Socio‐economic impact classification of alien taxa ( SEICAT )

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.

Rural Households' Demand Status for Mitigation of Prosopis juliflora (Sw.) DC Invasion and Its Determinant Factors in Ethiopia: Empirical Evidence from Afar National Regional State

Ethiopia is among the world's poorest nations, and its economy is growing extremely slowly; thus, the government's budget to manage environmental amenities is not always sufficient. Thus, for the provision of environmental management services such as the eradication of Prosopis juliflora, the participation of local households and other stakeholders is crucial. This study is therefore initiated with the objective of assessing rural households' demands for mitigating Prosopis juliflora invasion in the Afar Region of Ethiopia. A multistage sampling technique was employed to obtain the 313 sample rural households that were used in the analysis, and those sample households were selected randomly and independently from the Amibara and Awash Fentale districts of Afar National Regional State, Ethiopia. In doing this, a seemingly unrelated bivariate probit model was used to determine factors affecting rural households' demands for mitigating Prosopis juliflora invasion. Consequently, as per the inferential statistical results, there was a significant mean/percentage difference between willing and nonwilling households for the hypothesized variables, except for some variables such as farm experience; years lived in the area, distance from the market, and dependency ratio. Furthermore, the seemingly unrelated bivariate probit model result indicates that sex, family size, tenure security, livestock holding, frequency of extension contact, and years lived in the area were important factors influencing the willingness to participate in Prosopis juliflora management practices positively, whereas age, off-farm/nonincome, and bid value affected willingness to pay negatively and significantly. Hence, to improve the participation level of households, policymakers should target these variables.

Using the IUCN Environmental Impact Classification for Alien Taxa to inform decision-making

The Environmental Impact Classification for Alien Taxa (EICAT) is an important tool for biological invasion policy and management and has been adopted as an International Union for Conservation of Nature (IUCN) standard to measure the severity of environmental impacts caused by organisms living outside their native ranges. EICAT has already been incorporated into some national and local decision-making procedures, making it a particularly relevant resource for addressing the impact of non-native species. Recently, some of the underlying conceptual principles of EICAT, particularly those related to the use of the precautionary approach, have been challenged. Although still relatively new, guidelines for the application and interpretation of EICAT will be periodically revisited by the IUCN community, based on scientific evidence, to improve the process. Some of the criticisms recently raised are based on subjectively selected assumptions that cannot be generalized and may harm global efforts to manage biological invasions. EICAT adopts a precautionary principle by considering a species' impact history elsewhere because some taxa have traits that can make them inherently more harmful. Furthermore, non-native species are often important drivers of biodiversity loss even in the presence of other pressures. Ignoring the precautionary principle when tackling the impacts of non-native species has led to devastating consequences for human well-being, biodiversity, and ecosystems, as well as poor management outcomes, and thus to significant economic costs. EICAT is a relevant tool because it supports prioritization and management of non-native species and meeting and monitoring progress toward the Kunming-Montreal Global Biodiversity Framework (GBF) Target 6.

Taming the terminological tempest in invasion science

Standardised terminology in science is important for clarity of interpretation and communication. In invasion science - a dynamic and rapidly evolving discipline - the proliferation of technical terminology has lacked a standardised framework for its development. The result is a convoluted and inconsistent usage of terminology, with various discrepancies in descriptions of damage and interventions. A standardised framework is therefore needed for a clear, universally applicable, and consistent terminology to promote more effective communication across researchers, stakeholders, and policymakers. Inconsistencies in terminology stem from the exponential increase in scientific publications on the patterns and processes of biological invasions authored by experts from various disciplines and countries since the 1990s, as well as publications by legislators and policymakers focusing on practical applications, regulations, and management of resources. Aligning and standardising terminology across stakeholders remains a challenge in invasion science. Here, we review and evaluate the multiple terms used in invasion science (e.g. 'non-native', 'alien', 'invasive' or 'invader', 'exotic', 'non-indigenous', 'naturalised', 'pest') to propose a more simplified and standardised terminology. The streamlined framework we propose and translate into 28 other languages is based on the terms (i) 'non-native', denoting species transported beyond their natural biogeographic range, (ii) 'established non-native', i.e. those non-native species that have established self-sustaining populations in their new location(s) in the wild, and (iii) 'invasive non-native' - populations of established non-native species that have recently spread or are spreading rapidly in their invaded range actively or passively with or without human mediation. We also highlight the importance of conceptualising 'spread' for classifying invasiveness and 'impact' for management. Finally, we propose a protocol for classifying populations based on (i) dispersal mechanism, (ii) species origin, (iii) population status, and (iv) impact. Collectively and without introducing new terminology, the framework that we present aims to facilitate effective communication and collaboration in invasion science and management of non-native species.

The wild cost of invasive feral animals worldwide

Invasive non-native species are a growing burden to economies worldwide. While domesticated animals (i.e. livestock, beasts of burden or pets) have enabled our ways of life and provide sustenance for countless individuals, they may cause substantial impacts when they escape or are released (i.e. become feral) and then become invasive with impacts. We used the InvaCost database to evaluate monetary impacts from species in the Domestic Animal Diversity Information System database. We found a total cost of $141.95 billion from only 18 invasive feral species. Invasive feral livestock incurred the highest costs at $90.03 billion, with pets contributing $50.93 billion and beasts of burden having much lower costs at $0.98 billion. Agriculture was the most affected sector at $80.79 billion, followed by the Environment ($43.44 billion), and Authorities-Stakeholders sectors ($5.52 billion). Damage costs comprised the majority ($124.94 billion), with management and mixed damage-management costs making up the rest ($9.62 and $7.38 billion, respectively). These economic impacts were observed globally, where Oceania, North America and Europe were the most impacted regions. Islands recorded a higher economic burden than continental areas, with livestock species dominating costs more on islands than mainlands compared to other feral species. The costs of invasive feral animals were on average twice higher than those of wild species. The management of invasive feral populations requires higher investment, updated regulations, and comprehensive risk assessments. These are especially complex when considering the potential conflicts arising from interventions with species that have close ties to humans. Effective communication to raise public awareness of the impacts of feral populations and appropriate legislation to prevent or control such invasive feral populations will substantially contribute to minimizing their socioeconomic and environmental impacts.

Considerations for developing and implementing a safe list for alien taxa

Many species have been intentionally introduced to new regions for their benefits. Some of these alien species cause damage, others do not (or at least have not yet). There are several approaches to address this problem: prohibit taxa that will cause damage, try to limit damages while preserving benefits, or promote taxa that are safe. In the present article, we unpack the safe list approach, which we define as "a list of taxa alien to the region of interest that are considered of sufficiently low risk of invasion and impact that the taxa can be widely used without concerns of negative impacts." We discuss the potential use of safe lists in the management of biological invasions; disentangle aspects related to the purpose, development, implementation, and impact of safe lists; and provide guidance for those considering to develop and implement such lists.

