Rarity,Species Richness,and the Threat of Extinction—Are Plants the Same as Animals?

Assessment of conservation status is done both for areas or habitats and for species (or taxa). IUCN Red List categories have been the principal method of categorising species in terms of extinction risk, and have been shown to be robust and helpful in the groups for which they have been developed. A recent study highlights properties associated with extinction risk in flowering plants, focusing on the species-rich hot spot of the Cape region of South Africa, and concludes that merely following methods derived from studies of vertebrates may not provide the best estimates of extinction risk for plants. Biology, geography, and history all are important factors in risk, and the study poses many questions about how we categorise and assess species for conservation priorities.     

Present day risk of extinction may exacerbate the lower species richness of dioecious clades

Dioecious clades have been observed to have lower species richness than their non‐dioecious sister groups indicating that dioecious species experience higher extinction rates and (or) lower speciation rates. To determine whether current threats to biodiversity may exacerbate this pattern, we examined the threat to exclusively dioecious families of angiosperms among the 13,013 species of threatened plants included in the IUCN Red List of Threatened Species. When examined phylogenetically, dioecious families had proportionally more species listed than their sister groups. We then examined whether ecological traits correlated with dioecy, namely tropical distribution, woody growth form, and fleshy fruits, are associated with having higher proportions of threatened species. Ignoring breeding system, woody growth form was the only trait that was associated with a greater than expected proportion of threatened species per family. Red‐Listed dioecious families were more likely to have a woody growth form than non‐dioecious families. Woody growth habit is likely contributing to the higher incidence of dioecious species being at risk of extinction but is not solely responsible for the pattern because higher risk within dioecious groups was also apparent in a comparison of exclusively woody sister‐group pairs. Our results indicate that dioecious plants may warrant special attention in conservation practices.     

Conus: First Comprehensive Conservation Red List Assessment of a Marine Gastropod Mollusc Genus

Marine molluscs represent an estimated 23% of all extant marine taxa, but research into their conservation status has so far failed to reflect this importance, with minimal inclusion on the authoritative Red List of the International Union for the Conservation of Nature (IUCN). We assessed the status of all 632 valid species of the tropical marine gastropod mollusc, Conus (cone snails), using Red List standards and procedures to lay the groundwork for future decadal monitoring, one of the first fully comprehensive global assessments of a marine taxon. Three-quarters (75.6%) of species were not currently considered at risk of extinction owing to their wide distribution and perceived abundance. However, 6.5% were considered threatened with extinction with a further 4.1% near threatened. Data deficiency prevented 13.8% of species from being categorised although they also possess characteristics that signal concern. Where hotspots of endemism occur, most notably in the Eastern Atlantic, 42.9% of the 98 species from that biogeographical region were classified as threatened or near threatened with extinction. All 14 species included in the highest categories of Critically Endangered and Endangered are endemic to either Cape Verde or Senegal, with each of the three Critically Endangered species restricted to single islands in Cape Verde. Threats to all these species are driven by habitat loss and anthropogenic disturbance, in particular from urban pollution, tourism and coastal development. Our findings show that levels of extinction risk to which cone snails are exposed are of a similar magnitude to those seen in many fully assessed terrestrial taxa. The widely held view that marine species are less at risk is not upheld.     

