Expert perceptions of the relative importance of ecological impacts of biological invasions.

Invasive species pose a major threat to biodiversity and ecosystem functioning. Although it is widely recognized that invasion impacts differ across habitats and taxonomic groups, a systematic evaluation of their perceived ecological importance has remained unexplored. We surveyed over 400 international experts in invasion science to systematically assess the importance of the 19 different types of ecological impacts across habitats, taxa, and levels of biological organization. We found consistent patterns in expert perceptions, where changes in assemblage structure, population size, and species loss were rated as most important, while others, like soundscape, fire regime, and microclimate, consistently received lower scores. Scores between taxa varied more than scores between habitats, while responses were more consistent among respondents with greater experience in the field. Our results highlight the impact types that would require greater management efforts (i.e., the higher scores), as well as those that could benefit from further research (i.e., the lower scores).