Indicators for monitoring biological invasions at a national level

Returning to the Wilderness: Potential Habitat Suitability of Non-Native Pet Birds in South Africa

The global trade of non-native pet birds has increased in recent decades, and this has accelerated the introduction of invasive birds in the wild. This study employed ensemble species distribution modelling (eSDM) to assess potential habitat suitability and environmental predictor variables influencing the potential distribution of non-native pet bird species reported lost and sighted in South Africa. We used data and information on lost and found pet birds from previous studies to establish and describe scenarios of how pet birds may transition from captivity to the wild. Our study revealed that models fitted and performed well in predicting the suitability for African grey (Psittacus erithacus), Budgerigar (Melopsittacus undulatus), Cockatiel (Nymphicus hollandicus), Green-cheeked conure (Pyrrhura molinae), Monk parakeet (Myiopsitta monachus), and Rose-ringed parakeet (Psittacula krameri), with the mean weighted AUC and TSS values greater than 0.765. The predicted habitat suitability differed among species, with the suitability threshold indicating that between 61% and 87% of areas were predicted as suitable. Species with greater suitability included the African grey, Cockatiel, and Rose-ringed parakeet, which demonstrated significant overlap between their habitat suitability and reported lost cases. Human footprint, bioclimatic variables, and vegetation indices largely influenced predictive habitat suitability. The pathway scenario showed the key mechanisms driving the transition of pet birds from captivity to the wild, including the role of pet owners, animal rescues, adoption practices, and environmental suitability. Our study found that urban landscapes, which are heavily populated, are at high risk of potential invasion by pet birds. Thus, implementing a thorough surveillance survey is crucial for monitoring and evaluating the establishment potential of pet species not yet reported in the wild.

Global indicators of the environmental impacts of invasive alien species and their information adequacy

Monitoring the extent to which invasive alien species (IAS) negatively impact the environment is crucial for understanding and mitigating biological invasions. Indeed, such information is vital for achieving Target 6 of the Kunming-Montreal Global Biodiversity Framework. However, to-date indicators for tracking the environmental impacts of IAS have been either lacking or insufficient. Capitalizing on advances in data availability and impact assessment protocols, we developed environmental impact indicators to track realized and potential impacts of IAS. We also developed an information status indicator to assess the adequacy of the data underlying the impact indicators. We used data on 75 naturalized amphibians from 82 countries to demonstrate the indicators at a global scale. The information status indicator shows variation in the reliability of the data and highlights areas where absence of impact should be interpreted with caution. Impact indicators show that growth in potential impacts are dominated by predatory species, while potential impacts from both predation and disease transmission are distributed worldwide. Using open access data, the indicators are reproducible and adaptable across scales and taxa and can be used to assess global trends and distributions of IAS, assisting authorities in prioritizing control efforts and identifying areas at risk of future invasions. This article is part of the theme issue 'Ecological novelty and planetary stewardship: biodiversity dynamics in a transforming biosphere'.

Economic costs of non-native species in Türkiye: A first national synthesis

Biological invasions are increasingly recognised as a major global change that erodes ecosystems, societal well-being, and economies. However, comprehensive analyses of their economic ramifications are missing for most national economies, despite rapidly escalating costs globally. Türkiye is highly vulnerable to biological invasions owing to its extensive transport network and trade connections as well as its unique transcontinental position at the interface of Europe and Asia. This study presents the first analysis of the reported economic costs caused by biological invasions in Türkiye. The InvaCost database which compiles invasive non-native species' monetary costs was used, complemented with cost searches specific to Türkiye, to describe the spatial and taxonomic attributes of costly invasive non-native species, the types of costs, and their temporal trends. The total economic cost attributed to invasive non-native species in Türkiye (from 202 cost reporting documents) amounted to US$ 4.1 billion from 1960 to 2022. However, cost data were only available for 87 out of 872 (10%) non-native species known for Türkiye. Costs were biased towards a few hyper-costly non-native taxa, such as jellyfish, stink bugs, and locusts. Among impacted sectors, agriculture bore the highest total cost, reaching US$ 2.85 billion, followed by the fishery sector with a total cost of US$ 1.20 billion. Management (i.e., control and eradication) costs were, against expectations, substantially higher than reported damage costs (US$ 2.89 billion vs. US$ 28.4 million). Yearly costs incurred by non-native species rose exponentially over time, reaching US$ 504 million per year in 2020-2022 and are predicted to increase further in the next 10 years. A large deficit of cost records compared to other countries was also shown, suggesting a larger monetary underestimate than is typically observed. These findings underscore the need for improved cost recording as well as preventative management strategies to reduce future post-invasion management costs and help inform decisions to manage the economic burdens posed by invasive non-native species. These insights further emphasise the crucial role of standardised data in accurately estimating the costs associated with invasive non-native species for prioritisation and communication purposes.