Ecological correlates of extinction risk in Chinese birds

China is one of the countries with the richest bird biodiversity in the world. Among the 1372 Chinese birds, 146 species are considered threatened and three species are regionally extinct according to the officially released China Biodiversity Red List in 2015. Here, we conducted the first extensive analysis to systematically investigate the patterns and processes of extinction and threat in Chinese birds. We addressed the following four questions. First, is extinction risk randomly distributed among avian families in Chinese birds? Second, which families contain more threatened species than would be expected by chance? Third, which species traits are important in determining the extinction risk in Chinese birds using a multivariate phylogenetic comparative approach? Finally, is the form of the relationship between traits additive or nonadditive (synergistic)? We found that the extinction risk of Chinese birds was not randomly distributed among taxonomic families. The families that contained significantly more threatened species than expected were the hornbills, cranes, pittas, pheasants and hawks and eagles. We obtained eleven species traits that are commonly hypothesized to influence extinction risk from the literature: body size, clutch size, trophic level, mobility, habitat specificity, geographical range size, nest type, nest site, flocking tendency, migrant status and hunting vulnerability. After phylogenetic correction, model selection based on Akaike's information criterion identified the synergistic interaction between body size and hunting vulnerability as the single best correlate of extinction risk in Chinese birds. Our results suggest that, in order to be effective, priority management efforts should be given both to certain extinction‐prone families, particularly the hornbills, pelicans, cranes, pittas, pheasants and hawks and eagles, and to bird species with large body size and high hunting vulnerability.     

Red Listed medicinal plants of South Africa: Status,trends, and assessment challenges

In 2009, South Africa completed the IUCN Red List assessments of 20,456 indigenous vascular plant taxa. During that process, medicinal plant species (especially those sold in informal muthi markets) were identified so that potential extinction risks posed to these species could be assessed. The present study examines and analyses the recently documented threat statuses of South African ethnomedicinal taxa, including the number of species used, revealing family richness and the degree of endemism, and calculates the Red List Index (RLI) of species survival to measure the relative degree of threat to medicinal species. Approximately 2062 indigenous plant species (10% of the total flora) have been recorded as being used for traditional medicine in South Africa, of which it has been determined that 82 species (0.4% of the total national flora) are threatened with extinction at a national level in the short and medium terms and a further 100 species are of conservation concern (including two species already extinct in the wild). Thirty-two percent of the taxa have been recorded in traditional medicine markets in the provinces of KwaZulu-Natal, Gauteng, Eastern Cape, Mpumalanga and Limpopo. The study also reflects on the challenges associated with Red List evaluations of medicinal species, many of which, based on market reports, are extracted at a seemingly unsustainable rate. In contrast to the majority of species enumerated in the Red List of South African plants, medicinal taxa are often widespread, with large extents of occurrence. Accordingly, the population decline criteria have necessarily been applied to assess threats to their existence, even though accurate figures for numbers of remaining individuals, areas of occupancy, quantities harvested, and regeneration times are often found lacking. Factors leading to susceptibility of plant species to extinction as a result of harvesting pressure are discussed. The current findings reveal a need for greater emphasis on focussed population level research on prioritised medicinal plant species.     

Palm economic and traditional uses,evolutionary history and the IUCN Red List

The growing demand for natural resources to sustain human population has increased the loss and modification of natural habitats, enhancing the number of species threatened with extinction. Commonly tools such as Red Lists guide conservation actions and policies. However, Red Lists are based in population parameters, and important aspects of biodiversity such as phylogenetic diversity are not considered. Here we evaluated the amount of economic and traditional uses and evolutionary history of palms captured by the global IUCN Red List and the national Red Lists of Colombia and Madagascar. We estimated palms plant use diversity (PUD) and phylogenetic diversity (PD) for all species in the IUCN Red List and for each threat category at global and national scale. We also investigated if the number of uses, PUD and PD predict palm threat level. Species covered by IUCN Red List have lower PUD and PD than expected by chance. At global scale, palms with higher extinction risk have lower number of uses, PUD and PD. However, whereas in Colombia least concern species had lower PUD and PD, in Madagascar only Data Deficient species had lower PUD than expected by chance. Our findings highlight the need of palm specialists to expand the list of palms they have assessed and submit them for inclusion in Red Lists, enabling Red Lists to capture a more random sample of palm evolutionary history and economic uses. That would improve the success of biodiversity conservation actions by taking into account other aspects of biodiversity rather than taxonomic identity.     

