title: Impact of alternative metrics on estimates of extent of occurrence for extinction risk assessment.
abstract: In International Union for Conservation of Nature (IUCN) Red List assessments, extent of occurrence (EOO) is a key measure of extinction risk. However, the way assessors estimate EOO from maps of species' distributions is inconsistent among assessments of different species and among major taxonomic groups. Assessors often estimate EOO from the area of mapped distribution, but these maps often exclude areas that are not habitat in idiosyncratic ways and are not created at the same spatial resolutions. We assessed the impact on extinction risk categories of applying different methods (minimum convex polygon, alpha hull) for estimating EOO for 21,763 species of mammals, birds, and amphibians. Overall, the percentage of threatened species requiring down listing to a lower category of threat (taking into account other Red List criteria under which they qualified) spanned 11-13% for all species combined (14-15% for mammals, 7-8% for birds, and 12-15% for amphibians). These down listings resulted from larger estimates of EOO and depended on the EOO calculation method. Using birds as an example, we found that 14% of threatened and near threatened species could require down listing based on the minimum convex polygon (MCP) approach, an approach that is now recommended by IUCN. Other metrics (such as alpha hull) had marginally smaller impacts. Our results suggest that uniformly applying the MCP approach may lead to a one-time down listing of hundreds of species but ultimately ensure consistency across assessments and realign the calculation of EOO with the theoretical basis on which the metric was founded.
authors.affiliation: Microsoft Research, 1 Microsoft Way, Redmond, WA, U.S.A.
authors.forename: Lucas N
authors.initials: LN
authors.lastname: Joppa
authors.affiliation: BirdLife International, Unit 1, Wellbrook Court, Cambridge, CB23 0NA, United Kingdom.
authors.forename: Stuart H M
authors.initials: SH
authors.lastname: Butchart
authors.affiliation: IUCN Species Survival Commission, International Union for Conservation of Nature, 28 rue Mauverney, CH-1196, Gland, Switzerland.|United Nations Environment Programme World Conservation Monitoring Centre, 219c Huntingdon Road, Cambridge, CB3 0DL, United Kingdom.
authors.forename: Michael
authors.initials: M
authors.lastname: Hoffmann
authors.affiliation: Royal Botanic Gardens, Kew, Richmond, Surrey, TW9 3AB, United Kingdom.|School of Geography, Sir Clive Granger Building, University of Nottingham, University Park, Nottingham, NG7 2RD, United Kingdom.
authors.forename: Steve P
authors.initials: SP
authors.lastname: Bachman
authors.affiliation: Department of Ecology and Evolution, Stony Brook University, 650 LSB Stony Brook, New York, 11794, U.S.A.
authors.forename: H Resit
authors.initials: HR
authors.lastname: Akçakaya
authors.affiliation: Royal Botanic Gardens, Kew, Richmond, Surrey, TW9 3AB, United Kingdom.|School of Geography, Sir Clive Granger Building, University of Nottingham, University Park, Nottingham, NG7 2RD, United Kingdom.
authors.forename: Justin F
authors.initials: JF
authors.lastname: Moat
authors.affiliation: Institute of Zoology, Zoological Society of London, Regent's Park, London, NW1 4RY, United Kingdom.
authors.forename: Monika
authors.initials: M
authors.lastname: Böhm
authors.affiliation: Centre for Biological Sciences, University of Southampton, Southampton, United Kingdom.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Holland
authors.affiliation: Department of Life and Environmental Science, Bournemouth University, Dorset, United Kingdom.
authors.forename: Adrian
authors.initials: A
authors.lastname: Newton
authors.affiliation: School of Mathematical and Natural Sciences, Arizona State University - West, Phoenix, U.S.A.
authors.forename: Beth
authors.initials: B
authors.lastname: Polidoro
authors.affiliation: Royal Society for the Protection of Birds, The Lodge, Potton Road, Sandy, Bedfordshire, SG19 2DL, United Kingdom.
authors.forename: Adrian
authors.initials: A
authors.lastname: Hughes
mesh_terms: D000663:Amphibians / Q000502:physiology; D000818:Animals; D001717:Birds / Q000502:physiology; D003247:Conservation of Natural Resources / Q000379:methods*; D056727:Endangered Species; D053476:Extinction, Biological; D008322:Mammals / Q000502:physiology; D018570:Risk Assessment
keywords: IUCN Red List; Lista Roja UICN; amenazado; distribution maps; mapas de distribución; threatened