About 100 flightless kiwis and other rare native species have been resettled in a pioneering sanctuary in the suburb of Karori, just two kilometres from the centre of New Zealand's capital city, Wellington.

The birds can come and go as they please from a 2.5 km² reservoir valley flanked by hills covered in regenerating forest. But an 8.6-kilometre-long, fine-mesh fence winds over the hills to keep out the introduced mammals that have decimated the antipodean nation's unique fauna over the last 800 years.

University of California biologist, Jared Diamond, once described New Zealand as the closest we could get to studying life on another planet because its environment had developed in isolation for up to 85 million years.

But nearly half of all the native bird species have disappeared since the arrival of the first human beings, dogs and rats around 700 years ago.

THE KARORI SANCTUARY IS UNIQUE in being inside the city and for being the first mainland refuge to succeed in eliminating introduced pests.

None of the birds have clipped wings and nearby residents can see some of the world's rarest species feeding in their gardens. Karori is also one of the few New Zealand sanctuaries which is easily accessible to visitors.

"You can't find another sanctuary anywhere else in the world that is so close to the middle of the city," says sanctuary CEO, Nancy Ward.

When the reserve idea was first mooted during the 1990s and a community trust set up to transform the former city reservoir, many thought it would fail. "There was lots of cynicism at that stage, people saying it won't work," Ward said. "They were saying that the birds wouldn't stay and you couldn't keep the pests out."

But the critics have been proved wrong. Thirteen different species of introduced animals, which prey on native species and their young or compete with them for food, were eradicated over two years. Gone are stoats, weasels, feral cats, rats and the Australian possum among others.

"The people can actually see the benefit. Wellington is the only city in New Zealand with an increase in native bird life," she said.

Fifteen native species have been introduced into the sanctuary. Some like the stitchbird (Notiomystis cincta), little spotted kiwi (Apteryx owenii), and North Island saddleback (Philesturnus carunculatus) are extinct elsewhere on the mainland of the North Island.

So too is the tuatara (Sphenodon), which looks like a dinosaur in miniature and is the last surviving species of a family of lizard-like creatures which flourished 200 million years ago.

ANOTHER DINOSAUR-ERA SURVIVOR brought to Karori is the weta, which comes from the word native Maori word wetapunga – the god of ugly things. It lives up to its name – an oversized cross between a large flightless cricket and a cockroach. The giant weta (Deinacrida) species grows up to 10 cm long and can weigh more than a sparrow.

Kevin Hackwell, advocacy manager for conservation group, the Royal Forest and Bird Protection Society of New Zealand, based in Wellington, says the Karori sanctuary has been an inspiration to the conservation cause.

"It has led to an explosion of mainland island reserves, both fenced and unfenced," he said. "It brought a heap of species back to the mainland that weren't there – it's fabulous people now have saddlebacks in their garden."

Karori is part of a last gasp effort to save some of New Zealand's most endangered species.

Until recently many of the surviving native species – including the kiwi (Apteryx spp.) – were marching towards extinction. An astonishing 40 per cent of bird species have disappeared since Polynesians arrived in the 13th century, followed by Europeans 600 years later. But the eradication of introduced pests from a number of offshore islands, and more recently the development of a few fenced mainland reserves, has halted the slide.

WHAT MAKES NEW ZEALAND ANIMAL LIFE UNIQUE and so vulnerable was the absence of mammals – except for bats –prior to the arrival of humans. Over around 85 million years, New Zealand developed in isolation after its land mass split from Australia and Antarctica.

Grazing grasslands and forests, the world's largest bird, the moa, grew up to 3.6 metres tall and weighed as much as 250 kg. The moa's only predator was Haast's eagle (Harpagornis moorei), which had a wingspan of three metres and claws as big as a Bengal tiger. Both were among the early casualties of the arrival of the Maori, who had hunted the moa to extinction by about 1400.

In the absence of predatory mammals, many birds like the moa and kiwi gave up flying. To compound the problem of introduced predators, many bird species were fearless, making them easy. Early European hunters reported being able knock birds off branches with a stick.

The world's largest parrot, the flightless and nocturnal kakapo (Strigops habroptilus) weighs up to four kilograms and is believed to live up to 60 years. A decade ago there were only around 50 left but a desperate recovery mission has seen numbers rise to 80-something today.

In one of the most famous rescue programmes, the number of black robins (Petroica traversi) has risen to around 250 after falling to just five – including one breeding pair – on the outlying Chatham Islands by 1980. When the first new chick was hatched, the news was announced in the New Zealand parliament.

THE GOOD NEWS IS THAT the development of new sanctuaries should mean no more bird extinctions, Hackwell says. "We are miles better off with the key bird species than we were 20 years ago, that's fair to say," he said.

The Forest & Bird Society has a vision that pests will eventually be eradicated from much larger areas, such as the country's third largest land mass, Stewart Island at the bottom of the South Island. "I can see that happening in next 10 to 20 years," Hackwell said.

The Karori sanctuary will play its part, introducing more species and building up numbers of tuatara and the giant weta. They also plan to build a visitor centre within two years, lifting the number of visitors from 60,000 last year to around 150-200,000 in the next few years.

Gradually, they hope, all the introduced plant life, such as pine trees, will be removed and within 500 years the sanctuary will offer a glimpse of what nature created over 85 million years and man nearly destroyed in 800.

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