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Before undertaking Red List assessments using the IUCN Red List Categories and Criteria (IUCN 2012a, available in several languages), users are advised to consult the IUCN Red List website for detailed information about the assessment process. An online IUCN Red List training course is also freely available.

Assessment of the threatened status of species using the IUCN Red List Categories and Criteria (IUCN 2012a) is essentially a four to five-step process:

Collate and document data for each taxon.
(Undertake remedial studies).
Evaluate the taxon against the IUCN Red List criteria.
Collate relevant information about populations of the species in neighbouring countries and apply the IUCN Red List regional criteria, if the taxon is being assessed at regional level (e.g. national assessments of non-endemic species).
Submit global assessments to IUCN for publication.

1. Collate and document data for each taxon

Seven data types should be collated for each taxon (also see Box ‘Summary of data types used in Red Listing’):

taxonomic;
distribution;
population;
habitat and ecology;
use and trade;
threats;
conservation actions.

These data are gathered from a number of sources, including taxon experts, published and grey literature, databases, websites, herbaria and genebanks. If needed, and if possible, field data should also be obtained. To know more about the limitations of using herbarium data in the Red List assessment process (see the Box on 'Use of herbarium data in Red Listing').

Structure of the IUCN Red List categories (IUCN 2012a).

2. [Undertake remedial studies]

If there is not enough data to assess target taxa, further remedial studies in demography, reproductive biology, chorology, genetics etc., could be carried out.

3. Evaluate the taxon against the IUCN Red List criteria

Each taxon is evaluated against the IUCN Red List criteria (IUCN 2012a) and a Red List category is then selected (see the Figure on the right). There are five main Red List criteria:

(A) population reduction,

(B) geographic range (see the Box on 'Geographic range measurements used in criterion B'),

(D) very small or restricted population,

(E) quantitative analysis indicating the probability of extinction.

Each main criterion includes a number of sub-criteria against which the species is evaluated (see Table below). Use this Red List summary sheet (also available in French and Spanish), outlining all five criteria, to evaluate if a taxon belongs in an IUCN Red List threatened category. If the species meets the criteria in at least one of the main classes, it is assigned one of the following threatened categories: Critically Endangered (CR), Endangered (EN) or Vulnerable (VU). If the species meets the criteria in more than one main class, it is assigned the highest category of threat but any other threat categories and criteria that are met are also documented. If the species does not meet any of the criteria A–E needed to evaluate it as threatened, another category is selected. These categories are: Extinct (EX), Extinct in the Wild (EW), Regionally Extinct (RE), Near Threatened (NT), Least Concern (LC), Data Deficient (DD) or Not Applicable (NA) (for definitions of the categories, see IUCN 2001). Before proceeding with the Red List assessment please read the Guidelines for Using the IUCN Red List Categories and Criteria (IUCN Standards and Petitions Subcommittee 2016). If the compiled data are insufficient to make a reasoned judgement about the threatened status of a taxon, the taxon is assessed as Data Deficient (DD). These species should be prioritized for further study in order to gather the required data. Look here for tools that can be used to estimate some of the parameters needed to carry out Red List assessments.

Parameters of the subcriteria against which species are evaluated (*requires data from at least two time points) (source: Magos Brehm et al. 2008b) [for more on the measurements of extent of occurrence (EOO) and area of occupancy (AOO) see Box on ‘Geographic range measurements used in criterion B’].

4. Collate relevant information about populations of the species in neighbouring countries and apply the IUCN Red List regional criteria, if the taxon is being assessed at regional level.

Basic scheme of how to undertake a regional Red List assessment (from Magos Brehm et al. 2008b and adapted from IUCN 2003).

