The Role of Geographic Range Metrics in Determining National Threat Status of Species; A Case Study of Anatidae in Iran

Geographic range metrics، important predictors of extinction risk، are commonly used in international and national red listing processes. Criterion B of IUCN Red List is based on these metrics، especially the Extent of Occurrence (EOO) and the Area of Occupancy (AOO). Inconsistencies in interpreting the two metrics and methods for calculating them have caused criterion B to be the most commonly misused among the Red List criteria. With an aim to introduce a nationally practical and repeatable method for calculating EOO and AOO، in this study these metrics were calculated for Anatidae in Iran. For calculating EOOs، distribution ranges were considered without exclusion of discontinuities and areas of unsuitable habitat. For calculating AOOs، since the scale of the present distribution maps (cell size of 25 km) differed from the IUCN reference scale (cell size of 2 km)، scale correction factors (C) were used to determine AOOs in the reference scale. Of the 29 non-breeding and 14 breeding species we assessed، three breeding species have the potential to be classified under threatened categories based on EOO while 27 non-breeding and 14 breeding species have the potential to belong to threatened categories based on AOO. The methods used in this study clearly showed the differences in definition and purpose of EOO and AOO. Considering the scarcity of population data on wildlife species in Iran، which hampers the use of other Red List criteria، calculating EOOs and AOOs and assessing species based on criterion B can make the preparation of national red lists practicable.