Exploring the association between social media and farmers' knowledge of a worldwide invasive agricultural pest, Spodoptera frugiperda (Lepidoptera: Noctuidae)

BACKGROUND

Public education has profound effects on the management effectiveness of invasive alien species by shaping stakeholders' knowledge systems. However, our understanding of the association between social media and farmers' knowledge is lacking for the majority of invasive agricultural pests. In this study, we used the fall armyworm (FAW), Spodoptera frugiperda, one of the most invasive insects globally, as a case to test the hypothesis that social media has a significant association with farmers' knowledge of FAW. To address this, we developed a theoretical framework, conducted extensive household questionnaires in the China-Myanmar-Laos border region (China), and used quantitative descriptions and binary logistic regressions in statistical analyses.

RESULTS

Our results showed that (1) farmers frequently reported using 12 social media applications on smartphones (SMASs), and obtained FAW-relevant information from six of them, with high preferences for WeChat and TikTok, (2) farmers possessed a generally high level of knowledge of FAW which was significantly associated with their socio-demographic profiles, and (3) FAW-relevant information from SMASs was significantly associated with certain aspects of farmers' knowledge of FAW.

CONCLUSIONS

We concluded that social media has a significant association with farmers' knowledge of FAW. We suggest that well-designed and -conducted educational programs based on the use of SMASs could help improve the management of FAW, and the Department of Agricultural Extension could play an important and necessary role. Our findings provide insights into this novel educational approach for the management of serious invasive agricultural pests. © 2023 Society of Chemical Industry.

Impacts, Potential Benefits and Eradication Feasibility of Aquatic Alien Species in an Integral Natural State Reserve

Riverine wetlands are stepping-stone environments for the protection of local biodiversity, but they are particularly vulnerable to biological invasions. In order to take action against biological invasions, it is crucial to assess the impacts of alien species. However, it is also important to assess the potential benefits on ecosystem services that alien species could have. Once it has been verified that negative impacts are higher than potential benefits, it is important to propose feasible actions to contrast them. In this study, we assessed eight freshwater alien species recorded in an integral protected wetland using the Invasive Species Effects Assessment Tool (INSEAT) to quantify their negative impacts and potential benefits on ecosystem services. Moreover, for each species, we evaluated the feasibility of the main eradication techniques currently proposed in the literature using the Non-Native Risk Management scheme (NNRM), with the final aim of suggesting effective actions for their management. The INSEAT results indicated that all the assessed species had more impacts than benefits while NNRM provided useful indications on the best practical conservation actions to use for reducing the density, and therefore, the negative impacts on ecosystem services and the local biodiversity of the assessed alien species.

The economic costs of invasive aquatic plants: A global perspective on ecology and management gaps

Safeguarding aquatic ecosystems from invasive species requires a comprehensive understanding and quantification of their impacts, as this information is crucial for developing effective management strategies. In particular, aquatic invasive plants cause profound alterations to aquatic ecosystem composition, structure and productivity. Monetary cost assessments have, however, lacked at large scales for this group. Here, we synthesize the global economic impacts of aquatic and semi-aquatic invasive plants to describe the distributions of these costs across taxa, habitat types, environments, impacted sectors, cost typologies, and geographic regions. We also examine the development of recorded costs over time using linear and non-linear models and infer the geographical gaps of recorded costs by superimposing cost and species distribution data. Between 1975 and 2020, the total cost of aquatic and semi-aquatic invasive plants to the global economy exceeded US$ 32 billion, of which the majority of recorded costs (57 %) was attributable to multiple or unspecified taxa. Submerged plants had $8.4 billion (25.5 %) followed by floating plants $4.7 billion (14.5 %), emergent $684 million (2.1 %) and semi-aquatic $306 million (0.9 %). Recorded costs were disproportionately high towards freshwater ecosystems, which have received the greatest cost research effort compared to marine and brackish systems. Public and social welfare and fisheries were the sectors most affected, while agriculture and health were most underreported. Cost attributed to management (4.8 %; $1.6 billion) represented only a fraction of damages (85.8 %; $28.2 billion). While recorded costs are rising over time, reporting issues e.g., robustness of data, lack of higher taxonomic resolution and geographical gaps likely have led to a dampening of trajectories. In particular, invasive taxa currently occupy regions where monetary cost reports are lacking despite well-known impacts. More robust and timely cost estimates will enhance interpretation of current and future impacts of aquatic invasive plants, assisting the long-term sustainability of our aquatic ecosystems and associated economic activities.

Tracking long-term shifts in non-native freshwater macroinvertebrates across three European countries

Non-native species introductions have been acknowledged as one of the main drivers of freshwater biodiversity decline worldwide, compromising provided ecosystem services and functioning. Despite growing introduction numbers of non-native species, their impacts in conjunction with anthropogenic stressors remain poorly documented. To fill this gap, we studied temporal changes in α (local scale) and γ (regional scale), as well as β (ratio between γ and α) diversity of non-native freshwater macroinvertebrate species in three European countries (the Netherlands, England and Hungary) using long-term time series data of up to 17 years (2003-2019). We further calculated four ecological and four biological trait metrics to identify changes in trait occurrences over time. We found that α and γ diversities of non-native species were increasing across all countries whereas β diversity remained stable. We did not identify any significant changes in any trait metric over time, while the predictors tested (land use, climatic predictors, site-specific factor) were similar across countries (e.g., site characteristics or climatic predictors on non-native species trends). Additionally, we projected trends of α, β, and γ diversity and trait metrics until 2040, which indicated that non-native species will decline across all countries to lower levels except in England for γ diversity and the Netherlands for α diversity where an increase was observed. Thus, our findings indicate shifts in non-native freshwater macroinvertebrate diversity at both local and regional scales in response to the various growing anthropogenic pressures. Our findings underscore the continuous dynamics of non-native species distribution, with the diversity of individual communities and overall landscapes witnessing changes. However, the differentiation in species composition between communities remains unaltered. This could have profound implications for conservation strategies and ecological management in the face of continuously changing biodiversity patterns.

A general framework to quantify and compare ecological impacts under temporal dynamics

Biodiversity is diminishing at alarming rates due to multiple anthropogenic drivers. To mitigate these drivers, their impacts must be quantified accurately and comparably across drivers. To enable that, we present a generally applicable framework introducing fundamental principles of ecological impact quantification, including the quantification of interactions between multiple drivers. The framework contrasts biodiversity variables in impacted against those in unimpacted or other reference situations while accounting for their temporal dynamics through modelling. Properly accounting for temporal dynamics reduces biases in impact quantification and comparison. The framework addresses key questions around ecological impacts in global change science, namely, how to compare impacts under temporal dynamics across stressors, how to account for stressor interactions in such comparisons, and how to compare the success of management actions over time.

