Alice Hughes, Michael C. Orr, Ruben D. Palacio, Yan Xuan, Huijie Qiao

The IUCN RedList is the most extensive source of information on the global extinction risk including over 157000 species. The sheer scale of this initiative presents challenges in data standards and reporting, especially given that legacy issues may reduce accuracy. Here, we assess the bibliographic underpinnings of RedList assessments for five taxa with fairly complete assessments (four terrestrial vertebrate and one invertebrate group, including 41647 species). We assess the number of publications referenced, their age, their specificity, and use of primary data. Body-size and popularity are then explored as potential drivers of bibliographic trends. Disturbingly, many references are old and general (especially in smaller and less popular taxa), with many lacking specific references (e.g., only 1.3% of Odonata species have species-specific references). Public data are virtually never mentioned (GBIF is cited once in Odonata and Reptiles) and private databases are often cited. Furthermore, the use of data for mapping of species remains completely opaque. Better methods and standards are urgently needed for data inclusion, wider participation, mapping, and data citation if the RedList is to fulfil its remit.