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Done but not dusted: Reflections on the first global reptile assessment and priorities for the second
Abstract
The IUCN recently coordinated the first assessment of extinction risk of the world's reptile species. This monumental undertaking allows, for the first time, an examination of threats and prioritization of conservation effort, not just for reptiles, but for land vertebrates as a whole. Reptiles are now the largest class of land vertebrates in terms of species numbers. The dynamic nature of reptile taxonomy, the 18 years it took for the Global Reptile Assessment to be completed, the poor state of knowledge for many species – especially of squamates – and the evolving nature of threats, however, all highlight the need for continued monitoring of reptile species and threats. Here we review the status of reptile conservation assessments, and identify the challenges facing the next reptile assessments. We then recommend potential avenues that could facilitate efficient, accurate and timely future assessments.
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The frequency, duration, and intensity of extreme thermal events are increasing and are projected to further increase by the end of the century. Despite the considerable consequences of temperature extremes on biological systems, we do not know which species and locations are most exposed worldwide. Here we provide a global assessment of land vertebrates’ exposures to future extreme thermal events. We use daily maximum temperature data from 1950 to 2099 to quantify future exposure to high frequency, duration, and intensity of extreme thermal events to land vertebrates. Under a high greenhouse gas emission scenario (Shared Socioeconomic Pathway 5–8.5 (SSP5–8.5); 4.4 °C warmer world), 41.0% of all land vertebrates (31.1% mammals, 25.8% birds, 55.5% amphibians and 51.0% reptiles) will be exposed to extreme thermal events beyond their historical levels in at least half their distribution by 2099. Under intermediate-high (SSP3–7.0; 3.6 °C warmer world) and intermediate (SSP2–4.5; 2.7 °C warmer world) emission scenarios, estimates for all vertebrates are 28.8% and 15.1%, respectively. Importantly, a low-emission future (SSP1–2.6, 1.8 °C warmer world) will greatly reduce the overall exposure of vertebrates (6.1% of species) and can fully prevent exposure in many species assemblages. Mid-latitude assemblages (desert, shrubland, and grassland biomes), rather than tropics, will face the most severe exposure to future extreme thermal events. By 2099, under SSP5–8.5, on average 3,773 species of land vertebrates (11.2%) will face extreme thermal events for more than half a year period. Overall, future extreme thermal events will force many species and assemblages into constant severe thermal stress. Deep greenhouse gas emissions cuts are urgently needed to limit species’ exposure to thermal extremes.
The Red List Index (RLI) measures change in the aggregate extinction risk of species. It is a key indicator for tracking progress toward nine of the Aichi and many proposed post‐2020 Global Biodiversity Framework Targets. Here, we consider two formulations of the RLI used for reporting biodiversity trends at national scales. Disaggregated global RLIs measure changing national contributions to global extinction risk and are currently based on five taxonomic groups, while national RLIs measure changing national extinction risk and are based on taxonomic groups assessed multiple times in country. For 74% of nations, the disaggregated global RLI is currently based on three or fewer taxonomic groups. Meanwhile, national RLIs from selected pilot countries Finland, South Africa, and Brazil are computed from twelve, eight, and nine taxonomic groups, respectively. The national RLI and the disaggregated global RLI measure different aspects of biodiversity, in that the former detects national trends in populations of species for which each country is responsible while the latter provides standardized comparisons of nations' contributions to the global extinction risk of the same species groups. As governments commit to the post‐2020 Global Biodiversity Framework, we encourage them to monitor a standard set of taxonomic groups representing different biomes using both RLI formulations to ensure effective target tracking and accurate feedback on their conservation investments. The Red List Index (RLI) measures change in the aggregate extinction risk of species. It is a key indicator for tracking progress toward nine of the Aichi and many proposed post‐2020 Global Biodiversity Framework Targets. Here, we compare and promote two formulations of the RLI used for reporting biodiversity trends at national scales.
The IUCN Red List of Threatened Species is essential for practical and theoretical efforts to protect biodiversity. However, species classified as “Data Deficient” (DD) regularly mislead practitioners due to their uncertain extinction risk. Here we present machine learning-derived probabilities of being threatened by extinction for 7699 DD species, comprising 17% of the entire IUCN spatial datasets. Our predictions suggest that DD species as a group may in fact be more threatened than data-sufficient species. We found that 85% of DD amphibians are likely to be threatened by extinction, as well as more than half of DD species in many other taxonomic groups, such as mammals and reptiles. Consequently, our predictions indicate that, amongst others, the conservation relevance of biodiversity hotspots in South America may be boosted by up to 20% if DD species were acknowledged. The predicted probabilities for DD species are highly variable across taxa and regions, implying current Red List-derived indices and priorities may be biased.
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 likelihood of extinction within the next 20 years was determined for 47 Australian mammal, bird, reptile, frog and freshwater fish taxa previously identified as being highly imperilled. A 14-member expert elicitation panel, consisting of a mix of taxon experts and government managers of threatened species, estimated that there was a > 50% chance that nine taxa would be extinct by 2041. The panel estimated that there was a > 50% likelihood that a further 16 taxa (considered extant under Australian legislation), for which there are no recent independently verified records, are already extinct, with four almost certainly extinct. For five of these taxa, there was a > 50% chance that they would persist for 20 more years if they are currently extant, notwithstanding the lack of recent records. Most of the taxa considered occur within conservation areas and in south-eastern Australia, where human population density is highest. All the highly imperilled taxa occur wholly or partly in conservation reserves, within a total reserved area of 1994 km2, 0.13% of the total area conserved in Australia. Highly imperilled taxa also occur on 313 km2 of non-conservation government-owned land, and 242 km2 of private land. The total area that needs management intervention to prevent extinction of Australia's most imperilled vertebrate taxa in the next 20 years represents 0.06% of the area of Australia's terrestrial and freshwater environments.
