Larval settlement is an important process that drives population and community dynamics of marine invertebrates. Barnacles are frequently used to investigate settlement mechanisms of marine invertebrate larvae. Adult barnacles induce settlement of conspecific larvae nearby which ultimately facilitates copulation with neighbouring individuals. A significant factor involved in the larval induction process is the proteinaceous waterborne settlement pheromone (WSP), which is purified from adult barnacles. A previous study suggested that the concentration of WSP informs barnacle cyprid larvae about the abundance of adult barnacles in the environment nearby but it is unclear whether WSP works in a species-specific or non-species-specific manner. In this study, we conducted settlement assays using recombinant WSPs and cyprids of two congenic barnacle species, Amphibalanus amphitrite and A. improvisus, to investigate the species specificity of WSPs. We found that A. amphitrite and A. improvisus cyprids responded similarly to con-specific WSPs as to allo-specific WSP stimuli indicating that WSPs are not species-specific. Our findings suggest that cyprids approach potential settlement sites using WSPs, non-species-specific settlement pheromones, before performing a closer search of the substratum using a species-specific pheromone.

The genus Maculabatis is a group of batoid rays from the Dasyatidae family, consisting of two main complexes: the gerrardi (spotted species) and the pastinacoides (plain species). This study investigated the diversity within the Maculabatis gerrardi complex, revealing the presence of two distinct geographical lineages, with a potential new species captured off the coast of Mozambique. Molecular analysis showed a significant divergence: COI sequences from Mozambique specimens exhibited over 99% similarity with M. gerrardi from South Africa but more than 2% divergence from those in the Indo-Pacific. Phylogenetic analysis identified two distinct subclades, suggesting at least two hidden lineages within the genus Maculabatis and consequently possible new undescribed species within M. gerrardi complex. These findings emphasize the importance of conducting additional research that integrates both morphological and molecular methods to better understand the group's diversity and evolutionary dynamics, ultimately supporting the development of effective conservation strategies.

Starting in the summer 2023 and peaking in late 2023, large amounts of Sargassum were observed floating off the coast of Madeira Islands, Portugal. The analysis of the samples revealed the presence of the three most common morphotypes of the two known species of pelagic Sargassum: S. natans I, S. natans VIII, and S. fluitans III. This is the first record for the subtropical eastern Atlantic Ocean for S. natans VIII and S. fluitans III. Both species were found entangled, and even though the main purpose of the study was to document the occurrence of pelagic Sargassum in the Madeira archipelago, some associated fauna were also recorded: the crab Planes minutus (Linnaeus, 1758), the amphi-Atlantic shrimps Latreutes fucorum (Fabricius, 1798) and Hippolyte coerulescens (Fabricius, 1775), and the nudibranch Scyllaea pelagica Linnaeus, 1758. The last two are new records for the Madeira archipelago.

This study presents the first comprehensive annotated checklist of polychaetes collected from floating dock communities across New England and adjacent New York areas, emphasizing the significance of rapid biodiversity assessment surveys in understanding marine biodiversity. With 61% of the identified species classified as cryptogenic, the research highlights the complexity of marine biogeography and the challenges of distinguishing between native and non-native species. The incorporation of DNA barcoding has significantly improved species identification and revealed the presence of cryptic species complexes. The study's findings illustrate the prevalence of tubicolous families (Spionidae, Serpulidae, Sabellidae, and Terebelllidae) that are susceptible to anthropogenic dispersal mechanisms. It also addresses the challenge posed by the high proportion of cryptogenic species, calling for enhanced taxonomic and genetic analyses to resolve their origins and ecological roles. Despite the temporal variation in polychaete composition across years, the absence of distinct community assemblages suggests a level of resilience within floating dock communities. Our study advocates for the continuation and expansion of rapid assessment surveys, coupled with the integration of genetic methodologies, to provide a clearer picture of marine biodiversity.

1. 1. Understanding whether a species still persists, or the timing of its extinction is challenging, however, such knowledge is fundamental for effective species management.

