Abstract
The IUCN (International Union for Conservation of Nature) Red List categories and criteria are the most widely used framework for assessing the relative extinction risk of species. The criteria are based on quantitative thresholds relating to the size, trends, and structure of species’ distributions and populations. However, data on these parameters are sparse and uncertain for many species and unavailable for others, potentially leading to their misclassification or classification as data deficient. We devised an approach that combines data on land‐cover change, species‐specific habitat preferences, population abundance, and dispersal distance to estimate key parameters (extent of occurrence, maximum area of occupancy, population size and trend, and degree of fragmentation) and hence predict IUCN Red List categories for species. We applied our approach to nonpelagic birds and terrestrial mammals globally (∼15,000 species). The predicted categories were fairly consistent with published IUCN Red List assessments, but more optimistic overall. We predicted 4.2% of species (467 birds and 143 mammals) to be more threatened than currently assessed and 20.2% of data deficient species (10 birds and 114 mammals) to be at risk of extinction. Incorporating the habitat fragmentation subcriterion reduced these predictions 1.5–2.3% and 6.4–14.9% (depending on the quantitative definition of fragmentation) for threatened and data deficient species, respectively, highlighting the need for improved guidance for IUCN Red List assessors on the application of this aspect of the IUCN Red List criteria. Our approach complements traditional methods of estimating parameters for IUCN Red List assessments. Furthermore, it readily provides an early‐warning system to identify species potentially warranting changes in their extinction‐risk category based on periodic updates of land‐cover information. Given our method relies on optimistic assumptions about species distribution and abundance, all species predicted to be more at risk than currently evaluated should be prioritized for reassessment.
Highlights
The International Union for Conservation of Nature (IUCN) Red List of Threatened Species is the most authoritative and widely used framework for assessment of extinction risk of species (Rodrigues et al 2006; IUCN 2017a)
Predictions for data deficient were concordant with those produced by previous authors using alternative methods for 76.2% of birds and 56.6% of mammals (Supporting Information)
The extent of this reduction depended on the quantitative definition of fragmentation applied, but overall as the minimum population size per fragment increased, the number of species qualifying as threatened under criteria B1 and B2 decreased (Supporting Information)
Summary
The International Union for Conservation of Nature (IUCN) Red List of Threatened Species is the most authoritative and widely used framework for assessment of extinction risk of species (Rodrigues et al 2006; IUCN 2017a). The assessments result in species being listed under 1 of 7 categories, from least concern (LC) to extinct (or data deficient if insufficient information is available to apply the criteria). The IUCN Red List covers >90,000 species, and a key challenge is to reassess. Towards an Automatic Red List Screening the status of a large proportion of these species periodically and consistently with up-to-date data to identify conservation priorities. Reassessments currently rely on information from published and unpublished sources and expert knowledge, but collating relevant data from the literature and from experts for hundreds or thousands of species across wide geographic areas can render the process slow and costly (Rondinini et al 2014). A more systematic, quantitative, and comprehensive approach is needed to support and complement the painstaking work of IUCN Red List assessors
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