Today marks six months since the Government announced an ambitious plan to rid New Zealand of pest predators by 2050. Now that scientists have had time to chew over the concept, is it possible, or even safe? The New Zealand Science Media Centre put the burning questions to top researchers.
1. The use of genetic engineering has been mentioned as a potential avenue to eradicate pests. What possible technologies does this encompass and how might these work?
"I suspect genetic technologies will be the key to developing pest control that is species-specific, works at a large scale, and is cheap and persistent," said Professor Neil Gemmell, of Otago University's Department of Anatomy.
Fundamentally, these would predominately focus on exploiting genetic weaknesses in a given species, and he suspected key areas to target would be around reducing reproductive potential.
"Prior work surveying people's view on issues such as possum control suggests that there is more public support for tools that might impair an animal's fertility compared with any other form of manipulation or control measure that may cause the animal harm and suffering."
The first target of eradicating a pest species by 2025 was only eight years away - and this was likely going to be hard to achieve, he said.
"If we start today we need six months to plan, likely several years in the lab, then a few years for controlled field trials, before eventual deployment at landscape scales, which will take massive effort and years to achieve eradication.
"This is the New Zealand version of the space race and we need commitment and resource to achieve this.
It was likely, Gemmell said, that a quasi-business/military model, as seen during the space race, might be needed to achieve this goal.
2. The announcement of the initiative came with additional funding; what sorts of technologies or programmes should be advanced to get an effective technology mix?
Landcare Research scientist Dr Andrea Byrom, who is director of the Biological Heritage National Science Challenge, said people often asked about the new technologies for killing pests or reducing their populations to extremely low numbers.
"There is no question that we will need new tools in the toolkit.
"For example, we will need to re-consider biological control, which is a catch-all term for approaches like causing infertility in mammals or using a virus to reduce a population to very low levels."
Byrom also noted the development of promising new methods such as gene drive technology - a new approach of breeding an all-male line into a pest population until eventually it declines to extinction with no females to breed with.
"This all sounds futuristic and scary to most people, but the reality is that there are many technological hurdles to overcome in the world's laboratories before we can apply these technologies in a field situation - many years down the track - and when we do take them to the field, we could trial them on a remote island first, which would guard against any risk of an unwanted organism escaping."
"I would prefer that we take a step back and consider the wider picture, and in my mind there are issues other than a technological 'fix' that are equally important.
"For example: will we need to alter legislation to allow the release of a virus or new organism into the environment?
"How should we make use of existing tools in the toolkit, as well as developing new ones?
"Should we begin with peninsulas or islands, and how should we 'roll out' predator-free status across the North and South Island?
"How will we respond to public concerns about new technologies?
"How will other pests respond when rats, stoats and possums are removed?
"And how can we incentivise the level of investment required to make PFNZ [pest-free New Zealand] a reality?
"All these questions point to the need for a 'whole system' approach: thinking about all the pieces of a gigantic jigsaw puzzle together rather than one piece at a time.
"But it will be worth it."
3. What are the barriers or risks to using genetic techniques to control pest populations?
"Take the risks of GMO crops and livestock, then imagine that the modified organisms will not be confined to field or paddock but will be released to range freely in the environment," said Professor Phil Seddon, of Otago University's Wildlife Management Programme.
"Environmental release of GMOs introduces new levels of risk and uncertainty, such as unanticipated expression of new genetic sequences, or the undesirable transfer of the modification to other species."
A major barrier would be public acceptance in the face of the "Monsanto effect", whereby GMOs are seen as being tied to big business and driven by corporate interests rather than having environmental and human health concerns a priority, he said.
But it was "essential" that genetic approaches gained social acceptance - which perhaps would be a bigger challenge than getting the technology right.
"We need a careful, controlled, early and successful case study to allay public fears and to demonstrate how environmental release of a GMO might be beneficial for conservation - perhaps getting rid of the mice on a small offshore island, where there are natural barriers to dispersal and the ability to apply conventional control to eradicate the mice should things not work out as planned."
"I think the general public might be more accepting of GMOs for conservation than some people think - we need to give an informed public a chance to consider the issue."
4. Has research so far pinpointed any risks with potential genetic control measures?
Assistant professor Kevin Esvelt, head of the Sculpting Evolution Group at the MIT Media Lab, who is leading a team developing gene drives, explained there were two basic kinds of gene drive: those that will affect a local population and then stop, and those that were likely to spread globally.