2. 2. For the vast majority of species our understanding of their existence is based solely on sighting data that can range from museum specimens and clear photographs, through vocalisations, to markings and oral accounts.

3. 3. Here we review the methods that have been developed to infer the extinction of species from a sighting record, providing an understanding of their assumptions and applications. We have also produced an RShiny package which can be used to implement some of the methods presented in the article.

4. 4. While there are a number of potential areas that could be further developed, the methods reviewed provide a useful tool for inferring species extinction.

Biodiversity shortfalls and taxonomic bias can lead to inaccurate assessment of conservation priorities. Previous literature has begun to explore practical reasons why some species are discovered sooner or are better researched than others. However, the deeper socio-cultural causes for undiscovered and neglected biodiversity, and the value of collectively analysing species at risk of unrecorded, or “dark”, extinction, are yet to be fully examined. Here, we argue that a new label (we propose “shadow diversity”) is needed to shift our perspective from biodiversity shortfalls to living, albeit unknown, species. We suggest this linguistic shift imparts intrinsic value to these species, beyond scientific gaze and cultural systems. We review research on undiscovered, undetected and hidden biodiversity in the fields of conservation biology, macroecology and genetics. Drawing on philosophy, geography, history and sociology, we demonstrate that a range of socio-cultural factors (funding, education and historical bias) combine with traditional, practical impediments to limit species discovery and detection. We propose using a spectrum of shadow diversity which enables a complex, non-binary and comprehensive approach to biodiversity unknowns. Shadow diversity holds exciting potential as a tool to increase awareness, appreciation and support for the conservation of traditionally less studied wildlife species and sites, from soil microbes to less charismatic habitat fragments. We advocate for a shift in how the conservation community and wider public see biodiversity and an increase in popular support for conserving a wider range of life forms. Most importantly, shadow diversity provides appropriate language and conceptual frameworks to discuss species absent from conservation assessment and at potential risk of dark extinction.

The Atlantic Forest is one of the most threatened biomes globally. Data from monitoring programs are necessary to evaluate the conservation status of species, prioritise conservation actions and to evaluate the effectiveness of these actions. Birds are particularly well represented in citizen-collected datasets that are used worldwide in ecological and conservation studies. Here, we analyse presence-only data from three online citizen science datasets of Atlantic Forest endemic bird species to evaluate whether the representation of these species was correlated with their global threat status, range and estimated abundance. We conclude that even though species are over- and under-represented with regard to their presumed abundance, data collected by citizen scientists can be used to infer species distribution and, to a lesser degree, species abundance. This pattern holds true for species across global threat status.

In the Anthropocene, recognising nature’s role in human well-being is pivotal for biodiversity conservation. Despite their significance, knowledge gaps persist regarding ecosystem services, even for well-studied species like vultures. Our study focuses on the Griffon Vulture Gyps fulvus in Sardinia, Italy, exploring their cultural and regulating services, including carcass disposal and resulting greenhouse gas (GHG) mitigation. Through surveys of natural reserve visitors and data on carcass provision and GHG emissions, we assess public perception, economic value, and environmental impacts associated with vultures. The public perception of Griffon Vultures is predominantly positive, with a strong acknowledgment of their role in disease prevention and carcass disposal, highlighting their contribution to regulation services. Furthermore, vultures are widely recognised as a key element characterising the agropastoral landscapes of Sardinia, underscoring their cultural importance. The economic evaluation, through willingness to pay for vulture-watching and photography opportunities, indicates a significant appreciation of these birds, with almost three-quarters of respondents willing to pay an entrance fee at vulture observation sites. We also show that supplanting the disposal role of vultures at studied feeding sites (during 2017–2022) would result in the emission of 96 tons of CO2 equivalent, which highlights the critical role of vultures in climate mitigation. This study not only sheds light on the ecological and cultural significance of Griffon Vultures in Sardinia but also underscores the economic and environmental benefits of their conservation. It emphasises the need for continued efforts in vulture conservation, integrating ecological, cultural, and economic perspectives to foster a sustainable coexistence between humans and wildlife.

