Extinction: locally extinct for n years — a spatial and temporal measure.

Abstract

LOCAL extinction is often presented as a value judgment where the extinction is regarded as self-evident within a single survey. Thus it has not been subjected to evaluation by the IUCN criteria for ‘extinct’ or ‘extinct in the wild’ and may give a misleading impression of the local status of the species (IUCN 2012). I propose an expression for local extinctions as locally extinct for n number of years (i.e., L. E., n). This format allows a taxon to be identified as locally extinct within a certain geographical range, and most importantly adds a temporal component to the expression. The veracity of claiming extinction is gauged by the number of years since the taxon was last reported. The utility of the temporal component is to be taken in context with the reliability of the survey methods used in searching for the taxon. A taxon that has not been recorded for nine or 49 years would be recorded as locally extinct (L. E. 9 or L. E. 49). The veracity will vary depending on the survey methods and the biology of the taxon. For example, to understand the status of a rare form of a widespread penguin absent for 9 or 49 years from an uninhabited sub-Antarctic island, its term of absence must be considered with its biology and the survey methods employed to find it. How often were surveys conducted and does the penguin show any significant dispersal ability? Once the methods and biology of the penguin are understood a relative value can be considered for the 9 and 49 years. In this way the number of years that a taxon has not been detected can provide a degree of veracity to the statement of local extinction.