The tropical Andes Mountains exhibit high levels of endemism and spatial turnover in the distribution of species. The lizard genus Stenocercus Duméril & Bibron, 1837, contains 76 species and most of them occur in the tropical Andes, reaching elevations up to 4,000 m. We describe four new species of Stenocercus based on the examination of newly collected material from the Amazonian slopes of the Peruvian Andes. Stenocercus asenlignus sp. nov. inhabits the premontane forest of northern and central Peru, departments of Amazonas, San Martín and Huánuco, at elevations between 1,500 and 2,036 m, in the basins of the Mayo, Huayabamba, and Huallaga rivers. Stenocercus leybachi sp. nov. inhabits the premontane forest of the upper Huallaga River, Huánuco department in central Peru, at elevations between 824 and 1,270 m. Stenocercus qalaywasi sp. nov. was collected in a small village at the headwaters of the Mantaro River, Junín department in central Peru, at an elevation of 2,587 m. Finally, S. nigrocaudatus sp. nov. inhabits the montane forest from extreme northern Peru, Cajamarca department, at elevations of 1,700 and 1,892 m. These species are characterized by having granular scales on the posterior surface of the thighs, relatively short tail, caudals spinose, two caudal whorls per autotomic segment, and the ability to change coloration from green to brown or gray; they differ from other species of Stenocercus in scutellation features and color pattern.
After environmental disasters, species with large population losses may need urgent protection to prevent extinction and support recovery. Following the 2019–2020 Australian megafires, we estimated population losses and recovery in fire‐affected fauna, to inform conservation status assessments and management. Temperate and subtropical Australia. 2019–2030 and beyond. Australian terrestrial and freshwater vertebrates; one invertebrate group. From > 1,050 fire‐affected taxa, we selected 173 whose distributions substantially overlapped the fire extent. We estimated the proportion of each taxon’s distribution affected by fires, using fire severity and aquatic impact mapping, and new distribution mapping. Using expert elicitation informed by evidence of responses to previous wildfires, we estimated local population responses to fires of varying severity. We combined the spatial and elicitation data to estimate overall population loss and recovery trajectories, and thus indicate potential eligibility for listing as threatened, or uplisting, under Australian legislation. We estimate that the 2019–2020 Australian megafires caused, or contributed to, population declines that make 70–82 taxa eligible for listing as threatened; and another 21–27 taxa eligible for uplisting. If so‐listed, this represents a 22–26% increase in Australian statutory lists of threatened terrestrial and freshwater vertebrates and spiny crayfish, and uplisting for 8–10% of threatened taxa. Such changes would cause an abrupt worsening of underlying trajectories in vertebrates, as measured by Red List Indices. We predict that 54–88% of 173 assessed taxa will not recover to pre‐fire population size within 10 years/three generations. We suggest the 2019–2020 Australian megafires have worsened the conservation prospects for many species. Of the 91 taxa recommended for listing/uplisting consideration, 84 are now under formal review through national processes. Improving predictions about taxon vulnerability with empirical data on population responses, reducing the likelihood of future catastrophic events and mitigating their impacts on biodiversity, are critical.
Newly discovered species are often threatened with extinction but in many cases have received limited conservation effort. To guide future conservation, it is important to determine the extinction risk of newly described species. Here, we test how time since formal description of a species is linked to its threat status to obtain a better insight into the possible threat status of newly described species and as yet undescribed species. We compiled IUCN Red List data for 53,808 species from five vertebrate groups described since 1758. Extinction risk for more recently described species has increased significantly over time; the proportion of threatened species among newly described species has increased from 11.9% for species described between 1758 and 1767 to 30.0% for those described between 2011 and 2020. Based on projections from our analysis, this could further increase to 47.1% by 2050. The pattern is consistent across vertebrate taxonomic groups and biomes. Current species extinction rates estimated from data of all known species are therefore highly likely to be underestimated. Intensive fieldwork to boost discovery of new species and immediate conservation action for newly described species, especially in tropical areas, is urgently required.
The Living Planet Report1, which has been published biannually since 1998, is key for understanding trends in wildlife populations and promoting sound conservation. Leung et al. 2020 recently disagreed with the conclusions of the Living Planet Report and found that the overall pattern of population declines stems from very few populations (extreme clusters), beyond which global vertebrate populations are not declining. However, when properly accounting also for the influence of the fastest-increasing populations, we find that the overall declines in the Living Planet Report are practically unchanged. Moreover, the Living Planet Database is heavily biased towards populations that receive more conservation attention, indicating that the true population trends are indeed dire and may actually be worse than depicted in the Living Planet Report.
The current perception that climate change is the principal threat to biodiversity is at best premature. Although highly relevant, it detracts focus and effort from the primary threats: habitat destruction and overexploitation. We collated causes of vertebrate extinctions since 1900, threat information for amphibia, birds, and mammals from the IUCN Red List, and scrutinized others’ attempts to compare climate change with commensurate anthropogenic threats. In each analysis, none of the arguments founded on climate change's wide-ranging effects are as urgent for biodiversity as those for habitat loss and overexploitation. Present conservation efforts must refocus on these issues. Conserving ecosystems by focusing on these major threats not only protects biodiversity but is the only available, economically viable, global strategy to reverse climate change.
Deciphering global trends in phylogenetic endemism is crucial for understanding broad-scale evolutionary patterns and the conservation of key elements of biodiversity. However, knowledge to date on global phylogenetic endemism and its determinants has been lacking. Here, we conduct the first global analysis of phylogenetic endemism patterns of land vertebrates (>30,000 species), their environmental correlates, and threats. We found that low temperature seasonality and high topographic heterogeneity were the main global determinants of phylogenetic endemism. While phylogenetic endemism hotspots cover 22% of Earth, these regions currently have a high human footprint, low natural land cover, minimal protection, and will be greatly affected by climate change. Evolutionarily unique, narrow-range species are crucial for sustaining biodiversity in the face of environmental change. Our global study advances the current understanding of this imperilled yet previously overlooked facet of biodiversity.