Green Plants in the Red: A Baseline Global Assessment for the IUCN Sampled Red List Index for Plants

Plants provide fundamental support systems for life on Earth and are the basis for all terrestrial ecosystems; a decline in plant diversity will be detrimental to all other groups of organisms including humans. Decline in plant diversity has been hard to quantify, due to the huge numbers of known and yet to be discovered species and the lack of an adequate baseline assessment of extinction risk against which to track changes. The biodiversity of many remote parts of the world remains poorly known, and the rate of new assessments of extinction risk for individual plant species approximates the rate at which new plant species are described. Thus the question ‘How threatened are plants?’ is still very difficult to answer accurately. While completing assessments for each species of plant remains a distant prospect, by assessing a randomly selected sample of species the Sampled Red List Index for Plants gives, for the first time, an accurate view of how threatened plants are across the world. It represents the first key phase of ongoing efforts to monitor the status of the world’s plants. More than 20% of plant species assessed are threatened with extinction, and the habitat with the most threatened species is overwhelmingly tropical rain forest, where the greatest threat to plants is anthropogenic habitat conversion, for arable and livestock agriculture, and harvesting of natural resources. Gymnosperms (e.g. conifers and cycads) are the most threatened group, while a third of plant species included in this study have yet to receive an assessment or are so poorly known that we cannot yet ascertain whether they are threatened or not. This study provides a baseline assessment from which trends in the status of plant biodiversity can be measured and periodically reassessed.     

Comparing and contrasting threat assessments of plant species at the global and sub-global level

Evidence-based assessments of extinction risk are established tools used to inform the conservation of plant species, and form the basis of key targets within the framework of the Global Strategy for Plant Conservation (GSPC). An overall picture of plants threat assessments is challenging due to the use of a variety of methodologies and range in scope from global to subnational. In this study, we quantify the state of progress in assessing the extinction risk of all land plants, determine the key geographic and taxonomic gaps with respect to our understanding of plant extinction risk, and evaluate the impact of different sources and methodologies on the utility of plant assessments. To this end, we have analyzed a cleaned dataset compiled from IUCN Red List of Threatened Species and Regional Red Lists. We reveal that there are assessments available for 89,810 distinct species or 25% of all accepted land plant species. However unlike with other major organismal lineages the bulk of the plant species assessments are derived from Regional Red Lists, and not the Global IUCN Red List. We demonstrate that this bias towards regional assessments results in distinct taxonomic and geographic strengths and weaknesses, and we identify substantial taxonomic and geographic gaps in the assessment coverage. With species that have been assessed in common at both global and regional levels, we explore the implications of combining threat assessments from different sources. We find that half of global and regional assessments do not agree on the exact category of extinction risk for a species. Regional assessments assign a higher risk of extinction; or underestimate extinction risk with almost equal frequency. We conclude with recommended interventions, but support the suggestion that all threat assessments should be pooled to provide more data and broaden the scope of threat assessments for monitoring progress towards GSPC targets.     

Tourism and recreation a global threat to orchids

Orchidaceae is a mega diverse family accounting for 10% of the world’s flowering plants. Due to factors such as small dispersed populations, specific symbiosis with fungi and with pollinators and their desirability for collecting, many orchids are threatened with extinction. Tourism and recreation is increasingly recognised as a global threat for plants, but is it an issue for orchids? When data on orchids from the International Union for Nature Conservation (IUCN) Red List was reviewed, we found that 149 (40%) of the 442 orchid species with threat data were at risk from tourism and recreation. This included: 98 (22%) species threatened by residential and commercial development for tourism and recreation, 75 (17%) by intentional collecting within protected areas, and 90 (20%) by human intrusions and disturbance from recreational activities. The three threats often co-occurred and hence can be treated as a threat syndrome. The proportion of species threatened varied among locations with 80% of the 65 species in East Asia, 32% of 68 species in South and Southeast Asia and 94% of 16 orchid species in Europe threatened by tourism and recreation. Terrestrial orchids and those growing in forests were more likely to be at risk from these threats. With so many species at risk, increased awareness and recognition of these threats combined with improved management to reduce impacts is needed. Gaps and inconsistencies in the IUCN Red List must also be addressed to obtain a better understanding of the extent of this, and other threats to plants.     

