Correction, 27 September 2026. An earlier version of this article, relying on a campaign website, said about 70 percent of infected kauri in the Waitākere Ranges stood within 50 metres of a walking track, and that infection had risen from 8 percent to 19 percent of trees. The Auckland Council report behind those figures found 71 percent of mapped kauri dieback zones were within 50 metres of a track, and measured the rise as a share of kauri forest area, not of trees. The article now reports that council report directly, along with the council’s more recent 2021 survey, which found the link with tracks uncertain.
About 2000 young kauri grown from the seed of healthy trees are now in the ground in west Auckland’s Waitākere Ranges, in the hope that they carry some natural resistance to kauri dieback, the soil-borne disease that has been killing the forest’s oldest giants.
The last of the seedlings were planted on Wednesday 23 September, RNZ reported. The project brings together the west Auckland iwi Te Kawerau ā Maki, government scientists, Auckland Council and volunteers.
Seed was gathered from about 650 “mother” kauri that scientists and iwi identified as healthy, despite growing in a forest where the disease is widespread. The idea is simple. If a tree has stayed well while its neighbours sickened, its offspring may have inherited something that helps them fight off the pathogen.
Among the parent trees was one that did not survive. Stuart Leighton, lead ranger for Te Kawerau ā Maki, told RNZ that a thousand-year-old kauri known as Aunt Agatha had since died of the disease. “She’s still there as a sort of dead skeleton tree now, but we did take seeds from that tree,” he said. He hoped Aunt Agatha’s offspring would thrive in the ranges.
Leighton said the disease had made it plain that something was badly wrong with the forest as a whole. “When your biggest, oldest thing starts to die, then that’s a real sign that we need to really start to focus our attentions on looking after this place.”
The Bioeconomy Science Institute collected the seed and raised the seedlings at its nursery in Rotorua. Selwyn Insley, the institute’s Māori partnership lead, described the process to RNZ. “Specialist teams went up and collected the cones. The cones were then taken back to our nursery, dried and put into pots to grow up into the kauri trees that we see in the regional park today.”
“The team that looked after these trees from seed to small seedlings, I’m just rapt that they’re here,” Insley said.
Kauri dieback is caused by Phytophthora agathidicida, a fungus-like water mould whose scientific name translates roughly as “plant destroyer, kauri killer”. It lives in the soil and attacks the roots, starving the tree. A pinhead of mud on a boot is enough to carry it to a new site.
Auckland Council’s principal biosecurity advisor, Dr Sarah Killick, told RNZ the project had taught them a lot about kauri dieback, and they were still learning. “We know it’s a soil-borne pathogen and that’s really important for us, so we know that because it lives in the dirt, the best thing we can do for kauri protection is to stop the dirt from moving between forests.”
That logic is why so much of the Waitākere Ranges has been off limits for years. In December 2017 Te Kawerau ā Maki placed a rāhui, a customary restriction on access, over the forest, closing its tracks. Since 2018 Auckland Council has worked with the iwi to reopen them one by one, but only once they have been rebuilt to keep walkers off kauri roots and out of the mud, and only with the iwi’s agreement. The rāhui still applies to every track that remains closed. Auckland Council’s kauri dieback page sets out the regional rules, including a ban on moving soil or kauri material into or out of any area within three times the dripline of a kauri anywhere in Auckland.
Nationally, 10 rules under a national pest management plan took effect on 2 August 2022, aimed at stopping contaminated soil from moving and protecting kauri roots. The council also treats some trees with phosphite, which can slow the disease but is not a cure and must be repeated every five years.
The scale of the damage explains why a planting of 2000 seedlings is being greeted as good news. An Auckland Council report on its 2015 and 2016 surveys, which checked 22,477 kauri in the ranges, found the share of kauri forest area with kauri dieback had risen from 7.9 percent in 2011 to 18.95 percent in 2016. It found 71 percent of the mapped dieback zones lay within 50 metres of a track, and named soil disturbance from human activity, such as visitor tracks, as the highest-risk way for the pathogen to reach new sites.
The council’s later 2021 survey, a peer-reviewed study of 2140 randomly selected trees, gave a more complicated picture. It found 16.5 percent of kauri showing symptoms, and the pathogen in the soil under 10 percent of sampled trees, clustered around the edges of the park. Trees nearer tracks were more likely to carry the pathogen in its simpler models, but that link became uncertain once the researchers allowed for the way the disease clusters. The report said an association with tracks was biologically plausible and needed more study.
Kauri matter well beyond their own survival. The Waitākere Rāhui campaign says at least 17 other plant species depend entirely on kauri forest, because the trees create their own distinctive soil type that few other plants can live in. Lose the kauri and those species go with them.
There is reason for caution about how far resistance can carry the fight. The same campaign warns that natural resistance is unlikely to be common, because logging removed the great bulk of kauri from their original range and left a narrow gene pool. Kauri live for hundreds to thousands of years, far too long a lifespan to evolve resistance to a disease that can kill a tree within a few. Even if resistant trees are confirmed, it says, restoring mature forest would take two centuries or more, so keeping the pathogen out of healthy stands remains the priority.
The only forests known to be free of the disease, according to the campaign, are the Hūnua Ranges, most of the Coromandel and most offshore islands. Auckland Council runs a dedicated exclusion zone in the Hūnua, where kauri material and soil may not be brought in unless it comes from a certified nursery.
For the people who planted them this week, the new trees are a long game. Kauri seedlings can sit small for decades under the canopy, waiting for a gap in the forest before they shoot up towards the light. RNZ described the planting as a start on repopulating the ranges, maybe not for this generation but for those to come.
Anyone walking in the Waitākere Ranges can help the seedlings along by sticking to open tracks, scrubbing every trace of soil off boots and gear at the cleaning stations, and staying out of closed areas.
Have you walked the reopened Waitākere tracks, or seen kauri dieback in a forest near you? Tell us what you have noticed in the comments below.
This article was written by AI, briefed to report the facts, hopefully without some of the bias people bring to the job 🙂
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