Unsustainable exploitation of wild species represents a serious threat to biodiversity and to the livelihoods of local communities and Indigenous peoples. However, managed, sustainable use has the potential to forestall extinctions, aid recovery, and meet human needs. We analyzed species‐level data for 30,923 species from 13 taxonomic groups on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species to investigate patterns of intentional biological resource use. Forty percent of species (10,098 of 25,009 species from 10 data‐sufficient taxonomic groups) were used. The main purposes of use were pets, display animals, horticulture, and human consumption. Intentional use is currently contributing to elevated extinction risk for 28 – 29% of threatened or near threatened (NT) species (2,752 – 2,848 of 9,753 species). Intentional use also affected 16% of all species used (1,597 – 1,631 of 10,098). However, 72% of used species (7,291 of 10,098) were least concern, of which nearly half (3,469) also had stable or improving population trends. The remainder were not documented as threatened by biological resource use, including at least 172 threatened or NT species with stable or improving populations. About one‐third of species that had use documented as a threat had no targeted species management actions to directly address this threat. To improve use‐related red‐list data, we suggest small amendments to the relevant classification schemes and required supporting documentation. Our findings on the prevalence of sustainable and unsustainable use, and variation across taxa, can inform international policy making, including the Intergovernmental Science‐Policy Platform on Biodiversity and Ecosystem Services, the Convention on Biological Diversity, and the Convention on International Trade in Endangered Species. This article is protected by copyright. All rights reserved
The Anthropocene is characterized by unparalleled human impact on other species, potentially ushering in the sixth mass extinction. Yet mitigation efforts remain hampered by limited information on the spatial patterns and intensity of the threats driving global biodiversity loss. Here we use expert-derived information from the International Union for Conservation of Nature Red List on threats to 23,271 species, representing all terrestrial amphibians, birds and mammals, to generate global maps of the six major threats to these groups: agriculture, hunting and trapping, logging, pollution, invasive species, and climate change. Our results show that agriculture and logging are pervasive in the tropics and that hunting and trapping is the most geographically widespread threat to mammals and birds. Additionally, current representations of human pressure underestimate the overall pressure on biodiversity, due to the exclusion of threats such as hunting and climate change. Alarmingly, this is particularly the case in areas of the highest biodiversity importance.
Overexploitation is a key driver of biodiversity loss but the relationship between the use and trade of species and conservation outcomes is not always straightforward. Accurately characterizing wildlife trade and understanding the impact it has on wildlife populations are therefore critical to evaluating the potential threat trade poses to species and informing local to international policy responses. However, a review of recent research that uses wildlife and trade‐related databases to investigate these topics highlights three relatively widespread issues: (1) mischaracterization of the threat that trade poses to certain species or groups, (2) misinterpretation of wildlife trade data (and illegal trade data in particular), resulting in the mischaracterization of trade, and (3) misrepresentation of international policy processes and instruments. This is concerning because these studies may unwittingly misinform policymaking to the detriment of conservation, for example by undermining positive outcomes for species and people along wildlife supply chains. Moreover, these issues demonstrate flaws in the peer‐review process. As wildlife trade articles published in peer‐reviewed journals can be highly influential, we propose ways for authors, journal editors, database managers, and policymakers to identify, understand, and avoid these issues as we all work towards more sustainable futures.
Recognizing the imperative to evaluate species recovery and conservation impact, in 2012 the International Union for Conservation of Nature (IUCN) called for development of a "Green List of Species" (now the IUCN Green Status of Species). A draft Green Status framework for assessing species' progress toward recovery, published in 2018, proposed 2 separate but interlinked components: a standardized method (i.e., measurement against benchmarks of species' viability, functionality, and preimpact distribution) to determine current species recovery status (herein species recovery score) and application of that method to estimate past and potential future impacts of conservation based on 4 metrics (conservation legacy, conservation dependence, conservation gain, and recovery potential). We tested the framework with 181 species representing diverse taxa, life histories, biomes, and IUCN Red List categories (extinction risk). Based on the observed distribution of species' recovery scores, we propose the following species recovery categories: fully recovered, slightly depleted, moderately depleted, largely depleted, critically depleted, extinct in the wild, and indeterminate. Fifty-nine percent of tested species were considered largely or critically depleted. Although there was a negative relationship between extinction risk and species recovery score, variation was considerable. Some species in lower risk categories were assessed as farther from recovery than those at higher risk. This emphasizes that species recovery is conceptually different from extinction risk and reinforces the utility of the IUCN Green Status of Species to more fully understand species conservation status. Although extinction risk did not predict conservation legacy, conservation dependence, or conservation gain, it was positively correlated with recovery potential. Only 1.7% of tested species were categorized as zero across all 4 of these conservation impact metrics, indicating that conservation has, or will, play a role in improving or maintaining species status for the vast majority of these species. Based on our results, we devised an updated assessment framework that introduces the option of using a dynamic baseline to assess future impacts of conservation over the short term to avoid misleading results which were generated in a small number of cases, and redefines short term as 10 years, to better align with conservation planning. These changes are reflected in the IUCN Green Status of Species Standard.
Global biodiversity loss is a profound consequence of human activity. Disturbingly, biodiversity loss is greater than realized because of the unknown number of undocumented species. Conservation fundamentally relies on taxonomic recognition of species, but only a fraction of biodiversity is described. Here, we provide a new quantitative approach for prioritizing rigorous taxonomic research for conservation. We implement this approach in a highly diverse vertebrate group—Australian lizards and snakes. Of 870 species assessed, we identified 282 (32.4%) with taxonomic uncertainty, of which 17.6% likely comprise undescribed species of conservation concern. We identify 24 species in need of immediate taxonomic attention to facilitate conservation. Using a broadly applicable return-on-investment framework, we demonstrate the importance of prioritizing the fundamental work of identifying species before they are lost.
The Convention on Biological Diversity’s post-2020 Global Biodiversity Framework will probably include a goal to stabilize and restore the status of species. Its delivery would be facilitated by making the actions required to halt and reverse species loss spatially explicit. Here, we develop a species threat abatement and restoration (STAR) metric that is scalable across species, threats and geographies. STAR quantifies the contributions that abating threats and restoring habitats in specific places offer towards reducing extinction risk. While every nation can contribute towards halting biodiversity loss, Indonesia, Colombia, Mexico, Madagascar and Brazil combined have stewardship over 31% of total STAR values for terrestrial amphibians, birds and mammals. Among actions, sustainable crop production and forestry dominate, contributing 41% of total STAR values for these taxonomic groups. Key Biodiversity Areas cover 9% of the terrestrial surface but capture 47% of STAR values. STAR could sup- port governmental and non-state actors in quantifying their contributions to meeting science-based species targets within the framework.
Amniote vertebrates share a suite of extra-embryonic membranes that distinguish them from anamniotes. Other than that, however, their reproductive characteristics could not be more different. They differ in basic ectothermic vs endothermic physiology, in that two clades evolved powered flight, and one clade evolved a protective shell. In terms of reproductive strategies, some produce eggs and others give birth to live young, at various degrees of development. Crucially, endotherms provide lengthy parental care, including thermal and food provisioning—whereas ectotherms seldom do. These differences could be expected to manifest themselves in major differences between clades in quantitative reproductive traits. We review the reproductive characteristics, and the distributions of brood sizes, breeding frequencies, offspring sizes and their derivatives (yearly fecundity and biomass production rates) of the four major amniote clades (mammals, birds, turtles and squamates), and several major subclades (birds: Palaeognathae, Galloanserae, Neoaves; mammals: Metatheria and Eutheria). While there are differences between these clades in some of these traits, they generally show similar ranges, distribution shapes and central tendencies across birds, placental mammals and squamates. Marsupials and turtles, however, differ in having smaller offspring, a strategy which subsequently influences other traits.