Application of the IUCN Red Listing system to setting species targets for conservation planning purposes

Biodiversity targets, or estimates of the quantities of biodiversity features that should be conserved in a region, are fundamental to systematic conservation planning. We propose that targets for species should be based on the quantitative thresholds developed for the Vulnerable category of the IUCN Red List system, thereby avoiding future listings of species in an IUCN Red List threat category or an increase in the extinction risk, or ultimate extinction, of species already listed as threatened. Examples of this approach are presented for case studies from South Africa, including threatened taxa listed under the IUCN Red List criteria of A to D, a species listed as Near Threatened, a species of conservation concern due to its rarity, and one species in need of recovery. The method gives rise to multiple representation targets, an improvement on the often used single representation targets that are inadequate for long term maintenance of biodiversity or the arbitrary multiple representation and percentage targets that are sometimes adopted. Through the implementation of the resulting conservation plan, these targets will ensure that the conservation status of threatened species do not worsen over time by qualifying for higher categories of threat and may actually improve their conservation status by eliminating the threat of habitat loss and stabilizing population declines. The positive attributes ascribed to the IUCN Red List system, and therefore to the species targets arising from this approach, are important when justifying decisions that limit land uses known to be detrimental to biodiversity.     

Phylogenetic Patterns of Extinction Risk in the Eastern Arc Ecosystems,an African Biodiversity Hotspot

There is an urgent need to reduce drastically the rate at which biodiversity is declining worldwide. Phylogenetic methods are increasingly being recognised as providing a useful framework for predicting future losses, and guiding efforts for pre-emptive conservation actions. In this study, we used a reconstructed phylogenetic tree of angiosperm species of the Eastern Arc Mountains – an important African biodiversity hotspot – and described the distribution of extinction risk across taxonomic ranks and phylogeny. We provide evidence for both taxonomic and phylogenetic selectivity in extinction risk. However, we found that selectivity varies with IUCN extinction risk category. Vulnerable species are more closely related than expected by chance, whereas endangered and critically endangered species are not significantly clustered on the phylogeny. We suggest that the general observation for taxonomic and phylogenetic selectivity (i.e. phylogenetic signal, the tendency of closely related species to share similar traits) in extinction risks is therefore largely driven by vulnerable species, and not necessarily the most highly threatened. We also used information on altitudinal distribution and climate to generate a predictive model of at-risk species richness, and found that greater threatened species richness is found at higher altitude, allowing for more informed conservation decision making. Our results indicate that evolutionary history can help predict plant susceptibility to extinction threats in the hyper-diverse but woefully-understudied Eastern Arc Mountains, and illustrate the contribution of phylogenetic approaches in conserving African floristic biodiversity where detailed ecological and evolutionary data are often lacking.     

Where are threatened ferns found? Global conservation priorities for pteridophytes

Recent efforts to improve the representation of plant species included on the IUCN Red List of Threatened Species through the IUCN Sampled Red List Index (SRLI) for Plants have led to the assessment of almost 1000 additional species of pteridophytes and lycophytes under IUCN Red List criteria. Species were selected at random from all lineages of pteridophytes and lycophytes and are taxonomically as well as ecologically representative of pteridophyte and lycophyte diversity. 16% of pteridophyte and lycophyte species are globally threatened with extinction and 22% are of elevated conservation concern (threatened or Near Threatened); of species of pteridophytes and lycophytes previously included on the Red List, 54% were considered threatened. Over half of pteridophyte and lycophyte species assessed for the SRLI use estimates of range size; therefore the method used to measure range may affect the Red List category assigned. We evaluated this using two alternative metrics for estimating range, species distribution modelling (SDM) and ecologically suitable habitat (ESH), for 227 species endemic to the Neotropical biogeographic realm. Differences between range estimates were small when ranges were small but increased with increasing range size. For 58 (25.6%) species alternative modelling techniques result in the species meeting the threshold for a different IUCN Red List category from using extent of occurrence. Modelling threatened species distributions also highlights priority areas for conservation in tropical and subtropical montane forests that are the most species-rich habitat for small-range pteridophyte and lycophyte species, but which are now increasingly subject to rapid conversion to agriculture.     

