Measuring Terrestrial Area of Habitat (AOH) and Its Utility for the IUCN Red List
The IUCN Red List of Threatened Species assesses the extinction risk of nearly 100 000 species, including documentation of a range map, habitat, and elevation data for each species.Numerous recent studies have matched these habitat and elevation data with remotely sensed land cover and elevation datasets to map AOH (also known as extent of suitable habitat) within the range of each species.AOH differs from the two spatial metrics used in the IUCN Red List criteria for extinction risk assessment: EOO (minimum convex polygon around all present native occurrences of a species); and AOO (area actually occupied by a species).AOH can be of value in locating target areas for species-specific field surveys, assessing the proportion of a species’ habitat within protected areas, and monitoring habitat loss and fragmentation. The International Union for Conservation of Nature (IUCN) Red List of Threatened Species includes assessment of extinction risk for 98 512 species, plus documentation of their range, habitat, elevation, and other factors. These range, habitat and elevation data can be matched with terrestrial land cover and elevation datasets to map the species’ area of habitat (AOH; also known as extent of suitable habitat; ESH). This differs from the two spatial metrics used for assessing extinction risk in the IUCN Red List criteria: extent of occurrence (EOO) and area of occupancy (AOO). AOH can guide conservation, for example, through targeting areas for field surveys, assessing proportions of species’ habitat within protected areas, and monitoring habitat loss and fragmentation. We recommend that IUCN Red List assessments document AOH wherever practical. The International Union for Conservation of Nature (IUCN) Red List of Threatened Species includes assessment of extinction risk for 98 512 species, plus documentation of their range, habitat, elevation, and other factors. These range, habitat and elevation data can be matched with terrestrial land cover and elevation datasets to map the species’ area of habitat (AOH; also known as extent of suitable habitat; ESH). This differs from the two spatial metrics used for assessing extinction risk in the IUCN Red List criteria: extent of occurrence (EOO) and area of occupancy (AOO). AOH can guide conservation, for example, through targeting areas for field surveys, assessing proportions of species’ habitat within protected areas, and monitoring habitat loss and fragmentation. We recommend that IUCN Red List assessments document AOH wherever practical. The IUCN Red List of Threatened Species [1International Union for Conservation of Nature The IUCN Red List of Threatened Species (Version 2018-1).2018Google Scholar] aspires to assess the extinction risk of the world’s species, and to serve as a ‘barometer of life’ of the state of nature [2Stuart S.N. et al.The barometer of life.Science. 2010; 328: 177Crossref PubMed Scopus (121) Google Scholar]. Of the approximately 2 million named species [3Scheffers B.R. et al.What we know and don’t know about Earth’s missing biodiversity.Trends Ecol. Evol. 2012; 27: 501-510Abstract Full Text Full Text PDF PubMed Scopus (251) Google Scholar], the IUCN Red List has assessed 98 512 species (having increased from fewer than 20 000 in 2002i). The process of assessment classifies species in different categories of extinction risk. It does so through an open, rigorously defined process [4International Union for Conservation of Nature Rules of Procedure for IUCN Red List Assessments 2017–2020 (Version 3.0).2016Google Scholar] that is objective and transparent. Petitioners can challenge decisions made by Red List Authorities. An important use of the IUCN Red List is the assessment of changes in species extinction risk to monitor changes in the status of individual species, classes and other groups of species, and species-level biodiversity overall [5Butchart S.H.M. et al.Measuring global trends in the status of biodiversity: Red List indices for birds.PLoS Biol. 2004; 2e383Crossref PubMed Scopus (334) Google Scholar, 6Rodrigues A.S.L. et al.Spatially explicit trends in the global conservation status of vertebrates.PLoS One. 2014; 9e113934Crossref PubMed Scopus (49) Google Scholar]. These are essential, for example, in reporting on the Aichi Targets [7Secretariat of the Convention on Biological Diversity Global Biodiversity Outlook 4.Convention on Biological Diversity. 2014Google Scholar] and Sustainable Development Goals [8United Nations The Sustainable Development Goals Report 2017. United Nations, 2017Crossref Google Scholar], as well as progress in conserving species [9Hoffmann M. et al.The impact of conservation on the status of the world’s vertebrates.Science. 2010; 330: 1503-1509Crossref PubMed Scopus (971) Google Scholar]. The need for rigour and consensus in assessing extinction risk can potentially bring the process into conflict with those who seek to harness rapidly expanding geographic databases and remote sensing technologies to assess species’ status [10Ocampo-Peñuela N. Pimm S.L. Setting practical conservation priorities for birds in the Western Andes of Colombia.Conserv. Biol. 2014; 28: 1260-1270Crossref PubMed Scopus (28) Google Scholar, 11Ocampo-Peñuela N. et al.Incorporating explicit geospatial data shows more species at risk of extinction than the current Red List.Sci. Adv. 2016; 2e1601367Crossref PubMed Scopus (67) Google Scholar, 12Ramesh V. et al.IUCN greatly underestimates threat levels of endemic birds in the Western Ghats.Biol. Conserv. 