Sabrina Kumschick

The negative impact of alien species is recognised as a major threat to biodiversity. An impact indicator, a measurable proxy of the status of alien species impacts over space and time, is essential for informing biological invasion policies and management strategies. We introduce an open-source workflow for computing impact indicators of alien species, combining occurrence data from the Global Biodiversity Information Facility (GBIF) with assessments of Environmental Impact Classification for Alien Taxa (EICAT). To implement the workflow, we developed an R package, impIndicator, which allows users to compute and visualise impact indicators for individual species and sites, as well as regional impact indicators. This tool can support ecological research and management by providing standardised insights into where alien species pose the greatest threats and whether current interventions are effectively reducing them. Such information is directly relevant to policy frameworks, including Target 6 of the Convention on Biological Diversity’s Kunming–Montreal Global Biodiversity Framework and the Sustainable Development Goals. We demonstrate the workflow using Acacia species in the Iberian Peninsula, South Africa and California, showcasing the spatiotemporal dynamics of their impacts and highlighting sites with higher impact risk. The resulting impact indicators were sensitive to variation in sampling effort and the completeness of the underlying occurrence data, highlighting the importance of well-sampled and systematically curated biodiversity datasets for robust impact assessment.

Over the last decades, invasion science has attempted to identify general patterns to explain which alien plant species become invasive, where, and why. However, many of these generalisations have proven inconsistent across spatial and taxonomic scales, leading to the widespread perception that invasions are largely context-dependent and there are no useful generalizations. We argue that trying to generalise across all invasions is unlikely to be productive, but that there are recurrent invasion patterns, conceptualised as invasion syndromes, i.e. “a combination of pathways, alien species traits, and characteristics of the ecosystem which collectively result in predictable dynamics and impacts, and that can be managed effectively using specific policy and management actions”. This idea is being tested in the Biodiversa+ project InvaSyn and extended through the Spanish national project PRISMA focusing on mountain ecosystems worldwide. Together, these initiatives aim to identify generalisable and useful patterns of plant invasions. Our approach is structured around three main steps. First, we compile and generate datasets capturing both ecological and human dimensions of invasions. Second, using integrative analyses, we classify invasion events into groups sharing similar ecological and socioeconomic characteristics, species attributes, invasion dynamics, and impacts. This syndrome-based approach allows us to reconcile context dependency with generality by identifying recurrent types of invasions rather than seeking universal patterns across all cases. Third, we identify actionable recommendations by co-developing response options tailored to each invasion syndrome. The invasion syndromes approach allows us to improve prediction, prioritisation and management of alien plant invasions, while fostering collaboration between researchers, practitioners and policymakers. Ultimately, this research contributes to a more holistic and actionable understanding of biological invasions, providing a basis for more efficient and context-aware management strategies.

The removal of invasive alien plants is a common practice to passively restore native biodiversity and ecosystem functioning. However, invasive plants can generate legacy effects: persistent alterations in evolutionary, ecological, and/or socio-economic processes that hinder or prevent recovery after their removal. Management actions themselves can generate and exacerbate legacy effects. Despite increasing awareness, legacies remain under-reported and poorly understood, particularly those related to management actions. Here we propose an expanded definition of legacy effects, and a conceptual framework to identify and analyze the factors influencing their magnitude, persistence in time, and temporal dynamics. We propose classifying legacies as either evolutionary, ecological, or socio-economic according to (i) the mechanisms that generate them, (ii) the level of biological organization affected (species, population, community, or ecosystem), and (iii) the role of management actions in generating, exacerbating, and mitigating persistent impacts. (i) the mechanisms that generate them, (ii) the level of biological organization affected (species, population, community, or ecosystem), and (iii) the role of management actions in generating, exacerbating, and mitigating persistent impacts. Our framework provides a structured approach to predict post-removal dynamics and anticipate constraints on recovery to a desired reference state. We show that recognizing and addressing legacy effects is essential for improving invasive species management and for designing restoration strategies that are context-dependent and robust to long-term ecosystem change.