In 2021, scientists published a preprint stating that the dugong population of Okinawa had declined below the minimum viable population and should be considered extinct. The publication led to an outcry amongst Japanese/Okinawan environmentalists and to criticism by international dugong specialists. Two issues were raised: 1) Declaring dugongs extinct, although feeding trails were found in several locations, misrepresented the reality in Okinawan waters, and could have negative impacts on conservation measures; 2) Three authors were sitting on the Environmental Monitoring Committee for a controversial military base construction project in an area where dugongs were frequently spotted before construction commenced. The presence/absence of dugongs at the site had become a political issue, as the animal’s protected status and its depiction in folklore gave it symbolic meaning in the anti-base movement. The declaration of dugong extinction reminded protesters of a former Environmental Impact Assessment conducted by Japan’s Ministry of Defence, declaring the site to be no relevant dugong habitat. The paper explores the implications of the preprint for the political situation in Okinawa and questions the certainty of dugong extirpation in the region. It argues that speculations about extinction cannot be divorced from the political contexts to which they are invariably tied.

Different stakeholders and actors frequently describe environmental challenges as ‘crises’. These crises are often wicked problems that are difficult to resolve due to the complex and contradictory nature of the evidence and knowledge systems surrounding them. Here, we examine a crisis narrative surrounding the IUCN-declared Asian Songbird Crisis (ASC), with its epicentre in Indonesia, where an extensive birdkeeping culture persists. We investigate how bird extinction is perceived by different actors, particularly conservation law enforcement and practitioners working in this space. We unravel local perspectives on the complex relationship between bird trade and extinction through one-to-one interviews and focus groups. Our examination reveals a diversity of attitudes to the ASC, with many law enforcement actors not recognising the crisis label. Market mechanisms result in complex shifts in harvesting pressure onto one or more closely related similar species. The findings challenge the prevailing notion that species extinction significantly affects wildlife trades, emphasising the plastic nature of trade and the coming and going of species fashions. By revealing the divergent views of actors on extinction and the ASC, we highlight the need for shared language, particularly the implications of the ‘crisis’ label, around species extinction.

The integrated water systems (IWSs) concept involves managing water quantity and quality through dynamic interactions. This paper reviews the terrestrial water cycle, focusing on resilience and adaptive planning (AP) approaches within IWSs. We examine how integrating these approaches can improve IWS management and planning, addressing their inherent complexities. Using a performance-based resilience definition, we consider the system’s ability to absorb, recover from and adapt to adverse events. The AP focuses on flexible management pathways for uncertain future conditions. Although both resilience and AP aim to enhance water system performance and address uncertainties, they differ in their assessment and implementation approaches. We propose an Adaptive Resilience Planning (ARP) framework that merges both approaches. The ARP uses resilience metrics for performance assessment and incorporates AP’s methods for conceptualising uncertainties and optimising management portfolios. Implementing the ARP framework raises four research questions: (1) holistic characterisation of uncertainties and options in IWSs, (2) using resilience metrics for IWS adaptation, (3) balancing trade-offs among management goals through optimal portfolio selection and (4) monitoring portfolio performance and uncertainties for informed adaptation. The ARP framework offers a structured method for dynamic and adaptive resilience planning, enhancing IWS management’s responsiveness to evolving challenges.

We report the non-breeding range of an adult Rapa Shearwater Puffinus myrtae, as estimated from data collected by one light logger deployed from 31 August 2019 to 22 July 2020. The Rapa Shearwater is classified as “Critically Endangered”, with a strong decline in breeding numbers reported recently. As the species is threatened by various introduced mammals on the breeding colonies, the main objective of this tracking essay was to identify the oceanic regions where the birds forage during the non-breeding season. The non-breeding range of this bird was located south-east of Rapa Island, where fishery activities are limited. The conservation efforts for the Critically Endangered Rapa Shearwater should first focus on securing mammal-free sites for breeding colonies.