Until recently, the reptile fauna of Christmas Island in the Indian Ocean comprised five endemic species (two skinks, two geckos, and one snake) and one native, non-endemic skink. Four of these species were common and widespread until at least 1979, but by 2012 had disappeared from the wild. During the years of decline, little research was undertaken to examine why the species were disappearing. Here, we use a retrospective expert elicitation to rank potential factors that contributed to the loss of Christmas Island's reptiles and to assess the likelihood of re-establishing populations of two species now listed as Extinct in the Wild. We additionally considered why one endemic lizard, the Christmas Island giant gecko (Cyrtodactylus sadleiri), and three introduced lizards remain common. Experts considered that the introduced common wolf snake (Lycodon capucinus) was the most likely cause of decline, as its temporal and spatial spread across the island closely matched patterns of lizard disappearances. An Asian co-occurrence in recent evolutionary timeframes of the common wolf snake with the Christmas Island giant gecko and three introduced reptiles was the most marked point of difference between the extant and lost lizard species. The demise in less than 20 years of 80% of Christmas Island's native lizard assemblage highlights the vulnerability of island fauna to invading species.
Wildlife trade is a key driver of the biodiversity crisis. Unregulated, or under-regulated wildlife trade can lead to unsustainable exploitation of wild populations. International efforts to regulate wildlife mostly miss ‘lower-value’ species, such as those imported as pets, resulting in limited knowledge of trade in groups like reptiles. Here we generate a dataset on web-based private commercial trade of reptiles to highlight the scope of the global reptile trade. We find that over 35% of reptile species are traded online. Three quarters of this trade is in species that are not covered by international trade regulation. These species include numerous endangered or range-restricted species, especially hotspots within Asia. Approximately 90% of traded reptile species and half of traded individuals are captured from the wild. Exploitation can occur immediately after scientific description, leaving new endemic species especially vulnerable. Pronounced gaps in regulation imply trade is having unknown impacts on numerous threatened species. Gaps in monitoring demand a reconsideration of international reptile trade regulations. We suggest reversing the status-quo, requiring proof of sustainability before trade is permitted.
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.
Phylogenetic diversity measures are increasingly used in conservation planning to represent aspects of biodiversity beyond that captured by species richness. Here we develop two new metrics that combine phylogenetic diversity and the extent of human pressure across the spatial distribution of species-one metric valuing regions and another prioritising species. We evaluate these metrics for reptiles, which have been largely neglected in previous studies, and contrast these results with equivalent calculations for all terrestrial vertebrate groups. We find that regions under high human pressure coincide with the most irreplaceable areas of reptilian diversity, and more than expected by chance. The highest priority reptile species score far above the top mammal and bird species, and reptiles include a disproportionate number of species with insufficient extinction risk data. Data Deficient species are, in terms of our species-level metric, comparable to Critically Endangered species and therefore may require urgent conservation attention.
As anthropogenic climate change continues the risks to biodiversity will increase over time, with future projections indicating that a potentially catastrophic loss of global biodiversity is on the horizon1–3. However, our understanding of when and how abruptly this climate-driven disruption of biodiversity will occur is limited because biodiversity forecasts typically focus on individual snapshots of the future. Here we use annual projections (from 1850 to 2100) of temperature and precipitation across the ranges of more than 30,000 marine and terrestrial species to estimate the timing of their exposure to potentially dangerous climate conditions. We project that future disruption of ecological assemblages as a result of climate change will be abrupt, because within any given ecological assemblage the exposure of most species to climate conditions beyond their realized niche limits occurs almost simultaneously. Under a high-emissions scenario (representative concentration pathway (RCP) 8.5), such abrupt exposure events begin before 2030 in tropical oceans and spread to tropical forests and higher latitudes by 2050. If global warming is kept below 2 °C, less than 2% of assemblages globally are projected to undergo abrupt exposure events of more than 20% of their constituent species; however, the risk accelerates with the magnitude of warming, threatening 15% of assemblages at 4 °C, with similar levels of risk in protected and unprotected areas. These results highlight the impending risk of sudden and severe biodiversity losses from climate change and provide a framework for predicting both when and where these events may occur. Using annual projections of temperature and precipitation to estimate when species will be exposed to potentially harmful climate conditions reveals that disruption of ecological assemblages as a result of climate change will be abrupt and could start as early as the current decade.
Monitoring trends in the extinction risk of species is important for tracking conservation effectiveness. The Red List index (RLI) reflects changes in aggregate extinction risk for sets of species over time (a value of zero means that all species are extinct, a value of one means that all species are categorized as Least Concern). We calculated the first national RLI for birds in Colombia for the period 2002-2016, and disaggregated indices by ecosystems , regions, and species groups. Overall, the status of birds in Colombia has moderately deteriorated during 2002-2016, declining by 0.0000714% per year (the global RLI for birds declined by 0.0297% per year). High Andean forest, paramo, and freshwater are the ecosystems in worst condition. The two regions with the greatest avian diversity contrasted: the Andes has the lowest RLI, and the Amazon the highest. Among species groups, gamebirds, parrots, large frugivores, and forest raptors are the most threatened. Habitat loss from expansion of illicit crops and population declines from hunting were the most important threats. Agricultural expansion, invasive alien animal species, illegal logging and illegal mining are significant threats for some species. Tracking species' extinction risk is important in a country with the highest bird species richness in the world, dynamic spatial patterns of habitat loss, and high levels of endemism. Recent developments provide reasons for both hope and despair. In 2016, a peace agreement ended 50 years of armed conflict. New opportunities for biodiversity conservation, local development based on bird-watching tourism , and advancement in scientific knowledge of birds now occur alongside dramatic increases in deforestation. These new conservation opportunities and challenges provide strong motivation to take advantage of the fact that the overall risk of extinction of birds in Colombia is still relatively low and stable. Effective action is urgently needed while there still is the opportunity to prevent extinctions and safeguard species, particularly those in higher risk categories.
