Red List Index

Last updated: 2025

Introduction

The Red List Index measures changes in the overall combined global extinction risk of species found within the UK. It reflects the UK’s contribution to the status of global biodiversity by tracking the global threat status of species in taxonomic groups with sufficient Red List coverage, whilst giving greater weight to those species with a higher proportion of their global distribution found in the UK. The Red List Index is based on the global extinction risk of species that occur in the UK, rather than the extinction risk of species at the UK scale. Red List Index values can range from 1 to 0. A value of 1 would indicate that all species are listed as Least Concern (the lowest threat category), while a value of 0 would indicate that all species are listed as Extinct.

This indicator is already published for the UK as Sustainable Development Goal (SDG) indicator 15.5.1 and can be viewed on the UN Statistics page for the UK. Therefore, it is not published here as an official statistic and does not form part of the UK Biodiversity Indicators publication.

This page is being published as part of the UK’s response to the Convention on Biological Diversity’s Kunming-Montreal Global Biodiversity Framework (GBF). This indicator relates to GBF Goal A and Target 4.

Further detail

Detailed methods for this indicator are available in the metadata for SDG indicator 15.5.1, including limitations and sources of uncertainty associated with Red List Index values and trends. It is produced by the International Union for the Conservation of Nature (IUCN) and BirdLife International.

The indicator is calculated from the IUCN Red List of Threatened Species, using global Red List assessments that are weighted by the proportion of each species’ global range that is within the UK.

The IUCN Red List of Threatened Species is an internationally recognised inventory of conservation status for species of animals, fungi and plants. The Red List criteria provide a standardised and repeatable method for assessing species extinction risk.

The indicator is calculated annually, although not all species are reassessed each year. Only taxonomic groups with complete or representative assessments are included in order to avoid spurious results from biased species selection. Changes to threat categories represent genuine changes in status, rather than changes in taxonomy or knowledge.

In addition to global Red List assessments, Red List assessments are carried out for species at the Great Britain (GB) scale. A Red List Index for England, using assessments of extinction risk at the GB scale for species native to England, is published in the Outcome Indicator Framework as indicator D5: Conservation of our native species. NatureScot maintain a Species at Risk database, which also includes GB-level Red List assessments. Red List assessments are also carried out at the island of Ireland scale and are available via Ireland’s National Biodiversity Data Centre.

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