JARA: ‘Just Another Red-List Assessment’

Abstract Identifying species at risk of extinction is necessary to prioritise conservation efforts. The International Union for Conservation of Nature’s (IUCN) Red List of Threatened Species is the global standard for quantifying extinction risk, with many species categorised according to population reduction thresholds. We introduce the Bayesian state-space framework ‘JARA’ (Just Another Red-List Assessment). Designed as decision-support tool, JARA allows both process error and uncertainty to be incorporated into IUCN Red List assessments under criterion A. JARA is implemented via an R package that is designed to be easy to use, rapid and widely applicable, so conservation practitioners can apply it to their own count or relative abundance data. JARA outputs display easy to interpret graphics of the posterior probability of the population trend against the corresponding IUCN Red List categories, as well as additional graphics to describe the timeseries and model diagnostics. We illustrate JARA using three real-world examples: (1) relative abundance indices for two elasmobranchs, Yellowspotted Skate Leucoraja wallacei and Whitespot Smoothhound Mustelus palumbes ; (2) a comparison of standardized abundance indices for Atlantic Blue Marlin Makaira nigricans and (3) absolute abundance data for Cape Gannets Morus capensis . Finally, using a simulation experiment, we demonstrate how JARA provides greater accuracy than two approaches commonly used to assigning a Red List Status under criterion A. Tools like JARA can help further standardise Red List evaluations, increasing objectivity and lowering the risk of misclassification, with substantial benefits for global conservation efforts.