Taxonomic research is of fundamental importance in conservation management of threatened species, providing an understanding of species diversity on which management plans are based. The grassland earless dragon lizards (Agamidae: Tympanocryptis) of southeastern Australia have long been of conservation concern but there have been ongoing taxonomic uncertainties. We provide a comprehensive taxonomic review of this group, integrating multiple lines of evidence, including phylogeography (mtDNA), phylogenomics (SNPs), external morphology and micro X-ray CT scans. Based on these data we assign the lectotype of T. lineata to the Canberra region, restrict the distribution of T. pinguicolla to Victoria and name two new species: T. osbornei sp. nov. (Cooma) and T. mccartneyi sp. nov. (Bathurst). Our results have significant conservation implications. Of particular concern is T. pinguicolla, with the last confident sighting in 1969, raising the possibility of the first extinction of a reptile on mainland Australia. However, our results are equivocal as to whether T. pinguicolla is extant or extinct, emphasizing the immediate imperative for continued surveys to locate any remaining populations of T. pinguicolla. We also highlight the need for a full revision of conservation management plans for all the grassland earless dragons.
Animal lifespan is determined by extrinsic and intrinsic factors causing mortality. According to the evolutionary theories of senescence, when mortality pressures are low, animals delay reproduction. This enables species to grow more slowly and, consequently, natural selection can act against harmful mutations in adulthood, thereby increasing lifespans. To test predictions of these theories we assembled a dataset on the maximum longevities and relevant ecological variables of 1320 reptilian species. Correcting for phylogeny, we modelled the link between reptile longevity and factors such as body size, microhabitat, activity period, insularity, annual temperature, temperature seasonality, elevation and clutch size that we hypothesized will affect extrinsic mortality rates and hence lifespan. Body mass explained a small proportion of the variance in reptile longevity. Species living on islands, and in colder and more seasonal environments, lived longer. Observed maximum longevity was positively associated with the number of individuals used to estimate it. Our results suggest that species exposed to reduced extrinsic and intrinsic mortality pressures (lower predation, lower metabolic rates and shorter activity periods) live longer. Sampling more individuals increases the chances of finding older specimens and should be corrected for when studying maximum longevity.
Effective conservation action relies on access to the best-available species data. Reptiles have often been overlooked in conservation prioritization, especially because of a paucity of population data. Using data for 549 reptile populations representing 194 species from the Living Planet database, we provide the first detailed analysis of this database for a specific taxonomic group. We estimated an average global decline in reptile populations of 54-55% between 1970 and 2012. Disaggregated indices at taxonomic, system, and biogeographical levels showed trends of decline, often with wide confidence intervals because of a prevalence of short time series. We assessed gaps in our reptile time-series data and examined what types of publication they primarily originated from to provide an overview of the range of data sources captured in the Living Planet database. Data were biased toward crocodilians and chelonians, with only 1% and 2% of known lizard and snake species represented, respectively. Population time-series data stemmed primarily from published ecological research (squamates) and data collected for conservation management (chelonians and crocodilians). We recommend exploration of novel survey and analytical techniques to increase monitoring of reptiles, especially squamates, over time. Open access publication and sharing of data sets are vital to improve knowledge of reptile status and trends, aided by the provision of properly curated databases and data-sharing agreements. Such collaborative efforts are vital to effectively address global reptile declines.
Accurate taxonomy is central to the study of biological diversity, as it provides the needed evolutionary framework for taxon sampling and interpreting results. While the number of recognized species in the class Mammalia has increased through time, tabulation of those increases has relied on the sporadic release of revisionary compendia like the Mammal Species of the World (MSW) series. Here, we present the Mammal Diversity Database (MDD), a digital, publically accessible, and updateable list of all mammalian species, now available online: https://mammaldiversity.org. The MDD will continue to be updated as manuscripts describing new species and higher taxonomic changes are released. Starting from the baseline of the 3rd edition of MSW (MSW3), we performed a review of taxonomic changes published since 2004 and digitally linked species names to their original descriptions and subsequent revisionary articles in an interactive, hierarchical database. We found 6,495 species of currently recognized mammals (96 recently extinct, 6,399 extant), compared to 5,416 in MSW3 (75 extinct, 5,341 extant)—an increase of 1,079 species in about 13 years, including 11 species newly described as having gone extinct in the last 500 years. We tabulate 1,251 new species recognitions, at least 172 unions, and multiple major, higher-level changes, including an additional 88 genera (1,314 now, compared to 1,226 in MSW3) and 14 newly recognized families (167 compared to 153). Analyses of the description of new species through time and across biogeographic regions show a long-term global rate of ~25 species recognized per year, with the Neotropics as the overall most species-dense biogeographic region for mammals, followed closely by the Afrotropics. The MDD provides the mammalogical community with an updateable online database of taxonomic changes, joining digital efforts already established for amphibians (AmphibiaWeb, AMNH’s Amphibian Species of the World), birds (e.g., Avibase, IOC World Bird List, HBW Alive), non-avian reptiles (The Reptile Database), and sh (e.g., FishBase, Catalog of Fishes).
Aim: Small geographic ranges make species especially prone to extinction from anthropogenic disturbances or natural stochastic events. We assemble and analyse a comprehensive dataset of all the world's lizard species and identify the species with the smallest ranges—those known only from their type localities. We compare them to wide-ranging species to infer whether specific geographic regions or biological traits predispose species to have small ranges.
Location: Global.
Methods: We extensively surveyed museum collections, the primary literature and our own field records to identify all the species of lizards with a maximum linear geographic extent of <10 km. We compared their biogeography, key biological traits and threat status to those of all other lizards.
Results: One in seven lizards (927 of the 6,568 currently recognized species) are known only from their type localities. These include 213 species known only from a single specimen. Compared to more wide-ranging taxa, they mostly inhabit relatively inaccessible regions at lower, mostly tropical, latitudes. Surprisingly, we found that burrowing lifestyle is a relatively unimportant driver of small range size. Geckos are especially prone to having tiny ranges, and skinks dominate lists of such species not seen for over 50 years, as well as of species known only from their holotype. Two-thirds of these species have no IUCN assessments, and at least 20 are extinct.
Main conclusions: Fourteen per cent of lizard diversity is restricted to a single location, often in inaccessible regions. These species are elusive, usually poorly known and little studied. Many face severe extinction risk, but current knowledge is inadequate to properly assess this for all of them. We recommend that such species become the focus of taxonomic, ecological and survey efforts.
