title: Geographic range size and extinction risk assessment in nomadic species.
abstract: Geographic range size is often conceptualized as a fixed attribute of a species and treated as such for the purposes of quantification of extinction risk; species occupying smaller geographic ranges are assumed to have a higher risk of extinction, all else being equal. However many species are mobile, and their movements range from relatively predictable to-and-fro migrations to complex irregular movements shown by nomadic species. These movements can lead to substantial temporary expansion and contraction of geographic ranges, potentially to levels which may pose an extinction risk. By linking occurrence data with environmental conditions at the time of observations of nomadic species, we modeled the dynamic distributions of 43 arid-zone nomadic bird species across the Australian continent for each month over 11 years and calculated minimum range size and extent of fluctuation in geographic range size from these models. There was enormous variability in predicted spatial distribution over time; 10 species varied in estimated geographic range size by more than an order of magnitude, and 2 species varied by >2 orders of magnitude. During times of poor environmental conditions, several species not currently classified as globally threatened contracted their ranges to very small areas, despite their normally large geographic range size. This finding raises questions about the adequacy of conventional assessments of extinction risk based on static geographic range size (e.g., IUCN Red Listing). Climate change is predicted to affect the pattern of resource fluctuations across much of the southern hemisphere, where nomadism is the dominant form of animal movement, so it is critical we begin to understand the consequences of this for accurate threat assessment of nomadic species. Our approach provides a tool for discovering spatial dynamics in highly mobile species and can be used to unlock valuable information for improved extinction risk assessment and conservation planning.
authors.affiliation: School of Biological Sciences, University of Queensland, Brisbane, QLD, 4072, Australia.
authors.forename: Claire A
authors.initials: CA
authors.lastname: Runge
authors.affiliation: School of Geography, Planning and Environmental Management, University of Queensland, Brisbane, QLD, 4072, Australia.
authors.forename: Ayesha
authors.initials: A
authors.lastname: Tulloch
authors.affiliation: School of Biological Sciences, University of Queensland, Brisbane, QLD, 4072, Australia.|School of the Environment, University of Technology, Sydney, NSW, 2007, Australia.
authors.forename: Edd
authors.initials: E
authors.lastname: Hammill
authors.affiliation: School of Biological Sciences, University of Queensland, Brisbane, QLD, 4072, Australia.|Imperial College London, Department of Life Sciences, Silwood Park, Ascot SL5 7PY, Berkshire, England, United Kingdom.
authors.forename: Hugh P
authors.initials: HP
authors.lastname: Possingham
authors.affiliation: School of Biological Sciences, University of Queensland, Brisbane, QLD, 4072, Australia.
authors.forename: Richard A
authors.initials: RA
authors.lastname: Fuller
mesh_terms: D025041:Animal Migration; D000818:Animals; D001315:Australia; D001717:Birds / Q000502:physiology*; D057231:Climate Change; D003247:Conservation of Natural Resources; D003889:Desert Climate; D053476:Extinction, Biological; D008954:Models, Biological; D018570:Risk Assessment
keywords: IUCN Red List; arid zone; conservation priority setting; especie amenazada; establecimiento de prioridades de conservación; geographic range size; lista roja de la UICN; migración; migration; modelado de distribución de especies; nomadism; nomadismo; species distribution modeling; tamaño de extensión geográfica; threatened species; zona árida