Is nativeness measurable?

Novel ecosystems are rapidly becoming dominant across the world due to globalization, changing land use and abiotic conditions, and climate change. Dominant paradigms to understand novel ecosystems, and introduced organisms more broadly, consider them to be drivers of biodiversity loss and ecosystem degradation because introduced organisms did not coevolve with native communities. If this is true, then native and introduced species should have measurably different effects and one should be able to empirically determine whether a species is native or introduced by their impacts without historic knowledge. I will report on meta-analytic results stemming from >10,000 effect sizes and ~400 articles where I compared the effects of introduced and native megafauna and found that introduced and native megafauna generally have similar impacts on vegetation, soils, and other animals. These results suggest that nativeness—at least for megafauna—may not be as important as usually considered. I will contextualize these results in relation to other similar meta-analytic tests and widely used frameworks for assessing the impacts of introduced organisms, such as the Environmental Impact Classification for Alien Taxa (EICAT) and suggest that the majority of literature on the effects of introduced organisms is rooted in tautological comparisons that do not use the proper controls to understand the effects of introduced organisms.

I will then discuss how alternative lenses towards introduced species can help reveal overlooked ecological patterns and processes, especially in the context of Earth’s history, and can provide new opportunities to prevent extinctions. Including introduced species in conservation decision making is not simple and requires broader and more pluralistic value systems towards non-human life. I will outline how these values can provide robust guideposts for conservation action and how they can also reduce the bias of our science, make our discipline more culturally inclusive, and help us navigate a time of rapid environmental change.