Recent advances in availability and synthesis of the economic costs of biological invasions

Biological invasions are a global challenge that has received insufficient attention. Recently available cost syntheses have provided policy- and decision makers with reliable and up-to-date information on the economic impacts of biological invasions, aiming to motivate effective management. The resultant InvaCost database is now publicly and freely accessible and enables rapid extraction of monetary cost information. This has facilitated knowledge sharing, developed a more integrated and multidisciplinary network of researchers, and forged multidisciplinary collaborations among diverse organizations and stakeholders. Over 50 scientific publications so far have used the database and have provided detailed assessments of invasion costs across geographic, taxonomic, and spatiotemporal scales. These studies have provided important information that can guide future policy and legislative decisions on the management of biological invasions while simultaneously attracting public and media attention. We provide an overview of the improved availability, reliability, standardization, and defragmentation of monetary costs; discuss how this has enhanced invasion science as a discipline; and outline directions for future development.

Spatial priorities for invasive alien species control in protected areas

Given the limited funds available for the management of invasive alien species (IASs), there is a need to design cost-effective strategies to prioritize their control. In this paper, we propose a cost-benefit optimization framework that incorporates the spatially explicit costs and benefits of invasion control, as well as the spatial invasion dynamics. Our framework offers a simple yet operational priority-setting criterion for the spatially explicit management of IASs under budget constraints. We applied this criterion to the control of the invasion of primrose willow (genus Ludwigia) in a protected area in France. Using a unique geographic information system panel dataset on control costs and invasion levels through space for a 20-year period, we estimated the costs of invasion control and a spatial econometric model of primrose willow invasion dynamics. Next, we used a field choice experiment to estimate the spatially explicit benefits of invasion control. Applying our priority criterion, we show that, unlike the current management strategy that controls the invasion in a spatially homogeneous manner, the criterion recommends targeted control on heavily invaded areas that are highly valued by users. We also show that the returns on investment are high, justifying the need to increase the allocated budgets and to treat the invasion more drastically. We conclude with policy recommendations and possible extensions, including the development of operational cost-benefit decision-support tools to assist local decision-makers in setting management priorities.

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.

Economic costs of protecting islands from invasive alien species

Biological invasions represent a key threat to insular systems and have pronounced impacts across environments and economies. The ecological impacts have received substantial focus, but the socioeconomic impacts are poorly synthesized across spatial and temporal scales. We used the InvaCost database, the most comprehensive assessment of published economic costs of invasive species, to assess economic impacts on islands worldwide. We analyzed socioeconomic costs across differing expenditure types and examined temporal trends across islands that differ in their political geography-island nation states, overseas territories, and islands of continental countries. Over US$36 billion in total costs (including damages and management) has occurred on islands from 1965 to 2020 due to invasive species' impacts. Nation states incurred the greatest total and management costs, and islands of continental countries incurred costs of similar magnitude, both far higher than those in overseas territories. Damage-loss costs were significantly lower, but with qualitatively similar patterns across differing political geographies. The predominance of management spending differs from the pattern found for most countries examined and suggests important knowledge gaps in the extent of many damage-related socioeconomic impacts. Nation states spent the greatest proportion of their gross domestic products countering these costs, at least 1 order of magnitude higher than other locations. Most costs were borne by authorities and stakeholders, demonstrating the key role of governmental and nongovernmental bodies in addressing island invasions. Temporal trends revealed cost increases across all island types, potentially reflecting efforts to tackle invasive species at larger, more socially complex scales. Nevertheless, the already high total economic costs of island invasions substantiate the role of biosecurity in reducing and preventing invasive species arrivals to reduce strains on limited financial resources and avoid threats to sustainable development goals.

Climatic Niche Differentiation between the Invasive Hornet Vespa velutina nigrithorax and Two Native Hornets in Europe, Vespa crabro and Vespa orientalis

The introduction and expansion of the Asian yellow-legged hornet (Vespa velutina nigrithorax) in Europe poses concern for multiple reasons, including biodiversity conservation. In addition to the predation of native insects (e.g., bees and wasps), this species may compete with native hornets due to an overlap of their climatic and trophic niches. The aim of this study is to investigate the realised climatic niche of V. v. nigrithorax and its response to climatic conditions and to evaluate the degree of overlap with the niches of the two native Vespa species present in Europe, Vespa crabro and Vespa orientalis. The niches of both native species partially overlap with the niche of the invasive species (Schoener’s D, 0.43 for V. crabro and 0.28 for V. orientalis), although some differences can be detected. V. crabro appears to be more adapted to cold and dry conditions than the invasive species, and V. orientalis is more adapted to arid climates. These differences may provide a competitive advantage to both native species in areas with a lower environmental suitability for V. v. nigrithorax, in the probable event that this species continues to spread, reaching all areas predicted to be suitable in Europe and in the Mediterranean basin.

The Alien to Cyprus Entomofauna (ACE) database: a review of the current status of alien insects (Arthropoda, Insecta) including an updated species checklist, discussion on impacts and recommendations for informing management

Alien insects represent one of the most species rich groups of organisms introduced to Europe, with some responsible for adverse social-economic, human-health, biodiversity and ecosystem impacts. The impacts of invasive alien species, especially on island ecosystems, have been a hot topic of research worldwide. Cyprus is a Mediterranean island at the biogeographic crossroads of Asia, Africa and Europe. This study presents the database of the alien insects of the island of Cyprus as a whole, created through an extensive review including grey literature and online sources. The Alien to Cyprus Entomofauna (ACE) triples the known number of alien insects and adds supplemental information to existing species. Data concerning a total of 349 alien insects are presented alongside an updated checklist and recommendations for informing management. The status of alien insects on the island, their origin, trophic guilds, establishment, pathways of introduction and impacts are discussed. Developing an alien species inventory for the island is challenging due to its geographic position and the increasing movement of people and goods leading to new species introductions. This publication constitutes an important first step towards providing information for effective actions to tackle invasive alien insects on Cyprus. The checklist and accompanying information can underpin understanding of the status and trends of alien species including providing information for risk assessments. ACE will continue to be maintained and updated as new records for Cyprus are made.

Quantifying impacts of human pressures on ecosystem services: Effects of widespread non-indigenous species in the Baltic Sea

Ecosystem services (ES) are the benefits natural ecosystems provide to society, such as food provisioning, water supply, climate regulation and recreational benefits. Biological invasions are a major driver of global change, and several non-indigenous species (NIS) may alter key ecological feedbacks with ultimate consequences to ES, livelihoods and human wellbeing. Nonetheless, the effects of NIS on ES supply remain largely unquantified. Here we present the first quantitative case study assessing the impacts of widespread NIS on ES in the Baltic Sea, by developing and employing a robust and repeatable data-driven approach. All NIS with a sufficient knowledge base pose large and highly significant effects on ES, resulting on average 55 % change in the intensity of ES. Most impacts affected regulation services, concerning both abiotic and biotic realms, with little evidence on cultural and provisioning services. The methodology can be easily employed beyond the current study realm e.g. to better understand the roles of human pressures on ES in any ecosystem. Importantly, the study also identified major biases not only in the availability of taxonomic and sub-regional evidence, but also in the different study types employed to create the evidence base.

