Many pasts, many futures: Navigating the complexities of species reshuffling to help prevent extinctions

Preventing human-caused extinctions is a foundational aim of conservation. However, in addition to causing extinctions, humans have moved numerous species to new areas. A considerable percentage of these are threatened in their native ranges. Broadening our conservation ethos to include introduced species is contentious and requires critical thinking in empirical and normative dimensions to negotiate between conflicting conservation goals. Here, we present a series of questions to inspire critical thinking in the negotiation of these conflicts. Empirically, we suggest that conservationists should consider whether the effects of introduced species are due to their non-nativeness <i>per se</i> or are simply a consequence of the organism having a metabolism and taking up space. Importantly, this requires proper scientific comparison to the effects of similar native organisms - otherwise many claims of 'harm' are unfalsifiable and could be used to justify the eradication of any organism. We further propose questions to help conservationists sort facts from normative values, which often wear empirical clothes. Through empirical rigor, value transparency and critical justification of these values, we believe that twenty- first century conservation can become a future-facing and pluralistic discipline with a heightened ability to prevent extinctions in an increasingly unpredictable and novel biosphere.