'The Ethics of Reviving Long Extinct Species' by Ronald Sandler in (2013) Conservation Biology comments that
There now appears to be a plausible pathway for reviving species that have been extinct for several decades, centuries, or even millennia. I conducted an ethical analysis of de-extinction of long extinct species. I assessed several possible ethical considerations in favor of pursuing de-extinction: that it is a matter of justice; that it would reestablish lost value; that it would create new value; and that society needs it as a conservation last resort. I also assessed several possible ethical arguments against pursuing de-extinction: that it is unnatural; that it could cause animal suffering; that it could be ecologically problematic or detrimental to human health; and that it is hubristic. There are reasons in favor of reviving long extinct species, and it can be ethically acceptable to do so. However, the reasons in favor of pursuing de-extinction do not have to do with its usefulness in species conservation; rather, they concern the status of revived species as scientific and technological achievements, and it would be ethically problematic to promote de-extinction as a significant conservation strategy, because it does not prevent species extinctions, does not address the causes of extinction, and could be detrimental to some species conservation efforts. Moreover, humanity does not have a responsibility or obligation to pursue de-extinction of long extinct species, and reviving them does not address any urgent problem. Therefore, legitimate ecological, political, animal welfare, legal, or human health concerns associated with a de-extinction (and reintroduction) must be thoroughly addressed for it to be ethically acceptable'Reintroduction and De-extinction' by Dolly Jørgensen in (2013) 63(9) BioScience 719 argues
We are entering an age in which species extinction may be reversible. De-extinction, as it has been labeled, can apply to any species for which DNA can be recovered, from woolly mammoths of the Pleistocene to thylacines and passenger pigeons from the twentieth century. These developments, which were showcased in March 2013 at a daylong conference called TEDxDeExtinction, held in Washington, DC, (http://tedxdeextinction.org), are exciting to some scientists and terrifying to others. If we are to embark on this de-extinction journey, an act some might label playing God, we need to establish the rules of the game. I want to suggest that the well-established standards for species reintroduction projects provide a solid foundation on which de-extinction can be built.
Critics of de-extinction in the popular science media have quickly pointed out drawbacks. From an ethical perspective, they have pointed to potential violations of animal welfare standards, the potential drain on resources that could be used in the conservation of still-existing species, and the implication that species destruction might be seen as permissible if it is reversible. The ecological objections have included the lack of ecosystems in which the re-created creatures could live, the potential invasiveness of the species in the ecosystem, and the potential for new disease vectors. Exploration of de-extinction's ethical dilemmas will require serious scientific and public debate, including a significant contribution from humanities researchers, including philosophers and historians, who have the appropriate theoretical background for conceptualizing what is at stake. I will not tackle those ethical issues here. The solution to the ecological dilemmas, however, may already be at hand through the application of reintroduction standards.