Seeking international agreement on what it means to be 'native'

The management of harmful nonnative species is a priority for governments worldwide. However, confusion concerning what constitutes a “native” species has led to ambiguous or even contradictory wording in adopted legislation. A key issue concerns the treatment of species dispersing beyond their normal ranges in response to global change. Range-expanding species can have negative impacts on the ecosystems they colonize, prompting some authorities to class them as “nonnatives.” However, range-shifts are becoming increasingly necessary for species persistence in response to climate and habitat change. Distinguishing these “desirable” range-shifts from other human-driven introductions is therefore a core requirement of legislation. Here, we propose a simplified framework that can be applied unambiguously across the policy arena. We suggest that the “nonnative” moniker should apply exclusively to species transported outside their native range by direct transport (defined herein), leaving species moving via unassisted dispersal as “natives,” even if they are responding indirectly to anthropogenic change. We believe that widespread adoption of this simplified approach will facilitate more consistent multinational policies to target problematic invasive species.