An inventory of native-alien populations in South Africa

Species can be both native and alien to a given administrative region. Here we present the first consolidated inventory of these 'native-alien populations' for South Africa, and provide an overview of the data it contains. To gather data, literature searches were performed and experts were consulted both directly and via an on-line survey. Putative native-alien populations were then scored based on a newly developed protocol. The final inventory contains information on 77 native species from 49 families across nine classes that have formed 132 native-alien populations across the terrestrial, freshwater, and marine environments. The phenomenon is rare when compared to the prevalence of related phenomena, such as alien species introduced from other countries (2033 alien species in South Africa), but is under-reported. However, they pose a specific problem for regulators and managers and their importance will likely increase with global change. These data will be integrated with an existing alien species list and, we hope, will provide a useful foundation to address the issue. We encourage those working on biodiversity to contribute more records.

The Diversity of Alien Plant Species in South Africa’s National Botanical and Zoological Gardens

The management of biological invasions, which pose a growing threat to natural resources and human well-being, is critical for reducing associated negative impacts. As part of the process of developing a strategy for the management of biological invasions in the South African National Biodiversity Institute’s (SANBI) gardens, we collated a list of alien plant species from 13 gardens as part of a situational analysis. We requested lists of alien plant species recorded in each of the SANBI’s gardens. A total of 380 records included 225 alien plant species belonging to 73 families. A significant number of species were intentionally introduced through horticultural trade as ornamentals (49%; n = 225), while 20.9% were consumed as either food or medicine by humans. Plant life forms included woody and herbaceous plants, graminoids, succulents and ferns. Herbaceous (42.7%; n = 225) and woody plants (3.8%) were the dominant life forms. The Walter Sisulu National Botanical Garden had the highest number of alien species (88 species), followed by Kirstenbosch (61 species) and Pretoria (46 species) National Botanical Gardens, with herbaceous species constituting the largest number in all gardens (i.e., 47, 19, and 27 species, respectively). The number of species that we recorded that were listed in the National Environmental Management: Biodiversity Act (NEM: BA) (Act No. 10 of 2004): Alien and Invasive Species Regulations’ categories were not notably different from the number of unlisted species (58.2% vs. 42.8%). The number of species listed in the different categories varied significantly across the different gardens, with a significantly higher number of unlisted species and of Category 1b species in the Walter Sisulu, Kirstenbosch and Pretoria National Botanical Gardens than in other gardens. That a significantly larger number of alien species originated from South America points to the need to improve biosecurity controls on existing relations. The results of this study provided a baseline database to help comparison between successive surveys in future.

The right tree in the right place? A major economic tree species poses major ecological threats

Tree species in the Pinaceae are some of the most widely introduced non-native tree species globally, especially in the southern hemisphere. In New Zealand, plantations of radiata pine (Pinus radiata D. Don) occupy c. 1.6 million ha and form 90% of planted forests. Although radiata pine has naturalized since 1904, there is a general view in New Zealand that this species has not invaded widely. We comprehensively review where radiata pine has invaded throughout New Zealand. We used a combination of observational data and climate niche modelling to reveal that invasion has occurred nationally. Climate niche modelling demonstrates that while current occurrences are patchy, up to 76% of the land area (i.e. 211,388 km2) is climatically capable of supporting populations. Radiata pine has mainly invaded grasslands and shrublands, but also some forests. Notably, it has invaded lower-statured vegetation, including three classes of naturally uncommon ecosystems, primary successions and secondary successions. Overall, our findings demonstrate pervasive and ongoing invasion of radiata pine outside plantations. The relatively high growth rates and per individual effects of radiata pine may result in strong effects on naturally uncommon ecosystems and may alter successional trajectories. Local and central government currently manage radiata pine invasions while propagule pressure from existing and new plantations grows, hence greater emphasis is warranted both on managing current invasions and proactively preventing future radiata pine invasions. We therefore recommend a levy on new non-native conifer plantations to offset costs of managing invasions, and stricter regulations to protect vulnerable ecosystems. A levy on economic uses of invasive species to offset costs of managing invasions alongside stricter regulations to protect vulnerable ecosystems could be a widely adopted measure to avert future negative impacts.

