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Impact of alternative metrics on estimates of extent of occurrence for extinction risk assessment

Impact of alternative metrics on estimates of extent of occurrence for extinction risk assessment
Impact of alternative metrics on estimates of extent of occurrence for extinction risk assessment
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.
IUCN red list, threatened, distribution maps
0888-8892
362-370
Joppa, Lucas N.
39e3df1a-9c00-4c7a-af4d-591eb9a59c94
Butchart, Stuart H.M.
402f033c-e3a7-4c05-920f-97735de39334
Hoffmann, Michael
4c894e5c-b004-4d85-818c-01361017671b
Bachmann, Steve P.
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Akçakaya, H. Resit
3b2f33ce-19c4-4e00-b716-54e6fa527e44
Moat, Justin F.
a6d81e56-138d-428d-81df-2ae9daff6eec
Böhm, Monika
1250957d-90f4-4d66-af9a-89c72e2989ca
Holland, Robert A.
9c245e65-06bb-4b0e-8214-2b00ad2a47df
Newton, Adrian
5b704d39-6d88-4f91-8201-bacf55d3d377
Polidoro, Beth
1d9d70ea-7592-4a82-a18c-eea16ddd1175
Hughes, Adrian
5ff9a2b5-0168-4682-8acc-bdbeb652d8ae
Joppa, Lucas N.
39e3df1a-9c00-4c7a-af4d-591eb9a59c94
Butchart, Stuart H.M.
402f033c-e3a7-4c05-920f-97735de39334
Hoffmann, Michael
4c894e5c-b004-4d85-818c-01361017671b
Bachmann, Steve P.
09aa769e-78e1-4701-898a-2e883e4a32f9
Akçakaya, H. Resit
3b2f33ce-19c4-4e00-b716-54e6fa527e44
Moat, Justin F.
a6d81e56-138d-428d-81df-2ae9daff6eec
Böhm, Monika
1250957d-90f4-4d66-af9a-89c72e2989ca
Holland, Robert A.
9c245e65-06bb-4b0e-8214-2b00ad2a47df
Newton, Adrian
5b704d39-6d88-4f91-8201-bacf55d3d377
Polidoro, Beth
1d9d70ea-7592-4a82-a18c-eea16ddd1175
Hughes, Adrian
5ff9a2b5-0168-4682-8acc-bdbeb652d8ae

Joppa, Lucas N., Butchart, Stuart H.M., Hoffmann, Michael, Bachmann, Steve P., Akçakaya, H. Resit, Moat, Justin F., Böhm, Monika, Holland, Robert A., Newton, Adrian, Polidoro, Beth and Hughes, Adrian (2016) Impact of alternative metrics on estimates of extent of occurrence for extinction risk assessment. Conservation Biology, 30 (2), 362-370. (doi:10.1111/cobi.12591).

Record type: Article

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.

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Accepted/In Press date: 14 July 2014
e-pub ahead of print date: 2 November 2015
Published date: 8 March 2016
Keywords: IUCN red list, threatened, distribution maps
Organisations: Environmental

Identifiers

Local EPrints ID: 379682
URI: http://eprints.soton.ac.uk/id/eprint/379682
ISSN: 0888-8892
PURE UUID: 63455f6a-bec3-4f5e-acea-46d755137486
ORCID for Robert A. Holland: ORCID iD orcid.org/0000-0002-3038-9227

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Date deposited: 06 Aug 2015 12:16
Last modified: 19 Nov 2022 02:41

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Contributors

Author: Lucas N. Joppa
Author: Stuart H.M. Butchart
Author: Michael Hoffmann
Author: Steve P. Bachmann
Author: H. Resit Akçakaya
Author: Justin F. Moat
Author: Monika Böhm
Author: Adrian Newton
Author: Beth Polidoro
Author: Adrian Hughes

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