Comment permalink

A gene drive is key to achieving a predator-free New Zealand, writes Prof John Knight.

Your editorial "Saving kiwi by being bold" (ODT 4.10.16) includes the statement that "a genetically engineered solution would likely be needed to reach the 2050 target".

I fully agree.

However, the statement attributed to  the Department of Conservation that one possibility is "editing animals' genes to instil infertility throughout an entire population" seems to be a misconception.

Animals that are infertile will leave no offspring.

So how will this spread?

In contrast, animals that are fully fertile but produce only male offspring will drive this character through the population and eventually cause it to crash.

Foreign invaders such as mice, rats, stoats, rabbits and possums are indeed a scourge that is destroying New Zealand’s unique native bird species, devastating farmland and costing New Zealand hundreds of millions of dollars every year.

We need to develop new methods that have the capacity to eliminate species of pests entirely.

Reaching an endpoint seems unlikely to happen if we rely on poisons, diseases, traps, shooting, or other conventional methods.

Disease-resistant, bait-shy, trap-shy, animals will always survive and outbreed those that succumb.

Darwin coined the term "survival of the fittest" to explain this.

We all know the problem.

We have a 1080 drop, or introduce RCD, and a few years later the pests are back.

In 1967, the great evolutionary biologist W. D. Hamilton postulated in science a situation where the male-determining Y-chromosome mutated in such a way that Y sperms always win the race to  fertilise.

Males carrying such chromosomes would produce only sons.

Hamilton argued that such a characteristic would drive through the population until eventually the population would crash, through lack of females.

Prof Rob Knight, a New Zealander based at the University of California San Diego, is keen to co-ordinate an international effort to help solve this massive problem facing New Zealand.

Dunedin-born, in the 1990s he proposed using gene drive to eliminate mammalian pests from New Zealand. Five attempts have been made to gain funding for this research. Supportive comments include: "The potential for this revolutionary approach is enormous as it eliminates the constraints of Mendelian genetics ... would be game-changing ... to transform our approach to vertebrate pest control and move beyond our traditional reliance on mechanical devices like traps and chemical toxicants, into a space where genetic options can be added to our toolbox. it would be irresponsible of us to ignore what we might do here in the small mammal pest control space." — Dr Geoff Hicks, then chief scientist, Doc.

Edward Ellison, chairman of Te Runanga o Ngai Tahu HSNO Komiti "has a long-standing interest in the development of sustainable methods of vertebrate pest management. In the long-term, reliance on the use of toxins or traps to protect endangered taonga species is neither desirable nor feasible. We support in principle novel approaches to pest control".

"The gene drive proposal provides the greatest hope for turning back the relentless and debilitating tide of invasive mammalian pests in New Zealand."— Emeritus Prof Sir Alan Mark

Despite these and many other highly positive assessments, it has never been funded, blocked by anti-GM nay-sayers. It was deemed "too risky", in terms of upsetting people who feared genetic engineering. Never mind the risk of doing nothing, or of dropping 90% of the world’s production of 1080 poison out of aircraft — and hoping. Most now accept GM medicines such as human insulin and vaccines. Most concerns are about food. Using gene editing to combat serious pests should be acceptable.

Rob Knight’s PhD in evolutionary biology from Princeton on "The Origin and Evolution of the Genetic Code" won a prize for best PhD thesis in life sciences in the United States.

Now professor of computer engineering and director of the  Centre for Microbiome Innovation at the University of California San Diego, he really wants to help New Zealand solve this problem. He has enlisted world experts in mammalian reproductive genetics and gene drive to help, in collaboration with researchers at the University of Otago (Prof Warren Tate,  Prof Hamish Spencer, me).

The first requirement is modest funding to identify the most suitable genetic target to edit, using a new technology that makes it more feasible to drive a population of pests extinct.

The CRISPR-Cas9 gene drive system could be used to engineer males that produce only male offspring.

These males will in turn mate with females in the wild, and only produce male offspring.

Eventually the wild population will be eliminated through lack of females.

Carrier animals would need to be spread around.

Then they will do the job themselves, by having sex.

No animal cruelty, no toxins, no risk of spreading to other species, since this can only spread by copulation.

Stoats, rats and possums can’t mate with kiwis, bats, or sea lions.

Because the effect will be gradual, predators such as stoats and ferrets, that depend on target species such as rats and rabbits, will slowly diminish in numbers, so prey-switching to birds will be  minimised.

If aiming to achieve a predator-free New Zealand really is to be our "Apollo Project" (as envisaged by Sir Paul Callaghan), then we really do need "rocket science" to achieve this goal of reaching the "moon".

John Knight is a professor in the marketing department of the Otago School of Business at the University of Otago. He has a special interest in innovation, particularly biotechnology.


Gene drive is our best hope or worst fear? Part of the fear comes from the unknown. What is required is a very extensive public education effort to explain to people what gene drive is, how CRISPR works and what are the ethical issues. For pest control the objective would be to produce only male offsprings and thereby control the population.

Being an island nation, we are ideally situated to use this method — we have been bold with innovation before — here is our chance again.

For more information, see:

James Kalmakoff
Former Director
Centre for Gene Research
University of Otago

This was a super interesting article. I'm very interested in biodiversity protection and pest control, but am anti-GM on the whole (you're right, food is my main concern). What I love about this proposal is that it's self-limiting. The fact that it's GM but that the genetics will die out within a few generations is quite appealing, and I assume no trace would be left in eradicated areas.

My only concern would be whether there are any unintended consequences (and I guess the problem with that is that they can't be predicted, so no-one can satisfy me or others that there is a 0% chance of something going awry and creating say, a super predator that breeds twice as fast).

Still, I think this technology is quite possibly the magic bullet that will enable NZ to reach it's ambitious predator-free status within the time frame sought. Nice work. I hope the necessary funding becomes available. Perhaps a chat with Gareth Morgan and the NEXT foundation should be in order?