If the taxon is being assessed at regional—not global—level (e.g. national assessments of non-endemic species), the next step is to collate relevant information about populations of the species in neighbouring countries and assess whether it is necessary to downgrade (or rarely to upgrade) the taxon’s global Red List category. Information may be sourced from Red List assessments and conservation status data from the neighbouring countries, from expert knowledge and available literature and knowledge of the taxon’s breeding and dispersal system, combined with its distribution in the region. For a regional Red List assessment, the taxon is subjected to a series of questions which aim to determine whether the taxon’s regional Red List category should remain the same, be downgraded or upgraded from the global assessment (see Figure on the right). For detailed guidance on the information required to undertake a regional Red List assessment, see Table 3 ‘Checklist for judging whether extra-regional populations may affect the extinction risk of the regional population’ and Figure 15 ‘Conceptual scheme of the procedure for assigning an IUCN Red List Category at the regional level’ in the Guidelines for Application of IUCN Red List Criteria at Regional Levels (IUCN 2012b). The regional categories are the same as the global ones, but there are two additional categories: Regionally Extinct (RE) and Not Applicable (NA). The category NA is applied for species with marginal populations in the region or when a species is not native to the region. The regional assessments are the result of downgrades (or very rarely upgrades) from global assessments and they are based on a series of questions essentially concerning conspecific populations outside the region and the status of regional populations as sinks.

5. Submit global assessments to IUCN for publication

Global Red List assessments (i.e. species assessed at global level as well as national/regional endemics) can be submitted for publication in the IUCN Red List of Threatened Species (see here how the assessment process is generally carried out). The IUCN has developed the Species Information Service (SIS), which is a web application and standalone database for conducting and managing species assessments for the IUCN Red List of Threatened Species. The system is intended for use by IUCN SSC Specialist Group members and other IUCN partners working on global Red List assessments as well as regional assessment initiatives led by IUCN. As such, access to SIS is controlled but the the use of SIS facilitates the Red List assessment procedure. For further information about using SIS, users should consult the IUCN Red List website.

TOOLKIT MENU FLOWCHART

Summary of data types used in Red Listing
Summary of data types used in Red Listing

Taxonomy:
Nomenclature (taxon name, authority, synonyms etc.).
Recent taxonomic changes, any current taxonomic doubts or debates about the validity or identity of the species, or issues of synonymy.
Note any subspecific taxa.
Crop(s) the species is related to (common and scientific names) and information on the degree of relatedness between the wild relative and the crop (where known) using the Gene Pool concept (Harlan and de Wet 1971) or Taxon Group concept (Maxted et al. 2006).
Distribution and occurrence:
Summary of the current information available regarding the geographic range of the species.
Countries of occurrence (and sub-national unit(s), where applicable) recorded using built-in descriptors in IUCN’s Species Information Service (SIS).
Extent of occurrence and/or area of occupancy (See the Box on ‘Geographic range measurements used in criterion B’).
A map showing the distribution of the species.
Population:
Summary of the size and trend information available (i.e. increasing, decreasing or stable) of the overall population of the species. If the population is severely fragmented, this is also recorded.
Information about sizes and trends of subpopulations or populations of subspecific taxa, or trends in particular areas of the species’ range can also be included when available.
Where no quantitative information on population sizes or trends is available, an indication of whether the species is common, abundant, or rare etc. should be noted where possible. If there really is no information about the population, this should be noted.
Habitats and ecology:
A summary account of the suitable habitats and ecological requirements of the species, highlighting any potential traits that may be of interest for crop improvement (e.g. drought and salt tolerance).
Comments on the area, extent and/or quality of habitat. In particular, whether the habitat is thought to be stable or declining.
The habitat(s) in which the species occurs, documented using IUCN’s Habitats Classification Scheme.
Use and trade:
A summary account of the information available for any utilization and/or trade of the taxon (local, national and international trade).
A note of any known or potential uses of the species as a gene donor for crop improvement.
Threats:
Major threats that have affected the species in the past, those that are affecting the species now, or those that are likely to affect the species in the future.
The main reason for the threat, the scale of the threat and the stress placed on the species are also recorded where the information is available.
Threats are documented using IUCN’s Threats Classification Scheme.
Conservation:
Any conservation actions currently in place and any realistic actions needed to mitigate threats causing declines, including information on both in situ and ex situ conservation measures.
Conservation actions are documented using IUCN’s Conservation Actions Classification Scheme.
Source: adapted from Kell et al. (2012)
Use of herbarium data in Red Listing

