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The Red List of Threatened Species, published by the International Union for Conservation of Nature (IUCN), is a crucial tool for conservation decision-making. However, despite substantial effort, numerous species remain unassessed or have insufficient data available to be assigned a Red List extinction risk category. Moreover, the Red Listing process is subject to various sources of uncertainty and bias. The development of robust automated assessment methods could serve as an efficient and highly useful tool to accelerate the assessment process and offer provisional assessments. Here, we aimed to (1) present a machine learning–based automated extinction risk assessment method that can be used on less known species; (2) offer provisional assessments for all reptiles—the only major tetrapod group without a comprehensive Red List assessment; and (3) evaluate potential effects of human decision biases on the outcome of assessments. We use the method presented here to assess 4,369 reptile species that are currently unassessed or classified as Data Deficient by the IUCN. The models used in our predictions were 90% accurate in classifying species as threatened/nonthreatened, and 84% accurate in predicting specific extinction risk categories. Unassessed and Data Deficient reptiles were considerably more likely to be threatened than assessed species, adding to mounting evidence that these species warrant more conservation attention. The overall proportion of threatened species greatly increased when we included our provisional assessments. Assessor identities strongly affected prediction outcomes, suggesting that assessor effects need to be carefully considered in extinction risk assessments. Regions and taxa we identified as likely to be more threatened should be given increased attention in new assessments and conservation planning. Lastly, the method we present here can be easily implemented to help bridge the assessment gap for other less known taxa. The Red List of Threatened Species, published by the IUCN, is a crucial tool for conservation decision making, but is subject to various sources of uncertainty and bias. Modelling the threat status of all global reptiles identifies increased threat to many groups of reptiles across many regions of the world, beyond those currently recognized; moreover, it highlights the effects of the IUCN assessment procedure on eventual threat categories. [ABSTRACT FROM AUTHOR]

Aim: Identification of particular traits that predispose species to elevated extinction risk is an important component of proactive conservation. We capitalise on a recent strategic extinction risk assessment of all Australian squamate reptiles to identify intrinsic life history traits and extrinsic threats that correlate with extinction risk. We further assess whether extinction risk correlates differ between species impacted by different threatening processes (habitat loss vs. invasive species). Location: Australia. Taxon: Squamate reptiles. Methods: We used the IUCN Red List data for Australian squamates, and publicly available datasets for 14 intrinsic and extrinsic traits. We used phylogenetically controlled Bayesian inference to test hypotheses regarding relationships between extinction risk and species traits, environment, and threat measures. Results: We found that intrinsic characteristics (habitat specialisation, small range size and large body size), as well as extrinsic factors (high human footprint, accessibility from human population centres, cold temperatures and high rainfall), predispose a species to extinction. Similar predictors were important in threat‐specific analyses, although relationships were generally more uncertain. Conclusions: Our results largely accord with those of global and regional studies of extinction risk in reptiles and of terrestrial vertebrates more broadly. Our findings illustrate that there is no single pathway to extinction among Australian squamates. [ABSTRACT FROM AUTHOR]

Australia hosts approximately 10% of the world's reptile species, the largest number of any country. Despite this and evidence of widespread decline, the first comprehensive assessment of the conservation status of Australian terrestrial squamates (snakes and lizards) was undertaken only recently. Here we apply structured expert elicitation to the 60 species assessed to be in the highest IUCN threat categories to estimate their probability of extinction by 2040. We also assessed the probability of successful reintroduction for two Extinct in the Wild (EW) Christmas Island species with trial reintroductions underway. Collation and analysis of expert opinion indicated that six species are at high risk (>50%) of becoming extinct within the next 20 years, and up to 11 species could be lost within this timeframe unless management improves. The consensus among experts was that neither of the EW species were likely to persist outside of small fenced areas without a significant increase in resources for intense threat management. The 20 most imperilled species are all restricted in range, with three occurring only on islands. The others are endemic to a single state, with 55% occurring in Queensland. Invasive species (notably weeds and introduced predators) were the most prevalent threats, followed by agriculture, natural system modifications (primarily fire) and climate change. Increased resourcing and management intervention are urgently needed to avert the impending extinction of Australia's imperilled terrestrial reptiles. The first comprehensive assessment of conservation status for Australian terrestrial squamates was undertaken only recently. We used structured expert elicitation to complement and extend this work by identifying the species in most immediate risk of extinction. Of the 60 species assessed, six had high likelihoods of extinction (>50%) in the next 20 years, and up to 11 species could be lost within this timeframe without substantial improvements to current management regimes. Increased resourcing and management intervention are urgently needed to avert future extinctions of Australia's reptiles. [ABSTRACT FROM AUTHOR]

