Developing a Red List Index at the subnational scale in British Columbia


This case study shows how the IUCN Red List Index method can be adapted for use at a regional scale. Quayle et al. (2007) were the first to adapt the global Red List Index for use at a regional scale, looking at birds in British Columbia, Canada. They took their data from the species ranks assigned by the BC Conservation Data Centre.Their work showed it was important to take several considerations into account, particularly the effects of immigration of species in and out of the region.

1. Retrospective rank correction

The authors used the BC CDC rankings from 1992 to the most recent assessment, and, following recommendations in Butchart et al. (2007), examined changes in conservation status rank for species in the analysis, and determined the reason for the change. They then retrospectively corrected the rank to reflect the true status of the species at each point in time if the rank changes in the species status were as a result of any changes other than genuine changes in conservation status. Non-genuine changes could be criteria changes, or changes in knowledge or taxonomy.

2. Rank comparisons and weighting

In order to use the CDC data to create the RLI, the CDC status ranks had to be converted to a numerical value. This conversion required some adaptation. For example, the CDC ranks place species in a rank range, which allows for uncertainty in an assessment. In this case, the authors took the most imperilled rank in the range as the value.

Once the conversion was complete, the authors could use the method from Butchart et al. (2007) to create an RLI.

For more information on this case study, see also Teucher & Ramsay (2013).