Just as novel ecosystems challenge conservation thinking, so does the expansion of our ability to synthesize nature. Conservationists are facing new appeals to adopt bold approaches embracing advances in genetic technologies (Piaggio et al., 2016). These advances offer a vast array of putative technological applications for addressing conservation problems. But none have grabbed as many headlines as proposals to use cloning and gene-editing techniques (notably CRISPR-Cas9) to resurrect extinct species, in a new field known as de-extinction.
We do not yet share the planet with any creatures created through de-extinction. But, if current trends continue, one day soon we will (Folch et al., 2009). Lets assume that when that day comes our goal is to use de-extinction to help ecosystems and not just create zoo curiosities. How might de-extinction help? One driver of novelty in ecosystems the loss of ecosystem function due to extinction. If we could restore lost species to landscapes then we should also be able to restore the ecological functions they provided, right? The highly speculative nature of de-extinction makes it hard to draw meaningful conclusions about how well this would work. But one thing seems clear — de-extinction will have little ecological value to offer if we target the wrong species. Choosing de-extinction candidates wisely could make the difference between restoring a valuable ecosystem function and creating an “eco-zombie” (McCauley et al., In Press). Writing in the journal of Functional Ecology, McCauley and his co-authors give some guidelines for selecting de-extinction candidates most likely to restore ecosystem function. How does the list of current and proposed de-extinction projects line up? Lets hope eco-zombies don’t have an appetite for brains.
Proposed candidates for de-extinction exhibit obvious biases. They are mostly furry, feathered, terrestrial and include many long-lost but iconic species such as the mammoth, Tasmanian tiger, passenger pigeon and, more recently, the dodo (McCauley et al., In Press; Seddon et al., 2014). McCauley et al.’s guidelines do not identify “charismatic” as a criterion for species selection. Yet ecologically important but less beloved groups of species, including many marine and invertebrate species, are all but entirely ignored by de-extinction enthusiasts. Well then, according to the guidelines, how do we choose wisely? First, avoid species that went extinct a long time ago. The adage “absence makes the heart grow fonder” does not apply to ecosystems. When a species disappears, the ecosystem moves on and the remaining species settle into new relationships. And if a reintroduced species has been gone too long, there may no longer be a suitable niche for it to occupy.
Martha, the last passenger pigeon, skinned. Courtesy of R. W.Schufeldt/Wikimedia Commons
The guidelines also advise choosing species that provided unique ecosystem services — a characteristic common among marine species, for example. Finally, it is important to be mindful that some species only provide an ecological function when restored in very large numbers. The abundance-dependent nature of the passenger pigeon’s ecological impact, for example, would present a steep barrier to restoring ecosystem function. Unlike a top predator, such as wolves, which can provide an important ecological function with a relatively small number of individuals, the passenger pigeons would require millions or even billions of birds.
Even if one strictly adheres to these guidelines, there remains room to question whether releasing de-extinct creatures onto wild landscapes amounts to restoration. One might argue that de-extinction creates novel organisms not familiar to any landscape. Many argue, and I would tend to agree, that de-extinction would create a new and distinct class of beings rather than the biological and behavioral equivalents of extinct animals (Martinelli et al., 2014). In its draft report, Guiding Principles on De-extinction for Conservation Benefit, the IUCN (World Conservation Union) Species Survival Commission refers to species created through de-extinction as “proxy species,” rather than regarding them as faithful recreations of the extinct animals’ original forms (IUCN/SSC, 2016). Many authors have begun following IUCN’s lead in acknowledging the novel character that would distinguish these creatures from their extinct ancestors, referring to them as proxy species, or similarly “ecological proxies” or “analogues” (e.g. Adams, 2016; McCauley et al., In Press; Piaggio et al., 2016; Shapiro, 2016).
Why might the creatures we make through de-extinction be different? First, de-extinction requires another species to donate an “empty” egg cell and serve as a maternal host. Consequently, the resulting clone’s mitochondrial DNA, microbiome and epigenetics won’t match that of the extinct ancestor (Friese, 2013; Shapiro, 2015). And for long-extinct species (e.g. mammoth, passenger pigeon, Tasmanian tiger), departures from extinct ancestors will be much greater because we must piece them together using incomplete DNA fragments. Finally, who would teach these novel creatures how to find food, migrate, communicate and care for their young? But perhaps these differences are less ecologically consequential than we might be inclined to think.
In a “TEDxDe-extinction” conference talk in 2013, conservation biologist Kent Redford challenges the significance we attribute to species purity.
As he points out, the bison repopulating plains in Western U.S. are ‘tainted’ with cattle genes. Yet they retain behaviors responding “to fire and grazing and predators like bison,” and defending “their calves from wolves like bison.” And the same goes for wolves, which are sometimes tainted with domestic dog genes but are still “taking down elk, [and] re-arranging energy flows” with top-down predatory behaviors.
Unsurprisingly, Redford does not suggest that we start referring to “proxy” bison or wolf “analogues.” Yet in a recent article, Redford and his coauthors describe de-extinction as “creating a proxy species that hopefully fills the same ecological role as the extinct species” (italics added) (Piaggio et al., 2016). Proxy probably won’t displace “de-extinction” anytime soon. But perhaps its growing use signals an increasing recognition for the need to ground the hyperbolic rhetoric that has emerged around this technology. And perhaps a recognition for the need to adopt vocabulary that will set proper expectations about its promise for addressing ecological and biodiversity problems.
~By Patrice Kohl~
Adams, W. M. (2016). Geographies of conservation I De-extinction and precision conservation. Progress in Human Geography, 0309132516646641.
Folch, J., Cocero, M. J., Chesné, P., Alabart, J. L., Domínguez, V., Cognié, Y., . . . Vignon, X. (2009). First birth of an animal from an extinct subspecies (Capra pyrenaica pyrenaica) by cloning. Theriogenology, 71(6), 1026-1034. doi:http://dx.doi.org/10.1016/j.theriogenology.2008.11.005
Friese, C. (2013). Cloning wild life: zoos, captivity, and the future of endangered animals: NYU Press.
IUCN/SSC. (2016). Draft IUCN SSC Guiding Principles on Creating Proxies of Extinct Species for Conservation Benefit. Gland, Switzerland: IUCN Species Survival Commission.
Martinelli, L., Oksanen, M., & Siipi, H. (2014). De-extinction: a novel and remarkable case of bio-objectification. Croatian Medical Journal, 55(4), 423.
McCauley, D. J., Hardesty‐Moore, M., Halpern, B. S., & Young, H. S. (In Press). A mammoth undertaking: harnessing insight from functional ecology to shape de‐extinction priority setting. Functional Ecology.
Piaggio, A. J., Segelbacher, G., Seddon, P. J., Alphey, L., Bennett, E. L., Carlson, R. H., . . . Wheeler, K. (2016). Is It Time for Synthetic Biodiversity Conservation? Trends in Ecology & Evolution. doi:10.1016/j.tree.2016.10.016
Seddon, P. J., Moehrenschlager, A., & Ewen, J. (2014). Reintroducing resurrected species: selecting DeExtinction candidates. Trends in Ecology & Evolution, 29(3), 140-147.
Shapiro, B. (2015). How to clone a mammoth: the science of de-extinction: Princeton University Press.
Shapiro, B. (2016). Pathways to de‐extinction: how close can we get to resurrection of an extinct species? Functional Ecology.