A critical step towards reducing the incidence of extinction is to identify and rank the species at highest risk, while implementing protective measures to reduce the risk of extinction to such species. Existing global processes provide a graded categorisation of extinction risk. Here we seek to extend and complement those processes to focus more narrowly on the likelihood of extinction of the most imperilled Australian birds and mammals. We considered an extension of existing IUCN and NatureServe criteria, and used expert elicitation to rank the extinction risk to the most imperilled species, assuming current management. On the basis of these assessments, and using two additional approaches, we estimated the number of extinctions likely to occur in the next 20 years. The estimates of extinction risk derived from our tighter IUCN categorisations, NatureServe assessments and expert elicitation were poorly correlated, with little agreement among methods for which species were most in danger - highlighting the importance of integrating multiple approaches when considering extinction risk. Mapped distributions of the 20 most imperilled birds reveal that most are endemic to islands or occur in southern Australia. The 20 most imperilled mammals occur mostly in northern and central Australia. While there were some differences in the forecasted number of extinctions in the next 20 years among methods, all three approaches predict further species loss. Overall, we estimate that another seven Australian mammals and 10 Australian birds will be extinct by 2038 unless management improves. [ABSTRACT FROM AUTHOR]

Reptiles are the most species-rich group of terrestrial vertebrates, yet we lack a comprehensive understanding of their extinction risk. Only 45% of described reptile species have been assessed by IUCN to date (4648 of 10,400 species); of these, 20% (945 species) are threatened with extinction, and 19% (867 species) are Data Deficient. The goal of this special issue is to improve our understanding of reptile conservation needs and extinction risk by (i) investigating patterns and drivers of extinction risk and data deficiency at a global scale; (ii) identifying and addressing taxonomic and regional gaps in our understanding of extinction risk and data deficiency; and (iii) drawing upon detailed case studies to highlight conservation approaches to mitigate extinction. By doing so, the special issue will guide future conservation efforts toward the taxa and regions in greatest need of assessment, and toward risks requiring immediate mitigation. We conclude with potential avenues for future research, including the need to address regional knowledge gaps, conduct macroecological and retrospective analyses of extinction risk, and implement targeted monitoring of conservation intervention outcomes. [ABSTRACT FROM AUTHOR]

Aim The 'two sides of the same coin' hypothesis posits that biological traits that predispose species to extinction and invasion lie on opposite ends of a continuum. Conversely, anthropogenic factors may have similar effects on extinction and invasion risk. We test these two hypotheses using data on more than 1000 reptile species. Location Global. Methods We used hierarchical Bayesian models to determine whether biological traits and anthropogenic factors were correlated with whether a species was: (1) listed as Threatened versus Least Concern on the IUCN Red List, and (2) successful versus unsuccessful at establishing a viable population once introduced outside of its native geographical range. The 'two sides of the same coin' hypothesis predicts that model coefficients for each trait should be opposite in sign between these two models. Results Seventy-three per cent of model coefficients describing 10 aspects of a species' life history, ecology, biogeography and environmental niche breadth were opposite in sign between the two groups; however, most effect sizes for variables that showed contrasting relationships were small and/or uncertain. The only exception was body size: larger-bodied species were more likely to be threatened, whereas smaller-bodied species were more likely to be invasive. As predicted, human population density across a species' native geographical range was positively correlated with both threat and invasion probabilities. Other anthropogenic variables did not have strong analogous effects. Main conclusions The assumption that threatened and invasive species lie on opposite ends of a continuum, while consistent with life-history theory, appears to be an oversimplification. Our results do suggest, however, that anthropogenic variables can be important predictors of a species' fate, and should be more routinely incorporated in trait-based analyses of extinction and invasion risk. [ABSTRACT FROM AUTHOR]

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Highlights: [•] Understanding the factors that determine extinction risk is vital for effective conservation. [•] Relative to other vertebrate groups, extinction risk has rarely been examined in reptiles. [•] We conduct the most comprehensive study of extinction risk within a reptile group. [•] Body size, geographic range size and habitat specialization were the strongest predictors of extinction risk. [•] We place our results in context with studies on extinction risk in other vertebrate groups. [ABSTRACT FROM AUTHOR]

Australia is a global hotspot of reptile diversity, hosting ~10% of the world's squamate (snake and lizard) species. Yet the conservation status of the Australian squamate fauna has not been assessed for >25 years; a period during which the described fauna has risen by ~40%. Here we provide the first comprehensive conservation assessment of Australian terrestrial squamates using IUCN Red List Categories and Criteria. Most (86.4%; n = 819/948) Australian squamates were categorised as Least Concern, 4.5% were Data Deficient, and 7.1% (range 6.8%–11.3%, depending on the treatment of Data Deficient species) were threatened (3.0% Vulnerable, 2.7% Endangered, 1.1% Critically Endangered). This level of threat is low relative to the global average (~18%). One species (Emoia nativitatis) was assessed as Extinct, and two species (Lepidodactylus listeri and Cryptoblepharus egeriae) are considered Extinct in the Wild: all three were endemic to Christmas Island. Most (75.1%) threat assessments were based on geographic range attributes, due to limited data on population trends or relevant proxies. Agriculture, fire, and invasive species were the threats that affected the most species, and there was substantial geographic variation in the number of species affected by each threat. Threatened species richness peaked on islands, in the Southern Alps, and across northern Australia. Data deficiency was greatest in northern Australia and in coastal Queensland. Approximately one-in-five threatened species were not represented in a single protected area. Our analyses shed light on the species, regions, and threats in most urgent need of conservation intervention. [ABSTRACT FROM AUTHOR]