Threats to Australian squamates: A systematic and spatially explicit method to enhance species assessments

Conservation assessments, such as those conducted by the IUCN Red List, depend on accurate threat identification and listing. However, due to differences in background and expertise, assessors may introduce inconsistencies during the assessment process, potentially influencing outcomes and undermining conservation efforts. We aimed to reduce these inconsistencies by developing a systematic protocol for quantifying threats, using Australian squamates as a case study. Further, we asked: 1) Which threats might have been potentially overlooked in species assessments? 2) What are the most serious threats to native squamates? 3) Which species are likely to become threatened in the near future? The systematic quantification of threats produced a dataset describing how 957 squamates spatially overlap with 77 threats. By comparing this dataset with previous status assessments, we found numerous discrepancies in species-threat overlaps, with invasive species having discrepancies in 54 % of the comparisons, on average. Feral cat (Felis catus) was the most serious threat, with increased overlap significantly raising the likelihood of squamates being listed as threatened. Conversely, increases in overlap with areas with grazing over native vegetation decreased the likelihood of squamates being listed as threatened. Finally, by identifying squamates with small ranges and an overlap of 80 % or more with key threats, we found 105 squamate species to be potential candidates for threatened statuses. Our study, by providing a dataset of threats to squamates, contributes to improving the consistency of conservation assessments. Our approach for listing threats can be applied in any taxonomic group, and is particularly valuable for understudied taxa.