Red List Index

Summary of 2006 IUCN Red List categories.

The Red List Index (RLI), based on the IUCN Red List of Threatened Species, is an indicator of the changing state of global biodiversity. It defines the conservation status of major species groups, and measures trends in extinction risk over time. By conducting conservation assessments at regular intervals, changes in the threat status of species in a taxonomic group can be used to monitor trends in extinction risk. RLIs have been calculated for birds and amphibians, using changes in threat status for species in each of the groups.

As well as taxonomic groups, RLIs can show trends in extinction risk according to biogeographic realm, habitat type, and dominant threat process.

Producing indices of change in extinction risk by comprehensively assessing whole species groups, while feasible for well studied groups with relatively few species, is not suitable for all taxonomic groups. Assessing every species in the larger and lesser known groups which comprise the majority of the world’s biodiversity, such as fungi, invertebrates (particularly insects) and plants, is not practical.

The Red List Index (sampled approach) (SRLI) has been developed in order to determine the threat status and also trends of lesser-known and less charismatic species groups. It is a collaboration between IUCN members and is coordinated through the Institute of Zoology (IoZ), the research division of the Zoological Society of London (ZSL). The SRLI is based on a representative sample of species selected from taxonomic groups within animals (invertebrates and vertebrates), fungi and plants.

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