IUCN Red List Index

The Red List Index (RLI) shows trends in overall extinction risk for species, and is used by governments to track their progress towards targets for reducing biodiversity loss.

Most species that move between categories on The IUCN Red List (see the section Reasons for Changing Category) do so because of improved knowledge or revised taxonomy. It is therefore impossible to determine any meaningful trends in the status of biodiversity simply by looking at overall changes in numbers of threatened species between updates. For this reason, the figures presented in the Summary Statistics for numbers of threatened species in each IUCN Red List since 1996 must be interpreted with extreme care; these figures illustrate increasing assessment efforts by IUCN and its Partners since 1996, helping to refine our current understanding of the status of biodiversity, rather than showing genuine status changes over time.

To address this, the Red List Index (RLI) has been developed, which shows trends in the status of groups of species based only on genuine improvements or deteriorations in status of sufficient magnitude to qualify species for listing in more threatened or less threatened Red List Categories.