Pervasive human-induced environmental changes are increasingly causing species to move, with profound implications for their conservation and survival (e.g. Chen et al. 2011; Dawson et al. 2011). In a recently published piece on “Global policy for assisted colonization of species”, Brodie et al. (2021) call for assisted colonisation (also called managed relocation) to be embraced as a viable management option in post-2020 global conservation policies. They suggest that species, deliberately introduced beyond their historic native range and species that expand their ranges on their own in response to climate changes, should be treated identically for the purposes of policy. They also suggest expanding the use of the term “neonative” – which we previously proposed for range-expanding species that track environmental changes without human assistance (Essl et al. 2019) – so that this term also applies to species targeted for assisted colonisation.

We recognise the need to proactively consider the opportunities and risks of species translocations as a key tool in policies and management in the Anthropocene. However, we agree with Ricciardi and Simberloff (2021) and consider it crucial to treat distinct phenomena and different categories of species of conservation concern differently in policies. Very careful attention must be given to the precise definition of core concepts and terminology. Human-induced translocations differ from range-expanding species (i.e. ‘neonatives’ as we defined them in Essl et al. 2019) in key aspects (Table 1), which makes lumping these two categories of species highly problematical with regard to fundamental features that relate to policy. These aspects include dispersal potential, the rate and direction of range expansions, the number and characteristics of species involved and the associated risks and uncertainties. Whereas species targeted for assisted colonisation are currently a limited number of charismatic taxa (Hällfors et al. 2017), range-expansions by “neonatives” (as in our definition) involve a wide range of biota (Essl et al. 2019), some of them with a great potential to spread. Additionally, the risks and benefits associated with the two phenomena differ (IUCN 2013; Ricciardi and Simberloff 2014). Finally, although human decisions on whether or not to move species are pivotal in assisted colonisation (Richardson et al. 2009), this is not the case for species undergoing range expansions independently of direct human action. For the latter, measures to preserve or restore connectivity are most relevant (e.g. Wessely et al. 2017). Consequently, these profoundly different key characteristics of range-expanding species tracking environmental change vs. those subject to assisted colonisation result in very different conservation challenges (Table 1).

We call upon conservation bodies, such as the IUCN and the Convention of Biological Diversity (CBD), to evaluate the full range of conservation opportunities and risks created by species on the move. These efforts should recognise the profoundly different nature of translocated species and those undergoing range changes due to global change, but without direct human assistance. We are convinced that only such a nuanced approach will lead to appropriate conservation action to ensure species survival in the Anthropocene. We argue that species selected for assisted colonisation are a distinct category that should be subject to exactly the same classification as all other species. As they are introduced purposefully outside their natural range, they should be considered as aliens. The protocols for evaluating associated risks are well established (Richardson et al. 2009; Karasov-Olson et al. 2021). However, given that translocated species also differ in some important characteristics from other alien species, it may be warranted to classify these species in a distinct (sub)category.

FE appreciates funding from the Austrian Science Foundation FWF (grant I 3757-B29). PP was supported by EXPRO grant no. 19-28807X (Czech Science Foundation) and long-term research development project RVO 67985939 (Czech Academy of Sciences). DMR acknowledges the DSI-NRF Centre of Excellence for Invasion Biology. We thank the Handling Editor, Ingolf Kühn for helpful suggestions.