DASCO: A workflow to downscale alien species checklists using occurrence records and to re-allocate species distributions across realms

Information about occurrences of alien species is often provided in so-called checklists, which represents lists of reported alien species in a region. In many cases, available checklists cover whole countries, which is too coarse for many analyses and limits capabilities of assessing status and trends of biological invasions. Information about point-wise occurrences is available in large quantities at online facilities such as GBIF and OBIS, which, however, do not provide information about the invasion status of individual populations. To close this gap, we here provide a semi-automated workflow called DASCO to downscale regional checklists using occurrence records obtained from GBIF and OBIS. Within the workflow, coordinate-based occurrence records for species listed in the provided regional checklists are obtained from GBIF and OBIS, and the status of being an alien population is assigned using the information in the provided checklists. In this way, information in checklists is made available at the local scale, which can then be re-allocated to any other spatial categorisation as provided by the user. In addition, habitats of species are determined to distinguish between marine, brackish, terrestrial, and freshwater species, which allows splitting the provided checklists to the respective realms and ecoregions. By using checklists of global databases, we showcase the usage of the DASCO workflow and revealed > 35 million occurrence records of alien populations in terrestrial and marine regions worldwide, which were back-transformed to terrestrial and marine regions for comparison. DASCO has the potential to be used as a basis for the widely applied species distribution models or assessments of status and trends of biological invasions at large geographic scales. The workflow is implemented in R and in full compliance with the FAIR data principles of open science.

GIRAE: a generalised approach for linking the total impact of invasion to species' range, abundance and per-unit effects

The total impact of an alien species was conceptualised as the product of its range size, local abundance and per-unit effect in a seminal paper by Parker et al. (Biol Invasions 1:3-19, 1999). However, a practical approach for estimating the three components has been lacking. Here, we generalise the impact formula and, through use of regression models, estimate the relationship between the three components of impact, an approach we term GIRAE (Generalised Impact = Range size × Abundance × per-unit Effect). We discuss how GIRAE can be applied to multiple types of impact, including environmental impacts, damage and management costs. We propose two methods for applying GIRAE. The species-specific method computes the relationship between impact, range size, abundance and per-unit effect for a given species across multiple invaded sites or regions of different sizes. The multi-species method combines data from multiple species across multiple sites or regions to calculate a per-unit effect for each species and is computed using a single regression model. The species-specific method is more accurate, but it requires a large amount of data for each species and assumes a constant per-unit effect for a species across the invaded area. The multi-species method is more easily applicable and data-parsimonious, but assumes the same relationship between impact, range size and abundance for all considered species. We illustrate these methods using data about money spent managing plant invasions in different biomes of South Africa. We found clear differences between species in terms of money spent per unit area invaded, with per-unit expenditure varying substantially between biomes for some species-insights that are useful for monitoring and evaluating management. GIRAE offers a versatile and practical method that can be applied to many different types of data to better understand and manage the impacts of biological invasions.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10530-022-02836-0.

Diversity, distribution and extinction risk of native freshwater fishes of South Africa

Extinction risk for 101 valid species and 18 unique genetic lineages of native freshwater fishes of South Africa was assessed in 2016 following the IUCN Red List criteria. An additional five species (three new species that were described and two species that were revalidated subsequent to the 2016 assessments) were assessed in the present study. A synthesis of the outcome of the assessments of the 106 valid species and 18 genetic lineages indicates that 45 (36%) of South Africa's freshwater fish taxa are threatened (7 Critically Endangered, 25 Endangered, 13 Vulnerable). Of the remaining taxa, 17 (14%) are listed as Near Threatened, 57 (46%) are Least Concern and five (4%) are Data Deficient. More than 60% of the endemic taxa are threatened. The Cape Fold Ecoregion has the highest proportion of threatened taxa (67%) due to the existence of a unique assemblage of narrow-range endemic species. Galaxias and Pseudobarbus have the highest number of highly threatened taxa as most of the species and lineages in these genera are classified as either CR or EN. Major threats to the native freshwater fishes of the country are invasive fish species, deterioration of water quality, impoundments and excessive water abstraction, land use changes and modification of riverine habitats. Immediate conservation efforts should focus on securing remnant populations of highly threatened taxa and preventing deterioration in threat status, because recovery is rare. Accurate delimitation of species boundaries, mapping their distribution ranges, improved knowledge of pressures and long-term monitoring of population trends need to be prioritised to generate credible data for the 2026 IUCN threat status assessments and designation of important fish areas as part of the National Freshwater Ecosystem Priority Areas (NFEPA) initiative.