Freshwater ecosystems are disproportionately affected by biological invasions, yet global databases of invasive and alien species often underrepresent freshwater taxa. Global alien species databases often lack information on freshwater species. Existing efforts are fragmented, focusing on continental scales (e.g., the European Alien Species Information Network, EASIN), national scales (e.g., the United States Geological Survey), or on specific groups such as the Global Naturalized Alien Flora database GLONAF (van Kleunen et al. 2018), global avian invasions atlas GAVIA (Dyer et al. 2017), and the World Register of Introduced Marine Species WRiMS (Costello et al. 2021). Although valuable for policy research, databases such as GRIIS (Pagad et al. 2022) are not freshwater-specific, and are difficult to update dynamically. Also, they often lack additional essential information for a comprehensive study of biological invasion patterns and dynamics, such as introduction pathways, native range, functional group, year of introduction, or level of impact, hindering global assessments of freshwater invasions and their ecological consequences. In this study, we developed a traceable, transparent, standardized, and replicable workflow in R that compiles a global registry of freshwater alien species (Fig. 1. 1). First, we screened databases and the scientific literature to compile information about the presence of freshwater invasive species worldwide, covering all taxonomic groups. We standardized scientific names and filtered freshwater species. Second, we harmonized variables in each individual database under a common framework. Third, we added additional information to support risk assessments, such as higher taxonomy levels, functional feeding group, native and recipient ranges, establishment means, introduction pathways, impact type and severity, affected taxa, first introduction dates in each country, habitats and data sources used. This workflow, available through GitHub, can be used as reference to develop other taxa or region-specific workflows. We used the workflow to compile a comprehensive global dataset of FReshwater Invasive and Alien Species (FRIAS) with over 3,800 species drawn from 94 online sources and the literature. The FRIAS masterlist provides the most comprehensive checklist of freshwater invasive and alien species worldwide that can be easily corrected and updated periodically. By compiling, harmonizing and standardising this information, the FRIAS workflow will facilitate the monitoring of invasion patterns and macroecological trends, and support comparative studies aimed at understanding and mitigating the impacts of invasive and alien species on freshwater ecosystems.

This paper presents a comprehensive list of alien taxa in South Africa developed as part of triennial national status reports on biological invasions. It includes: taxa that are, have been, or were proposed to be regulated; alien taxa that are or have been present in South Africa (including those only ever recorded in quarantine facilities); taxa that are native to a part of South Africa that have formed native-alien populations in another part of the country; and taxa which have been categorised at some point as alien or for which the risk of invasion in South Africa has been evaluated. Names used previously are included so it is clear why taxa listed in historical sources are no longer considered alien or present, and how such names have been interpreted in terms of the latest authoritative taxonomic sources. The list also includes information on the invasion status of the taxa, their pathways, distributions, impacts and management, with metadata provided for all 38 variables, including confidence and data sources for 23 of them. The development of documented and repeatable workflows ensures it is clear why taxa (and associated information) are included in the list and facilitates reviews and updates. Based on information up to the end of December 2022, the list includes over 6 000 taxa, of which over 3 500 are alien taxa confirmed as present outside of captivity or cultivation. However, several key data sources still need to be verified and integrated into the list (particularly taxa in captivity or cultivation). Thus, this list should not yet be regarded as a complete baseline of the knowledge of alien taxa present in South Africa. The list is presented in a manner that is tidy and FAIR (findable, accessible, interoperable, reusable) and will be maintained, expanded and updated, so that the list will be dynamic and aim for completeness. By so doing, the list will allow the number and status of alien taxa to be tracked over time, informing management planning and regulatory decisions.

Background: Biological invasions are a major threat to biodiversity and sustainable development. A global assessment of biological invasions released in 2023 by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES), concluded that while invasions ‘…cause dramatic and, in some cases, irreversible changes…’ they can be ‘…overcome through a context-specific integrated governance approach’. Aim: Here we evaluate insights from the IPBES assessment in the context of South Africa and explore how these insights could inform the development of a national policy and strategy to address biological invasions. Results: Trends and status of biological invasions in South Africa are similar to those seen globally, but there are some distinct local nuances. South Africa has: 1) a long history of invasions with negative impacts caused especially by invasive trees and freshwater fishes, whilst invasive marine invertebrates have transformed large parts of the coastline; 2) a long history of control (biological control was first implemented in 1913) with large-scale, state-run invasive species management programmes currently in place; 3) a comprehensive regulatory system (e.g., there is provision for beneficial invasive species to be used under permits); 4) relatively high levels of awareness and engagement (at least among some stakeholder groups); and 5) a well-connected community of practice. Discussion: Efforts to limit introductions (intentional or unintentional) are difficult given South Africa’s extensive and porous borders and the pressing need to increase trade and travel. Regulatory and implementation efforts aimed at prevention are improving, with the newly established Border Management Authority aiming to integrate biosecurity interventions at ports of entry. Such integrated governance is, we argue, needed more broadly if affected sectors, society groups and stakeholders are to be effectively included in decision-making and management. A more systematic flow of information from observation to action is essential, as is better feedback between research, policy and implementation at all scales. Biological invasions will continue to pose threats, but many of these can be effectively mitigated through focussed interventions. Co-ordinating such interventions in the context of other cross-cutting global change challenges and initiatives is a cost-effective way of protecting and improving livelihoods, human health, quality of life and biodiversity.