Use of herbarium data in Red Listing

Application of the IUCN Red List Categories and Criteria (IUCN 2012a) requires the use of ‘the best available evidence’. For plants, herbarium and genebank collections usually provide the only source of information for the threat assessment and must therefore qualify as ‘best available evidence’ (Willis et al. 2003), even though they can provide little help in estimating population changes over time. Schatz et al. (2000) and Golding (2002) consider that these data are sufficiently reliable to enable conservation decisions. However, information provided by specimens can result in inconsistent Red List classifications because of the uncertainty associated with population and distribution parameters that arise from the decision rules of the IUCN Red List (IUCN 1994, 2012a).

Often, information used in Red List assessments is interpreted from locality and habitat information contained on specimen labels and inferences and projections are made regarding distribution ranges, scarcity and declines of species. When limited information is available, data often need to be extrapolated in order to make informed estimates, inferences and projections (Golding 2004). On the other hand—while collections made over the last 50 to 60 years usually provide data regarding scientific name, locality, habitat, ecology, date of collection, collector name and collector number—the historical specimens (before or from early 20th century) may only contain few hand written details of the plant name, collector and locality and therefore may be of limited value to conservation assessments. MacDougall et al. (1998) refer to herbarium specimen sheets as a qualitative rather than quantitative data source. Locality coordinate data acquired from herbarium specimen data will often only provide an approximation of species distribution (Willis et al. 2003).

Therefore, the use of specimen passport information from a single population sample should be regarded as provisional because it can result in an inaccurate assignment of Red List statuses of poorly known species, and consequently, influence conservation recommendations (Golding 2004). However, despite the uncertainty, herbarium specimens can be a good start when assessing species extinction risk.
Geographic range measurements used in criterion B

Geographic range measurements used in criterion B

Geographic range measurements used in criterion B

Location: “The term ‘location’ defines a geographically or ecologically distinct area in which a single threatening event can rapidly affect all individuals of the taxon present. The size of the location depends on the area covered by the threatening event and may include part of one or many subpopulations. Where a taxon is affected by more than one threatening event, location should be defined by considering the most serious plausible threat.”

Extent of occurrence (EOO): “Extent of occurrence is defined as the area contained within the shortest continuous imaginary boundary which can be drawn to encompass all the known, inferred or projected sites of present occurrence of a taxon, excluding cases of vagrancy. This measure may exclude discontinuities or disjunctions within the overall distributions of taxa (e.g. large areas of obviously unsuitable habitat). Extent of occurrence can often be measured by a minimum convex polygon (the smallest polygon in which no internal angle exceeds 180 degrees and which contains all the sites of occurrence).”

Area of occupancy (AOO): “Area of occupancy is defined as the area within its 'extent of occurrence' (see above), which is occupied by a taxon, excluding cases of vagrancy. The measure reflects the fact that a taxon will not usually occur throughout the area of its extent of occurrence, which may contain unsuitable or unoccupied habitats. In some cases, (e.g. irreplaceable colonial nesting sites, crucial feeding sites for migratory taxa) the area of occupancy is the smallest area essential at any stage to the survival of existing populations of a taxon. The size of the area of occupancy will be a function of the scale at which it is measured, and should be at a scale appropriate to relevant biological aspects of the taxon, the nature of threats and the available data.”

Source: IUCN (2012a)

The Interactive Toolkit for Crop Wild Relative Conservation Planning was developed within the framework of the SADC CWR project www.cropwildrelatives.org/sadc-cwr-project (2014-2016),
which was co-funded by the European Union and implemented through ACP-EU Co-operation Programme in Science and Technology (S&T II) by the African, Caribbean and Pacific (ACP) Group of States.
Grant agreement no FED/2013/330-210.