As New Zealanders head to the sand and surf this summer, Isaac Davison investigates the environmental issues at our most popular North Island beaches. Today it is Tawharanui.

According to some, the Garden of Eden is an hour and a half north of Auckland.

At the end of a gravel road 15 minutes from Matakana, a peninsula covered in farmland gives way to coastal forest and wetlands, flanked by white-sand surf beaches.

Tawharanui Regional Park is such a finely tuned conservation estate that rare native bird species have appeared in its forests to breed.

Ranger Maurice Puckett lives in one of the few houses on the narrow peninsula, which reaches into the Hauraki Gulf.
He says years of hard work have turned the spot into a conservationist's paradise.

"The mornings are brilliant. When the sun comes up, the whole peninsula starts to sing, comes alive."

But the path to a thriving sanctuary was a complicated one, with at least one environmental skirmish.

Before the reserve could host wildlife, the "destroyer fleet" of feral cats, brushtail possums, rats, mustelids and hedgehogs had to be eradicated from the 588ha site.

The peninsula was chosen because of its shape - the narrow finger of land meant only a single pest control fence was required, with the ocean providing the rest of the barrier to intruders.

Funded mostly by the Tawharanui Open Sanctuary Society (Tossi), a 2.5km fence was built, with a spiral design at each end to draw in predators moving along the outside of the fence.

The Auckland Regional Council then planned an aerial bombardment of the peninsula with brodifacoum. But it came up against stiff opposition.

Environmental watchdog Friends of the Earth strongly opposed the drop, saying it would kill more than the targets and pose a risk to people.

The council claimed that without brodifacoum it would need 57,000 trap stations, some of them in difficult coastal areas.

After arguing its case to three independent commissioners, the council was given the go-ahead.

The eradication was hailed as a success, killing off ship rats, Norway rats, cats, possums, weasels, stoats and ferrets.

A year after the sanctuary opened in 2004, Mr Puckett witnessed wood pigeons, which are often shy birds, standing on the ground and drinking out of puddles. The sight was confirmation that a pest-free habitat had begun to develop.

"It was a sign to us that the whole project was starting to take off."

In 2006, Mr Puckett noticed the distinctive melody of the bellbird in the forest's branches. The delicate olive-green birds had arrived of their own accord.

Bellbirds had been extinct from the northern mainland since ship rats and stoats arrived 150 years ago.

They had thrived on the protected Hauraki Gulf islands of Little Barrier and Tiritiri Matangi, and were now using Tawharanui as a stepping stone.

Tossi chairman Steve Palmer says the bellbird song was a reassuring sound and a vindication for the park.

"I had heard them around South Island rivers before. But when they began calling at Tawharanui, it was a sort of stress relief. It was a joyous noise."

Since Tawharanui's transition to an open sanctuary, 10 species have returned to breed or have been re-introduced to the spot, including kiwi, pateke, robins, kaka and whiteheads.

Tawharanui was also chosen as a safe location for one of the most ambitious conservation projects attempted in New Zealand.

Four years ago, Mexican-born conservationist Luis Ortiz-Catedral moved kakariki, a native parrot, in helicopter transfers from the Hauraki Gulf's Little Barrier Island to Tawharanui and other sanctuaries.

Nine of the fragile, 80g birds died in the painstaking, three-year move. But 124 made it and survive in the sanctuary today.

A similar translocation to the Waitakeres in the 1990s had failed.

Mr Ortiz-Catedral says the complex translocation was made possible by the reliable, pest-free destination.

"Only in New Zealand could you do such a thing."

The park is also unique because it combines farming, conservation and recreation. About 160,000 visitors flock to the reserve each year, with hundreds camping on its grounds in summer.

Mr Palmer says he personally would like the peninsula to be completely covered in bush and free of people.

But he admits he is just being selfish and says it is important to show that conservation can co-exist with recreation and agriculture.

The rangers say visitors find the place irresistible. "You never come once and don't return."

Mr Puckett says he is now seeing third-generation campers at the park's sprawling grounds.

"Many, many people hold this place dear in their heart. People who camp here with their children had usually camped here with their parents."

Tossi has a long-term vision of visitors camping and walking among native kiwi, brown teal, bellbirds and tuatara, and picnicking in a puriri and nikau forest alive with birdsong.

With the park's administration moving seamlessly into the new Auckland Council, Mr Palmer says that goal is within reach. "To think we are making a small part of New Zealand close to what its natural being was ... It's my end-of-life mission."