Trends in Ecology & Evolution
OpinionReintroducing resurrected species: selecting DeExtinction candidates
Section snippets
DeExtinction and conservation
Technological advances have opened up the possibility of species DeExtinction, the recreation of once-extinct species [1]. The potential for DeExtinction burst upon the public scene in March 2013 at the TEDxDeExtinction conference (http://tedxdeextinction.org). Associated meetings proposed DeExtinction candidate species (Table 1), debated criteria for their selection, and discussed the pros and cons of this new conservation approach. Although the prospect of recreating woolly mammoth (Mammuthus
DeExtinction as a conservation translocation issue
The prospect of being able to resurrect extinct species captures the imagination of many scientists and the general public alike. Inevitably thoughts turn to which species one might like to see come back to life and, unsurprisingly, given the clear taxonomic biases already evident [11], some of the wish lists emphasize species that are iconic, beloved, and missed. However, restoration of an extinct species is not a trivial matter to be focused on single charismatic species while extant species
Defining translocations of resurrected species
The IUCN Guidelines set out a typology of translocations to enable practitioners to position proposed projects according to accepted definitions. It is assumed that the intentional movement and release of members of a resurrected species would constitute a conservation translocation [10] primarily for conservation benefit, in relation to the focal species or to restoring ecosystem functions or processes.
If the chosen release area sits within the indigenous range of the species, defined as the
Applying the IUCN Guidelines to DeExtinction candidate species selection criteria
We use the template of the IUCN Guidelines as the basis for a priori evaluation of DeExtinction candidate species. Some components of the IUCN Guidelines are not appropriate for first-stage evaluation (Table 2). Across five components, we pose ten yes/no questions. A candidate species may be rejected by failure at any of the ten questions, or lack of information or high levels of uncertainty may trigger further analysis before reassessment. Some questions subsume several complex issues, but the
Question 1: can the past cause(s) of decline and extinction be identified and addressed?
Even for recent and localized extinctions, the precise cause of declines may be obscure. The IUCN Guidelines acknowledge this uncertainty and do not close the door on further investigations, including carefully designed experimental releases to identify threats and limiting factors (Annex 3.2.10, [10]), providing all formal requirements have been met and the outcomes of releases will be monitored.
Question 2: can potential current and future cause(s) of decline and extinction be identified and addressed?
Although the emphasis is necessarily on the identification and mitigation of the causes of the original extinction, it is also necessary to anticipate potential current and future threats to released animals, and to evaluate the feasibility of addressing these.
Question 3: are the biotic and abiotic needs of the candidate species sufficiently well understood to determine critical dependencies and to provide a basis for release area selection?
This question subsumes all the information about the biology and ecology of the candidate species and is framed in terms of adequacy of information to enable the next, critical aspect, that of release area habitat, to be assessed.
Question 4: is there a sufficient area of suitable and appropriately managed habitat available now and in the future?
This question combines the need to understand the habitat requirements of the focal species, with evaluation of the existence, extent, and status of suitable habitat currently and under realistic scenarios of changing climate and land-use patterns. One answer to this question could be ‘maybe’ if a suitable release area could be created following active restoration, improved management, or appropriate legal protection.
Human concerns
No conservation translocation can operate in disregard of stakeholders. Critically, human communities near the release area will have legitimate interests in the translocation, and success can be dependent on local community support. This is important where resurrected species have cultural, economic, or human health significance. The release of predatory species can be perceived as a threat to human life or livestock. By contrast, tangible benefits might accrue to having a resurrected species
Risk assessment
Formal risk assessment entails evaluation of the probability of a given risk factor occurring and some estimate of its likely impact; the range of potential risks creates a ‘risk landscape’ [10]. For example, information on the biology, pathogens and parasites, and invasive potential of the candidate species needs to be considered. By incorporating risk within the decision process, such as in structured decision-making and adaptive management, it is possible to compare potential risks against
Question 7: is there an acceptable risk of the translocated species having a negative impact on species, communities, or the ecosystem of the recipient area?
This question combines many aspects and might seem too complex to answer with any certainty. Given that this is a coarse filter to eliminate patently unsuitable DeExtinction candidate species, it would be sufficient to rule out a subset of the most obvious risks, and conduct more in-depth risk assessment as part of detailed translocation planning.
Socioeconomic risk
Released species can pose direct risks by threatening human safety or livelihoods. Indirect effects can include impacts on ecosystem services, such as food availability, clean water, erosion control, pollination, or nutrient cycling. Unforeseen negative effects can cause financial and other social impacts that might lead to public opposition to the translocations [10], even where projects have commenced with local community support. Socioeconomic impacts in recipient ecosystems might be more
Reversibility
Any translocation may not proceed as planned and failure to achieve project objectives must be considered as part of planning. The IUCN Guidelines stress the need for an exit strategy when investment of further resources is not justifiable. Here, we consider the specific case where harmful impacts or other unintended effects mean that free-ranging animals must be removed from the release area.
Question 10: will it be possible to remove or destroy translocated individuals and/or their offspring from the release site or any wider area in the event of unacceptable ecological or socioeconomic impacts?
It can be problematic to recapture and remove or destroy free-ranging animals if they have a low probability of detection, range more widely than anticipated, or occupy inaccessible areas.
Case studies
We present three case studies of DeExtinction candidates (Box 1, Box 2, Box 3) that disappeared recently and which represent different continents, taxa, habitats, and extinction causes. The evaluation of these within our framework is not intended to be definitive; we have used the available published literature to model how, in general, the ten questions relating to translocation feasibility and risk might be approached to inform decision-makers on the feasibility of release for some proposed
Concluding remarks
Perceived benefits of DeExtinction include scientific knowledge, technological advancement, ‘justice’ in terms of correcting past human wrongs, ‘wonder’ in terms of restoring ‘cool’ species, and concrete environmental benefits. DeExtinction candidate lists tend to focus on a few iconic species 7, 33, so-called ‘charismatic necrofauna’ (Alex Steffen, see http://www.salon.com/2013/09/06/de_extinction_wont_make_us_better_conservationists_partner/). Such species could be suitable candidates for
Acknowledgments
The authors thank Sam Turvey, Nick Mooney, Jessica Hellmann, Elina Vaara, and two anonymous referees for their insightful comments that greatly improved the manuscript. A.M. was supported by the Husky Energy Endangered Species Program and the Canadian Wildlife Federation.
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