This study addresses the regulatory impacts on an innovative project seeking to introduce autonomous robots into the potable water network, Pipebots. It does so through the lens of adaptive governance, principally the under-explored area of adaptive governance and formal law. Through this study, suggestions are made to improve the regulatory regime, including a separate authorisation process for novel or complex products, built-in feedback loops to encourage learning and reflection and the need for early engagement by innovators in the regulatory process. Further, the analysis exposes a wider, serious tension: How do we encourage the innovation and flexibility we need to ensure the resilience and sustainability of our systems and at the same time safeguard strict human and environmental protections? The Pipebots project is used to explore the law’s role within adaptive governance, and suggestions to improve water governance are proposed.

During the ill-fated 1897 Andrée balloon expedition, Nils Strindberg allegedly dropped a small tin containing a last message for his fiancée onto the island Fuglesongen in northwestern Svalbard, as the expedition crew passed over it in their hydrogen balloon, Örnen. Despite at least one lengthy search on Fuglesongen, the tin has never been found. This paper investigates the hypothesis that the tin was accidentally dropped onto Klovningen, a neighbouring island similar in size and shape, situated approximately 2.4 km east of Fuglesongen. A re-analysis of Strindberg’s original handwritten notes from the balloon flight, along with other primary sources and meteorological analyses, suggests that a targeted search for the tin on Klovningen could be a promising next step in solving this enduring mystery.

There has been great popular and scholarly interest in the activities of non-Arctic actors in the Arctic region, and in the Arctic Council specifically. We find controversy around the activities of Observers in the Council, with some seeing challenges to Arctic states and others seeing positive co-operation. The Arctic Council is the preeminent governance forum for the Arctic region, consisting of the Arctic states (as of 2023, minus Russia) and six Indigenous peoples’ organisations. Non-Arctic states, intergovernmental organisations and non-governmental organisations can be Observers in the institution. Existing literature has examined the significance, interest and powers of these actors; this paper answers the research question, what do Observers actually do in the Arctic Council? To answer this question, this paper presents the results of content analysis of official Arctic Council Observer reviews and reports, which catalogue their activities. The answer may seem obvious: Observers observe. However, Arctic Council Observers do more than this simple function. This paper proposes that all of the activities of Observers fit into a typology of six types of activity. The ultimate finding is that Observers in the Arctic Council work with Arctic states to enhance institutional work around climate change and sustainable development; we see examples of positive co-operation that enhances regional governance. It is another example of peaceful international relations in the Arctic.

Gecarcinid crabs have their life cycles in antagonistic scenarios, with their larvae developing in the sea and the juvenile/adult phases occurring on land. Adults migrate from land to sea to release their larvae, which return to land upon reaching the megalopa stage. Recruitment and early instar traits in gecarcinids crabs remain unknown, leading to some species lacking age-specific information. Despite massive recruitment observed in some insular gecarcinid species (e.g. Gecarcoidea natalis), recruits are generally expected to be few and exhibit cryptic behaviour, potentially occupying the burrows of conspecifics. We evaluated whether recruits of Johngarthia lagostoma on Trindade Island, Brazil, co-inhabit larger conspecific burrows, analysing this occurrence and examining their growth patterns, density, and body size across different lunar phases. Johngarthia lagostoma recruits inhabit conspecific burrows, either abandoned or occupied by adult crabs, but always with leaves stored in the inner chamber. Recruits in co-inhabiting behaviour reach a maximum carapace width of 7.3 mm, and after that, they are likely detected by the adults and possibly cannibalized or leave burrows naturally. During the full moon, the higher density and smaller size of recruits were recorded, indicating a recruitment lunar phase. It is crucial to ascertain the prevalence of co-inhabitation behaviours in other land crab species to expand the knowledge about recruitment patterns in these key community species.

