The Economic Costs of Biological Invasions Around the World

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Risk management assessment improves the cost-effectiveness of invasive species prioritisation.

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

The EICAT+ framework enables classification of positive impacts of alien taxa on native biodiversity

Species introduced through human-related activities beyond their native range, termed alien species, have various impacts worldwide. The IUCN Environmental Impact Classification for Alien Taxa (EICAT) is a global standard to assess negative impacts of alien species on native biodiversity. Alien species can also positively affect biodiversity (for instance, through food and habitat provisioning or dispersal facilitation) but there is currently no standardized and evidence-based system to classify positive impacts. We fill this gap by proposing EICAT+, which uses 5 semiquantitative scenarios to categorize the magnitude of positive impacts, and describes underlying mechanisms. EICAT+ can be applied to all alien taxa at different spatial and organizational scales. The application of EICAT+ expands our understanding of the consequences of biological invasions and can inform conservation decisions

The EICAT+ framework enables classification of positive impacts of alien taxa on native biodiversity

Species introduced through human-related activities beyond their native range, termed alien species, have various impacts worldwide. The IUCN Environmental Impact Classification for Alien Taxa (EICAT) is a global standard to assess negative impacts of alien species on native biodiversity. Alien species can also positively affect biodiversity (for instance, through food and habitat provisioning or dispersal facilitation) but there is currently no standardized and evidence-based system to classify positive impacts. We fill this gap by proposing EICAT+, which uses 5 semiquantitative scenarios to categorize the magnitude of positive impacts, and describes underlying mechanisms. EICAT+ can be applied to all alien taxa at different spatial and organizational scales. The application of EICAT+ expands our understanding of the consequences of biological invasions and can inform conservation decisions.Agencia Estatal de Investigación PCI2018-092939, PCI2018-092986Swiss National Science Foundation 31003A_179491, 31BD30_184114Austrian Fonds zur Förderung der Wissenschaftlichen Forschung 4011-B32German Bundesministerium für Bildung und Forschung 16LC1803A, 01LC1807CFrench National Research Agency ANR-18-EBI4-0001-06US National Science Foundation ICER-1852060National Research Foundation of South Africa 89967Australian Research Council DP200101680UK Natural Environment Research Council NE/V007548/1Hellenic Foundation for Research and Innovation (H.F.R.I.) HFRIFM17-159

A Framework for Global Twenty-First Century Scenarios and Models of Biological Invasions

Biological invasions have emerged as an eminent feature of global change, with substantial impacts on the environment and human livelihoods. Current research demonstrates that the numbers and impacts of alien species are rising unabatedly. At the same time, we lack a thorough understanding of potential future trajectories for the decades to come. With the recent establishment of comprehensive global databases, it is, for the first time, feasible to develop and quantify future scenarios of biological invasions. Therefore, we propose a conceptual framework for how to develop alien species scenarios for the twenty-first century and how to identify relevant steps and challenges along the way. The concept will be important to inform research, policy, stakeholders, and the general public. Furthermore, we call for the scientific community to join forces and to operationalize the framework for scenarios and models of biological invasions to develop an important baseline for understanding and managing future biological invasions

A four‐component classification of uncertainties in biological invasions: implications for management

Although uncertainty is an integral part of any science, it raises doubts in public perception about scientific evidence, is exploited by denialists, and therefore potentially hinders the implementation of management actions. As a relatively young field of study, invasion science contains many uncertainties. This may explain why, despite international policies aimed at mitigating biological invasions, the implementation of national- and regional-scale measures to prevent or control alien species has done little to slow the increase in extent of invasions and the magnitude of impacts. Uncertainty is therefore a critical aspect of invasion science that should be addressed to enable the field to progress further. To improve how uncertainties in invasion science are captured and characterized, we propose a framework, which is also applicable to other applied research fields such as climate and conservation science, divided into four components: the need (1) to clearly circumscribe the phenomenon, (2) to measure and provide evidence for the phenomenon (i.e., confirmation), (3) to understand the mechanisms that cause the phenomenon, and (4) to understand the mechanisms through which the phenomenon results in consequences. We link these issues to three major types of uncertainty: linguistic, psychological, and epistemic. The application of this framework shows that the four components tend to be characterized by different types of uncertainty in invasion science.We explain how these uncertainties can be detrimental to the implementation of management measures and propose ways to reduce them. Since biological invasions are increasingly tightly embedded in complex socio-ecological systems, many problems associated with these uncertainties have convoluted solutions. They demand the consensus of many stakeholders to define and frame the dimensions of the phenomenon, and to decide on appropriate actions. While many of the uncertainties cannot be eliminated completely, we believe that using this framework to explicitly identify and communicate them will help to improve collaboration between researchers and managers, increase scientific, political, and public support for invasion research, and provide a stronger foundation for sustainable management strategies

