NO ONE can accuse New Zealand’s government of a lack of ambition for the country’s wildlife. Earlier this year it came up with a new plan to save what might be regarded as the planet’s most unconservable bird—a flightless parrot called the kakapo that is basically a ready-meal with feathers. Now, it proposes to top this by eliminating almost all ground-dwelling predators from the entire archipelago, thus making New Zealand safe not just for kakapos, but for myriad other creatures that evolved there unhunted until humans introduced rats, cats, stoats, possums and so on.

The project, “Predator Free New Zealand”, was announced on July 25th. It will be run by a public-private partnership similar to the one that looks after the kakapo. New Zealand’s taxpayers will seed it with NZ$28m ($20m) on condition that twice this sum is raised elsewhere. The objective is to eliminate three types of introduced predator—rats, weasels and possums—by 2050. To placate the country’s moggy lovers, cats are mostly off the list at the moment, though feral felines living on public land will be legitimate targets.

Eradicating introduced predators is not too hard on small islands, especially those uninhabited by people who might worry about the poison bait often used in the process. New Zealand itself has done so on more than 100 occasions—and the size of the islands involved has increased by a factor of ten during every decade since the 1960s. The country’s North and South Islands are, respectively, the 14th- and 12th-largest in the world, so the new project is certainly a bigger one than these previous eradications. But the North Island is 1,000 times the size of Campbell Island, the largest of New Zealand’s islands cleared so far, and the South Island is about 1,300 bigger. This means that if the tenfold-per-decade improvement continues, the target of 2050 looks within reach.

The plan is to proceed in stages. Between now and 2020 there will be a modest increase in the amount of land (currently 7,000 hectares) involved in existing predator-control schemes, a few new projects and a bringing together of various groups now ploughing separate anti-predator furrows. After that, things get more ambitious. By 2025 a further 20,000 hectares must, for the project to continue, be on the way to being predator-free. Crucially, this must be achieved without the use of fences, which are costly and sometimes impractical to build and maintain. On top of that, the plan envisages that there will, by 2025, be “a scientific breakthrough capable of removing at least one small mammalian predator from New Zealand entirely”. This done, it becomes a question of rolling out the lessons learned—first, in more isolated areas, and eventually everywhere.

Technical advances in predator elimination have certainly happened in the past. One such was the invention in 2009, by a New Zealand firm called Good Nature, of a self-resetting trap that abolishes the need to visit and reset mechanical traps each time they are sprung. One search for a future breakthrough is being conducted by Zero Invasive Predators, another public-private partnership. This outfit opened a research centre near Christchurch in June, with the intention of creating an “invisible barrier” made of repellents and lures that will combine to nudge target predators in the direction of traps laid out at regular intervals. Current prototypes require these traps to be set a maximum of ten metres apart—a density too high to be practical. But the group’s researchers hope to reduce this density as they get better at replicating compounds which predators are attracted to or repelled by.

Another, more speculative idea is to use genetic manipulation to interfere with predators’ reproduction. One research team at the University of Otago is working on a gene drive—encouraging a biased gene inheritance that would cause only sperm bearing Y chromosomes to be produced, and thereby create only male offspring. Another is working on a “Trojan female” technique of editing mutations that impair sperm function into mitochondrial DNA, which is passed on to offspring only by the mother. The idea is that as this DNA spreads through a population’s females, more and more of its males will be born sterile. Both of these suggestions aim to make the population extinct, one through a lack of females and the other via a lack of fertile males.

How much it will all cost in the end, if that ambitious end is achieved, is anybody’s guess. A recent study suggested the price of clearing Stewart Island, the country’s third-biggest, of predators could be NZ$25m. Extrapolating that to the whole archipelago arrives at a total of NZ$3.7 billion. However, the project is supposed to continue only if the requisite technical improvements are delivered, and those would certainly bring the cost down—particularly the idea of Trojan females, if that could be realised, for this is a solution that would spread itself.

The benefits, beyond the intangible ones of preserving the country’s unique and diverse flora and fauna (which include New Zealand’s famed symbolic bird, the kiwi (pictured), another flightless meal ticket), may come in ecotourism—and in a reduction of bovine tuberculosis, which is spread in New Zealand by possums. But in most New Zealanders’ minds it is the intangibles that count.