The Waitakere Ranges could be closed to the 1 million people who visit every year under a dramatic proposal to save the West Auckland park from kauri dieback disease.
It is one of five options due to be put before Auckland Council early next week, and will follow a rahui, or exclusion zone, being placed on the 16,000ha park on Saturday by West Auckland iwi Te Kawerau a Maki.
Authorities are struggling to contain the spread of kauri dieback infection.
Concerns have mounted with infection rates jumping from 8 per cent to 19 per cent in just five years — and concentrating around where people walk.
More than half the substantial kauri areas in the ranges now contained symptoms of infection.
Shutting the entire park to visitors would set a national and global precedent, throw up a regulatory headache and, officials say, ultimately might not halt the spread.
But the situation had now become so serious councillors had asked officers to "pull out all the stops", Environment and Community Committee chairwoman Penny Hulse said last night.
The five options being tabled include giving up efforts, maintaining the status quo, ramping up work, closing all medium and high-risk tracks, and closing the park completely.
"The issue that makes this so complicated is the ranges area is everywhere from Pae O Te Rangi, to Piha, to the backblocks of Swanson and Waitakere village, with farms, communities and houses," Hulse said.
"That's making this a lot more complicated than just closing a simple park."
Officials have not worked out how such a closure would be enforced but one possibility was a Controlled Area Notice — a major measure never before used by Auckland Council and which would try to manage spread of the disease.
"We'd have to look at how we manage activities through a Controlled Area Notice to prevent the disease from spreading — essentially preventing people from moving mud," biosecurity team manager Phil Brown said.
"The scale of this would be quite different from many of the others that have been put in place."
Enforcing a closure could cost hundreds of thousands of dollars and require new infrastructure and warranted officers on the ground — likely stretching outside current council resources.
Regional parks manager Rachel Kelleher said enforcement had been "particularly difficult" where there had been closures in other places.
"There have been some sites that have been closed to manage disease, and visitation has actually increased, rather than decreased."
But while there were no comparable examples of such an intervention anywhere else in the world - and it still wasn't clear how the infection could be spread by other means - some scientists have suggested an enforced exclusion zone could have merit.
News of Te Kawerau a Maki's rahui had drawn a range of concerns and views from the public, with some backing a restriction and others against it.
Hulse expected many Aucklanders would support the move, but others would be worried about how it would affect them.
"We've got people who run businesses in the ranges and their concerns are for how they retain their livelihoods and businesses that are predicated on tourism, so we need to hear from them, too," she said.
"We want to try to do the best, but we also have to make sure that we spend ratepayers' money on solutions that are actually going to help."
With councillors still to read the officers' report, she couldn't say which way the committee might vote.
Ten areas across the Waitakere Ranges Regional Park's 250km of walking tracks have already been closed to trampers as the infection has intensified.
Meanwhile, the council has been upgrading cleaning stations and track surfaces, installed more signage and run a region-wide awareness programme.
But groups including The Tree Council, the Waitakere Ranges Protection Society, Forest and Bird and the Friends of Regional Parks have called for bolder efforts — and a full closure until they were completed.
Those included closing tracks to healthy kauri, stopping events like the Hillary Trail Marathon, boosting the programme of building boardwalks and "dry" tracks and using phosphite treatment on public land to keep individual trees alive.
The groups estimated the cost of adopting these measures would be around $50 million, and said the council would need extra funding from government.
They supported Te Kawerau a Maki's rahui, a cultural approach to guardianship.
"Although the Government and Auckland Council will not assist us with the closure now, it is hoped they will assist in the future," the iwi said in a statement.
"The health of the forest is reaching an ecological tipping point, and Te Kawerau a Maki will act to protect the forest for future generations."
WHAT IS KAURI DIEBACK?
Phytophthora agathidicida, the pathogen that causes kauri dieback, was discovered less than a decade ago and can sense a kauri tree's roots, and swim towards them using a tail-like flagella. These could move through water-logged soil at incredible speeds of up to 0.7m an hour. Once they find their target kauri roots, they form a cyst and initiate an infection that eventually starves the tree to death. There is no cure and the disease kills most, if not all, the kauri it infects.
WHERE IS IT FOUND CURRENTLY?
The Waitakere Ranges Regional Park, along with private land throughout the Auckland region, forest plantations at Omahuta, Glenbervie and Russell in Northland, Department of Conservation reserves at Okura, Albany, Pakiri, Great Barrier, the Coromandel Peninsula, Trounson Kauri Park and Waipoua Forest in Northland, home of our most iconic kauri - Tane Mahuta.
WHAT CAN I DO?
People walking in areas where kauri grow could help prevent dieback spread by ensuring shoes, tyres and equipment were cleaned to remove all visible soil and plant material before and after visiting forests. They should also use cleaning stations installed on major tracks, keep to paths and away from kauri roots, and keep dogs on leashes at all times.