Exploring The IUCN Red List of Threatened Species

If you were told that a species was classed as ‘Vulnerable’ on the IUCN Red List of Threatened Species, would you know what it meant?

With guidance from Mike Hoffmann from the Zoological Society of London, we will explore the IUCN Red List of Threatened Species, the world’s most comprehensive tool for assessing the extinction status of species.

The IUCN Red List was first conceived in the 1960s by Peter Scott, also a founder of WWF, and since then, it has come a long way. It now includes ∼140,000 assessed species, with 25% of these being classed as threatened. Its primary aim is to identify species in the wild that are at risk of extinction through reliable scientific data, making the IUCN Red List a trusted and credible source of information that can help inform conservation decisions.

How Does It Work?

For a species to be added to the IUCN Red List, it must go through an assessment process, after which its extinction risk status is assigned from a selection of eight different categories:

  • Extinct –When there is no reasonable doubt that the last individual of a taxon has died.
  • Extinct in the Wild – Only present in captive or naturalised populations outside its original range.
  • Critically Endangered – Extremely high risk of extinction in the wild.
  • Endangered – Very high risk of extinction in the wild.
  • Vulnerable – High risk of extinction in the wild.
  • Near Threatened - Close to qualifying for a threatened category or is likely to qualify in the near future.
  • Least Concern – Low risk of extinction in the wild. Includes widespread and abundant species.
  • Data Deficient – Inadequate information for extinction risk assessment.

<a href="https://commons.wikimedia.org/wiki/File:Status_iucn3.1_expanded.svg">Peter Halasz</a>, <a href="https://creativecommons.org/licenses/by/2.5">CC BY 2.5</a>, via Wikimedia CommonsPeter Halasz, CC BY 2.5, via Wikimedia Commons

Any species can be included on the Red List, with a few exceptions, such as hybrid or domesticated species.  An assessment must be completed for an extinction risk category to be allocated, following the quantitative criteria detailed in the ‘IUCN Red List Categories and Criteria’ document.

Assessments must also consider the species globally, rather than focusing on national or regional populations – although there are exceptions to this rule, which Mike Hoffman explains in our video ‘A Primer on the IUCN Red List’, included later on in this blog.

What’s On The List?

Despite its name including the term ‘Threatened Species’, the IUCN Red List will cover any animal, plant or fungi species, regardless of their extinction risk.

It includes common species such as the House Mouse (Mus musculus), which is widespread globally and classed as ‘Least Concern’. At the other end of the scale, some species at risk of extinction may only exist in a tiny population, like the freshwater fish known as Grey’s Char (Salvelinus grayi). This species is classed as ‘Critically Endangered’, and its only known population is Lough Melvin Lake in Ireland.

Previously, there has been bias towards the inclusions and assessments of mammals and birds over other taxa, particularly invertebrates. However, the IUCN is working to increase the number of invertebrates on the list as more population data on species becomes available.

'Spineless: Status Trends of The World's Invertebrates' - This 2012 report by the Zoological Society of London uses data from the IUCN Red List to discuss the status and trends of the world’s invertebrates.


Why Is It Important?

Although the IUCN Red List is well known for categorising species into extinction status categories (Endangered, Least concern etc.), it also provides information on species distribution and range maps, different populations, taxonomy, habitat preferences, threats, and actions.
Information on range and distribution can be used by conservationists and others to help identify sites that are important for the persistence of biodiversity and need safeguarding into the future. This can be particularly important for species with only one population globally and can help identify areas of land that need protecting for the species’ survival.  

Data from the IUCN Red List can also be used by conservation programs to help inform decisions and actions – although it should be used alongside other relevant research.
A perfect example of this is the EDGE (Evolutionary Distinct and Globally Endangered) programme. EDGE brings together information about phylogenetic diversity and species’ threat level from the IUCN Red List to aid conservation work. It is a programme that ‘highlights and protects some of the most unique species on the planet, which are on the verge of extinction’.

 A Primer to the IUCN Red List - By Mike Hoffmann

Mike Hoffmann heads up global wildlife recovery programmes at the Zoological Society of London. He has more than two decades of experience in international conservation, including having spent 10 years with the International Union for Conservation of Nature (IUCN), where he worked extensively on the Red List. He is the former Chair of the IUCN Red List Committee and has participated in more than 1000 species assessments for multiple taxa ranging from mammals to seagrasses.
Mike joined us to discuss categories, criteria and applications of the IUCN Red List, plus some handy tips on how to get the most out of it. Following on from the video we have the answers to your questions and some helpful resources.


Q & A with Mike Hoffmann

Is there a category called “Conservation Dependant” and has this been removed or changed recently?
There used to be a category called Least Concern/conservation dependent, but this category was removed when the system was revised in 2001. A provision has remained in the system for species that are otherwise Least Concern, but remain conservation dependent, to be listed as Near Threatened, but this provision will be removed from the system very soon.

Do criteria for measuring the health of species change or get updated regularly?
The criteria haven’t changed since 2001, but the guidelines do change. Two key documents to be aware of are the “Red List Categories and Criteria” booklet, and the “Guidelines for the Application of the Categories and Criteria” booklet.

How do you see the relationship between the IUCN and CITIES?
The Red List and CITES perform very different functions. The Red List is primarily an independent tool for assessing risk of extinction to species in the wild and CITES is primarily used to understand where species are threatened by international trade. Information on the Red List can be used to help inform where a species may be eligible for listing on a CITES appendix due to international trade. But ultimately, they are different lists with different processes and protocols.

At what point is a managed population considered suitable for assessment for the Red List, for example, with reintroduction programs where the aim is to eventually build a wild population?
It is species dependent and there are specific rules that apply. For example, if a subpopulation is dependent on extensive direct care, such as providing most of the food needs, then it would not be considered eligible for inclusion. There is guidance on this in the “Guidelines for the Applications of the Categories and Criteria” booklet.

Observation- It is strange that the Tawny Mining Bee, Andrena fulva, is listed as “Data Deficient”, as it seems to be well recorded?
It is likely that there is a significant amount of uncertainty that the species is “Least Concern” or in very serious category of threat. It is also possible that a species that is well recorded in the UK, and potentially even Least Concern, may be poorly known globally, leading to a global assessment of “Data Deficient”.

Who does the Red List assessments- is it volunteers or is it professionals?
It depends if it is at a national level or global level. Nationally, individuals are contracted to coordinate and lead a lot of the assessments, and different countries have different protocols for doing this. Globally, many of the assessments are done by the IUCN themselves, or by its Red List partner organisations. Many of the assessments are also done by Specialist Groups- these are volunteer networks of experts that sit underneath the IUCN and they range in focus from antelopes to cycads to butterflies.

What can we do to help contribute, so that other people can contribute to the national Red List, and help support future global assessments?
JNCC have set up an inter-agency working group coordinated/chaired by JNCC, with reps from the Natural England etc. It will have responsibility maintaining and publishing GB Red Lists in future (including prioritizing lists for development) and so they are still busy working through a whole bunch of things to figure out efficiencies, optimal working arrangements etc. So, at the moment, there isn’t a clear means of contributing… but watch this space!

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