Geographic range size and extinction risk assessment in nomadic species |
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| Authors: | Ayesha Tulloch Edd Hammill Hugh P. Possingham Richard A. Fuller |
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| Affiliation: | 1. School of Geography, Planning and Environmental Management, University of Queensland, Brisbane, QLD, Australia;2. School of Biological Sciences, University of Queensland, Brisbane, QLD, Australia;3. School of the Environment, University of Technology, Sydney, NSW, Australia;4. Imperial College London, Department of Life Sciences, Berkshire, England, United Kingdom |
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| 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. |
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| Keywords: | arid zone conservation priority setting geographic range size IUCN Red List migration nomadism species distribution modeling threatened species especie amenazada establecimiento de prioridades de conservació n lista roja de la UICN migració n modelado de distribució n de especies nomadismo tamañ o de extensió n geográ fica zona á rida |
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