Standard CRISPR-based gene drives were extraordinarily efficient at copying themselves, so it took very few escaped organisms for them to spread.
"To be blunt, I am highly sceptical that these global drive systems can be reliably contained, and strongly recommend against their use for conservation," he said.
"Local CRISPR-based drive systems such as the 'daisy drives', which my lab are developing, are still early in development."
Esvelt added it was important to note that humanity had no experience engineering systems that could evolve outside of our control.
"We're developing nematode worms, which reproduce twice per week and are readily grown in the hundreds of millions, as a model in which to study gene drives in the laboratory.
"Since evolution is a numbers game, we need to run experiments on populations of comparable size to those we anticipate affecting in the wild to predict the behaviour of these systems once released."
CRISPR-based gene drive systems were "unfailingly" detectable by sequencing, spread slowly over generations, and were readily blocked and overwritten should something goes wrong.
"However, we haven't yet demonstrated a way to reliably restore populations to their original genomic sequences, though we're actively working on it."
5. How important is it that we get this right? What is at stake and how will New Zealand benefit from these outcomes?
"It's critical that we ramp-up our efforts to preserve our native species to prevent any more of them going extinct," said Dr James Russell, a conservation biologist at the University of Auckland.
"It's critical that we ramp-up our efforts to preserve our native species in order to prevent any more of them going extinct."
It was no longer enough to rely on conservation in the "back-country" in the face of pervasive threats such as invasive species and climate change, Russell said.
"It is, therefore, important that we find solutions for their conservation that have longevity and provide good returns on conservation investment.
"Otherwise, we risk wasting labour and resources."
"New Zealand had to make sure the programme was implemented properly, so that it didn't have unintended side-effects, or distract or delay from other urgent conservation issues."
It won't just be New Zealand's native species that benefit from PFNZ though.
"Benefits of eradicating these [pests] will also extend to primary industries - where invasive pests are vectors of disease - as well as offer boosts to tourism and public health.
"Generally, the economic benefits of eradicating these eight species are predicted to outweigh the costs, especially when you consider that we already invest millions every year in their control just to stay in a 'holding pattern'."
6. The goals for Predator Free NZ were ambitious but do you think it's possible for the project to meets its targets by 2050 using current methods and technologies?
"No, but ongoing improvements and wider use of current technology are essential to minimise short-term damage to vulnerable populations," said Professor Carolyn King of the University of Waikato.
"We must do whatever we can to protect what is left of our heritage from continuing stress, otherwise, by the time it becomes possible to achieve eradication, there may not be much left."
King said it had to be accepted that at this stage, pests removed could always be replaced.
"So pest control is like cleaning toilets, you just have to keep on doing it.
"Above all, it's important not to get carried away with ideas that turn out to be impractical, as these exhaust everyone's emotional capital and lead them to give up.
"There is no need to despair, only to be realistic, and patient."
King said the biggest challenge would be to accelerate fertility control or, if possible, render impossible any breeding and reinvasion of the pests removed.
"Killing pests is easy and getting easier - but the most important thing is not how many are killed, but how many were left, and how quickly those that are removed can be replaced.
"Preventing that is much more difficult, which is why we still have pests after centuries of throwing everything we can think of at them."
7. How important will public buy-in and support be to achieving the PFNZ goals?
Emeritus Professor of Ecology Professor Charles Daugherty, of the Victoria University of Wellington, said in many respects, public backing was the single most important key to success.
"New programmes to educate the public to understand the need for predator removal and the many benefits that will arise from doing so will need to be implemented in coming years."
Many schools were already contributing significantly.
"People often do not understand, for example, that doing nothing regarding introduced pest species is a decision to impose large ongoing costs on all New Zealanders - for example, on our national wealth arising from dairy, horticulture and tourism.
"Doing nothing is also a decision to violate our national and international commitments."
The New Zealand Biodiversity Strategy 2000-2020 committed New Zealand to stopping the decline of indigenous biodiversity.
New Zealand has been a party to the Convention on Biological Diversity since 1993.
"This commits us to the same goal - halting the decline in indigenous biodiversity, and predator control is a key element of achieving this goal.
"We have a simple choice as a nation: eradicate the most dangerous introduced predatory species, or accept that they will eradicate our native species.
"Only New Zealanders can save our rarest and most unique species which, like the kiwi, are often national symbols."