Economic costs of invasive rodents worldwide: the tip of the iceberg

Background

Rodents are among the most notorious invasive alien species worldwide. These invaders have substantially impacted native ecosystems, food production and storage, local infrastructures, human health and well-being. However, the lack of standardized and understandable estimation of their impacts is a serious barrier to raising societal awareness, and hampers effective management interventions at relevant scales.

Methods

Here, we assessed the economic costs of invasive alien rodents globally in order to help overcome these obstacles. For this purpose, we combined and analysed economic cost data from the InvaCost database-the most up-to-date and comprehensive synthesis of reported invasion costs-and specific complementary searches within and beyond the published literature.

Results

Our conservative analysis showed that reported costs of rodent invasions reached a conservative total of US$ 3.6 billion between 1930 and 2022 (annually US$ 87.5 million between 1980 and 2022), and were significantly increasing through time. The highest cost reported was for muskrat Ondatra zibethicus (US$ 377.5 million), then unspecified Rattus spp. (US$ 327.8 million), followed by Rattus norvegicus specifically (US$ 156.6 million) and Castor canadensis (US$ 150.4 million). Of the total costs, 87% were damage-related, principally impacting agriculture and predominantly reported in Asia (60%), Europe (19%) and North America (9%). Our study evidenced obvious cost underreporting with only 99 documents gathered globally, clear taxonomic gaps, reliability issues for cost assessment, and skewed breakdowns of costs among regions, sectors and contexts. As a consequence, these reported costs represent only a very small fraction of the expected true cost of rodent invasions (e.g., using a less conservative analytic approach would have led to a global amount more than 80-times higher than estimated here).

Conclusions

These findings strongly suggest that available information represents a substantial underestimation of the global costs incurred. We offer recommendations for improving estimates of costs to fill these knowledge gaps including: systematic distinction between native and invasive rodents' impacts; monetizing indirect impacts on human health; and greater integrative and concerted research effort between scientists and stakeholders. Finally, we discuss why and how this approach will stimulate and provide support for proactive and sustainable management strategies in the context of alien rodent invasions, for which biosecurity measures should be amplified globally.

Habitat suitability and connectivity modeling predict genetic population structure and priority control areas for invasive nutria (Myocastor coypus) in a temperate river basin

The nutria (Myocastor coypus), also known as the coypu, is a semi-aquatic, invasive rodent native to South America that causes damage to natural riverine and wetland habitats in many parts of the world, including South Korea. Understanding habitat use, connectivity, and gene flow of nutria populations is critical for the sound management of local and regional ecosystems. Here, we assessed habitat suitability and connectivity in relation to the genetic structure of nutria populations in the Nakdong River Basin of South Korea. A total of 321 nutria occurrence sites and seven environmental variables were used to perform ensemble habitat suitability modeling using five species distribution models (SDMs), including boosted regression trees, maximum entropy model, random forest, generalized linear model, and multivariate adaptive regression splines. Using graph and circuit theory approaches, we assessed the population gene flow and current flow betweenness centrality (CFBC) of suitable habitats derived from the ensemble SDM. All SDMs performed well with a range of test AUC values from 0.962 to 0.970 (mean = 0.966) with true skill statistic values over 0.8. The minimum temperature of the coldest month, mean temperature of the warmest quarter, precipitation of the driest quarter, and distance from water bodies were important predictors in nutria habitat modeling. Nutria population gene flow was significantly correlated with the least-cost path distance on a cost resistance surface based on ensemble habitat suitability modeling and roads (Mantel's r = 0.60, p < 0.05). Finally, the CFBC positively correlated with the genetic diversity of nutria populations was used to identify priority control areas. Habitat suitability and connectivity modeling not only revealed environmental conditions and areas that support the survival and spread of nutrias, but also improved our understanding of the animals' genetic population structure, thereby indicating priority areas to target for eradication.

Do non-native and dominant native species carry a similar risk of invasiveness? A case study for plants in Turkey

Most risk analysis studies in invasion biology have focused on the invasiveness of non-native species, even though some native species also can pose a high risk to the environment and human well-being. This is especially true under current global change, which may cause dominant native species to expand their range of distribution and have substantial effects on the ecosystem. In this study, the risk of invasiveness of five non-native and five native plant species in Turkey was evaluated using a standard risk screening protocol. All ten species selected for screening are known to be invasive in several parts of the world, i.e. non-native Ailanthus altissima, Cuscuta campestris, Phytolacca americana, Robinia pseudoacacia and Sicyos angulatus, and native Cirsium arvense, Hedera helix, Onopordum acanthium, Phragmites australis and Sorghum halepense. The Australian Weed Risk Assessment decision-support tool adapted to Turkey’s geographical and climatic conditions was used for screening the study species based on their biological traits, ecology and management approaches. All species were classified as high-risk, with R. pseudoacacia among non-natives and P. australis among natives achieving the highest scores followed by S. halepense, C. campestris, C. arvense, O. acanthium, P. americana, S. angulatus, A. altissima and H. helix. Based on their risk scores, all non-native species were classified as invasive and all native species as ‘expanding’ for Turkey. An ordination based on the risk scores showed similarities between invasive and expanding species. The outcomes of this study indicate that species can have several risk-related traits resulting in high risk scores irrespective of their origin. Such species can modify their environment and interact with other species with severe consequences for biodiversity. It is argued that dominant species with highly negative environmental and socioeconomic impacts in their habitats should be included in priority lists for management measures irrespective of their origin (i.e. native or non-native). More studies are needed to evaluate the magnitude and prevalence of the present findings for other regions worldwide.

Climate change may exacerbate the risk of invasiveness of non-native aquatic plants: the case of the Pannonian and Mediterranean regions of Croatia

Non-native aquatic plants are amongst the major threats to freshwater biodiversity and climate change is expected to facilitate their further spread and invasiveness. To date, in Croatia, no complete list of non-native extant and horizon aquatic plants has been compiled nor has a risk screening been performed. To address this knowledge gap, 10 extant and 14 horizon aquatic plant species were screened for their risk of invasiveness in the Pannonian and Mediterranean regions of Croatia under current and predicted (future) climate conditions. Overall, 90% and 60% of the extant species were classified as high risk for the Pannonian and Mediterranean regions, respectively, under both climate scenarios. Of the horizon species, 42% were classified as high risk under current conditions and, under climate change, this proportion increased to 78%. The ‘top invasive’ species (i.e. scored as very high risk) under both climate conditions and for both regions were extant Elodea nuttallii and horizon Lemna aequinoctialis. The horizon Hygrophila polysperma was very high risk for the Mediterranean Region under current climate conditions and for both regions under projected climate conditions. Azolla filiculoides, Elodea canadensis, Egeria densa and Utricularia gibba were also classified as high risk under current climate conditions and, after accounting for climate change, they became of very high risk in both regions. Further, Gymnocoronis spilanthoides and Lemna minuta were found to pose a very high risk under climate change only for the Pannonian Region. It is anticipated that the outcomes of this study will contribute to knowledge of the invasiveness of aquatic plants in different climatic regions and enable prioritisation measures for their control/eradication.