The distributions of amphibians, birds and mammals have underpinned global and local conservation priorities, and have been fundamental to our understanding of the determinants of global biodiversity. In contrast, the global distributions of reptiles, representing a third of terrestrial vertebrate diversity, have been unavailable. This prevented the incorporation of reptiles into conservation planning and biased our understanding of the underlying processes governing global vertebrate biodiversity. Here, we present and analyse the global distribution of 10,064 reptile species (99% of extant terrestrial species). We show that richness patterns of the other three tetrapod classes are good spatial surrogates for species richness of all reptiles combined and of snakes, but characterize diversity patterns of lizards and turtles poorly. Hotspots of total and endemic lizard richness overlap very little with those of other taxa. Moreover, existing protected areas, sites of biodiversity significance and global conservation schemes represent birds and mammals better than reptiles. We show that additional conservation actions are needed to effectively protect reptiles, particularly lizards and turtles. Adding reptile knowledge to a global complementarity conservation priority scheme identifies many locations that consequently become important. Notably, investing resources in some of the world’s arid, grassland and savannah habitats might be necessary to represent all terrestrial vertebrates efficiently.
Responding to purported taxonomic anarchy, in an article published in the widely read journal Nature, Garnett & Christidis (2017) [hereafter GC] opined on the need for “standardized global species lists”, at the behest of conservationists, and proposed the construction of a judicial committee to “restrict … freedom of taxonomic action” and promote taxonomic stability. Here we reflect on this perspective and contest that the view of GC conflicts with some basic and indisputable principles underpinning the philosophy of science, most notably: it must be free. They appear to believe that taxonomic revisions should be based on political, economic and conservation concerns, and they treat species as fixed real entities, instead of refutable scientific hypotheses. In addition to such theoretical misconceptions, GC did not consider important practical aspects of what they term taxonomic anarchy, most significantly the participation of conservationists as authors of taxonomic works, and the importance of alternative management units, a well-established discussion in conservation biology.
This is our 8th edition of an annotated checklist of all recognized and named taxa of the world’s modern chelonian fauna, documenting recent changes and controversies in nomenclature through early 2017, and including all primary synonyms, updated from 7 previous checklists (Turtle Taxonomy Working Group 2007b, 2009, 2010, 2011, 2012, 2014; Rhodin et al. 2008). We provide an updated comprehensive listing of taxonomy, names, and conservation status of all turtles and tortoises of the world, including detailed distribution maps. We strive to record the most recent justified taxonomic assignment of taxa in a hierarchical framework, providing annotations, including alternative possible arrangements, for some proposed changes. We provide common English names and detailed distributional data for all taxa, listing occurrence by countries and many smaller political or geographic subunits (states or regions), including indications of native, extirpated, and introduced (modern or prehistoric) populations. We include current published and draft IUCN Red List status assessments for all turtles, as well as CITES listings. The diversity of turtles and tortoises in the world that has existed in modern times (since 1500 AD) and currently generally recognized as distinct and included in this checklist, now consists of 356 species. Of these, 60 are polytypic, representing 122 additional recognized subspecies, or 478 total taxa of modern turtles and tortoises. Of these, 7 species and 3 subspecies, or 10 taxa (2.1%), have gone extinct. As of the current IUCN 2017 Red List, 148 turtle species (60.4% of 245 species listed, 41.6% of all 356 recognized modern species) are officially regarded as globally Threatened (Critically Endangered [CR], Endangered [EN], or Vulnerable [VU]). We record additional draft Red List assessments by the IUCN Tortoise and Freshwater Turtle Specialist Group (TFTSG) of previously “unevaluated” species, and updated draft re-assessments of previously listed species, allowing us to evaluate the overall current threat levels for all turtles and tortoises. Of the 356 total species of turtles and tortoises, 114 (32.0%) are CR or EN, 179 (50.3%) are Threatened (CR, EN, or VU), and 186 (52.2%) are Threatened or Extinct. If we provisionally adjust for predicted threat rates of Data Deficient and Not Evaluated species, then ca. 59% of all extant turtles are Threatened. These numbers and percentages of Threatened species have increased since our last checklist. Turtles are among the most threatened of the major groups of vertebrates, in general more than birds, mammals, cartilaginous or bony fishes, or amphibians.
The classification of complex organisms is in chaos. Stephen T. Garnett and Les Christidis propose a solution.
Aim A major Late Quaternary vertebrate extinction event affected mostly large-bodied 'megafauna'. This is well documented in both mammals and birds, but evidence of a similar trend in reptiles is scant. We assess the relationship between body size and Late Quaternary extinction in reptiles at the global level. Location Global. Methods We compile a body size database for all 82 reptile species that are known to have gone extinct during the last 50,000 years and compare them with the sizes of 10,090 extant reptile species (97% of known extant diversity). We assess the body size distributions in the major reptile groups: crocodiles, lizards, snakes and turtles, while testing and correcting for a size bias in the fossil record. We examine geographical biases in extinction by contrasting mainland and insular reptile assemblages, and testing for biases within regions and then globally by using geographically weighted models. Results Extinct reptiles were larger than extant ones, but there was considerable variation in extinction size biases among groups. Extinct lizards and turtles were large, extinct crocodiles were small and there was no trend in snakes. Lizard lineages vary in the way their extinction is related to size. Extinctions were particularly prevalent on islands, with 73 of the 82 extinct species being island endemics. Four others occurred in Australia. The fossil record is biased towards large-bodied reptiles, but extinct lizards were larger than extant ones even after we account for this. Main conclusions Body size played a complex role in the extinction of Late Quaternary reptiles. Larger lizard and turtle species were clearly more affected by extinction mechanisms such as over exploitation and invasive species, resulting in a prevalence of large-bodied species among extinct taxa. Insularity was by far the strongest correlate of recent reptile extinctions, suggesting that size-biased extinction mechanisms are amplified in insular environments.
While greater research on threatened species alone cannot ensure their protection, understanding taxonomic bias may be helpful to address knowledge gaps in order to identify research directions and inform policy. Using data for over 10 000 animal species listed on the International Union for Conservation of Nature Red List, we investigated taxonomic and geographic biodiversity conservation research trends worldwide. We found extreme bias in conservation research effort on threatened vertebrates compared with lesser-studied invertebrates in both terrestrial and aquatic habitats at a global scale. Based on an analysis of common threats affecting vertebrates and invertebrates, we suggest a path forward for narrowing the research gap between threatened vertebrates and invertebrates.
