I) Introduction HTMLNEWLINE HTMLNEWLINE 1.The threatened species categories now used in Red Data Books and Red Lists have been in place, with some modification, for almost 30 years. Since their introduction these categories have become widely recognised internationally, and they are now used in a whole range of publications and listings, produced by IUCN as well as by numerous governmental and non-governmental organisations. The Red Data Book categories provide an easily and widely understood method for highlighting those species under higher extinction risk, so as to focus attention on conservation measures designed to protect them.
2.The need to revise the categories has been recognised for some time. In 1984, the SSC held a symposium, 'The Road to Extinction' (Fitter and Fitter 1987), which examined the issues in some detail, and at which a number of options were considered for the revised system. However, no single proposal resulted. The current phase of development began in 1989 with a request from the SSC Steering Committee to develop a new approach that would provide the conservation community with useful information for action planning.
In this document, proposals for new definitions for Red List categories are presented. The general aim of the new system is to provide an explicit, objective framework for the classification of species according to their extinction risk.
The revision has several specific aims:
3.The proposals presented in this document result from a continuing process of drafting, consultation and validation. It was clear that the production of a large number of draft proposals led to some confusion, especially as each draft has been used for classifying some set of species for conservation purposes. To clarify matters, and to open the way for modifications as and when they became necessary, a system for version numbering was applied as follows:
Version 1.0: Mace and Lande (1991) - The first paper discussing a new basis for the categories, and presenting numerical criteria especially relevant for large vertebrates.
Version 2.0: Mace et al. (1992) - A major revision of Version 1.0, including numerical criteria appropriate to all organisms and introducing the non-threatened categories.
Version 2.1: IUCN (1993) - Following an extensive consultation process within SSC, a number of changes were made to the details of the criteria, and fuller explanation of basic principles was included. A more explicit structure clarified the significance of the non-threatened categories.
Version 2.2: Mace and Stuart (1994) - Following further comments received and additional validation exercises, some minor changes to the criteria were made. In addition, the Susceptible category present in Versions 2.0 and 2.1 was subsumed into the Vulnerable category. A precautionary application of the system was emphasised.
Final Version - This final document, which incorporates changes as a result of comments from IUCN members, was adopted by the IUCN Council in December 1994.
All future taxon lists including categorisations should be based on this version, and not the previous ones.
4.In the rest of this document the proposed system is outlined in several sections. The Preamble presents some basic information about the context and structure of the proposal, and the procedures that are to be followed in applying the definitions to species. This is followed by a section giving definitions of terms used. Finally the definitions are presented, followed by the quantitative criteria used for classification within the threatened categories. It is important for the effective functioning of the new system that all sections are read and understood, and the guidelines followed.
References:
Fitter, R. and Fitter, M. (eds) 1987. The Road to Extinction. IUCN, Gland, Switzerland.
IUCN. 1993. Draft IUCN Red List Categories. IUCN, Gland, Switzerland.
Mace, G. M. et al. 1992. The development of new criteria for listing species on the IUCN Red List. Species 19:16-22.
Mace, G. M. and Lande, R. 1991. Assessing extinction threats: toward a re-evaluation of IUCN threatened species categories. Conservation Biology 5(2):148-157.
Mace, G. M. and Stuart. S. N. 1994. Draft IUCN Red List Categories, Version 2.2. Species 21-22:13-24. HTMLNEWLINE
II) Preamble HTMLNEWLINE The following points present important information on the use and interpretation of the categories (= Critically Endangered, Endangered, etc.), criteria (= A to E), and sub-criteria (= a,b etc., i,ii etc.) :
1.Taxonomic level and scope of the categorisation process
The criteria can be applied to any taxonomic unit at or below the species level. The term 'taxon' in the following notes, definitions and criteria is used for convenience, and may represent species or lower taxonomic levels, including forms that are not yet formally described. There is a sufficient range among the different criteria to enable the appropriate listing of taxa from the complete taxonomic spectrum, with the exception of micro-organisms. The criteria may also be applied within any specified geographical or political area although in such cases special notice should be taken of point 11 below. In presenting the results of applying the criteria, the taxonomic unit and area under consideration should be made explicit. The categorisation process should only be applied to wild populations inside their natural range, and to populations resulting from benign introductions (defined in the draft IUCN Guidelines for Re-introductions as "..an attempt to establish a species, for the purpose of conservation, outside its recorded distribution, but within an appropriate habitat and eco-geographical area").
2.Nature of the categories
All taxa listed as Critically Endangered qualify for Vulnerable and Endangered, and all listed as Endangered qualify for Vulnerable. Together these categories are described as 'threatened'. The threatened species categories form a part of the overall scheme. It will be possible to place all taxa into one of the categories (see Figure 1).
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