Economic costs of biological invasions in Asia

Invasive species have caused severe impacts on biodiversity and human society. Although the estimation of environmental impacts caused by invasive species has increased in recent years, economic losses associated with biological invasions are only sporadically estimated in space and time. In this study, we synthesized the losses incurred by invasions in Asia, based on the most comprehensive database of economic costs of invasive species worldwide, including 560 cost records for 88 invasive species in 22 countries. We also assessed the differences in economic costs across taxonomic groups, geographical regions and impacted sectors, and further identified the major gaps of current knowledge in Asia. Reported economic costs of biological invasions were estimated between 1965 and 2017, and reached a total of US$ 432.6 billion (2017 value), with dramatic increases in 2000–2002 and in 2004. The highest costs were recorded for terrestrial ectotherms, for species estimated in South Asia, and for species estimated at the country level, and were related to more than one impacted sector. Two taxonomic groups with the highest reported costs were insects and mammals, and two countries with the highest costs were India and China. Non-English data covered all of 12 taxonomic groups, whereas English data only covered six groups, highlighting the importance of considering data from non-English sources to have a more comprehensive estimation of economic costs associated with biological invasions. However, we found that the estimation of economic costs was lacking for most Asian countries and for more than 96% of introduced species in Asia. Further, the estimation is heavily biased towards insects and mammals and is very limited concerning expenditures on invasion management. To optimize the allocation of limited resources, there is an important need to better and more widely study the economic costs of invasive alien species. In this way, improved cost reporting and more collaborations between scientists and stakeholders are needed across Asia.

A multiregional assessment of transnational pathways of introduction

Information on the pathways by which alien taxa are introduced to new regions is vital for prioritising policy and management responses to invasions. However, available datasets are often compiled using disparate methods, making comparison and collation of pathway data difficult. Using a standardised framework for recording and categorising pathway data can help to rectify this problem and provide the information necessary to develop indicators for reporting on alien introductions. We combine the Convention on Biological Diversity’s Pathways Categorisation Scheme (CPC) with data compiled by the Invasive Species Specialist Group (ISSG) to report on multiregional trends on alien introduction pathways over the past 200+ years. We found a significant increase in the documented number of multiregional alien introduction events across all pathways of the CPC’s three hierarchical levels. The ‘escape’ pathway is the most common documented pathway used by alien taxa. Transport stowaways via shipping-related pathways are a rapidly increasing contribution to alien introductions. Most alien introduction events were of unknown pathway origin, highlighting the challenge of information gaps in pathway data and reiterating the need for standardised information-gathering practices. Combining the CPC framework with alien introduction pathways data will standardise pathway information and facilitate the development of global indicators of trends in alien introductions and the pathways they use. These indicators have the potential to inform policy and management strategies for preventing future biological invasions and can be downscaled to national and regional levels that are applicable across taxa and ecosystems.

Appropriate uses of EICAT protocol, data and classifications

The Environmental Impact Classification for Alien Taxa (EICAT) can be used to classify alien taxa according to the magnitude and type of their environmental impacts. The EICAT protocol, classifications of alien taxa using the protocol (EICAT classification) and the data underpinning classifications (EICAT data) are increasingly used by scientists and practitioners such as governments, NGOs and civil society for a variety of purposes. However, the properties of the EICAT protocol and the data it generates are not suitable for certain uses. Therefore, we present guidelines designed to clarify and facilitate the appropriate use of EICAT to tackle a broad range of conservation issues related to biological invasions, as well as to guide research and communication more generally. Here we address common misconceptions and give a brief overview of some key issues that all EICAT users need to be aware of to take maximal advantage of this resource. Furthermore, we give examples of the wide variety of ways in which the EICAT protocol, classifications and data can be and have been utilised and outline common errors and pitfalls to avoid.