While biological extinctions are predicted to rise sharply during the Anthropocene, extinction declarations are rare, partly due to inherent uncertainties in knowing when the last individual of a species has died. This has led to the growth of a group of ‘lost’ species that have not been observed in decades or even centuries, yet are not declared extinct, and as such possess an uncertain conservation status. The existence of such species may prove increasingly problematic as the extinction crisis worsens, given that their presence may create uncertainty with respect to conservation prioritization efforts and to our understanding of extinction rates. We provide the first assessment of the extent of lost taxa, defined as species that have not been reliably observed in >50 years yet are not declared extinct, for terrestrial vertebrates (amphibians, reptiles, birds and mammals). We reviewed information from IUCN Red List accounts within these Classes using a hybrid code‐based search/manual assessment approach, supplemented with consultation of recent literature. In total, we identify a total of 562 lost species (137 amphibians, 257 reptiles, 38 birds and 130 mammals). Of these, 13% (75 species) are listed as ‘Possibly Extinct’ by the IUCN. Lost species outnumber extinct species for all studied Classes except birds. They were mainly confined to the tropics (92.5%), with distributions being particularly concentrated in ‘mega‐diverse’ countries, as expected. Indonesia (69 species), Mexico (33 species) and Brazil (29 species) possessed the most lost species overall. Our results highlight the prevalence of lost taxa among terrestrial vertebrates and identify ‘hotspots’ for these species where future survey efforts should be prioritized. We suggest minor adjustments to IUCN Red List accounts to allow lost species to be better tracked, including more consistent use of the ‘Possibly Extinct’ marker and wider application of the ‘last seen date’ field. Conceptual diagram showing the uncertain classification of lost species, which simultaneously overlap with both extant and extinct species. These lost species may become an increasingly important source of uncertainty in conservation prioritization efforts in the coming decades, particularly if their numbers grow as the effects of the Anthropocene intensify. Efforts to resolve their status represent an important priority for field scientists and conservation organizations.
The mechanisms that underpin ecological speciation, morphological convergence and the evolution of ecological morphotypes (ecomorphs) in squamates have allowed for a better appreciation of the speciation process in chameleons. In particular, attention has been drawn to several populations of chameleons (Sauria, Chamaeleonidae, Bradypodion) from the Cape Fold Mountains, South Africa. Previous work suggested that these populations are genetically divergent, but with strong similarities in phenotype. Using an integrative taxonomic approach that accounts for genetic diversity, habitat and morphology, three of these populations are described as species. One population is from an isolated forest patch and is genetically different at the species level, but morphologically similar to Bradypodion damaranum (Boulenger, 1887) from forested areas in the Knysna region. Although not sister species, the two are in the same clade and probably diverged through vicariance of the forest. Two other populations are from fynbos habitat in adjacent mountain ranges (Tsitsikamma/Langkloof/Kouga mountains and Baviaanskloof Mountains) and are also morphologically similar, but genetically divergent at the species level. These two species are not sister taxa and are not in the same clade yet have a virtually identical phenotype presumably as the result of convergent evolution for the fynbos habitat. Within the context of morphological taxonomy, these populations have been difficult to evaluate. However, when viewed in the context of ecological speciation, convergence and morphological conservatism, the species boundaries are apparent, allowing for them to be described as new taxa.
The International Union for Conservation of Nature (IUCN) Red List of Threatened Species is central in biodiversity conservation, but insufficient resources hamper its long-term growth, updating, and consistency. Models or automated calculations can alleviate those challenges by providing standardised estimates required for assessments, or prioritising species for (re-)assessments. However, while numerous scientific papers have proposed such methods, few have been integrated into assessment practice, highlighting a critical research–implementation gap. We believe this gap can be bridged by fostering communication and collaboration between academic researchers and Red List practitioners, and by developing and maintaining user-friendly platforms to automate application of the methods. We propose that developing methods better encompassing Red List criteria, systems, and drivers is the next priority to support the Red List.
The Convention on International Trade in Endangered Species (CITES) bans international trade in species threatened with extinction. We investigate the effects of these bans on species’ endangerment, as assessed by the International Union for Conservation of Nature (IUCN). Our analysis exploits changes in CITES bans between 1979 and 2017. We find that CITES bans lead to subsequent improvements in mammalian species’ IUCN status, relative to species in which trade was not banned. These effects are primarily due to improvements in the status of commercially targeted species. On the other hand, CITES bans lead to deteriorations in reptilian species’ IUCN status. We find that major spikes in trade volume occurred in anticipation of the bans on reptilian species but not in anticipation of those on mammalian species.
This is our 9th edition of an annotated checklist and atlas of all recognized taxa of the world’s modern turtle and tortoise fauna, documenting recent changes and controversies through mid-2021, and including all primary synonyms, updated from eight previous checklists. We provide an updated comprehensive listing of taxonomy and nomenclature, including type localities, type specimens, detailed distribution maps, as well as calculated presumed historic indigenous ranges, conservation status, and maximum known sex-based carapace lengths for all taxa. We strive to record the most recent justified taxonomic assignment of taxa in a hierarchical framework, providing detailed annotations, including alternative arrangements for a few taxa. We include current published and provisional IUCN Red List status assessments for all species, as well as current listings on CITES appendices. The diversity of turtles and tortoises in the world that has existed in modern times (since 1500 CE) and currently generally recognized as distinct and included in this checklist, now consists of 357 species. Of these, 58 are polytypic, representing 129 additional recognized subspecies (one unnamed), or 486 total taxa of modern chelonians, increased from 478 taxa in our previous checklist. Of these, 5 species and 5 subspecies (one unnamed), or 10 taxa (2.1%), are extinct. We also include a supplementary checklist of 17 taxa of terrestrial chelonians that went extinct during the Holocene from ca. 10,000 BCE to 1500 CE. As of the current IUCN 2021 Red List, 171 turtle species (62.4% of the 274 species red-listed, 47.9% of all 357 recognized modern species) are officially regarded as globally Threatened (Critically Endangered [CR], Endangered [EN], or Vulnerable [VU]). We record additional provisional Red List assessments by the IUCN Tortoise and Freshwater Turtle Specialist Group, allowing us to evaluate the overall current threat levels for all 357 species of turtles and tortoises. Of these, 183 (51.3%) are Threatened (CR, EN, or VU); if we provisionally adjust for predicted threat rates of Data Deficient (DD) species, then ca. 55.9% of all extant turtles are Threatened. These numbers and percentages of Threatened species have increased since our last checklist, although our reclassification of 12 Threatened Galápagos tortoises as subspecies rather than species has moderated the results; the number and percentage of Threatened species increases to 193 (52.3% of 369) if they are considered full species. Turtles and tortoises are among the most threatened of the major groups of vertebrates.