Phylogenetic correlates of extinction risk in mammals: species in older lineages are not at greater risk

Phylogenetic information is becoming a recognized basis for evaluating conservation priorities, but associations between extinction risk and properties of a phylogeny such as diversification rates and phylogenetic lineage ages remain unclear. Limited taxon-specific analyses suggest that species in older lineages are at greater risk. We calculate quantitative properties of the mammalian phylogeny and model extinction risk as an ordinal index based on International Union for Conservation of Nature Red List categories. We test for associations between lineage age, clade size, evolutionary distinctiveness and extinction risk for 3308 species of terrestrial mammals. We show no significant global or regional associations, and three significant relationships within taxonomic groups. Extinction risk increases for evolutionarily distinctive primates and decreases with lineage age when lemurs are excluded. Lagomorph species (rabbits, hares and pikas) that have more close relatives are less threatened. We examine the relationship between net diversification rates and extinction risk for 173 genera and find no pattern. We conclude that despite being under-represented in the frequency distribution of lineage ages, species in older, slower evolving and distinct lineages are not more threatened or extinction-prone. Their extinction, however, would represent a disproportionate loss of unique evolutionary history.     

The Sampled Red List Index for Plants,phase II: ground-truthing specimen-based conservation assessments

The IUCN Sampled Red List Index (SRLI) is a policy response by biodiversity scientists to the need to estimate trends in extinction risk of the world''s diminishing biological diversity. Assessments of plant species for the SRLI project rely predominantly on herbarium specimen data from natural history collections, in the overwhelming absence of accurate population data or detailed distribution maps for the vast majority of plant species. This creates difficulties in re-assessing these species so as to measure genuine changes in conservation status, which must be observed under the same Red List criteria in order to be distinguished from an increase in the knowledge available for that species, and thus re-calculate the SRLI. However, the same specimen data identify precise localities where threatened species have previously been collected and can be used to model species ranges and to target fieldwork in order to test specimen-based range estimates and collect population data for SRLI plant species. Here, we outline a strategy for prioritizing fieldwork efforts in order to apply a wider range of IUCN Red List criteria to assessments of plant species, or any taxa with detailed locality or natural history specimen data, to produce a more robust estimation of the SRLI.     

Historical drivers of extinction risk: using past evidence to direct future monitoring

Global commitments to halt biodiversity decline mean that it is essential to monitor species'' extinction risk. However, the work required to assess extinction risk is intensive. We demonstrate an alternative approach to monitoring extinction risk, based on the response of species to external conditions. Using retrospective International Union for Conservation of Nature Red List assessments, we classify transitions in the extinction risk of 497 mammalian carnivores and ungulates between 1975 and 2013. Species that moved to lower Red List categories, or remained Least Concern, were classified as ‘lower risk''; species that stayed in a threatened category, or moved to a higher category of risk, were classified as ‘higher risk''. Twenty-four predictor variables were used to predict transitions, including intrinsic traits (species biology) and external conditions (human pressure, distribution state and conservation interventions). The model correctly classified up to 90% of all transitions and revealed complex interactions between variables, such as protected areas (PAs) versus human impact. The most important predictors were: past extinction risk, PA extent, geographical range size, body size, taxonomic family and human impact. Our results suggest that monitoring a targeted set of metrics would efficiently identify species facing a higher risk, and could guide the allocation of resources between monitoring species'' extinction risk and monitoring external conditions.     