Applying an invasion and risk framework to track non-native island floras: a case study of challenges and solutions in Hawai‘i

Islands are plant invasion hotspots, with some having more non-native than native species. Many plants are recent arrivals, leading to concerns that their full spread and impacts are not yet realised. Given that islands host extraordinary numbers of endemic and threatened species, schemes are urgently needed to track the complex, species-rich but data-poor scenarios typical of islands. This study applies the unified framework by Blackburn et al. (2011) for categorising invasion stages to Hawai‘i’s non-native plant checklist and identifies potential uses and complications for species tracking and invasion management. Data deficiencies and ambiguities required lumping Blackburn et al.’s categories to align with Hawai‘i’s available data; nonetheless, this coarser categorisation describes invasion phases relevant to managers and could provide the basis for an effective tracking system. However, the unified framework does not accommodate uncertain invasion statuses, which prevents clear categorisation of species that exist outside of cultivation but are not definitely naturalised. In response to this obstacle, scores from the Hawai‘i-Pacific Weed Risk Assessment (WRA) are explored to understand their application for predicting naturalisation, including standard WRA scores as well as alternative scoring methods. We show that this predictive tool may be a promising supplement to on-the-ground monitoring for data-deficient elements of a flora. Finally, a categorisation system for tracking statuses of an entire non-native flora is proposed that requires limited investments in additional data collection while following the rationale of Blackburn et al.’s scheme. This categorisation system may be used to reveal overall invasion patterns and trends in a region, leading to valuable insights into strategies for biodiversity management and conservation.

The Convention on Biological Diversity (CBD)’s Post-2020 target on invasive alien species – what should it include and how should it be monitored?

The year 2020 and the next few years are critical for the development of the global biodiversity policy agenda until the mid-21st century, with countries agreeing to a Post-2020 Global Biodiversity Framework under the Convention on Biological Diversity (CBD). Reducing the substantial and still rising impacts of invasive alien species (IAS) on biodiversity will be essential if we are to meet the 2050 Vision where biodiversity is valued, conserved, and restored. A tentative target has been developed by the IUCN Invasive Species Specialist Group (ISSG), and formally submitted to the CBD for consideration in the discussion on the Post-2020 targets. Here, we present properties of this proposal that we regard as essential for an effective Post-2020 Framework. The target should explicitly consider the three main components of biological invasions, i.e. (i) pathways, (ii) species, and (iii) sites; the target should also be (iv) quantitative, (v) supplemented by a set of indicators that can be applied to track progress, and (vi) evaluated at medium- (2030) and long-term (2050) time horizons. We also present a proposed set of indicators to track progress. These properties and indicators are based on the increasing scientific understanding of biological invasions and effectiveness of responses. Achieving an ambitious action-oriented target so that the 2050 Vision can be achieved will require substantial effort and resources, and the cooperation of a wide range of stakeholders.

Frameworks used in invasion science: progress and prospects

Our understanding and management of biological invasions relies on our ability to classify and conceptualise the phenomenon. This need has stimulated the development of a plethora of frameworks, ranging in nature from conceptual to applied. However, most of these frameworks have not been widely tested and their general applicability is unknown. In order to critically evaluate frameworks in invasion science, we held a workshop on ‘Frameworks used in Invasion Science’ hosted by the DSI-NRF Centre of Excellence for Invasion Biology in Stellenbosch, South Africa, in November 2019, which led to this special issue. For the purpose of the workshop we defined a framework as “a way of organising things that can be easily communicated to allow for shared understanding or that can be implemented to allow for generalisations useful for research, policy or management”. Further, we developed the Stellenbosch Challenge for Invasion Science: “Can invasion science develop and improve frameworks that are useful for research, policy or management, and that are clear as to the contexts in which the frameworks do and do not apply?”. Particular considerations identified among meeting participants included the need to identify the limitations of a framework, specify how frameworks link to each other and broader issues, and to improve how frameworks can facilitate communication. We believe that the 24 papers in this special issue do much to meet this challenge. The papers apply existing frameworks to new data and contexts, review how the frameworks have been adopted and used, develop useable protocols and guidelines for applying frameworks to different contexts, refine the frameworks in light of experience, integrate frameworks for new purposes, identify gaps, and develop new frameworks to address issues that are currently not adequately dealt with. Frameworks in invasion science must continue to be developed, tested as broadly as possible, revised, and retired as contexts and needs change. However, frameworks dealing with pathways of introduction, progress along the introduction-naturalisation-invasion continuum, and the assessment of impacts are being increasingly formalised and set as standards. This, we argue, is an important step as invasion science starts to mature as a discipline.

Classifying the introduction pathways of alien species: are we moving in the right direction?

