Risks may accompany gene drive technology

When it comes to genetic engineering for predator control,  proceed with caution, writes Colin Campbell-Hunt.

There is considerable excitement in the conservation community over the prospect of a technological advance that might  make the ambitious target of a predator-free New Zealand achievable.

Government ministers, too, are expressing enthusiasm for an innovation that could be a game-changer in our battle to protect New Zealand’s natural heritage.

But it will be some time before the potential of the technology is established, and its safety assessed.

The new technology works by altering the sex of offspring to produce only males. 

So-called gene drive engineering would gradually eliminate an entire population within a few generations through nothing more than the animal’s own reproduction.

Prof  John Knight (ODT, 10.10.16)  has set out the  advantages of the strategy over alternatives such as poisoning, trapping, or infections.

Many in the conservation community would probably agree with Prof  Knight that, if we are to make New Zealand predator-free, there may well be no alternative.

An editorial  (ODT, 4.10.16)  acknowledges  "there will be risks" but that, if genetic engineering is what is required to eliminate predators, then we should "be bold".

Non-scientists like myself may feel the need to understand  more about the risks that may come with this  technology.

The Royal Society of New Zealand is yet to complete its  assessment, but the US National Academy of Sciences (USNAS)  recently published its assessment of gene drive engineering.

Some key points from it should be part of an informed debate.

First, gene drive technology is still at an early stage  of development.

As of June this year,  four successful laboratory studies have demonstrated  its effectiveness in yeast, fruit flies and mosquitoes.

Further "proof of concept" studies will be needed to show  it will be effective in the species of concern to us: stoats, rats, possums etc.

Second, the USNAS tells us "research on the molecular biology of gene drives has outpaced research on population genetics and ecosystem dynamics, two fields essential for assessing the efficacy of gene drives and their biological and ecological outcomes".  

As a result, there are "considerable gaps in knowledge" on the potential for unintended effects, both within the organism (off target outcomes), and to other species (non-target outcomes).

Where proponents of gene drive engineering argue  its lethal effect is specific to the target species because (with rare, unsuccessful exceptions) species do not mate with each other, the USNAS says  the risks of unintended consequences must be considered, "especially in regard to the risk of transfer to non-target species". 

What this means is  the science on the outcomes of releasing gene-drive engineered males into the environment does not yet know enough about what those outcomes will be.

Only when some of these are identified, and a probability estimated, will we be able to speak of risks.

As things stand,  too many outcomes  are simply unknown.

Third, a better understanding of the effects of gene drive engineering on the target species and its environment, including unintended consequences, must be a prerequisite to the next stages in the development of the technology: taking it out of the lab, into field trials, and possible eventual release into the environment.

That understanding will be specific to each target species; it will differ between a stoat and a possum.

Each stage must be managed, step by step, with a "robust method to assess risks" and strong regulatory oversight.

The USNAS does not believe  the environmental impact assessments used in the US will be adequate to the task.

They believe these assessments must compare predicted outcomes and estimated risks with alternative strategies, and  assess these against society’s valuations of the benefits and tolerance of risk.

For  New Zealand, this could end up accepting  the risks of complete predator removal through gene drive engineering are just too high.

It is encouraging  Conservation Minister Maggie Barry is asking for an assessment of several strategies for reducing predator numbers.

In this case, lower-risk less extreme strategies may end up being the better bet.

And perhaps  some in our society  will take a less calculating approach to justifying use of gene drives.

Is this in fact the first time in human history that we have turned the act of creating life into the instrument for the destruction of an entire population or species?

No doubt  people captured by the potential of gene drive technology will be frustrated at these cautions.

But in a country with a long history of discovering too late the unintended consequences of ecological engineering — rabbits, possums, stoats — some caution is surely justified.  

The overall conclusion of the USNAS is that "although there is insufficient evidence available at this time to support the release of gene-drive modified organisms into the environment, the likely benefits of gene drives for basic and applied research are significant and justify proceeding with laboratory research and highly controlled field trials".

There is no justification yet for scaling back our current efforts to reduce predator numbers with every tool that we have available. 

At Orokonui, our science advisory body, the Orokonui Knowledge Group, is conducting its own assessment of the strategies now available.

We certainly do not intend to sit waiting for a white knight that may never come.

- Colin Campbell-Hunt is chairman of the Otago Natural History Trust (Orokonui Ecosanctuary).


While the writer of this article has done a reasonably good job of pointing out the major issues, their viewpoint is the typical kiwi attitude toward genetic engineering; fearful and mistrusting.

Honestly, New Zealand is one of the best testing grounds for releasing a gene drive into an mammalian/marsupial population. We are isolated, and except for rats and mice (which could escape on ships) our major predator species have little chance of escaping or interbreeding with closely related species. Gene flow to closely related species is a danger elsewhere, and why the USNAS warned against gene drives hopping species, But this danger is nonexistent in NZ, because there are no species that are even remotely related for the genes to flow to.

Mice and rats are something we should be careful with, due to the possibility of the gene drive escaping on docking ships, but realistically, there is little reason for New Zealand to prioritise rats as there are other places that will be developing and testing for rats too (Hawaii, etc.).

Target species in NZ, in order of priority would be possums/stoats, rats/mice (with precautions), feral cats, rabbits, and possibly goats/deer.

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