New Zealand's southernmost kauri forest has been confirmed as free of Phytophthora agathidicida (PA), the pathogen causing kauri dieback disease.
Kaimahi/workers from the Department of Conservation and the Kaimai Mamaku Restoration Project (including Ngāti Hako, Ngāti Tumutumu, Ngāti Hinerangi, Ngāti te Wai, and Ngamanawa Incorporation) spent more than 1,686 hours (70 full days) collecting data across more than 20,000 hectares of the park.
DOC Regional Lead Kauri Protection Tracy Mezger coordinated the extensive survey effort and says it's a relief to have confidence PA is absent from the forest.
"Our worst fear was it was already here and we'd be playing catch-up to protect these beautiful trees from the devastating impacts of kauri dieback disease. But the level of sampling done means we're very confident it's not there – and we're committed to keeping it that way."
The survey assessed the presence or absence of PA in the soil, and established baseline kauri health to inform ongoing protection, treatment, and forest health strategies.
"Almost 80 per cent of sites had kauri seedlings or saplings present, which is an encouraging sign of ongoing regeneration and ecosystem resilience," says Tracy.
There are estimated to be more than 23,000 mature canopy level kauri in the Kaimai Mamaku, and potentially millions of seedlings. Considered "ecosystem engineers", kauri root systems reduce erosion and downstream flooding, and create environments promoting other indigenous plant life.
Tracy says the survey was co-designed with iwi and hapū with their aspirations at the heart.
"Iwi kaimahi were empowered to take an active role in all aspects of the work, from tīkanga and planning, all the way to biosecurity protocols and taking samples. It was true collaboration and learning for all of us," says Tracy.
Although no PA was found, there were many signs of human and introduced animal disturbance, and other plant pathogens which could affect the health of the forest giants as the climate changes.
Tim Aoake, General Manager of Wairere Mahi, the conservation arm of Ngāti Hinerangi, says the job has just started.
"Doing this work felt like we were re-tracing the steps of our tūpuna. We were learning more about the significance of our mahi in the taiao, and how kauri contribute to the care and protection of our ngahere and wai.
"And now we know we have kauri free from PA, the question we ask is 'how do we protect them?'."
Kaimai Mamaku Conservation Park is the second forest in Aotearoa to have a clean bill of health from kauri dieback disease, after the Hūnua Ranges in 2025.
Riki Nelson, Ngāti Te Wai, says visitors to the Kaimai Mamaku should remain vigilant to ensure these taonga endure for generations to come.
"While we're relieved comprehensive testing has found no evidence of the disease, this is not a signal to relax. The risk remains, and we all have a responsibility to continue biosecurity measures that help protect these iconic forests for future generations," he says.
To help protect kauri, visitors heading out naturing in the Kaimai are encouraged to remove all visible soil from boots or shoes, use all hygiene stations, and stick to the tracks.
Louise Saunders, CEO of Manaaki Kaimai Mamaku Trust, coordinator of the Kaimai Mamaku Restoration Project, says the finding is timely news.
"Kauri are one of the tallest and most significant trees in the motu. When you see mature kauri, you can't help feeling inspired and connected to nature.
"Knowing our kauri forests are disease-free, we can significantly improve forest health with the DOC feral goat eradication programme and landscape-scale pest control projects, safeguarding these forest giants for future generations to feel inspired by too," she says.
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