The Rewilding Debate: Debating the Extinct to Death

Image created by Sergiodlarosa

Since 2005, due in no small part to a commentary article published in Nature, Pleistocene rewilding has been a source of friction in conservation biology. Pleistocene rewilding generally differs from traditional conservation biology in its support for introducing extinct megafauna or a proxy species to positively impact ecosystems at the landscape scale.

In an edge.org discussion, Ryan Phelan attempts to justify rewilding because extinction primarily is caused by man.  She frames the issue as such:

"One of the fundamental questions here is, is extinction a good thing? Is it "nature's way"? And if it's nature's way, who in the world says anyone should go about changing nature's way? If something was meant to go extinct, then who are we to screw around with it and bring it back? I don't think it's really nature's way. I think that the extinction that we've seen since man is 99.9 percent caused by man."

Phelan’s questions seem to accuse Pleistocene rewilding opponents as being not only the cause of anthropogenic eradication of species but also apathetic to the possibility of reversing that same eradication. There are several underlying assumptions in her questions worth questioning.

1. When does one start the clock on which extinctions should be considered “caused by man”?
2. Does the fact that man caused an extinction necessitate the reintroduction of the extinct species? 
3. Even if we conclude that man has a duty to reintroduce all animals since the Pleistocene, how would one go about it?

A key issue with rewilding is that the farther back in time one goes, the more justification for species restoration moves from black and white to grey. Support for extending the range of a species with a limited population is almost without question. The California condor is an example of taking this one step further. All wild condors were put into a captive breeding program which allowed the population to increase and resulted in eventual reintroduction. Again, this is supported by mainstream conservation biologists. The key being that these species were never truly "lost" from the landscape. 

There exists, at least in my mind, a key difference between expatriated and extinct. If nothing else, the amount of time that has passed since these species have been robustly in play in the ecosystem is significantly lower for expatriated compared to extinct species. Phelan seems to obscure this difference in her discussion of the peregrine falcon in suggesting that they were extinct from the east coast, instead of simply expatriated from that region. This time factor is an important one as the environmental landscape is not a static system keeping conditions the same for thousands of years in hopes of extinct species returning to the same landscape they once inhabited.  The passage of time is made up of an intricate web of biological, chemical and geological cycles.  

The passenger pigeon appears to be the first species those supporting rewilding propose to “bring back." This makes some sense as a starting point in that it has only been absent from the landscape for a little over one hundred years, several thousand years less than the American mastodon. Also, there is little to no debate that humans were the direct cause of the extinction. If humans were the cause of the extinction, should and how would we go about reintroducing the passenger pigeon?

Photograph of a female Passenger Pigeon (Ectopistes migratorius) in captivity from the year 1898

To Phelan’s credit, she does recognize the potentially negative effects on humans that a return of the passenger pigeon to the same role it filled in the landscape prior to extinction- making up an estimated 25-40% of the total American land bird population- would have. She suggests a modest population with enough for sportsman to hunt the species but not enough to black out the sky and consume crop fields. This raises a quandary…why would one go through the process of bringing a species back at all if the effort results in only a controlled and superficial presence in the wild? Such an endeavor would undoubtedly be quite different from the role passenger pigeons had prior to extinction and arguably make their zoo-like than natural and in effect return the species for perhaps beauty, if not purpose. The means by which she postulates that this could be done raise even more questions.

When is a pigeon a pigeon? Phelan’s discusses that one idea of how to bring back the passenger pigeon is to edit the genome of the most similar living species, the band tail pigeon, until it, in Phelan’s words, "walks, and talks, and flies like a passenger pigeon." I have no doubt that with enough effort an animal that is genetically identical to the passenger pigeon could through genome manipulation come into existence. By this I do not mean that what could be created would indeed be a passenger pigeon. I would suggest that what would exist under these circumstances is a simulacra of something that has never existed. No previous passenger pigeon existed in the wild without the learned behavior that comes from other passenger pigeons. Genetics, while undoubtedly a key component of what makes a species a species is not all that defines a specie’s existence on this earth. If we were to introduce them to the eastern United States it would be out of a desire to add a species of our own creation into an already humanized world.