o_19ko2dt161ng2j4e1tgnoqv1s45a.pdf

C. LUSTY, W.A.N.AMARAL, W. D.HAWTHORNE, L.T. HONG & S. OLDFIELD (2007)
entitled “Main differences between versions 2.3 and 3.1.”). A system for the application of
categories at a regional level was also devised and published in 2003 (IUCN 2003).
In version 2.3 and 3.1 the IUCN have striven to develop a scientifically thorough and robust
evaluation system to represent as accurately as possible the risk of species extinction. The
system is impressively flexible in being applicable to a wide range of life forms under very
different types of threat, everything from corals, colonial ants, obscure mosses known only
from one location, ancient redwoods, elephants and commercially-exploited fish species.
Such broad applicability has been achieved through the use of a range of criteria, of which
only one need apply for the allocation of a threat category:
A. Population reduction (past, present or future)
B. Limited geographic range, fragmented, declining or fluctuating
C. Small population size and fragmented, declining or fluctuating
D. Very small population or restricted distribution
E. Quantitative analysis of extinction risk
Each criterion has three quantitative thresholds corresponding to increasing extinction risk:
‘Critically Endangered’, ‘Endangered’ or ‘Vulnerable’. Species that do not meet any thresholds
are considered either to be ‘Near Threatened’, ‘Least Concern’, ‘Data Deficient’ or ‘Not
evaluated’. The thresholds are arbitrary but appear to be generally applicable to a wide range
of threatened taxa. For any one species, the thresholds of some criteria may be inappropriate
but at least one alternative criterion should be applicable. The spirit in which the system was
devised encourages the user to examine each species profile against all five criteria so that the
most relevant and precautionary assessment is attained. For more details you are directed to
the red list categories and guidelines (IUCN 2001; IUCN 2005; http://www.iucnredlist.org/
info/programme.html).
Main differences between versions 2.3 and 3.1 of the IUCN Red List Categories
• New A subcriterion with a more challenging threshold (reductions of at least 50% as
opposed to 20%) for species which are subject to population declines because of known
and reversible threats. This provides leeway for species undergoing a controllable
decline (e.g. commercial exploitation) to avoid classification as threatened until a
more serious population decline has taken place;
• The threshold for species classified under VU A have risen from a 20% population
decline to 30%;
• Allowance of population declines within a ‘moving window’ of the past or future in
A4
• Maximum time cap for derived future declines of 100 years;
• Addition of subcriterion on extreme fluctuations under C2;
• VU D2 guidelines for restricted area of occupancy reduced from 100km 2 to 20km 2
• Loss of ‘Lower Risk - Conservation Dependent’*
• Some important changes in definitions have taken place
• National and regional level assessments possible
* this affects the evaluation of 20% of Peninsular Malaysian tree species which were assessed
against version 3.0 categories – the most appropriate category for these species is now ‘Near
Threatened’
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