Guidelines for reintroducing resurrected species

If you read National Geographic or Salon or any of a growing number of popular press publications, you have probably heard about DeExtinction--the resurrection of extinct species via the kind of molecular techniques that seemed impossibly futuristic and fictional when they were shown in Jurassic Park20 years ago. The concept first gained widespread attention thanks to the TEDx program, and its application has since been discussed in relation to everything from passenger pigeons to woolly mammoths.


A recent National Geographic article asked whether woolly mammoths might eventually roam the Earth again. Image courtesy of the NHM.

Unsurprisingly, opinions on DeExtinction vary widely; the idea of bringing back long-lost species seemingly inspires equal measures of fear, excitement, and curiosity. Another characteristic, evident in a recent Trends in Ecology and Evolution paper written by an international trio of zoologists, is caution. The researchers point out that DeExtinction is, most likely, an inevitability. Given this, they suggest that humans proceed only after doing a bit of soul-searching and asking themselves "whether DeExtinction can assist conservation efforts, and what might be the relative risk and benefits of species resurrections."

At the heart of their discussion is the idea that the whole point of DeExtinction efforts is to return lost species back into the wild; as a result, each resurrection event should ultimately be accompanied by at least one subsequent translocation and/or reintroduction--management techniques for which the International Union for the Conservation of Nature (IUCN) has provided detailed guidelines. The aim of the current paper is to highlight how those guidelines can be re-framed as a series of ten questions about the past, present, and future of each resurrected species and its habitat. The resulting answers can act as a "filter" for selecting the organisms for which DeExtinction is likely to be most relevant and successful.


The thylacine, an extinct Tasmanian marsupial, was featured on the cover of this month's Trends in Ecology and Evolution as the face of DeExtinction. Image courtesy of Wikipedia.

All ten questions can be answered with either a "yes" or a "no," making decisions relatively clear-cut. As the authors point out, a negative response might indicate a doomed project or, alternatively, simply highlight the need to do additional research before proceeding. Importantly, the questions focus not only on biological and ecological issues associated with the reintroduction efforts, but also on potential social, economic, and legislative implications.

So what are the questions? It is, perhaps, most interesting to consider them in relation to one of the three case studies that the researchers include to illustrate the usefulness of the filtering process: that of the Xerces blue butterfly. This species, native to a small portion of California, was declared extinct in 1941. Judging by the answers to the authors' proposed questionnaire, the butterfly is a prime candidate for DeExtinction.

• Q1: Can the past cause(s) of decline and extinction be identified and addressed? Yes. The butterfly went extinct because of habitat loss and over-harvesting by collectors. Dune restoration, and banning of additional collection efforts, could prevent a repeat extinction event.
• Q2: Can potential current and future cause(s) of decline and extinction be identified and addressed? Yes.Assuming that no new threats emerge--and that climate change does not have a negative impact on either the butterflies or their habitat--the techniques proposed in response to Q1 should be sufficient to protect the butterfly post-reintroduction.
• Q3: 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? Yes.Species composition, soil characteristics, and light conditions within the butterfly's habitat have been well documented.
• Q4: Is there a sufficient area of suitable and appropriately managed habitat available now and in the future? Yes.The dunes originally inhabited by the species no longer exist, but alternative habitats can likely be created in a nearby park--however, the suitability of these may be compromised by climate change.
• Q5: Is the proposed translocation compatible with existing policy and legislation? Yes.There are no known relevant policies.
• Q6: Are the socioeconomic circumstances, community attitudes, values, motivations, expectations, and anticipated benefits and costs of the translocation likely to be acceptable for human communities in and around the release area? Yes.Public support is likely to be widespread, as evidenced by the fact that a nonprofit conservation group is named after the butterfly.
• Q7: Is there an acceptable risk of the translocated species having a negative impact on species, communities, or the ecosystem of the recipient area? Yes.No negative impacts anticipated.
• Q8: Is there an acceptable risk of pathogen-related negative impacts to the resurrected species and the recipient system? Yes.No harmful impacts anticipated.
• Q9: Is there an acceptable risk of direct harmful impacts on humans and livelihoods, and indirect impacts on ecosystem services? Yes.No harmful impacts anticipated.
• Q10: Will it be possible to remove or destroy translocated individuals and their offspring from the release site or any wider area in the event of unacceptable ecological or sociological impacts? Yes.Because the butterflies are dependent on a particular type of habitat that is not widespread, and because the insects emerge en masse in a single brood each year, it would not be difficult to collect them if needed.

The Xerces blue butterfly, shown here in a specimen collection housed in a museum, went extinct because of habitat loss and over-harvesting by collectors. Image courtesy of Wikipedia.

As evidenced by the case study evaluation of Yangtze River Dolphins, it is not even necessary to answer every single question on the list; where the first few questions elicit a negative response, it is immediately clear that there is too much uncertainty associated with the reintroduction to make it worthwhile. This may be a permanent state or may simply indicate that additional research, management, and/or policy goals need to be met before proceeding with DeExtinction efforts.

The authors conclude by acknowledging that there are many reasons why DeExtinction is appealing: In addition to giving people an opportunity to "[correct] past human wrongs" and to view fascinating wildlife in the flesh, the resurrected species might also provide any number of ecosystem services. Given these benefits--real or perceived--it seems highly likely that it is only a matter of time before DeExtinction is attempted. Recognizing this, the researchers advocate the early use of their planning criteria in the hopes that this simple question-and-answer technique "might eliminate several high-profile candidate species and, thus, avoid time, expense, animal welfare concerns, and the raising of false public expectations."
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Seddon, P.J., Moehrenschlager, A., and Ewen, J. 2014. Reintroducing resurrected species: selecting DeExtinction candidates. Trends in Ecology and Evolution 29(3):140-147.