Alien species are introduced to new regions in many different ways and for different purposes. A number of frameworks have been developed to group such pathways of introduction into discrete categories in order to improve our understanding of biological invasions, provide information for interventions that aim to prevent introductions, enable reporting to national and international organisations and facilitate the prediction of threats. The introduction pathway classification framework proposed by the Convention on Biological Diversity (CBD) as a global standard is comprised of six main categories and 44 sub-categories. However, issues have arisen with its implementation. In this position paper, we outline five desirable properties of an introduction pathway classification framework – it should be compatible (i.e. the level of detail of the categories is similar to that of the available data), actionable (i.e. categories link to specific interventions), general (i.e. categories are applicable across the contexts that are of interest (e.g. taxa, habitats and regions)), equivalent (i.e. categories are equivalent in their level of detail) and distinct (i.e. categories are discrete and easily distinguished) – termed the CAGED properties. The six main categories of the CBD framework have all of the CAGED properties, but the detailed sub-categories have few. Therefore, while the framework has been proposed by the CBD as a global standard and efforts have been made to put it into practice, we argue that there is room for improvement. We conclude by presenting scenarios for how the issues identified could be addressed, noting that a hybrid model might be most appropriate.

Is invasion science moving towards agreed standards? The influence of selected frameworks

The need to understand and manage biological invasions has driven the development of frameworks to circumscribe, classify, and elucidate aspects of the phenomenon. But how influential have these frameworks really been? To test this, we evaluated the impact of a pathway classification framework, a framework focussing on the introduction-naturalisation-invasion continuum, and two papers that outline an impact classification framework. We analysed how these framework papers are cited and by whom, conducted a survey to determine why people have cited the frameworks, and explored the degree to which the frameworks are implemented. The four papers outlining these frameworks are amongst the most-cited in their respective journals, are highly regarded in the field, and are already seen as citation classics (although citations are overwhelmingly within the field of invasion science). The number of citations to the frameworks has increased over time, and, while a significant proportion of these are self-citations (20–40%), this rate is decreasing. The frameworks were cited by studies conducted and authored by researchers from across the world. However, relative to a previous citation analysis of invasion science as a whole, the frameworks are particularly used in Europe and South Africa and less so in North America. There is an increasing number of examples of uptake into invasion policy and management (e.g., the pathway classification framework has been adapted and adopted into EU legislation and CBD targets, and the impact classification framework has been adopted by the IUCN). However, we found that few of the citing papers (6–8%) specifically implemented or interrogated the frameworks; roughly half of all citations might be viewed as frivolous (“citation fluff”); there were several clear cases of erroneous citation; and some survey respondents felt that they have not been rigorously tested yet.

Although our analyses suggest that invasion science is moving towards a more systematic and standardised approach to recording invasions and their impacts, it appears that the proposed standards are still not applied consistently. For this to be achieved, we argue that frameworks in invasion science need to be revised or adapted to particular contexts in response to the needs and experiences of users (e.g., so they are relevant to pathologists, plant ecologists, and practitioners), the standards should be easier to apply in practice (e.g., through the development of guidelines for management), and there should be incentives for their usage (e.g., recognition for completing an EICAT assessment).

A workflow for standardising and integrating alien species distribution data

Biodiversity data are being collected at unprecedented rates. Such data often have significant value for purposes beyond the initial reason for which they were collected, particularly when they are combined and collated with other data sources. In the field of invasion ecology, however, integrating data represents a major challenge due to the notorious lack of standardisation of terminologies and categorisations, and the application of deviating concepts of biological invasions. Here, we introduce the SInAS workflow, short for Standardising and Integrating Alien Species data. The SInAS workflow standardises terminologies following Darwin Core, location names using a proposed translation table, taxon names based on the GBIF backbone taxonomy, and dates of first records based on a set of predefined rules. The output of the SInAS workflow provides various entry points that can be used both to improve coherence among the databases and to check and correct the original data. The workflow is flexible and can be easily adapted and extended to the needs of different users. We illustrate the workflow using a case-study integrating five widely used global databases of information on biological invasions. The comparison of the standardised databases revealed a surprisingly low degree of overlap, which indicates that the amount of data may currently not be fully exploited in the original databases. We highly recommend the use and development of publicly available workflows to ensure that the integration of databases is reproducible and transparent. Workflows, such as SInAS, ultimately increase trust in data, study results, and conclusions.

