By Helen Taylor 09/05/2017

Most research on de-extinction focuses on the technology behind making it happen. It’s refreshing to see a group of conservation scientists examining what happens when you release these species into the wild.

What comes after de-extinction?

The latest issue of the  journal Functional Ecology has a special feature on de-extinction.

Unless you’ve been living under a rock, you won’t have missed the media excitement around so-called de-extinction projects recently. I’ve even shared my (largely cynical) thoughts on the topic on this very blog. Interestingly, almost all the conversation and research around de-extinction focuses on how we can bring these creatures back. The science of de-extinction gives little consideration to what happens after that is achieved, but the conservation implications are huge.

If we release resurrected species into the wild, then this is essentially a conservation re-introduction. Professor Phil Seddon at the University of Otago specialises in re-introduction biology. He believes the process is far more complicated than “step 5, release your mammoth”. No-one is giving much consideration to this though.

Now, in a special issue of the journal Functional Ecology, Phil has brought together a series of papers from prominent conservation scientists (including several NZ-based researchers). Across six papers, they discuss the various issues around releasing resurrected species into the wild.

On the genetic backfoot

Chatham Island black robins suffer from inbreeding depression
This Chatham Island black robin has just heard how inbred he is (Image credit: DOC)

A key issue for post-de-extinction release is genetic diversity. Any population founded with a small number of individuals (de-extinct or otherwise) is going to face difficulties with low genetic diversity and a high likelihood of inbreeding. We know this only too well from extant New Zealand species like kiwi, takahē, kākāpō, and Chatham Island black robin.

It’s also difficult to see how resurrected individuals could contain all of the genetic diversity previously held by their species. Especially when we don’t always know what that diversity was outside of whatever museum samples we can gather. Gene-editing could help address this problem. However, it’s clear that there are some big hurdles to creating a genetically diverse population of a resurrected species. If it’s not genetically diverse then the species will struggle to respond effectively to environmental challenges such as disease events and climate change.

Re-integrating into the ecosystem

There are also some ecological challenges to overcome for the release of resurrected species. Many of the ecosystems these animals used to live in have been heavily modified since extinction. It’s possible that these genetically engineered proxies for extinct species could fill important gaps and restore ecosystem functions. But they could also have unexpected impacts. Who can say what effect a resurrected moa would have on the roughly 2,400 naturalised exotic plant species currently in New Zealand. Importantly, do we need de-extinction to restore ecosystem function when extant species could also fill the gaps? Introduced tortoises from the Seychelles have taken over the grazing and seed dispersal functions of the extinct giant tortoise of Mauritius, for example.

Extinct parasites are an important part of the ecosystem
De-extincted trematodes anyone? (Image credit: NZ Geographic/TRANZ)

Resurrected species would play a far greater role in an ecosystem than consuming food. All animals represent their own ecosystem, containing communities of microbiota – bacteria, fungi, and microbes – as well as parasites. These micro-communities are often highly species specific. What happens if we resurrect a species, but not its parasites, for example? This could lead to compromised immune system function for the resurrected species.  Alternatively the resurrected species might acquire parasites from closely related species. This could mess up the transmission dynamics and potentially cause issues for the original host species. These are all hypotheticals, but they are not generally considered in discussions around de-extinction.

Who should win the de-extinction lottery?

Mammoths = too cool for school
Mammoths: inherently cooler than any other de-extinction candidate. (Image credit:

Finally, which species are selected for de-extinction attempts requires careful consideration using a proper decision-making framework. This framework would take into account risks, feasibility, and likely post-release outcomes and costs. The theme across the papers in Functional Ecology is that the best de-extinction candidates are those we lost recently. We know more about their biology and ecology. The ecosystems they once inhabited have undergone less change. So mammoths and moa are out. Yet research on creating functional proxies of these species continues because it’s cool. Sadly cool and conservation do not always go hand in hand. Just ask conservationists who try to get people to care about bugs, plants, or (worse!) lichen.

She’ll be right?

It’s perhaps not surprising to see kiwi scientists taking the lead on a pragmatic approach to de-extinction for conservation. New Zealand sadly is the backdrop for numerous, relatively recent extinction events and home to a whole bunch of species hanging on at the brink of extinction. Conservation scientists in this country are also keenly aware of what happens when we don’t properly consider the consequences of a conservation intervention (remember those stoats we introduced for rabbit control?). It will be interesting to see how this message plays with the de-extinction crowd. It would be great to see those involved properly considering what happens after you release your mammoth.

For more detail, see Phil Seddon‘s, Tammy Steeves’ and Jamie Woods’ Sciblogs guest posts on this topic.