Prioritising surveillance for alien organisms transported as stowaways on ships travelling to South Africa

The global shipping network facilitates the transportation and introduction of marine and terrestrial organisms to regions where they are not native, and some of these organisms become invasive. South Africa was used as a case study to evaluate the potential for shipping to contribute to the introduction and establishment of marine and terrestrial alien species (i.e. establishment debt) and to assess how this varies across shipping routes and seasons. As a proxy for the number of species introduced (i.e. 'colonisation pressure') shipping movement data were used to determine, for each season, the number of ships that visited South African ports from foreign ports and the number of days travelled between ports. Seasonal marine and terrestrial environmental similarity between South African and foreign ports was then used to estimate the likelihood that introduced species would establish. These data were used to determine the seasonal relative contribution of shipping routes to South Africa's marine and terrestrial establishment debt. Additionally, distribution data were used to identify marine and terrestrial species that are known to be invasive elsewhere and which might be introduced to each South African port through shipping routes that have a high relative contribution to establishment debt. Shipping routes from Asian ports, especially Singapore, have a particularly high relative contribution to South Africa's establishment debt, while among South African ports, Durban has the highest risk of being invaded. There was seasonal variation in the shipping routes that have a high relative contribution to the establishment debt of the South African ports. The presented method provides a simple way to prioritise surveillance effort and our results indicate that, for South Africa, port-specific prevention strategies should be developed, a large portion of the available resources should be allocated to Durban, and seasonal variations and their consequences for prevention strategies should be explored further. (Résumé d'auteur

Identifying, reducing, and communicating uncertainty in community science:A focus on alien species

Community science (also often referred to as citizen science) provides a unique opportunity to address questions beyond the scope of other research methods whilst simultaneously engaging communities in the scientific process. This leads to broad educational benefits, empowers people, and can increase public awareness of societally relevant issues such as the biodiversity crisis. As such, community science has become a favourable framework for researching alien species where data on the presence, absence, abundance, phenology, and impact of species is important in informing management decisions. However, uncertainties arising at different stages can limit the interpretation of data and lead to projects failing to achieve their intended outcomes. Focusing on alien species centered community science projects, we identified key research questions and the relevant uncertainties that arise during the process of developing the study design, for example, when collecting the data and during the statistical analyses. Additionally, we assessed uncertainties from a linguistic perspective, and how the communication stages among project coordinators, participants and other stakeholders can alter the way in which information may be interpreted. We discuss existing methods for reducing uncertainty and suggest further solutions to improve data reliability. Further, we make suggestions to reduce the uncertainties that emerge at each project step and provide guidance and recommendations that can be readily applied in practice. Reducing uncertainties is essential and necessary to strengthen the scientific and community outcomes of community science, which is of particular importance to ensure the success of projects aimed at detecting novel alien species and monitoring their dynamics across space and time

Around the world in 500 years: Inter‐regional spread of alien species over recent centuries

Aim: The number of alien species has been increasing for centuries world-wide, but temporal changes in the dynamics of their inter-regional spread remain unclear. Here, we analyse changes in the rate and extent of inter-regional spread of alien species over time and how these dynamics vary among major taxonomic groups. Location: Global. Time period: 1500–2010. Major taxa studied: Vascular plants, mammals, birds, fishes, arthropods and other invertebrates. Methods: Our analysis is based on the Alien Species First Record Database, which comprises >60,000 entries describing the year when an alien species was first recorded in a region (mostly countries and large islands) where it later established as an alien species. Based on the number and distribution of first records, we calculated metrics of spread between regions, which we termed “inter-regional spread”, and conducted statistical analyses to assess variations over time and across taxonomic groups. Results: Almost all (>90%) species introduced before 1700 are found in more than one region today. Inter-regional spread often took centuries and is ongoing for many species. The intensity of inter-regional spread increased over time, with particularly steep increases after 1800. Rates of spread peaked for plants in the late 19th century, for birds and invertebrates in the late 20th century, and remained largely constant for mammals and fishes. Inter-regional spread for individual species showed hump-shaped temporal patterns, with the highest rates of spread at intermediate alien range sizes. Approximately 50% of widespread species showed signs of declines in spread rates. Main conclusions: Our results show that, although rates of spread have declined for many widespread species, for entire taxonomic groups they have tended to increase continuously over time. The large numbers of alien species that are currently observed in only a single region are anticipated to be found in many other regions in the future