Expanding the invasion toolbox: including stable isotope analysis in risk assessment

Species introductions are a major concern for ecosystem functioning, socio-economic wealth, and human well-being. Preventing introductions proved to be the most effective management strategy, and various tools such as species distribution models and risk assessment protocols have been developed or applied to this purpose. These approaches use information on a species to predict its potential invasiveness and impact in the case of its introduction into a new area. At the same time, much biodiversity has been lost due to multiple drivers. Ways to determine the potential for successful reintroductions of once native but now extinct species as well as assisted migrations are yet missing. Stable isotope analyses are commonly used to reconstruct a species’ feeding ecology and trophic interactions within communities. Recently, this method has been used to predict potentially arising trophic interactions in the absence of the target species. Here we propose the implementation of stable isotope analysis as an approach for assessment schemes to increase the accuracy in predicting invader impacts as well as the success of reintroductions and assisted migrations. We review and discuss possibilities and limitations of this methods usage, suggesting promising and useful applications for scientists and managers.

Building a synthesis of economic costs of biological invasions in New Zealand

Biological invasions are a major component of anthropogenic environmental change, incurring substantial economic costs across all sectors of society and ecosystems. There have been recent syntheses of costs for a number of countries using the newly compiled InvaCost database, but New Zealand-a country renowned for its approach to invasive species management-has so far not been examined. Here we analyse reported economic damage and management costs incurred by biological invasions in New Zealand from 1968 to 2020. In total, US$69 billion (NZ$97 billion) is currently reported over this ∼50-year period, with approximately US$9 billion of this considered highly reliable, observed (c.f. projected) costs. Most (82%) of these observed economic costs are associated with damage, with comparatively little invested in management (18%). Reported costs are increasing over time, with damage averaging US$120 million per year and exceeding management expenditure in all decades. Where specified, most reported costs are from terrestrial plants and animals, with damages principally borne by primary industries such as agriculture and forestry. Management costs are more often associated with interventions by authorities and stakeholders. Relative to other countries present in the InvaCost database, New Zealand was found to spend considerably more than expected from its Gross Domestic Product on pre- and post-invasion management costs. However, some known ecologically (c.f. economically) impactful invasive species are notably absent from estimated damage costs, and management costs are not reported for a number of game animals and agricultural pathogens. Given these gaps for known and potentially damaging invaders, we urge improved cost reporting at the national scale, including improving public accessibility through increased access and digitisation of records, particularly in overlooked socioeconomic sectors and habitats. This also further highlights the importance of investment in management to curtail future damages across all sectors.

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.

Invasive species fouling Perna perna (Bivalvia: Mytilidae) mussel farms

Invasive, fouling species increase management costs and reduce mussel growth, which jeopardizes mariculture. We studied the distribution of eight invasive species in Santa Catarina, the leading mussel producer in Brazil. Our goals were to determine their spatial distribution and prevalence on farm structures (buoys, long lines, and mussel socks), as well as understand the relevance of propagule pressure (recruitment), port distance, and area of the farm in this distribution. Although present in all sites, adult and recruits distribution were spatially restricted, showing that species might have a metapopulation structure. The most prevalent species were the ascidian Styela plicata, the barnacle Megabalanus coccopoma, the bryozoan Schizoporella errata, and the polychaete Branchiomma luctuosum. Recruitment was the main driver of three species distribution while distance to port explained only one species distribution. Based on those results, we discuss policy options, management, and regulation enforcement, that can be used in the mussel aquaculture elsewhere.

The role of phylogenetic relatedness on alien plant success depends on the stage of invasion

Darwin's naturalization hypothesis predicts successful alien invaders to be distantly related to native species, whereas his pre-adaptation hypothesis predicts the opposite. It has been suggested that depending on the invasion stage (that is, introduction, naturalization and invasiveness), both hypotheses, now known as Darwin's naturalization conundrum, could hold true. We tested this by analysing whether the likelihood of introduction for cultivation, as well as the subsequent stages of naturalization and spread (that is, becoming invasive) of species alien to Southern Africa are correlated with their phylogenetic distance to the native flora of this region. Although species are more likely to be introduced for cultivation if they are distantly related to the native flora, the probability of subsequent naturalization was higher for species closely related to the native flora. Furthermore, the probability of becoming invasive was higher for naturalized species distantly related to the native flora. These results were consistent across three different metrics of phylogenetic distance. Our study reveals that the relationship between phylogenetic distance to the native flora and the success of an alien species changes from one invasion stage to the other.

An impact assessment of alien invasive plants in South Africa generally dispersed by native avian species

Invasive alien plant species have been identified as a major threat to biodiversity and the relationship with native avian dispersers may increase their invasion potential. The impact of invasive plant species needs to be quantified using comparable assessment tools across different habitats and species to allocate limited resources to high-priority species. Here, we used the Generic Impact Scoring System (GISS) to assess the impacts of 16 fleshy-fruited alien invasive plant species in South Africa generally dispersed by native avian species. The results showed that fleshy-fruited invasive species have both environmental and socio-economic impacts. The cumulated impact scores for lantana (Lantana camara) and the tree of heaven (Ailanthus altissima) were the highest, with scores of 42 and 32, respectively. Some species, such as white mulberry (Morus alba), camphor tree (Cinnamomum camphora), American bramble (Rubus cuneifolius) and Brazilian pepper tree (Schinus terebinthifolius), had low overall impact scores of 8, 18, 14 and 16, respectively, but scored the maximum impact of 5 for certain mechanisms. Environmental impacts of fleshy-fruited invasive plant species had a high impact magnitude through effects on the ecosystem and vegetation. Socio-economic impacts were mainly through effects on forest production, agriculture and human health. Species with large crop sizes, small seeds and fruit sizes had higher environmental and socio-economic impact magnitude. The information generated in this study is important for guiding resource allocation and preventing the uncontrolled introduction of invasive species in South Africa. The impact of the fleshy-fruited invasive species transcended sectors and, therefore, effective management of invasive species will require the collaboration of multiple and inter-sectoral stakeholders in South Africa.

Invasive Alien Species of Benthic Macroinvertebrates and Fish in the Bulgarian Sector of the Danube River—Results of the Joint Danube Survey 4 (JDS4)

The aim of this study was to assess the status of aquatic invasive alien species (IAS) in the shoreline zone of the Bulgarian sector of the Danube River, Danube tributaries, and adjacent standing water bodies in the frame of the Joint Danube Survey 4 (JDS4). Seven benthic macroinvertebrates and seven fish IAS were identified. The crayfish Faxonius limosus was frequently found and abundant in the tributaries. The mussels Corbicula fluminea, Dreissena rostriformis bugensis, and Sinanodonta woodiana dominated in the Danube River and the middle and lower reaches of the tributaries, while the fish Carassius gibelio, Perccottus glenii, and Lepomis gibbosus were most abundant in the standing water bodies. The integrated biocontamination estimated by taxonomic groups (crayfish, molluscs, and fish), sampling methods, and type of water bodies ranged from moderate in the shoreline zone of the Danube River, through moderate to high in the canals and lakes, to severe in the Danube tributaries and the reservoirs. The results demonstrate the importance of IAS in the assessment of the ecological status/potential of the water bodies in the DRB. The comprehensive evaluation of the aquatic IAS pressure will provide valuable information and support for the implementation of the national and EU IAS and water policies in the DRB.

