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.