IUCN Conservation Status Criteria
2001 criteria
A taxon is Critically Endangered (CE) 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 taxon is Endangered (EN) 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 taxon is Vulnerable (VU) 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 >=90% (CR) / >=70% (EN)/ >=50%(VU) 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 taxon
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 >=80%(CR) / >=50% (EN) / >=30% (VU) 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 >=80% (CR) / >=50% (EN) / >=30% (VU) 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 >=80% (CR) / >=50% (EN) / >=30% (VU) 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 (CR) / 5,000 kmē (EN) / 20,000 kmē (VU), and estimates indicating at least two of a-c:
a. Severely fragmented or known to exist at only a single (CR) / no more than five (EN) / no more than 10 (VU) location(s).
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(CR) / 500 kmē (EN) / 2,000 kmē (VU) and estimates indicating at least two of a-c:
a. Severely fragmented or known to exist at only a single (CR) / no more than five (EN) / no more than 10 (VU) location(s).
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 (CR) / 2,5000 (EN) / 10,000 (VU) mature individuals and either:
1. An estimated continuing decline of at least 25% within three years or one generation (CR) / 20% within five years or two generations (EN) / 10% within 10 years (VU) 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 (CR) / 250 (EN) mature individuals, OR
(ii) at least 90% (CR) / 95% (EN) / 1,000 (VU) of mature individuals in one subpopulation.
(b) Extreme fluctuations in number of mature individuals.
D. 1. Population size estimated to number fewer than 50 (CR)/ 250 (EN)/ 1,000 (VU) mature individuals or
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. (VU)
E. Quantitative analysis showing the probability of extinction in the wild is at least 50% within 10 years or three generations (CR), whichever is the longer (up to a maximum of 100 years) / 20% within 20 years or five generation, whichever is the longer (up to a maximum of 100 years) (EN) / 10% within 100 years(VU).
1994 criteria
A taxon is Critically Endangered (CE) 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 taxon is Endangered (EN) 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 taxon is Vulnerable (VU) 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. Declining Population
Reduction in population size of at least 80% (CR) / 50% (EN) / 20%(VU) over the last 10 years or three generations, whichever is the longer using either:
1. population size reduction observed, estimated, inferred or suspected in the past based on:
a. direct observation
b. an index of abundance appropriate to the taxon
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. population decline projected or suspected in the future based on (and specifying) any of (a) to (e) under A1.
B. Small Distribution and Decline of Fluctuation
Extent of occurrence estimated to be less than 100 kmē (CR) / 5,000 kmē (EN) / 20,000 kmē (VU), or area of occupancy estimated to be less than 10 kmē(CR) / 500 kmē (EN) / 2,000 kmē (VU) and 2 of the following 3:
1. Either severely fragmented (isolated subpopulations with a reduced probability of recolonization, if one extinct) or known to exist at only a single (CR) / no more than five (EN) / no more than 10 (VU) location(s).
2. Continuing decline in any of the following:
a. extent of occurrence
b. area of occupancy
c. area, extent and/or quality of habitat
d. number of locations or subpopulations
e. number of mature individuals.
3. Fluctuations of greater than 1 order of magnitude (CR) / less than 1 order of magnitude (EN) / less than 1 order of magnitude (VU) in any of the following
a. extent of occurrence
b. area of occupancy
c. number of locations or subpopulations
d. number of mature individuals.
C. Small Population Size and Decline
Number of mature individuals fewer than 250 (CR) / 2,5000 (EN) / 10,000 (VU) and either:
1. A rapid decline rate of at least 25% within three years or one generation (CR) / 20% within five years or two generations (EN)/ 10% within 10 years (VU) OR
2. A continuing decline in numbers of mature individuals AND either:
a. Fragmented with subpopulations estimated to contain <50 (CR) / <250 (EN) / <=1,000 (VU)
b. All individuals in a single subpopulation.
D. Very Small or Restricted Population
Either:
1. Number of mature individuals estimated to number fewer than 50 (CR) / 250 (EN) / 1000 (VU) or
2. Population susceptible with area of occupancy less than 100 kmē or number of locations less than five (VU)
E. Quantitative analysis
Indicating the probability of extinction in the wild is at least 50% within 10 years or three generations (CR) / 20% within 20 years or five generation (EN) / 10% within 100 years(VU).
Sources
Camhi, M., S.L. Fowler, J.A. Musick, A. Bräutigam, S.V. Fordham. 1998. Sharks and their Relatives - Ecology and Conservation. IUCN/SSC Shark Specialist Group. IUCN, Gland, Switzerland and Cambridge UK. iv + 39 pp.
Anonymous. 2003. IUCN Redlist Website www.redlist.org