Scanning the horizon for invasive plant threats using a data-driven approach

Early detection and eradication of invasive plants are more cost-effective than managing well-established invasive plant populations and their impacts. However, there is high uncertainty around which taxa are likely to become invasive in a given area. Horizon scanning that combines a data-driven approach with rapid risk assessment and consensus building among experts can help identify invasion threats. We performed a horizon scan of potential invasive plant threats to Florida, USA—a state with a high influx of introduced species, conditions that are generally favorable for plant establishment, and a history of negative impacts from invasive plants. We began with an initial list of 2128 non-native plant taxa that are known invaders or crop pests. We built on previous invasive species horizon scans by developing data-based criteria to prioritize 100 taxa for rapid risk assessment. The semi-automated prioritization process included selecting taxa “on the horizon” (i.e., not yet in the target location and not on a noxious weed list) with climate matching, naturalization history, “weediness” record, and global commonness. We derived overall invasion risk scores with rapid risk assessment by evaluating the likelihood of each of the taxa arriving, establishing, and having an impact in Florida. Then, following a consensus-building discussion, we identified six plant taxa as high risk, with overall risk scores ranging from 75 to 100 out of a possible 125. The six taxa are globally distributed, easily transported to new areas, found in regions with climates similar to Florida’s, and can impact native plant communities, human health, or agriculture. Finally, we evaluated our initial and final lists for potential biases. Assessors tended to assign higher risk scores to taxa that had more available information. In addition, we identified biases towards four plant families and certain geographical regions of origin. Our horizon scan approach identified taxa conforming to metrics of high invasion risk and used a methodology refined for plants that can be applied to other locations.

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.

A global review of socioeconomic and environmental impacts of ants reveals new insights for risk assessment

Risk assessments are fundamental to invasive species management and are underpinned by comprehensive characterization of invasive species impacts. Our understanding of the impacts of invasive species is growing constantly, and several recently developed frameworks offer the opportunity to systematically categorize environmental and socioeconomic impacts of invasive species. Invasive ants are among the most widespread and damaging invaders. Although a handful of species receives most of the policy attention, nearly 200 species have established outside their native range. Here, we provide a global, comprehensive assessment of the impacts of ants and propose a priority list of risk species. We used the Socioeconomic Impact Classification for Alien Taxa (SEICAT), Environmental Impact Classification for Alien Taxa (EICAT) and Generic Impact Scoring System (GISS) to analyze 642 unique sources for 100 named species. Different methodologies provided generally consistent results. The most frequently identified socioeconomic impacts were to human health. Environmental impacts were primarily on animal and plant populations, with the most common mechanisms being predation and competition. Species recognized as harmful nearly 20 years ago featured prominently, including Wasmannia auropunctata (little fire ant, electric ant), Solenopsis invicta (red imported fire ant), Anoplolepis gracilipes (yellow crazy ant), and Pheidole megacephala (African big-headed ant). All these species except W. auropunctata have been implicated in local extinctions of native species. Although our assessments affirmed that the most serious impacts have been driven by a small number of species, our results also highlighted a substantial number of less well publicized species that have had major environmental impacts and may currently be overlooked when prioritizing prevention efforts. Several of these species were ranked as high or higher than some of the previously recognized "usual suspects," most notably Nylanderia fulva (tawny crazy ant). We compared and combined our assessments with trait-based profiles and other lists to propose a consensus set of 31 priority species. Ever-increasing global trade contributes to growing rates of species introductions. The integrated approaches we used can contribute to robust, holistic risk assessments for many taxa entrained in these pathways.

Alien flora in Calabria (Southern Italy): an updated checklist

An updated checklist of the Calabrian alien vascular flora is presented. By way of field, bibliographic, and herbarium research, we recorded 382 alien taxa (representing almost 14% of all regional flora), of which 371 are angiosperms, nine gymnosperms, and two ferns. In relation to the state of spread, the majority of alien species are casual (207 taxa; 54%), followed by naturalized (127; 33%) and invasive (48; 13%), these last include four on the list of Union Concern, sensu Regulation (EU) no. 1143/2014. The most represented families are Asteraceae (39 taxa) and Poaceae (39). Among genera, Amaranthus (nine taxa), Prunus, Euphorbia, and Oxalis (seven taxa) make up those with the greatest number of taxa. A total of 21 taxa were reported for the first time, three of them are new to the European flora (Camptosema rubicundum, Musa ×paradisiaca and, only for continental Europe, Ipomoea hederacea), two to the Italian peninsula (Pelargonium graveolens, Schinus terebinthifolia) and 16 to the Calabrian flora (Aeonium arboreum, Asparagus asparagoides, Aspidistra elatior, Bidens sulphurea, Catalpa bignonioides, Citrus ×aurantium, Crassula ovata, Cucurbita ficifolia, Dimorphotheca ecklonis, Graptopetalum paraguayense subsp. paraguayense, Kalanchoë laxiflora, Nicotiana tabacum, Phytolacca dioica, Portulaca umbraticola, Talinum paniculatum, Tecomaria capensis). In terms of residence status, there are 291 neophytes (76%), 73 archaeophytes (19%), and 18 regional aliens (5%); neophytes are the most represented group (45 out of 48) among invasive taxa. Concerning life forms, the two most abundant groups are therophytes (30.1%, 115 taxa) and phanerophytes (29.6%, 113 taxa). Regarding habitats, 72% of alien taxa occur in artificial (199 taxa, 52%) and agricultural habitats (75 taxa, 20%). The majority of alien taxa are native to the Americas (159; 41.6%), numerous aliens also originated in Asia (76; 19.9%) and Africa (56; 14.7%). The majority of taxa were introduced for ornamental purposes (55%). Over the past decade, alien taxa in the flora in Calabria have increased from 190 to the current 382 taxa. While this trend could be linked to some extent to increasing awareness of the problem of alien species and the increasing intensity of research over recent decades, it is also most probably due to new introductions resulting from the globalization that relentlessly affects the whole planet.

An assessment of the environmental and socio-economic impacts of alien rabbits and hares

Directly comparable data on the environmental and socio-economic impacts of alien species informs the effective prioritisation of their management. We used two frameworks, the Environmental Impact Classification for Alien Taxa (EICAT) and Socio-Economic Impact Classification for Alien Taxa (SEICAT), to create a unified dataset on the severity and type of impacts caused by alien leporids (rabbits and hares). Literature was reviewed to collate impact data, which was categorised following EICAT and SEICAT guidelines. We aimed to use these data to identify: (1) alien leporid species with severe impacts, (2) their impact mechanisms, (3) the native species and local communities vulnerable to impacts and (4) knowledge gaps. Native species from a range of taxonomic groups were affected by environmental impacts which tended to be more damaging than socio-economic impacts. Indirect environmental impacts were particularly damaging and underreported. No impact data were found for several alien leporid species.

