IUCN CATEGORIES OF THREAT
The
IUCN Red List of Threatened Species (also known as the IUCN Red List or Red
Data List), created in 1963, is the world's most comprehensive inventory of the
global conservation status of plant and animal species. The International Union
for the Conservation of Nature and Natural Resources (IUCN) is the world's main
authority on the conservation status of species.
The
IUCN Red List is set upon precise criteria to evaluate the extinction risk of
thousands of species and subspecies. These criteria are relevant to all species
and all regions of the world. The aim is to convey the urgency of conservation
issues to the public and policy makers, as well as help the international
community to try to reduce species extinction.
Major
species assessors include Bird Life International, the Institute of Zoology
(the research division of the Zoological Society of London), the World
Conservation Monitoring Center, and many Specialist Groups within the IUCN's
Species Survival Commission (SSC). Collectively, assessments by these
organizations and groups account for nearly half the species on the Red List.
IUCN
Red List is widely considered to be the most objective and authoritative system
for classifying species in terms of the risk of extinction.
The
IUCN aims to have the category of every species re-evaluated every 5 years if
possible, or at least every ten years. This is done in a peer-reviewed manner
through IUCN Species Survival Commission (SSC) Specialist Groups, which are Red
List Authorities responsible for a species, group of species or specific
geographic area, or in the case of Bird Life International, an entire class
(Aves). There are over 7000 extant species in the 2006 Red List which have not
had their category evaluated since 1996.
The IUCN Red List Categories and
Criteria have several specific aims:
To provide a system
that can be applied consistently by different people;
To improve
objectivity by providing users with clear guidance on how to evaluate different
factors which affect the risk of extinction;
To provide a system
which will facilitate comparisons across widely different taxa;
To give people using
threatened species lists a better understanding of how individual species were
classified.
2006 release
The 2006 Red List, released on 4 May 2006 evaluated 40,168 species as a
whole, plus an
additional 2,160 subspecies, varieties,
aquatic stocks, and subpopulations.
From the species evaluated as a whole, 16,118 were considered threatened.
Of these, 7,725 were
animals, 8,390 were plants, and three were lichen and mushrooms.
This release listed 784 species extinctions recorded since 1500 CE,
unchanged from the 2004
release. This was an increase of 18 from the 766 listed as of 2000. Each
year a small number of
"extinct" species may be rediscovered, becoming Lazarus species,
or may be reclassified as "data
deficient". In 2002, the extinction list dropped to 759 species, but has
been rising ever since.
2007 release
On September 12, 2007, the World Conservation Union (IUCN) released the 2007
IUCN Red
List of Threatened Species, the latest update to their online database of species' extinction risks.
In this release, they have raised their classification of both the Western
Lowland Gorilla (Gorilla
gorilla gorilla) and
the Cross River Gorilla (Gorilla gorilla diehli) from Endangered to
Critically
Endangered, which is the last category before Extinct in the Wild, due to
Ebola virus and
poaching, along with other factors. Russ Mittermeier, chief of Swiss-based
IUCN's Primate
Specialist Group, stated that 16,306 species are endangered with
extinction, 188 more than in
2006 (total of 41,415 species on the Red List). The Red List includes the
Sumatran Orangutan
(Pongo abelii) in the Critically Endangered category and the Bornean
Orangutan (Pongo
pygmaeus) in the
Endangered category.
Species are classified in nine
groups, set through criteria such as rate of decline, population size,
area of geographic distribution, and
degree of population and distribution fragmentation. A
representation of the
relationships between the categories is shown in Figure
Extinct (EX) : 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.
Extinct in the Wild (EW) : A
taxon 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 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.
Critically Endangered (CR) : A
taxon 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.
Endangered (EN) : A taxon 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.
Vulnerable (VU) : A taxon 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.
Near Threatened (NT) : A taxon 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.
Least Concern (LC) : A taxon 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.
In the 2001 system, Near Threatened and
Least Concern have now become their own categories, while Conservation Dependent
is no longer used and has been merged into Near Threatened.
Data Deficient (DD) : A
taxon 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 taxon 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 taxon is suspected to be relatively
circumscribed, and a considerable period of time has elapsed since the last
record of the taxon, threatened status may well be justified.
Not Evaluated (NE) : A
taxon is Not Evaluated when it is has not yet been evaluated against the
criteria.
Note: As
in previous IUCN categories, the abbreviation of each category (in parenthesis)
follows the English denominations when translated into other languages. When
discussing the IUCN Red List, the official term "threatened" is a
grouping of three categories: Critically Endangered, Endangered, and
Vulnerable.
Possibly Extinct : The additional category of Possibly Extinct
(PE) is used by Birdlife International, the Red List Authority for birds for
the IUCN Red List. Birdlife International has recommended PE become an official
category. BirdLife International has not stated whether a "Possibly
Extinct in the Wild" category should also be added, although it is
mentioned that Spix's Macaw has this status. "Possibly Extinct" can
be considered a subcategory of "Critically Endangered".
Criticism
The IUCN Red List has come under criticism on the grounds of secrecy
surrounding the sources
of data, among other allegations.
Mass extinctions
Apparent fraction of genera going extinct at any
given time, as reconstructed from the fossil record. Does not attempt to
include recent Holocene extinction event.
There have been at least five mass
extinctions in the history of life, and four in the last 3.5 billion years in
which many species have disappeared in a relatively short period of geological
time. The most recent of these, the Cretaceous–Tertiary extinction event 65
million years ago at the end of the Cretaceous period, is best known for having
wiped out the non-avian dinosaurs, among many other species.
Modern mass
extinction :
According to a 1998 survey of 400 biologists
conducted by New York's American Museum of Natural History, nearly 70 percent
believed that they were currently in the early stages of a human-caused mass
extinction, known as the Holocene extinction event. In that survey, the same
proportion of respondents agreed with the prediction that up to 20 percent of
all living populations could become extinct within 30 years (by 2028).
Biologist E. O. Wilson estimated in 2002 that if current rates of human
destruction of the biosphere continue, one-half of all species of life on earth
would be extinct in 100 years. More significantly the rate of species
extinctions at present is estimated at 100 to 1000 times "background"
or average extinction rates in the evolutionary time scale of planet Earth.
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