Using a sampled approach to Red Listing


To identify trends using the RLI a group of species must be assessed at least two time points. For the IUCN Red List Index, this approach has only been applied to species groups where all taxa in the group have been assessed at more than one interval, such as birds and amphibians. Ideally all species groups could be comprehensively assessed at regular intervals, but this is impractical with many particularly large, species groups which represent the majority of biodiversity (e.g. fish, dicots, insects, crustaceans and molluscs). To address this issue, the IUCN Red List Index (sampled approach) has been designed.

The IUCN Red List Index (sampled approach) (SRLI) – carried out at a global scale – is based on a representative sample of species selected from taxonomic groups within vertebrates, invertebrates, plants, fungi and algae. The selected species will be re-assessed at regular intervals and genuine changes in conservation status identified to measure trends in extinction risk.

The following criteria were used to select species groups:

  • There must be a complete or near complete global species list
  • The list must be managed and will continue to be managed into the future
  • The list must contain over 1,500 species (to be useful for the sampling approach)
  • There must be experts capable of conducting conservation assessments
  • There must be sufficient data available to assess the species against the IUCN Red List criteria and for at least60% of them not to qualify as Data Deficient.

The SRLI can be applied at a regional or national level for highly species-rich taxa, e.g. such as vascular plants in Spain.

Find out more about the global SRLI here and in the IUCN Red List Index Guidelines for the Sampled Approach.