Introduction, spread, and impacts of invasive alien mammal species in Europe

Biological invasions have emerged as one of the main drivers of biodiversity change and decline, and numbers of species classed as alien in parts of their ranges are rapidly rising. The European Union established a dedicated regulation to limit the impacts of invasive alien species (IAS), which is focused on the species on a Union List of IAS of particular concern. However, no previous study has specifically addressed the ecology of invasive alien mammals included on the Union List.We performed a systematic review of published literature on these species. We retrieved 262 publications dealing with 16 species, and we complemented these with the most up-to-date information extracted from global databases on IAS.We show that most of the study species reached Europe as pets and then escaped from captivity or were intentionally released. On average each year in the period 1981-2020, 1.2 species were recorded for the first time as aliens in European countries, and most species are still expanding their alien ranges by colonising neighbouring territories. France is the most invaded nation, followed by Germany, Italy, and the Russian Federation, and the muskrat Ondatra zibethicus, the American mink Neovison vison, and the raccoon dog Nyctereutes procyonoides are the most widespread species, having invaded at least 27 countries each. Invasive mammals of European Union concern are threatening native biodiversity and human well-being: worryingly, 81% of the 16 study species are implicated in the epidemiological cycle of zoonotic pathogens.Containing secondary spread to further countries is of paramount importance to avoid the establishment of new populations of invasive mammals and the related impacts on native communities, ecosystem services, and human health.We present a compendium on the ecology and impacts of invasive mammals of European Union concern. It can be used to assist environmental policies, identify and subsequently fill knowledge gaps, and inform stakeholders.

What is valued in conservation? A framework to compare ethical perspectives

Perspectives in conservation are based on a variety of value systems. Such differences in how people value nature and its components lead to different evaluations of the morality of conservation goals and approaches, and often underlie disagreements in the formulation and implementation of environmental management policies. Specifically, whether a conservation action (e.g. killing feral cats to reduce predation on bird species threatened with extinction) is viewed as appropriate or not can vary among people with different value systems. Here, we present a conceptual, mathematical framework intended as a tool to systematically explore and clarify core value statements in conservation approaches. Its purpose is to highlight how fundamental differences between these value systems can lead to different prioritizations of available management options and offer a common ground for discourse. The proposed equations decompose the question underlying many controversies around management decisions in conservation: what or who is valued, how, and to what extent? We compare how management decisions would likely be viewed under three idealised value systems: ecocentric conservation, which aims to preserve biodiversity; new conservation, which considers that biodiversity can only be preserved if it benefits humans; and sentientist conservation, which aims at minimising suffering for sentient beings. We illustrate the utility of the framework by applying it to case studies involving invasive alien species, rewilding, and trophy hunting. By making value systems and their consequences in practice explicit, the framework facilitates debates on contested conservation issues, and complements philosophical discursive approaches about moral reasoning. We believe dissecting the core value statements on which conservation decisions are based will provide an additional tool to understand and address conservation conflicts.

Identifying economic costs and knowledge gaps of invasive aquatic crustaceans

Despite voluminous literature identifying the impacts of invasive species, summaries of monetary costs for some taxonomic groups remain limited. Invasive alien crustaceans often have profound impacts on recipient ecosystems, but there may be great unknowns related to their economic costs. Using the InvaCost database, we quantify and analyse reported costs associated with invasive crustaceans globally across taxonomic, spatial, and temporal descriptors. Specifically, we quantify the costs of prominent aquatic crustaceans - crayfish, crabs, amphipods, and lobsters. Between 2000 and 2020, crayfish caused US$ 120.5 million in reported costs; the vast majority (99%) being attributed to representatives of Astacidae and Cambaridae. Crayfish-related costs were unevenly distributed across countries, with a strong bias towards European economies (US$ 116.4 million; mainly due to the signal crayfish in Sweden), followed by costs reported from North America and Asia. The costs were also largely predicted or extrapolated, and thus not based on empirical observations. Despite these limitations, the costs of invasive crayfish have increased considerably over the past two decades, averaging US$ 5.7 million per year. Invasive crabs have caused costs of US$ 150.2 million since 1960 and the ratios were again uneven (57% in North America and 42% in Europe). Damage-related costs dominated for both crayfish (80%) and crabs (99%), with management costs lacking or even more under-reported. Reported costs for invasive amphipods (US$ 178.8 thousand) and lobsters (US$ 44.6 thousand) were considerably lower, suggesting a lack of effort in reporting costs for these groups or effects that are largely non-monetised. Despite the well-known damage caused by invasive crustaceans, we identify data limitations that prevent a full accounting of the economic costs of these invasive groups, while highlighting the increasing costs at several scales based on the available literature. Further cost reports are needed to better assess the true magnitude of monetary costs caused by invasive aquatic crustaceans.

Rescue data as an alternative for assessing trends and phenological changes in two invasive parakeet species

Monitoring population trends of alien species is pivotal to design effective management plans to preserve native biodiversity, particularly urban areas, where most populations of alien birds are established. Urban wildlife rescue centers, with personnel trained to record species, age and sex of each individual brought by the public, may represent a reliable citizen-science based method to estimate both local changes in alien species phenology and population trends. In this work, we analysed records of monk and ring-necked parakeets by comparing rescue records in the urban area of Rome from the last 15 years. We also tested whether breeding phenology of alien parakeets showed any changes since the start of the invasion processes.

We recorded a strong correlation between the number of rescued parakeets and their population trends, thus confirming the importance of wildlife rescue centers in monitoring populations of alien species in urban areas. We also observed a shift in the breeding phenology of these parakeet species. The hatching peak for ring-necked parakeet occurred in early spring, in line with previous studies on the reproduction of this species, but with a slight increase in the number of months with evidence of breeding in the last years. As to the monk parakeet, our findings support the expansion of its reproductive season between 2006 and 2020 in Rome, with chicks currently being observed for seven months a year. Therefore, data collected through wildlife rescue centers may help improving models of population growth of alien species established in urban areas.

Annual Censuses and Citizen Science Data Show Rapid Population Increases and Range Expansion of Invasive Rose-Ringed and Monk Parakeets in Seville, Spain

Simple Summary

Monitoring programs are crucial to understanding and managing invasive species populations. However, they are infrequent and not usually conducted in the long term. In this work, we used population censuses and observational data from citizen science platforms to monitor the growth and expansion of populations of two invasive species established in Seville (Spain): the rose-ringed parakeet and the monk parakeet. During our study period (2013–2021), rose-ringed and monk parakeet populations increased fivefold and twentyfold, respectively. These rapid population growths coincided with the increasing number of observations of both species recorded by volunteer birdwatchers, as well as the increasing expansion of monk parakeets throughout the study area. Citizen science can be useful for roughly knowing the population status of invasive species, but it cannot replace specific monitoring programs to understand their spatiotemporal dynamics.