Risk assessment is an important tool in invasive species prevention and management, providing a structured approach to identify and evaluate the risks posed by non-native species. Despite the widespread development of risk assessment and risk analysis (collectively referred to as RA here) methods, there is a lack of information on which methods are used in practice. We conducted a global survey of RA practitioners from diverse regional, professional, and taxonomic contexts to identify the tools and databases used, the qualifications and experience of assessors, and the implementation and accessibility of RA results. 107 responses were received from practitioners focussed on all continents except Antarctica, with the most from the United States and the United Kingdom. Respondents reported using more than 46 different RA tools, with the Fish Invasiveness Screening Kit and the USDA Plant Protection and Quarantine Weed Risk Assessment the most commonly mentioned tools, based on the number of users. Plants were the most frequently assessed taxonomic group and terrestrial species, though representation from all taxonomic groups and systems exist. Respondents listed 107 generally open-access databases that they frequently use to conduct RAs, with the most commonly used sources being the CABI Invasive Species Compendium, occurrence records from the Global Biodiversity Information Facility (GBIF), and taxonomic information from the Integrated Taxonomic Information System (ITIS). Assessors typically had tertiary education, with the majority holding at least a master’s degree, though many did not believe that a post-graduate degree was necessary to be an effective assessor. After RAs were completed, assessments were predominantly reported to government agencies. Most finalized RAs included some measure of certainty and were usually publicly accessible, though few included a formal process for stakeholders to comment. Almost all respondents identified the importance of training and certification programs to standardize qualifications for assessors. Based on the views expressed in the surveys we discuss the importance of: (1) training and capacity building, (2) open access databases and FAIR (Findable, Accessible, Interoperable and Reusable) data standards, (3) incorporating stakeholders in the process, and (4) standardisation of tools; if these measures are implemented, they may enhance the consistency, transparency, and effectiveness of RAs of non-native species.

Effective biodiversity management and policymaking requires timely access to accurate and reliable scientific data on biodiversity status, trends and threats. However, current biodiversity monitoring processes are often time‐consuming, complex and irreproducible. Moreover, the quality and types of biodiversity data are diverse, which challenges their integration and impedes effective monitoring. A major step to overcome such challenges would be the availability of standardized species occurrence data. However, challenges arise in aggregating and integrating these heterogeneous data with environmental and landscape data. By creating standardized biodiversity data cubes and automated workflows for post‐processing, we envision that (1) information from complex datasets will be available in a known format to efficiently communicate biodiversity variables to policymakers; (2) the adoption of repeatable Open Data workflows will make biodiversity data more accessible, efficient and cost‐effective; and (3) cloud computing will make it easier to analyse large datasets, benefit from a broader range of models, share resources and work together on biodiversity projects. This revolution in biodiversity monitoring will rely on community collaboration. By bridging the gap between policymakers' needs, bioinformation specialists' skills and data collectors' motivations, biodiversity monitoring can become a more inclusive and community‐driven effort. As such, we advocate for the development of tools and workflows in close consultation with stakeholders to enhance the impact and use of biodiversity information. Practical implication. The proposed approach faces challenges in maintaining software, data standards and addressing biodiversity data complexity. However, leveraging existing infrastructures like GBIF and Copernicus, and building on the knowledge from GEO and GEO BON offers a feasible path.

This paper presents what is intended to be a comprehensive checklist on alien taxa in South Africa developed as part of triennial national status reports on biological invasions. It thus includes: taxa that are, have been, or were proposed to be regulated; alien taxa that are or have been present in South Africa (including those only ever recorded in quarantine facilities); taxa that are native to a part of South Africa that have formed native-alien populations in another part of the country; and taxa which have been recorded at some point as alien or for which the risk of invasion has been evaluated. Names used previously are included so it is clear why taxa listed in historical sources are no longer considered alien or present, and how such names have been interpreted in terms of the latest authoritative taxonomic sources. The list also includes information on the invasion status of the taxa, their pathways, distributions, impacts, and management, with metadata provided for all 38 variables, including confidence and data sources for 23 of them. The development of documented and repeatable workflows ensures it is clear why taxa (and associated information) are included on the list and facilitates reviews and updates. Based on information up to the end of December 2022, the checklist includes over 6000 taxa, of which over 3500 are alien taxa confirmed as present outside of captivity or cultivation. However, several key data sources still need to be verified and integrated into the list (particularly taxa in captivity or cultivation). Thus, this list should not yet be regarded as a complete baseline of the knowledge of alien taxa present in South Africa. The checklist is presented in a manner that is tidy and FAIR (findable, accessible, interoperable, reusable) and will be maintained, expanded, and updated, with the aim for the list to become comprehensive and dynamic. By so doing, the checklist will allow the number and status of alien taxa to be tracked over time, informing management planning and regulatory decisions.

The Risk Analysis for Alien Taxa (RAAT) framework was developed to collate scientific information and interpret it in the context of South African regulations on biological invasions. Feedback from the past four years has shown RAAT to be a valuable tool for making evidence-based, transparent recommendations, but one that can be improved. We describe the changes made in creating RAAT v2.0. We note several issues that we suspect will apply to many similar processes, namely the need to i) clarify descriptions; ii) remove superfluous questions; and iii) add questions to fully justify recommendations. We also stress what RAAT v2.0 does not do—the framework does not summarise management best practices nor does it, or South Africa’s regulatory lists, provide sufficient information to prioritise management resources. We strongly recommend that explicit feedback mechanisms are set up to ensure that similar such frameworks can be improved over time.