New Zealand's war on predators commemorated this week

Possum and rat predators. Photo / Nga Manu Images

The start of a war will be commemorated this week -- one waged not on foreign battlefields, but across our own offshore islands.

A day-long symposium to be staged in Auckland today will look back on the sprawling, decades-long struggle to clear introduced predators from our island and save our cherished native species.

Auckland University ecologist Dr James Russell, helping organise the event, said Kiwis could be proud of the progress made.

In 1964, when the late Don Merton and fellow conservationists declared Maria Island in the Hauraki Gulf free of troublesome Norway rats, the area of our islands clear of mammalian predators stood at about 0.5 per cent.

Today, the rate is 10 per cent.

Over 90 per cent of our smaller, natural reserve islands have been cleared, most recently Campbell Island and Secretary and Resolution Islands.

These offshore strongholds provide safety for a diverse range of native species, including the kakapo, takahe, tuatara, hihi, black robin, tuatara, two key species of weta and New Zealand's largest living lizard, the Duvaucel's gecko.

Gold standard

"Although 10 per cent is a small number when we compare it to things like targets for marine reserves, it's still very impressive," Dr Russell said.

"It's something that any other country in the world would look enviously at."

According to Department of Conservation biologist Dr David Towns, they do.

New Zealand was viewed internationally as the "gold standard" for island management, he said.

"A lot of people come here to learn how to do it, so we can use the same techniques themselves, or hire New Zealanders to do it for them."

Biggest challenges still lay ahead

While our track record of predator eradication, covering literally hundreds of islands, was something we could take pride in, he said the biggest challenges still lay ahead in the bigger islands.

These included D'Urville, Great Barrier, Chatham, Stewart and Auckland islands, with each having their own strategic problems.

Kakapo, being conserved on several islands under an expensive programme, had originally been moved from Stewart Island.

Returning them there after eradication was really the most logical solution, Dr Towns said.

"As far as Great Barrier is concerned, there are a bunch of species out there that are quite rare, so if we are ever going to deal with those, the logical place to do it is on the island itself."

Because of its smaller size, Great Barrier appeared an easier option than Stewart Island for the next big push -- yet its scattered population made the more compactly-settled Stewart seem a better choice.

Whichever way the battle turned, continuing it would demand funding, capability and public buy-in.

On the whole, 45 per cent of the country is under some form of predator management, but just 0.25 per cent of this is considered adequate.

Landcare Research scientist Dr Jane Byrom believed it possible that within her lifetime, she could see realised the dream of the late Sir Paul Callaghan -- a vast network of fenced sanctuaries across mainland New Zealand, booming with birdsong.

"The bigger question is a completely predator free New Zealand," she said.

"I don't think that will happen in my lifetime, or even my children's', but I think it's important for future generations that we think about building native biodiversity back into landscapes."

Next article: Plastics may pose a greater threat than climate change