Abstract

Population changes of invasive species can go unnoticed long before population explosions, so long-term monitoring programs are needed to assess changes in population size. Although invasive populations of rose-ringed (Psittacula krameri) and monk parakeets (Myiopsitta monachus) are present worldwide, their current status and dynamics are mostly poorly known. Here, we provide a long-term population monitoring of both parakeet species established in a Mediterranean urban area. Between 2013 and 2021, we conducted systematic population censuses in the city of Seville and collected their occurrence and spatial distribution data from citizen science platforms. Our censuses showed a rapid population growth of both species: rose-ringed parakeets increased from 1200 to 6300 individuals, while monk parakeets increased from 70 to 1487 individuals. These population trends were weakly reflected by the number of parakeet observations and the number of cells with parakeet observations but not by the number of individuals recorded in citizen science platforms. Moreover, for the monk parakeet, the number of cells with observations was related to the spatial spread of its nests across the study area. Although resource-intensive, long-term monitoring programs are essential to assess population changes and develop effective management actions for invasive species. Thus, contrasting this information with data taken through citizen science platforms can validate the utility of the latter for assessing population status of invasive species.

Dramatic changes in the structure of shallow-water marine benthic communities following the invasion by Rugulopteryx okamurae (Dictyotales, Ochrophyta) in Azores (NE Atlantic)

Biological invasions are considered one of the most important drivers of biodiversity loss. Here we use a before-after-control-impact (BACI) design to investigate the impact of Rugulopteryx okamurae on the structure of shallow-water marine benthic communities in São Miguel island, Azores. After its first appearance in 2019, R. okamurae has rapidly invaded much of the southern coast of the island, where it became the dominant algae. This was followed by significant changes in the structure of shallow-water marine benthic communities, with substantial losses of natural variability and species richness. Compared to before, there has been dramatic reductions in the abundances of articulated coralline algae, corticated algae and corticated foliose algae in invaded locations. These results highlight its highly invasive character, not seen with other, more well-known, invasive species. It remains to be investigated if its impacts persist throughout time and to quantify the functional consequences of such dramatic changes.

The alignment of projects dealing with wetland restoration and alien control: A challenge for conservation management in South Africa

An inventory of wetland vegetation across the country generated a list of the most common invasive alien plants across South Africa. Many of the plants on that list do not correspond with the priorities in the programmes for alien control across the country, as they are not listed on a government produced list that guides the priorities for alien control. We explore the reasons for this situation. We argue that because wetlands are such important parts of the landscape, invasive aliens in wetlands are of special concern, and there should be more alignment between alien control programmes and wetland rehabilitation programmes. This alignment starts by considering the full number of species that form a threat to wetland habitats, but also considers which pesticides to use, erosion and recolonisation in wetlands, planting indigenous vegetation after aliens have been removed, and strategising by working from upstream to downstream. Existing alien control programmes for specific grasses (some relatively new to the country and in the phase of early detection) and floating aquatic plants may guide how to tackle the invasions of grasses and forbs that have been established in South African wetlands for an extended period of time.

Identifying Priorities, Targets, and Actions for the Long-term Social and Ecological Management of Invasive Non-Native Species

Formulating effective management plans for addressing the impacts of invasive non-native species (INNS) requires the definition of clear priorities and tangible targets, and the recognition of the plurality of societal values assigned to these species. These tasks require a multi-disciplinary approach and the involvement of stakeholders. Here, we describe procedures to integrate multiple sources of information to formulate management priorities, targets, and high-level actions for the management of INNS. We follow five good-practice criteria: justified, evidence-informed, actionable, quantifiable, and flexible. We used expert knowledge methods to compile 17 lists of ecological, social, and economic impacts of lodgepole pines (Pinus contorta) and American mink (Neovison vison) in Chile and Argentina, the privet (Ligustrum lucidum) in Argentina, the yellow-jacket wasp (Vespula germanica) in Chile, and grasses (Urochloa brizantha and Urochloa decumbens) in Brazil. INNS plants caused a greater number of impacts than INNS animals, although more socio-economic impacts were listed for INNS animals than for plants. These impacts were ranked according to their magnitude and level of confidence on the information used for the ranking to prioritise impacts and assign them one of four high-level actions-do nothing, monitor, research, and immediate active management. We showed that it is possible to formulate management priorities, targets, and high-level actions for a variety of INNS and with variable levels of available information. This is vital in a world where the problems caused by INNS continue to increase, and there is a parallel growth in the implementation of management plans to deal with them.

Risk Management Assessment Improves the Cost-Effectiveness of Invasive Species Prioritisation

Simple Summary

International agreements commit nations to control or eradicate invasive alien species. The scale of this challenge exceeds available resources and so it is essential to prioritise the management of invasive alien species. Species prioritisation for management may consider the likelihood and scale of impact (risk assessment) and the feasibility, costs and effectiveness of management (risk management). Risk assessment processes are widely used, risk management less so. To assess the cost effectiveness of prioritisation, we considered 26 high-risk species considered for eradication from Great Britain (GB) with pre-existing risk assessment and risk management outputs. We used these to consider the relative reduction in risk per unit cost when managing prioritised species based on different criteria. We showed that the cost effectiveness of prioritisation within our sample using risk assessment scores alone performed no better than a random ranking of the species. In contrast, prioritisation including management feasibility produced nearly two orders of magnitude improvement compared to random ranking. We concluded that basing management actions on priorities based solely on risk assessment without considering management feasibility risks the inefficient use of limited resources. In this study, the cost effectiveness of species prioritisation action was greatly increased by the inclusion of a risk management assessment.

Abstract

International agreements commit nations to control or eradicate invasive alien species. The scale of this challenge exceeds available resources and so it is essential to prioritise the management of invasive alien species. Species prioritisation for management typically involves a hierarchy of processes that consider the likelihood and scale of impact (risk assessment) and the feasibility, costs and effectiveness of management (risk management). Risk assessment processes are widely used, risk management less so, but are a crucial component of resource decision making. To assess the cost-effectiveness of prioritisation, we considered 26 high-risk species considered for eradication from Great Britain (GB) with pre-existing risk assessment and risk management outputs. We extracted scores to reflect the overall risk to GB posed by the species, together with the estimated cost and the overall feasibility of eradication. We used these to consider the relative reduction in risk per unit cost when managing prioritised species based on different criteria. We showed that the cost-effectiveness of prioritisation within our sample using risk assessment scores alone, performed no better than a random ranking of the species. In contrast, prioritisation including management feasibility produced nearly two orders of magnitude improvement compared to random. We conclude that basing management actions on priorities based solely on risk assessment without considering management feasibility risks the inefficient use of limited resources. In this study, the cost-effectiveness of species prioritisation for action was greatly increased by the inclusion of risk management assessment.