Saving Europe’s threatened flora: progress towards GSPC Target 8 in Europe

The European flora is of global significance but many species are facing an ever increasing range of threats, especially the growing impacts of climate change. While various estimates have been made for the number of threatened plant species in Europe, an up-to-date European plant Red List does not presently exist. Target 8 of the Global Strategy for Plant Conservation (GSPC) calls for 60% of threatened plant species to be conserved in ex situ collections by 2010. In the absence of a European plant Red List, it is difficult to monitor progress at the regional level towards this target. To address this gap Botanic Gardens Conservation International (BGCI) has developed a consolidated list of European threatened species as a step towards a formal Red List. The database consists of national Red List data from 28 European countries and includes records for over 11,000 taxa. National Red List data were supplemented by information on the critically endangered plants of Europe provided by the Museum National d’Histoire Naturelle/European Topic Centre on Biological Diversity and the Conservatoire Botanique National de Brest. A list of regionally threatened species was extracted from the database and screened against BGCI’s database of plants in cultivation in botanic gardens (PlantSearch) and ENSCONET’s (European Native Seed Conservation Network) database of plants conserved in European seed banks. This analysis revealed that 42% of European threatened species are currently included in ex situ conservation programmes in Europe.     

Climate change effects on animal and plant phylogenetic diversity in southern Africa

Much attention has been paid to the effects of climate change on species' range reductions and extinctions. There is however surprisingly little information on how climate change driven threat may impact the tree of life and result in loss of phylogenetic diversity (PD). Some plant families and mammalian orders reveal nonrandom extinction patterns, but many other plant families do not. Do these discrepancies reflect different speciation histories and does climate induced extinction result in the same discrepancies among different groups? Answers to these questions require representative taxon sampling. Here, we combine phylogenetic analyses, species distribution modeling, and climate change projections on two of the largest plant families in the Cape Floristic Region (Proteaceae and Restionaceae), as well as the second most diverse mammalian order in Southern Africa (Chiroptera), and an herbivorous insect genus (Platypleura) in the family Cicadidae to answer this question. We model current and future species distributions to assess species threat levels over the next 70 years, and then compare projected with random PD survival. Results for these animal and plant clades reveal congruence. PD losses are not significantly higher under predicted extinction than under random extinction simulations. So far the evidence suggests that focusing resources on climate threatened species alone may not result in disproportionate benefits for the preservation of evolutionary history.     

Automated assessment reveals that the extinction risk of reptiles is widely underestimated across space and phylogeny

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.     

Extinction risk of Chinese angiosperms varies between woody and herbaceous species

Aim

Understanding how species' traits and environmental contexts relate to extinction risk is a critical priority for ecology and conservation biology. This study aims to identify and explore factors related to extinction risk between herbaceous and woody angiosperms to facilitate more effective conservation and management strategies and understand the interactions between environmental threats and species' traits.

Location

China.

Taxon

Angiosperms.

Methods

We obtained a large dataset including five traits, six extrinsic variables, and 796,118 occurrence records for 14,888 Chinese angiosperms. We assessed the phylogenetic signal and used phylogenetic generalized least squares regressions to explore relationships between extinction risk, plant traits, and extrinsic variables in woody and herbaceous angiosperms. We also used phylogenetic path analysis to evaluate causal relationships among traits, climate variables, and extinction risk of different growth forms.

Results

The phylogenetic signal of extinction risk differed among woody and herbaceous species. Angiosperm extinction risk was mainly affected by growth form, altitude, mean annual temperature, normalized difference vegetation index, and precipitation change from 1901 to 2020. Woody species' extinction risk was strongly affected by height and precipitation, whereas extinction risk for herbaceous species was mainly affected by mean annual temperature rather than plant traits.

Main conclusions

Woody species were more likely to have higher extinction risks than herbaceous species under climate change and extinction threat levels varied with both plant traits and extrinsic variables. The relationships we uncovered may help identify and protect threatened plant species and the ecosystems that rely on them.