Scientists' warning on invasive alien species

Biological invasions are a global consequence of an increasingly connected world and the rise in human population size. The numbers of invasive alien species – the subset of alien species that spread widely in areas where they are not native, affecting the environment or human livelihoods – are increasing. Synergies with other global changes are exacerbating current invasions and facilitating new ones, thereby escalating the extent and impacts of invaders. Invasions have complex and often immense long‐term direct and indirect impacts. In many cases, such impacts become apparent or problematic only when invaders are well established and have large ranges. Invasive alien species break down biogeographic realms, affect native species richness and abundance, increase the risk of native species extinction, affect the genetic composition of native populations, change native animal behaviour, alter phylogenetic diversity across communities, and modify trophic networks. Many invasive alien species also change ecosystem functioning and the delivery of ecosystem services by altering nutrient and contaminant cycling, hydrology, habitat structure, and disturbance regimes. These biodiversity and ecosystem impacts are accelerating and will increase further in the future. Scientific evidence has identified policy strategies to reduce future invasions, but these strategies are often insufficiently implemented. For some nations, notably Australia and New Zealand, biosecurity has become a national priority. There have been long‐term successes, such as eradication of rats and cats on increasingly large islands and biological control of weeds across continental areas. However, in many countries, invasions receive little attention. Improved international cooperation is crucial to reduce the impacts of invasive alien species on biodiversity, ecosystem services, and human livelihoods. Countries can strengthen their biosecurity regulations to implement and enforce more effective management strategies that should also address other global changes that interact with invasions.

Stronger regional biosecurity is essential to prevent hundreds of harmful biological invasions

Biological invasions often transcend political boundaries, but the capacity of countries to prevent invasions varies. How this variation in biosecurity affects the invasion risks posed to the countries involved is unclear. We aimed to improve the understanding of how the biosecurity of a country influences that of its neighbours. We developed six scenarios that describe biological invasions in regions with contiguous countries. Using data from alien species databases, socio-economic and biodiversity data and species distribution models, we determined where 86 of 100 of the world's worst invasive species are likely to invade and have a negative impact in the future. Information on the capacity of countries to prevent invasions was used to determine whether such invasions could be avoided. For the selected species, we predicted 2,523 discrete invasions, most of which would have significant negative impacts and are unlikely to be prevented. Of these invasions, approximately a third were predicted to spread from the country in which the species first establishes to neighbouring countries where they would cause significant negative impacts. Most of these invasions are unlikely to be prevented as the country of first establishment has a low capacity to prevent invasions or has little incentive to do so as there will be no impact in that country. Regional biosecurity is therefore essential to prevent future harmful biological invasions. In consequence, we propose that the need for increased regional co-operation to combat biological invasions be incorporated in global biodiversity targets.

Invasion syndromes: a systematic approach for predicting biological invasions and facilitating effective management

Our ability to predict invasions has been hindered by the seemingly idiosyncratic context-dependency of individual invasions. However, we argue that robust and useful generalisations in invasion science can be made by considering “invasion syndromes” which we define as “a combination of pathways, alien species traits, and characteristics of the recipient ecosystem which collectively result in predictable dynamics and impacts, and that can be managed effectively using specific policy and management actions”. We describe this approach and outline examples that highlight its utility, including: cacti with clonal fragmentation in arid ecosystems; small aquatic organisms introduced through ballast water in harbours; large ranid frogs with frequent secondary transfers; piscivorous freshwater fishes in connected aquatic ecosystems; plant invasions in high-elevation areas; tall-statured grasses; and tree-feeding insects in forests with suitable hosts. We propose a systematic method for identifying and delimiting invasion syndromes. We argue that invasion syndromes can account for the context-dependency of biological invasions while incorporating insights from comparative studies. Adopting this approach will help to structure thinking, identify transferrable risk assessment and management lessons, and highlight similarities among events that were previously considered disparate invasion phenomena.

The world needs BRICS countries to build capacity in invasion science

Developed countries are producing policies to reduce the flow of invasive species and control or eradicate existing invasions, but most developing countries are under-resourced to tackle either aspect without help. Emerging economies, such as Brazil, Russia, India, China, and South Africa (BRICS), are responsible for donating many of the world's invasive species that have the potential to reach nearly all terrestrial biomes. Implementing a proactive 'facilitated network' model is urgently required to build capacity and stimulate effective appropriate invasion science. We contend that creating a BRICS network of invasion scientists will have the immediate impact required to meet future policy demands.