Does the Shoe Really Fit? IUCN Status Assessments

The International Union for Conservation of Nature (IUCN) Red List protocol is arguably the most objective and widely accepted tool available for assessing conservation status of organisms. As with other approaches, IUCN assigns ranks based on probability of extinction.  However, IUCN applies the same criteria to organisms whether they live on the expansive plains of the Serengeti or are confined to headwater streams in Tennessee.  We question whether IUCN criteria are equally accurate at estimating extinction risk for mobile taxa versus animals constrained to dendritic systems.  For example, do multiple headwater streams provide species security when all are subjected to drought and a downstream reservoir limits movement to suitable refuge?  Are “area of occupancy” calculations applicable when a dam similarly disrupts distribution?  With a focused effort, IUCN criteria could be modified for dendritic organisms, thus producing a more accurate estimation of probability of extinction. We review the red-listing method, explore various situations, and propose possible solutions.