Species’ declines are caused by a combination of factors that affect survival and/or breeding success. We studied the effects of a set of environmental and anthropogenic variables on the disappearance of Canarian Houbara Bustards Chlamydotis undulata fuertaventurae on Fuerteventura (Canary Islands), once the main stronghold of this endangered bird. Of 83 male display sites detected in 1997–1998, only 29 remained occupied in 2020–2021 (a 65% decrease in only 23 years). We compared habitat quality, density of conspecifics, other steppe birds and crows, presence of human infrastructure, and degree of environmental protection between these 29 extant sites and the 54 extinct sites using univariate analyses and generalised linear models (GLMs). The most influential variable in the abandonment of display sites was the Normalised Difference Vegetation Index (NDVI), an indicator of green vegetation productivity, which suggests a strong effect of habitat aridification due to climate change on the population’s extinction process. Powerline density was the second most important factor. This suggests that houbaras have survived where a greater abundance of food resources has enabled a higher breeding success, and where powerline fatalities have caused lower mortality over the years. Higher densities of houbaras, and other steppe birds and crows at extant display sites confirmed the better habitat quality in these areas. Extant display sites, located generally in protected areas, also had lower densities of human infrastructure (e.g. buildings, roads). We discuss the conservation implications of these results and provide management recommendations for this endangered subspecies.

The West Atlantic trumpetfish Aulostomus maculatus is a species of little commercial importance, but it is frequently used as a study organism in behavioural ecology, and it has been traded in the aquarium industry to some extent. The adult life stage is well described, however its early life history is nearly unknown. This paper provides the first description of post-flexion larvae of A. maculatus, including detailed illustrations, photographs, morphological data, and collection site data of specimens collected during a multipurpose research survey conducted within the Sargasso Sea Subtropical Convergence Zone. The collection site also implies a geographic range expansion, off the continental shelf, of the pelagic larvae stage. This paper hence advances the scientific knowledge about the early life stages, distribution and ecology of this species.

As a result of increasingly intensified agricultural practices in Europe over the last century, agroecosystems have experienced severe biodiversity declines. Among the species experiencing negative population trajectories in agricultural habitats are meadow and farmland birds, which have suffered a loss in both habitat and food availability in cultivated fields. In Denmark, biotope plans (a requirement to establish small agro-environmental habitats on properties with stocking of game birds) have been implemented as a measure to mitigate biodiversity declines in the agricultural landscape and, in this paper, we investigate to what extent these initiatives fulfil the intended purpose with respect to birds in the breeding season. We demonstrate that some initiatives like hedgerows, areas of open vegetation, scrub, and lakes seemed to increase avian diversity locally, but also that other measures such as vegetation strips, grass strips, and bare soil strips had little effect given the current implementation of these initiatives. Benefitting species were mostly scrub- and woodland species that now inhabited previously open landscapes after the establishment of suitable habitats, and the initiatives failed to show clear positive effects on meadow birds and farmland birds for which they were originally intended. The most commonly registered species in our data set was (released) Pheasant Phasianus colchicus, which emphasised that the stocking of game birds can have a clear effect on avian species composition in areas where this practice is exercised. Future studies are needed to clarify how this stocking may affect local biodiversity of different taxonomic groups.

Reintroduction includes the captive propagation and movement of extirpated animals or plants into areas of historical and native distribution. Many biotic or abiotic factors can affect a founder population when small numbers are released into unfamiliar novel environments, particularly at the early stage of reintroduction. The inclusion of behavioural and ecological components plays a crucial role in the decision-making process of endangered species conservation efforts such as reintroduction. Since the resident population of Oriental Storks Ciconia boyciana was locally extirpated in South Korea in 1971, its founders have been established through reintroduction since 2015. The aim of this study was to investigate the demography, habitat use, and movement patterns of stork founders using the first two-year demographic and tracking data. Stork founders maintained their population size, which slightly increased in the long term. The patterns of habitat use and movement depended on rice paddy fields for foraging and breeding along with mixed effects of breeding status and season. Considering ecological and life history-related perspectives, we also discuss the potential adaptiveness of founder Oriental Storks as a resident population in a novel environment in South Korea.