2017; 210: 205-221Crossref Scopus (32) Google Scholar]. Numerous publications have illustrated how increasingly sophisticated and high-resolution regional and global remote sensing and spatial datasets or models can the Red List criteria et remote sensing to conservation status assessment: of recent on and the endemic Conserv. Scopus Google Scholar, et of the impact of on the extinction risk of terrestrial Biol. 2016; PubMed Scopus Google Scholar]. The in the of these data the with to process has the of for of the of and for terrestrial It is to and how AOH is how to the Red List and of in we that AOH is to extent of occurrence (EOO) to area of occupancy (AOO). the area of the convex polygon around a species’ AOH can be used to the of a species’ AOH is at a 2 2 can be used to the of We by the of of terrestrial species’ area of habitat in conservation, for through targeting areas for field surveys, assessing proportions of species’ habitat within protected areas, monitoring habitat loss and and Red List different criteria are used to assess a species’ extinction risk Union for Conservation of Nature IUCN Red List and (Version Scholar]. for terrestrial species et of extinction risk assessment with the IUCN Red 2016; PubMed Scopus Google Scholar], the is the of plus of at two of or spatial metrics of are defined for of of have that are and Union for Conservation of Nature IUCN Red List and (Version Scholar]. 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The is more of for species with and used of and assessed as the and [1International Union for Conservation of Nature The IUCN Red List of Threatened Species (Version 2018-1).2018Google Scholar]. a species for the EOO is 000 and is of at two of on or more of extent of habitat, of or or or the categories have for and the of The for AOO are of the for for example, for documentation for the IUCN Red List also includes the of a and elevation, and of a range map Union for Conservation of Nature and for IUCN Red List Assessments and Species (Version Scholar]. range has an the range map to the current known of the within native The of are known occurrences of the and of habitat suitable habitat, elevation Union for Conservation of Nature and for IUCN Red List Assessments and Species (Version Scholar] the range and of spatial data to a species’ Union for Conservation of Nature and for IUCN Red List Assessments and Species (Version Scholar] current range from areas the species has The have a in the of regional and global spatial data that are in geographic to the and of of species These global of elevation at et for the Scholar], global a to global land cover from Scopus Google Scholar], and global cover at et global of cover PubMed Scopus Google Scholar, et of of with of Scopus Google Scholar]. species’ habitat as by of the IUCN Red List to these can be with the range map of terrestrial species to the area of habitat within a species’ has used the to et remote sensing to conservation status assessment: of recent on and the endemic Conserv. Scopus Google Scholar, et of the impact of on the extinction risk of terrestrial Biol. 2016; PubMed Scopus Google Scholar, et of metrics on of extent of occurrence for extinction risk Biol. 2016; PubMed Scopus Google Scholar, Union for Conservation of Nature Global for the of Biodiversity (Version International Union for Conservation of Scholar], we the AOH the is a by suitable for the species in area is more than the as in extent of AOH is defined as the habitat to a species, that habitat within in AOH is on range, habitat and the areas to be suitable for the species within to have used to The [10Ocampo-Peñuela N. Pimm S.L. Setting practical conservation priorities for birds in the Western Andes of Colombia.Conserv. Biol. 2014; 28: 1260-1270Crossref PubMed Scopus (28) Google Scholar, 11Ocampo-Peñuela N. et al.Incorporating explicit geospatial data shows more species at risk of extinction than the current Red List.Sci. Adv. 2016; 2e1601367Crossref PubMed Scopus (67) Google Scholar, 12Ramesh V. et al.IUCN greatly underestimates threat levels of endemic birds in the Western Ghats.Biol. Conserv. 2017; 210: 205-221Crossref Scopus (32) Google Scholar, et remote sensing to conservation status assessment: of recent on and the endemic Conserv. Scopus Google Scholar, et of the impact of on the extinction risk of terrestrial Biol. 2016; PubMed Scopus Google Scholar, et of metrics on of extent of occurrence for extinction risk Biol. 2016; PubMed Scopus Google Scholar, et the of species’ range and in the protected area Conserv. Scopus Google Scholar, et sensed data Red List and conservation priorities in One. 2016; Google Scholar, et the of protected areas and birds in Conserv. Scopus (67) Google Scholar, et al.Incorporating into conservation in Scopus Google Scholar, et areas for a global assessment for birds.PLoS One. 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PubMed Scopus Google et et habitat models of terrestrial PubMed Scopus Google Scholar] and et et for and extinction a global Scopus Google Scholar] used a different the habitat of all classes of areas and as or on the to habitat and a for of to habitat or for classes in more for species is to within a to all areas than from as used all from remote sensing and Global et the of species’ range and in the protected area Conserv. Scopus Google Scholar, et the world’s a assessment of all and One. PubMed Scopus Google Scholar, Pimm S.L. and extinction risk in Biol. PubMed Scopus Google Scholar] and et habitat models of terrestrial PubMed Scopus Google Scholar, et for and extinction a global Scopus Google Scholar]. the classes of these are matched to habitat for from in the by these to to of AOH these is increasingly as AOH for the and so from to species or Species and Scopus Google Scholar, et and Google Scholar], as and et models and the in conservation for Biol. 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Biol. 2014; 28: 1260-1270Crossref PubMed Scopus (28) Google Scholar, 11Ocampo-Peñuela N. et al.Incorporating explicit geospatial data shows more species at risk of extinction than the current Red List.Sci. Adv. 2016; 2e1601367Crossref PubMed Scopus (67) Google Scholar, 12Ramesh V. et al.IUCN greatly underestimates threat levels of endemic birds in the Western Ghats.Biol. Conserv. 2017; 210: 205-221Crossref Scopus (32) Google Scholar, et remote sensing to conservation status assessment: of recent on and the endemic Conserv. Scopus Google Scholar, et of the impact of on the extinction risk of terrestrial Biol. 2016; PubMed Scopus Google Scholar, et of metrics on of extent of occurrence for extinction risk Biol. 2016; PubMed Scopus Google Scholar, et the of species’ range and in the protected area Conserv. Scopus Google Scholar, et sensed data Red List and conservation priorities in One. 2016; Google Scholar, et the of protected areas and birds in Conserv. 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