A new report is giving hope to conservationists hoping to stem New Zealand’s biodiversity crisis

It’s been five years since the Government launched its ambitious goal of ridding the country of rats, possums, and mustelids by 2050. 

The programme aimed to move from piecemeal local projects to a strategic nationwide approach for eradicating the three worst offenders to our biodiversity.

Five years on, the programme is taking stock and reflecting in its first progress report, released at a summit in Wellington last week.

The report shows good progress on five of the seven goals the plan set to achieve by 2025, with one not likely to be achieved in that timeframe and the other not having enough data.

The past five years have also seen the start of 19 landscape-scale predator eradication projects, with six more currently in the planning stages.

These include projects across the country covering areas from Whangārei, to Waiheke, to Aoraki/Mt Cook. Some deal with urban landscape such as Predator Free Dunedin, while others like Pest Free Banks Peninsula include farm land.

One of the first to be funded was Taranaki Mounga, a project to secure 34,000 hectares of Taranaki mountain, ranges and islands from pests.

Director Jan Hania says the project aims to be a model for how pest eradication can work on a large scale.

Taranaki maunga. Photo: Rodney Allen

“We want to be an example of what’s possible,” says Hania.

“This is more than just a conservation project, this is about people connecting with our land.”

The update report shows that one of the programme’s major goals – an increase in suppressing predator species by one million hectares – has already been achieved.

Suppression generally involves trapping, poison and other control methods that bring pest numbers down to a level where they do less harm.

Eradication, on the other hand, gets rid of an entire species forever.

“It’s a bit like poker,” says Sarah Wilson, project leader for Pest Free Banks Peninsula.

“First you play your easy cards that can knock the animals down. From there you can move on to your power plays.”

For Wilson’s project on Banks Peninsula, the power plays include using hunters and trained dogs that can track the predators by smell.

They also include technology like virtual fences, where predators are kept out through an array of traps interspersed with infrared and thermal cameras.

Wilson says getting to predator-free status by 2050 is going to take every trick in the book, including some not invented yet.

“These are really clever animals and they eventually figure out that they are being targeted,” she says.

So far the Government has spent $300 million on predator-free projects, with funds often being matched by local government, mana whenua and community organisations.

The ambitious target was launched in 2016 to deal with what the Government described as a biodiversity crisis in New Zealand.

Its estimate that around 68,000 native birds are killed by introduced pests every night equates to about 25 million birds lost a year.

Native birds such as ruru and kōkako are vulnerable to rats, stoats, feral cats and possums, while lizards and invertebrates are vulnerable to rats, hedgehogs and mice.

The result is that almost 3000 native land species, including kiwi, kākāpō, and hoiho (yellow-eyed penguin) are now threatened with extinction.

That includes nearly 90 percent of seabirds, such as the tara iti (fairy tern) and toroa (albatross), and 84 percent of reptiles, including tuatara and moko kakariki (green gecko).

Without further intervention the situation is likely to get worse, with the extinction risk increasing for 86 species over the past 15 years.

The five-year update outlines four goals that, while not yet delivered, are on track for their 2025 target.

These include eradicating predators in an unfenced area of at least 20,000 hectares on mainland New Zealand, eradicating possums or mustelids from at least one city, and producing tools and education for removing pests from farmland.

They also include starting five mana whenua-led eradication projects, with the Ngāti Awa-led Korehāhā Whakahau project to eradicate possums from 4700 hectares of land within the rohe of Ngāti Awa already underway.

Students at Waitara East School learn about identifying pests through the Taranaki Mounga project. Photo: Denis Welch.

However, the report also accepts that the goal of eradicating mammalian predators from all of New Zealand’s uninhabited offshore islands is unlikely by 2025.

While over 110 uninhabited islands are now predator-free, the Department of Conservation says the size of the remaining islands such as subantarctic Auckland Island means eradication will take more time.

As for the final goal, to develop a breakthrough scientific solution that will eradicate at least one mammal predator from the New Zealand mainland, the report says not enough data is yet available.

However, it is this goal that may prove the most crucial.

Earlier this year, research from the University of Auckland suggested that the 2050 target may be unachievable without the help of major technological advance.

Researchers modelled the chances of eradicating rats on New Zealand’s offshore islands and found that just 14 out of 74 islands modelled were likely to be rat-free by 2050.

Fortunately, a number of projects are already underway to develop new methods for eradication.

Some of the most promising ideas include genetic tools that could create “trojan females” producing infertile male offspring. Others include species-specific poisons like norbormide that could be used to target rats only.

Ben Leonard writes on Treaty issues and the environment.

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