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

Parallels and discrepancies between non-native species introductions and human migration

Biological invasions and human migrations have increased globally due to socio-economic drivers and environmental factors that have enhanced cultural, economic, and geographic connectivity. Both processes involve the movement, establishment, and spread of species, yet unfold within fundamentally different philosophical, social and biological contexts. Hence, studying biological invasions (invasion science) and human migration (migration studies) presents complex parallels that are potentially fruitful to explore. Here, we examined nuanced parallels and differences between these two phenomena, integrating historical, socio-political, and ethical perspectives. Our review underscores the need for context-specific approaches in policymaking and governance to address effectively the challenges and opportunities of human migration and harm from biological invasions. We suggest that approaches to studying the drivers of biological invasions and human migration provide an excellent opportunity for transdisciplinary research; one that acknowledges the complexities and potential insights from both fields of study. Ultimately, integrating natural and social sciences offers a promising avenue for enriching the understanding of invasion biology and migration dynamics while pursuing just, equitable, and sustainable solutions. However, while human migration is a clear driver of biological invasions, drawing on principles from biological invasions to understand past and current human migration risks oversimplification and the potential for harmful generalisations that disregard the intrinsic rights and cultural dynamics of human migrations. By doing so, we provide insights and frameworks to support the development of context-specific policies that respect human dignity, foster cultural diversity, and address migration challenges in ways that promote global cooperation and justice. This interdisciplinary approach highlights the potential for transdisciplinary research that acknowledges complexities in both fields, ultimately enriching our understanding of invasion biology and migration dynamics while pursuing equitable and sustainable solutions.

Exposure and Sensitivity of Terrestrial Vertebrates to Biological Invasions Worldwide

While biological invasions continue to threaten biodiversity, most of current assessments focus on the sole exposure to invasive alien species (IAS), without considering native species' response to the threat. Here, we address this gap by assessing vertebrates' vulnerability to biological invasions, combining measures of both (i) exposure to 304 identified IAS and (ii) realized sensitivity of 1600 native vertebrates to this threat. We used the IUCN Red List of Threatened Species to identify species threatened by IAS, their distribution, and the species' range characteristics of their associated IAS. We found that 38% of worldwide terrestrial lands are exposed to biological invasions, but exposure alone was insufficient to assess vulnerability since we further found that most of the world hosted native species sensitive to biological invasions. We delineated areas highly vulnerable to biological invasions, that is, combining areas of high exposure and high sensitivity to IAS, located in Australia and coastal states of North America with a high confidence level, but also-depending on the group-in Pacific islands, Southern America, Western Europe, Southern Africa, Eastern Asia, and New-Zealand with a medium confidence level. Assessing the completeness in exposure data, we revealed strong biases in the global description of the well-known invasion hotspots, with limited areas being assessed with a medium to high confidence level. The completeness of sensitivity was overall very high, for the three studied taxonomic groups. We also demonstrated that coldspots of vulnerability to biological invasions were areas of low confidence in terms of data completeness, which coincided with biodiversity hotspots. There is thus a critical need to address these knowledge shortfalls which jeopardize efficient conservation initiatives, regarding the threats to well-known vertebrate taxa.

Forecasting potential invaders to prevent future biological invasions worldwide

The ever-increasing and expanding globalisation of trade and transport underpins the escalating global problem of biological invasions. Developing biosecurity infrastructures is crucial to anticipate and prevent the transport and introduction of invasive alien species. Still, robust and defensible forecasts of potential invaders are rare, especially for species without known invasion history. Here, we aim to support decision-making by developing a quantitative invasion risk assessment tool based on invasion syndromes (i.e., generalising typical attributes of invasive alien species). We implemented a workflow based on 'Multiple Imputation with Chain Equation' to estimate invasion syndromes from imputed datasets of species' life-history and ecological traits and macroecological patterns. Importantly, our models disentangle the factors explaining (i) transport and introduction and (ii) establishment. We showcase our tool by modelling the invasion syndromes of 466 amphibians and reptile species with invasion history. Then, we project these models to amphibians and reptiles worldwide (16,236 species [c.76% global coverage]) to identify species with a risk of being unintentionally transported and introduced, and risk of establishing alien populations. Our invasion syndrome models showed high predictive accuracy with a good balance between specificity and generality. Unintentionally transported and introduced species tend to be common and thrive well in human-disturbed habitats. In contrast, those with established alien populations tend to be large-sized, are habitat generalists, thrive well in human-disturbed habitats, and have large native geographic ranges. We forecast that 160 amphibians and reptiles without known invasion history could be unintentionally transported and introduced in the future. Among them, 57 species have a high risk of establishing alien populations. Our reliable, reproducible, transferable, statistically robust and scientifically defensible quantitative invasion risk assessment tool is a significant new addition to the suite of decision-support tools needed for developing a future-proof preventative biosecurity globally.