A review of the status of Canada's amphibian and reptile species: A comparison of three ranking systems

Abstract

We assigned national conservation priority ranks to the 93 native and introduced Canadian amphibian and reptile species using the International Union for the Conservation for Nature and Natural Resources (IUCN) [=World Conservation Union] criteria and The Association for Biodiversity Information (ABI) criteria independently. We used these results, along with national designations previously assigned to a number of these species by the Committee on the Status of Endangered Wildlife in Canada (COSEWlC), to compare the three ranking systems at the national scale. We also used existing IUCN and ABI ranks to compare these two systems at the global scale. At the global scale, considerable variability exists, and it is not possible to determine the rank under one system by determining the rank under the other - The only way to find out for certain is to evaluate the species against the criteria. At the national scale, there is not good correspondence between the COSEWlC system and the IUCN system. However, there is excellent correspondence between the COSEWlC and ABI systems: All 26 species with concern status assigned by COSEWlC (Endangered, Threatened, or Vulnerable) were ranked N1-N3, NX or NH using the ABI system. All five N4 and N5 species were ranked Not At Risk by COSEWIC. The ABI system appears to be more sensitive than the IUCN system at the lower risk levels, while the IUCN system focusses on the levels of higher risk. Species highly ranked using the ABI system (NX, NH, N1, or N2) always had a rank of concern using the IUCN system (RE, CR, EN, VU, or NT), whereas species ranked low in the ABI system (N4 or N5) were always ranked Least Concern (LC) using the IUCN system. We believe that this strong relationship will hold for other taxonomic groups. Both the IUCN and ABI ranking systems have merits, and it might be useful to evaluate species using both systems independently. We suggest combining the two ranks into a new national rank, and we present a simple way of doing this. This process should lead to a stronger justification for the status ultimately given. In the longer term, a single system incorporating the benefits of the ABI and IUCN systems is desirable. However, one drawback to making major changes to either system is that species already evaluated will have to be re-evaluated depending on the extent of the changes.