  • 2. Area of occupancy estimated to be less than 500 kmē, and estimates indicating at least two of a-c:
    • a. Severely fragmented or known to exist at no more than five locations.
    • b. Continuing decline, observed, inferred or projected, in any of the following:
      • (i) extent of occurrence     
      • (ii) area of occupancy     
      • (iii) area, extent and/or quality of habitat     
      • (iv) number of locations or subpopulations     
      • (v) number of mature individuals.
    • c. Extreme fluctuations in any of the following:
      • (i) extent of occurrence     
      • (ii) area of occupancy     
      • (iii) number of locations or subpopulations     
      • (iv) number of mature individuals.

C. Population size estimated to number fewer than 2500 mature individuals and either:

  • 1. An estimated continuing decline of at least 20% within five years or two generations, whichever is longer, (up to a maximum of 100 years in the future) OR 
  • 2. A continuing decline, observed, projected, or inferred, in numbers of mature individuals AND at least one of the following (a-b):
    • (a) Population structure in the form of one of the following:  
           
      • (i) no subpopulation estimated to contain more than 250 mature individuals, OR       
      • (ii) at least 95% of mature individuals in one subpopulation.
    •  (b) Extreme fluctuations in number of mature individuals.

D. Population size estimated to number fewer than 250 mature individuals.

E. Quantitative analysis showing the probability of extinction in the wild is at least 20% within 20 years or five generations, whichever is the longer (up to a maximum of 100 years).

Vulnerable

A species is Vulnerable when the best available evidence indicates that it meets any of the following criteria (A to E), and it is therefore considered to be facing a high risk of extinction in the wild:

A. Reduction in population size based on any of the following:

  • 1. An observed, estimated, inferred or suspected population size reduction of greater than or equal to 50% over the last 10 years or three generations, whichever is the longer, where the causes of the reduction are: clearly reversible AND understood AND ceased, based on (and specifying) any of the following:
    • (a) direct observation   
    • (b) an index of abundance appropriate to the species   
    • (c) a decline in area of occupancy, extent of occurrence and/or quality of habitat   
    • (d) actual or potential levels of exploitation   
    • (e) the effects of introduced taxa, hybridization, pathogens, pollutants, competitors or parasites.
  • 2. An observed, estimated, inferred or suspected population size reduction of greater than or equal to 30% over the last 10 years or three generations, whichever is the longer, where the reduction or its causes may not have ceased OR may not be understood OR may not be reversible, based on (and specifying) any of (a) to (e) under A1.
  • 3. A population size reduction of greater than or equal to 30%, projected or suspected to be met within the next 10 years or three generations, whichever is the longer (up to a maximum of 100 years), based on (and specifying) any of (b) to (e) under A1.
  • 4. An observed, estimated, inferred, projected or suspected population size reduction of greater than or equal to 30% over any 10 year or three generation period, whichever is longer (up to a maximum of 100 years in the future), where the time period must include both the past and the future, and where the reduction or its causes may not have ceased OR may not be understood OR may not be reversible, based on (and specifying) any of (a) to (e) under A1.

B. Geographic range in the form of either B1 (extent of occurrence) OR B2 (area of occupancy) OR both:

  • 1. Extent of occurrence estimated to be less than 20,000 kmē, and estimates indicating at least two of a-c: 
    • a. Severely fragmented or known to exist at no more than 10 locations. 
    • b. Continuing decline, observed, inferred or projected, in any of the following: 
      • (i) extent of occurrence     
      • (ii) area of occupancy     
      • (iii) area, extent and/or quality of habitat     
      • (iv) number of locations or subpopulations     
      • (v) number of mature individuals. 
    • c. Extreme fluctuations in any of the following: 
      • (i) extent of occurrence     
      • (ii) area of occupancy     
      • (iii) number of locations or subpopulations     
      • (iv) number of mature individuals.
  • 2. Area of occupancy estimated to be less than 2000 kmē, and estimates indicating at least two of a-c: 
    • a. Severely fragmented or known to exist at no more than 10 locations. 
    • b. Continuing decline, observed, inferred or projected, in any of the following: 
      • (i) extent of occurrence     
      • (ii) area of occupancy     
      • (iii) area, extent and/or quality of habitat     
      • (iv) number of locations or subpopulations     
      • (v) number of mature individuals.
    •  c. Extreme fluctuations in any of the following:
      • (i) extent of occurrence     
      • (ii) area of occupancy     
      • (iii) number of locations or subpopulations     
      • (iv) number of mature individuals.

C. Population size estimated to number fewer 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, (up to a maximum of 100 years in the future) OR
  • 2. A continuing decline, observed, projected, or inferred, in numbers of mature individuals AND at least one of the following (a-b):
    • (a) Population structure in the form of one of the following:    
       
      • (i) no subpopulation estimated to contain more than 1000 mature individuals, OR     
      • (ii) all mature individuals are in one subpopulation.
    • (b) Extreme fluctuations in number of mature individuals.

D. Population very small or restricted in the form of either of the following:

  • 1. Population size estimated to number fewer than 1000 mature individuals. 
  • 2. Population with a very restricted area of occupancy (typically less than 20 kmē) or number of locations (typically five or fewer) such that it is prone to the effects of human activities or stochastic events within a very short time period in an uncertain future, and is thus capable of becoming Critically Endangered or even Extinct in a very short time period.

E. Quantitative analysis showing the probability of extinction in the wild is at least 10% within 100 years.


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