Categories and Criteria

What are The Sixth Extinction Website's criteria for classifying a species or subspecies as Extinct or Extinct in the Wild?

 The Sixth Extinction Website follows IUCN's criteria for classifying a species or subspecies as Extinct (EX). These criteria are: "A taxon is Extinct when there is no reasonable doubt that the last individual has died. A taxon 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 taxon's life cycle and life form." And "a taxon is Extinct in the Wild (EW) when it is known only to survive in cultivation, in captivity or as a naturalized population (or populations) well outside the past range. A taxon 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 taxon's life cycle and life form." (IUCN, 2008)

What are the criteria for including a species or subspecies into The Sixth Extinction Website's list of recently extinct animals?

Species and subspecies that are classified as Extinct at the IUCN Red List of Threatened Species. For the IUCN Red List, IUCN only records "recent" extinctions, meaning those species known to have become Extinct since 1500 CE. However, The Sixth Extinction Website's lists of recently extinct animals also records other Holocene species and subspecies that became extinct before 1500 CE when this was due to human activities, directly or indirectly. The Sixth Extinction Website's list of recently extinct animals can also include species and subspecies that are classified as "Critically Endangered" or "Data Deficient" at the IUCN Red List. The reason for this is that many assessments on the IUCN Red List are "out of date". These species and subspecies are included into The Sixth Extinction Website's lists of recently extinct animals and plants when other various reliable information sources indicate that it can be classified as Extinct. (IUCN, 2008)

What are the criteria for including a species or subspecies into The Sixth Extinction Website's list of missing animals?

Species and subspecies that are not classified as Extinct at the IUCN Red List of Threatened Species, but have not been seen for many years. Often those are animals and plants that are classified as Critically Endangered or Data Deficient by the IUCN Red List. BirdLife International applies also 'Possibly Extinct' tag to certain Critically Endangered species: CR (PE). This is not an official category of the IUCN Red List, but is under review by the IUCN Red List. This tag is to identify those species and subspecies 'that are likely to be extinct, but for which there is a small chance that they may still be extant, and hence they should not be listed as Extinct until local or unconfirmed reports have been discounted, and adequate surveys have failed to find any individuals'. The Sixth Extinction Website applies Possibly Extinct for those missing animals and plants. (IUCN, 2008; BirdLife International, 2008)

The Sixth Extinction Website's and corresponding categories
The Sixth Extinction Website IUCN Red List 1 BirdLife International 2
EX Extinct EX Extinct EX Extinct
EW Extinct in the wild EW Extinct in the wild EW Extinct in the wild
PE Possibly Extinct - - CR(PE) Critically Endangered (Possibly Extinct)
PW Possibly Extinct in the Wild - - - -
- - CR Critically Endangered CR Critically Endangered
- - EN Endangered EN Endangered
- - VU Vulnerable VU Vulnerable
- - NT Neat Threatened NT Neat Threatened
- - LC Lower Risk LC Lower Risk
- - DD Data Deficient DD Data Deficient
NE Not Evaluated NE Not Evaluated NE Not Evaluated
RD Rediscovered - - - -
RI Reintroduced - - - -
NR Not Recognised - - NR Not Recognised

 

  1. IUCN (2008), 2001 IUCN Red List Categories and Criteria version 3.1.
  2. BirdLife International (2008), Species factsheets: Terms & Definitions

News Highlight

24 June 2012. The last Pinta giant tortoise (Chelonoidis abingdoni) Lonesome George dies. Read more: BBC News.

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