New Zealand's dream to be pest-free by 2050 will remain just that - a dream - if new technology like genetic tools aren't thrown into the fight, scientists warn.
Just as importantly, they say the public needs to be fully behind the predator-free mission.
University of Auckland researchers modelled whether New Zealand could be kept free of rats which, alongside possums and stoats, are targeted for elimination under the bold Predator Free 2050 plan.
Typically, the "time-to-event" analysis they drew on investigates how different therapeutic treatments will affect the lifespan of a patient suffering from a life-threatening disease.
But in this case, they used it to explore how different factors were likely to affect the amount of time a New Zealand island was invaded by rats.
They fed their model with a wide range of island data including size, distance to the mainland, public or private ownership, human habitation and whether rats had already been eradicated.
Islands were then ranked for the likelihood of rat eradication success and how long it might take to get underway.
The results were sobering.
Just two out of 18 highest-ranked islands in the model – the ones with the highest chance of eradication success – would be rat-free by 2025.
Overall, just 14 out of 74 islands were likely to be purged of the vermin by 2050.
If New Zealand's rate of eradication implementation continued as is, the country would not be rat-free anytime in the foreseeable future, said doctoral student Zachary Carter, who led the study.
"Our results should be viewed as an examination of Predator Free 2050's potential outcome if transformative eradication advances are not made.
"Fortunately, universities, government researchers and private enterprise are already involved in exploring new and exciting transformative technologies to overcome limitations in the existing eradication toolbox and they will be essential to PF2050's success."
Those new technologies include genetic tools which could produce a "Trojan female" whereby all male offspring are infertile, and species-specific toxins, such as norbormide, which could be highly effective and target only rats.
Social impact assessments, like those developed by University of Auckland conservation biologist Associate Professor James Russell, would also be critical.
"Advances in both technology and in attaining community buy-in that are more effective than what we have had in the past will be vital and they will need to be if we are to increase the rate at which projects succeed," Carter said.
It wasn't the first time experts have warned keeping with the status quo wasn't enough to deliver New Zealand its 2050 goal, which was set under the previous National-led government.
One 2019 scientific review also found current approaches wouldn't be enough.
While it singled out some genetic techniques, the most promising ones today might not be so a decade or two from now.
It also similarly found the ability to effectively reverse some of the new technologies could be critical to gaining public acceptance - not to mention stopping them from wiping out species in other countries where they weren't considered pests.
Despite calls from some conservation heavyweights, including the late Sir Rob Fenwick, the Government has largely held off pursuing genetic solutions.
The Government's current strategy focuses on three steps: mobilising groups and setting up collaborations around the country; developing "new and transformational tools and techniques" that will be required to eradicate the pests; and then applying these at scale across the countryside.
It wanted to see a "breakthrough science solution" capable of removing at least one small mammal predator from the mainland.
But the plan didn't go as far as singling out gene editing, which carried the potential to knock down populations by boosting the chance of certain genes being inherited, or by "silencing" gene sequences unique to particular pest species.
An accompanying action plan to the strategy set out seven specific goals for 2025: among them, increasing by one million hectares the area of New Zealand where predators were suppressed and proving that they could be wiped out and then kept out of at least 20,000ha of mainland countryside.
By 2025, the Government also wanted to finish the job of clearing all of our islands – one that was started more than half a century ago – and to have driven possums or mustelids like stoats out of at least one city.
The rats, possums, stoats and mice that infest our wilderness are today responsible for the slaughter of some 26 million native birds every year.
Almost 4000 of our known native species – among them kiwi, kākāpō, kōkako, Maui's dolphin and yellow-eyed penguins, or hoiho - are now threatened with extinction.
Remarkably, that includes 90 per cent of seabirds, 76 per cent of freshwater fish and 84 per cent of reptiles, along with 46 per cent of vascular plants.
Statistics show the extinction risk has worsened for 86 species in the past 15 years - compared with the conservation status of just 26 species improving in the past 10 years