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Extinction is deeper than death—it’s an irreversible biological loss that extends well beyond individuals.

At least, that’s what we’ve always understood it to be.

Now, some researchers are betting that, in certain cases, extinction might be able to be undone. The emerging seeks to revive lost species using advances in synthetic biology, including cloning. While resurrected individuals would not be exact genetic replicas of their ancestors, scientists believe that they can create very close proxies—so close that the animals would fill a niche left vacant by the species’ disappearance.

“The only thing we’re interested in is conservation benefit, which we’ve defined in terms of restoring some missing ecological function,” says Philip Seddon, a zoologist at the University of Otago in New Zealand who is involved with drafting de-extinction guidelines for the International Union for Conservation of Nature. 

Environments aren't static, however, and our understanding of nature is imperfect. As such, researchers are well aware that the reintroduction of Dodos, Tasmanian tigers, or other creatures might not go exactly as planned. Historic ranges might be too highly altered to support resurrected species, for example. Or conversely, those species might divide and conquer, outcompeting today’s animals for food or space.

“Species can either fail to thrive or thrive too well, or in a way that humans don’t like,” says George Church, a geneticist at Harvard University. “If you bring back one species that causes the demise of another, you get a zero sum or even negative sum game.”

While such questions have generated much discussion, few if any studies have tried to empirically evaluate them. Researchers at Trent University in Ontario recently did that, examining the potential habitat for three extinct bird species—the Carolina Parakeet, Ivory-billed Woodpecker, and Passenger Pigeon. The findings, reported in , surprised them: By 2100, the three birds, if reintroduced, might have an even larger distribution outside their historic range than within it. “The biggest take-home message is that recreating the historic distribution of the species would not be possible,” says lead author Michael Peers, now a doctoral candidate at the University of Alberta.  

To probe the revived birds’ potential fates, Peers and his colleagues built computer models of suitable habitat. Historic records told them where each species lived in the past, and they looked up land cover and climate, including average temperature and precipitation, for those locations. Using those parameters, the researchers calculated how much total suitable space existed for each species in the years 1900, 2000, and 2100. They found that, even after removing land humans had developed, the models predicted a significant future shift in habitat availability, with increases outside of the areas where those birds once lived. As a result, native species in the new range could find themselves in direct competition with revived ones.

The analysis, however, has many uncertainties, including which environmental variables most mattered for each bird in the past and how the climate and environment will change in the future. The paper also does not take into account essential information such as forest cover, species composition, or how plants and animals interact.

“Nomadic birds like passenger pigeons are really more dependent on the structure of the habitat, not the exact climate of where they’re going,” says Ben Novak, an evolutionary biologist who heads an effort to with the group Revive & Restore. “Ultimately, this approach seems too simple for what the authors were trying to do.”  

Peers points out that the study was not meant to reveal exactly what will happen in the future, should any of those species one day be revived, nor inform decisions about where to release them. Rather, he hopes it will stimulate more conversation and research. Indeed, as efforts to resurrect species gain momentum, more granular research, including detailed , will be necessary. After all, it won’t help conservation efforts to bring back a species only to find that it’s invasive.

Of course, it’s possible that some resurrected species positively influence ecosystems and the species now occupying them. Scientists have suggested that , also the subject of de-extinction efforts, could roam a large swath of Siberia set aside as Pleistocene Park. All of the species living in the park would benefit from the habitat’s protection, and the mammoth would restore to that environment the ecological benefits of a large herbivore, which has been missing for around 8,000 years.

While not the aim of most researchers’ work, such a real-life “Jurassic Park” might have a side benefit: getting people excited about conserving wildlife. As Seddon says: “Even the most dispassionate scientists say, ‘Oh yes, I’d pay $1,000 to see a mammoth.’”