Our knowledge of the conservation status of reptiles, the most diverse class of terrestrial vertebrates, has improved dramatically over the past decade, but still lags behind that of the other tetrapod groups. Here, we conduct the first comprehensive evaluation (~92% of the world's ~1714 described species) of the conservation 1 Joint senior authors. D.G. Chapple et al. Biological Conservation 257 (2021) 109101 3 Lizard Protected areas Reptile Skink Taxonomic bias status of skinks (Scincidae), a speciose reptile family with a worldwide distribution. Using International Union for Conservation of Nature (IUCN) criteria, we report that ~20% of species are threatened with extinction, and nine species are Extinct or Extinct in the Wild. The highest levels of threat are evident in Madagascar and the Neotropics, and in the subfamilies Mabuyinae, Eugongylinae and Scincinae. The vast majority of threatened skink species were listed based primarily on their small geographic ranges (Criterion B, 83%; Criterion D2, 13%). Although the population trend of 42% of species was stable, 14% have declining populations. The key threats to skinks are habitat loss due to agriculture, invasive species, and biological resource use (e.g., hunting, timber harvesting). The distributions of 61% of species do not overlap with protected areas. Despite our improved knowledge of the conservation status of the world's skinks, 8% of species remain to be assessed, and 14% are listed as Data Deficient. The conservation status of almost a quarter of the world's skink species thus remains unknown. We use our updated knowledge of the conservation status of the group to develop and outline the priorities for the conservation assessment and management of the world's skink species.
The complexity and transnational nature of environmental issues our societies are facing, and the need to build scientific capacity building in many regions of the world, require the establishment of global collaborative research networks that include a diverse representation of scientists from multiple geographical, cultural and socio-economical backgrounds. This topic is currently gaining relevance in the field of soil ecology, as awareness is increasing that recognizing, addressing, and predicting the changes that soils are facing requires global collaboration. However, the setup, management and operation of research networks imply multiple tasks and challenges that need to be carefully considered. While major issues related to the setup of such networks in ecology have already been described in the literature, here we focus on aspects that are important to make them truly global and inclusive. For doing so, we introduce a series of recommendations to successfully develop research networks that: i) explore ecological questions requiring data with a global coverage and ii) foster the participation of scientists who have been traditionally underrepresented in international research collaborations. These recommendations, which are based on our own experience, also provide practical advice to anyone aiming to initiate (or join) a global collaborative research network to the mutual benefit of all contributors.
Freshwater ecosystems are among the most diverse and dynamic ecosystems on Earth. At the same time, they are among the most threatened ecosystems but remain underrepresented in biodiversity research and conservation efforts. The rate of decline of vertebrate populations is much higher in freshwaters than in terrestrial or marine realms. Freshwater megafauna (i.e., freshwater animals that can reach a body mass ≥30 kg) are intrinsically prone to extinction due to their large body size, complex habitat requirements and slow life‐history strategies such as long life span and late maturity. However, population trends and distribution changes of freshwater megafauna, at continental or global scales, remain unclear. In the present study, we compiled population data of 126 freshwater megafauna species globally from the Living Planet Database and available literature, and distribution data of 44 species inhabiting Europe and the United States from literature and databases of the International Union for Conservation of Nature and NatureServe. We quantified changes in population abundance and distribution range of freshwater megafauna species. Globally, freshwater megafauna populations declined by 88% from 1970 to 2012, with the highest declines in the Indomalaya and Palearctic realms (−99% and −97%, respectively). Among taxonomic groups, mega‐fishes exhibited the greatest global decline (−94%). In addition, freshwater megafauna experienced major range contractions. For example, distribution ranges of 42% of all freshwater megafauna species in Europe contracted by more than 40% of historical areas. We highlight the various sources of uncertainty in tracking changes in populations and distributions of freshwater megafauna, such as the lack of monitoring data and taxonomic and spatial biases. The detected trends emphasize the critical plight of freshwater megafauna globally and highlight the broader need for concerted, targeted and timely conservation of freshwater biodiversity.
Addressing global environmental problems requires collaborative international arrangements that incorporate the strengths of multiple partners with cultural, infrastructural, educational, and economic differences to produce more robust research and improved environmental outcomes. This can be especially important for research in the tropics given the ecological importance and economic and social constraints. However, significant economic, social and institutional barriers exist towards establishing effective collaborative networks, especially between North–South partners. In this paper, we integrate best practices from the collaboration and social networking literatures to examine a teaching and research partnership between American and Costa Rican institutions. This case demonstrates the potential for research stations to serve as central nodes in establishing collaborative networks involving researchers, government, and community organizations.
Climate warming may lower environmental resource levels, growth, and fitness of many ectotherms. In a classic experiment, Brett and colleagues documented that growth rates of salmon depended strikingly on both temperature and food levels. Here we develop a simple bioenergetic model that explores how fixed temperatures and food jointly alter the thermal sensitivity of net energy gain. The model incorporates differing thermal sensitivities of energy intake and metabolism. In qualitative agreement with Brett's results, it predicts that decreased food intake reduces growth rates, lowers optimal temperatures for growth, and lowers the highest temperatures sustaining growth (upper thermal limit). Consequently, ectotherms facing reduced food intake in warm environments should restrict activity to times when low body temperatures are biophysically feasible, but-in a warming world-that will force ectotherms to shorten activity times and thus further reduce food intake. This "metabolic meltdown" is a consequence of declining energy intake coupled with accelerating metabolic costs at high temperatures and with warming-imposed restrictions on activity. Next, we extend the model to explore how increasing mean environmental temperatures alter the thermal sensitivity of growth: when food intake is reduced, optimal temperatures and upper thermal limits for growth are lowered. We discuss our model's key assumptions and caveats as well as its relationship to a recent model for phytoplankton. Both models illustrate that the deleterious impacts of climate warming on ectotherms will be amplified if food intake is also reduced, either because warming reduces standing food resources or because it restricts foraging time.