The Sampled Red List Index (SRLI)

The SRLI is a collaboration between IUCN members, coordinated through the Institute of Zoology.

By conducting conservation assessments at regular intervals, changes in the threat status of taxonomic species groups can be used to monitor trends in extinction risk.

RLIs have already been calculated for birds (photo) and amphibians – two species groups which have been comprehensively covered in the IUCN Red List.

The RLI has been adopted by the CBD as one of the indicators to measure progress towards this important target, and specifically to monitor changes in threat status of species.

How did the SRLI come about?

In recognition that targets such as CBD 2010 require a more rapid approach to generating conservation assessments across mega-diverse taxonomic groups, a sampled approach to the Red List Index (SRLI) has been developed in order to determine the threat status and trends of lesser-known and less charismatic species groups.

The SRLI is based on a representative sample of 1,500 species selected for a number of taxonomic groups within vertebrates, invertebrates, plants, and fungi.

Taxonomic groups consisting of less than 1,500 described species will be comprehensively assessed using the IUCN Red List Categories and Criteria. Find out more about the IUCN Categories and Criteria.

As a result, the SRLI will provide a more broadly representative picture of biodiversity change.

It will give us baseline information on the current status of biodiversity, which we can compare to potential future changes in threat status during reassessments of the SRLI taxa.

Who carries out the assessments?

Any project as ambitious as this requires a large network of contributors.

Different species groups are assessed by different organisations or initiatives. For example, comprehensive species assessments from the IUCN-led Global Mammal Assesment and Global Amphibian Assessment , as well as comprehensive bird assessments coordinated by Birdlife International, will feed into the SRLI.

Other species groups are being assessed by expert organisations: for example, plants are assessed at the Royal Botanical Gardens at Kew , corals by the Global Marine Species Assessment and dragonflies by the IUCN Dragonfly Specialist Group.

ZSL has led the SRLI assessments for a number of groups, such as crayfish, freshwater molluscs, reptiles, fish and lobsters.

How is the SRLI calculated?

In a nutshell, the SRLI uses weight scores based on the Red List status of each of the sample species.

These scores range from 0 (Least Concern) to Extinct/Extinct in the Wild (5).

Summing these scores across all species and relating them to the worst-case scenario - where all species are extinct - gives us an indication of how biodiversity is doing.

Repeating the assessments over time will then allow us to see whether the extinction risk of biodiversity is overall increasing, decreasing or staying the same.

For example, this can be seen in the picture at the top of the page which shows the RLI for all birds as calculated by Birdlife Internation in collaboration with the IUCN.