New Zealand's northernmost iwi has launched a bold plan to build a coast-to-coast predator-proof fence protecting Northland's most precious biodiversity hotspot.

If built, the fence will measure 8.5km from end to end and enclose an area of about 33,000ha.

It would cost an estimated $1.2 million and protect Te Paki, the country's northern tip, from animal invaders such as possums, stoats, rats and feral cats.

Ngāti Kuri announced the plan at a Forest and Bird Conference in Wellington, with trustee Sheridan Waitai telling delegates the concept was "a bit of Jurassic Park", though without the dinosaurs.

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She said it would help protect a vital, ecological area and keep pests like possums, rats, mice and stoats out. The iwi was keen to hear from anybody who could help build the fence.

Ngāti Kurī trustee Sheridan Waitai. PHOTO / FILE
Ngāti Kurī trustee Sheridan Waitai. PHOTO / FILE

The fence would start on the west coast at Ninety Mile Beach, about 25km from Cape Reinga and just south of the famous Te Paki dunes, and end on the east coast at Parengarenga Harbour, south of New Zealand's northernmost settlement at Te Hapua.

The iwi was still working out details of how traffic would be allowed through while pests were kept out, and where the funding would come from. A construction timeline was expected to be announced later this year.

Te Paki has the highest biodiversity of any area in Northland. Plants and animals found only at Te Paki include New Zealand's rarest tree, Bartlett's rata, of which only 14 are known to exist in the wild; three types of giant flax snail or pūpūharakeke; and a rare breeding colony of ōi, the northern mutton bird.

The landscapes, and plant and animal species, at Te Paki are unlike anything else in New Zealand. PHOTO / PETER DE GRAAF
The landscapes, and plant and animal species, at Te Paki are unlike anything else in New Zealand. PHOTO / PETER DE GRAAF

Building the fence will pose a number of significant challenges, however. It will be the same length as the fence enclosing Zealandia wildlife sanctuary in Wellington but will cross a highway and have a beach at each end.

Cape Reinga, Te Paki dunes, Te Hapua, iwi-owned Te Paki Station and the northern side of Pārengarenga Harbour will all be inside the fence.

Forest and Bird Northland advocate Dean Baigent-Mercer said Te Paki was once a series of islands cut off from the rest of New Zealand, so it was home to many unique plants and insects.

A flax snail or pūpūharakeke at Cape Maria van Diemen, Te Paki. PHOTO / Gregory Sherley, DOC
A flax snail or pūpūharakeke at Cape Maria van Diemen, Te Paki. PHOTO / Gregory Sherley, DOC

At least 30 species of plants, for example, were endemic north of the proposed fence, meaning they were found naturally nowhere else on Earth. Fossil records showed species such as kākā, kākāriki, kākāpō, weka, kiwi, tuatara and various burrowing seabirds used to live at Te Paki and potentially could be returned if a predator-proof fence was built.

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The Department of Conservation welcomed the plan, predator-free 2050 programme manager Brent Beaven said.

"DOC is supportive of local people looking to develop predator control or eradication initiatives in their regions ... Conceptually, DOC is supportive of the Ngāti Kurī's proposal and recognises the ecological values of Te Paki as one of the North's most significant biodiversity hotspots."

Cape Reinga lighthouse and Te Rerenga Wairua, the jumping-off place of the spirits, would be inside in the fenced-off area. PHOTO / PETER DE GRAAF
Cape Reinga lighthouse and Te Rerenga Wairua, the jumping-off place of the spirits, would be inside in the fenced-off area. PHOTO / PETER DE GRAAF

The area in Northland with the second-highest biodiversity ranking is Warawara Forest in North Hokianga, where a pest control project led by local iwi Te Rarawa has been under way since 2015.