Kauri are some of New Zealand’s most important taonga – both ecologically and culturally. But the trees are being killed by incurable kauri dieback disease – caused by a pathogen called Phytophthora agathidicida – and the fight to save them has been slow and convoluted. Stuff senior journalist Denise Piper and visual journalist Jason Dorday investigate what is happening to save kauri while they still stand.
In the fight to protect kauri, Aucklanders have opened their wallets to help, with ratepayers funding $107 million over 10 years through a natural environment targeted rate.
The funding – which towers over the Government’s $32 million for all of Aotearoa – is being used for everything from building new kauri-safe tracks to investing in the latest research.
The measures are working, according to Auckland Council’s new survey of the Waitākere Ranges, which found the pathogen which causes kauri dieback, Phytophthora agathidicida, is limited to its periphery.
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The survey mapped the 17,000ha forest with remote sensing technology and found there were at least 68,000 kauri trees in the regional park.
It then assessed a representative random sample of 2140 trees and took 761 soil samples to test for the pathogen.
Jason Dorday/Stuff
Auckland Council’s survey found there are at least 68,000 kauri trees in the Waitakere Ranges – pictured here from the Arataki Visitor Centre – and 16.5% of those surveyed have kauri dieback symptoms.
The results show Phytophthora agathidicida, or PA, is not present in the heart of the forest but is limited to its edges, particularly near the coast and historic timber sites.
Auckland Council kauri dieback manager Lisa Tolich said it was most likely the pathogen was brought to the Waitākere Ranges by humans, and then had spread naturally or with human help.
Of the kauri surveyed, 16.5% had symptoms of kauri dieback and a further 28% were slightly unwell – potentially from other factors like drought.
Jason Dorday/Stuff
Auckland Council kauri dieback biosecurity manager Lisa Tolich, pictured at the Matakohe Kauri Museum, says kauri are important for New Zealand and everyone needs to pull together to save them.
Not all sick trees were infected with PA, but they were at greatest risk if the pathogen got in, Tolich said.
“They’re like the residents in the rest home at risk of Covid-19,” she explained.
And while the pathogen was slow-moving, there was a risk of it spreading to other catchments in the Waitākere Ranges, or outside the ranges, the results found.
Tolich said everyone needed to play their part to ensure kauri stayed standing.
“If we don’t pull together – scientists, agencies, mana whenua – to come up with mitigations and protection measures to look after these trees, they won’t be here for future generations.”
Jason Dorday/Stuff
Kauri dieback can affect even mature kauri trees, infecting their roots, causing their leaves to fall off.
Unfortunately, there is nothing that will kill PA, but Tolich is hopeful scientific investigations will eventually lead to a kauri dieback cure.
Injections of phosphite – a method copied from the avocado industry – was a promising treatment, and the 12,000 trees in Auckland injected with phosphite were showing signs of dieback reversal, she said.
Auckland Council is also taking novel approaches to the disease, such as training kauri dieback detector dogs to sniff out PA, making for a much quicker diagnosis than a six-week lab test.
The three dogs are still in training, but it is hoped they can soon be used to check the likes of earthmoving equipment before they go to disease-free areas, such as Waiheke Island.
Jason Dorday/Stuff
Auckland Council manager of proactive compliance Adrian Wilson says most people who break the rules in the Waitākere Ranges know about kauri dieback but choose to ignore the signs.
But in order to be successful in its kauri protection, Auckland Council has also had to act as a stern gatekeeper.
It closed high-risk walking tracks – most notably more than 100 tracks in the popular Waitākere Ranges –then used compliance officers to enforce the closures with fines of up to $20,000.
Two high-profile prosecutions, where two breachers were fined $5700 and $4500 respectively, had helped change behaviour, said manager of proactive compliance, Adrian Wilson.
“That’s a very expensive walk in the park if you decide to breach the rules,” he said. “We will find out who you are and prosecute if necessary.”
Anyone can do their bit to help stop kauri dieback.
Wilson said most of the people breaking the rules were locals, who believed they were entitled to walk along their local track despite the risk of kauri dieback spread.
“Without a shadow of a doubt, people understand kauri dieback … A lot of it is self-entitlement – they think they should always be allowed to walk on tracks they have always walked on.”
But the council did have a tough balancing act, as bush tracks were an important part of Aucklanders’ recreation, Tolich said.
The council is trying to minimise the closures by making tracks kauri-safe – using the likes of boardwalks to keep boots away from kauri roots – and then reopening them.
Jason Dorday/Stuff
Te Kawerau ā Maki trustee Edward Ashby says kauri are so important in the Waitakere Ranges, urgent action needs to be taken to save them.
It is working with iwi Te Kawerau ā Maki, which first placed a rāhui (customary ban) on Waitākere Ranges in 2017.
Up to a million people a year use some of the more popular parts of the Waitākere Ranges, said iwi trustee Edward Ashby – 10 times as many walkers as those on all of New Zealand’s great walks.
“Mid-term, the aim is to create recreational infrastructure which recognises the mana of the forest and the mana of the people [who use it],” he said.
The council’s latest survey results showed the precautionary measures had been justified and needed to continue, Tolich said.
The survey results will continue to be analysed, with the data setting a baseline for repeated monitoring, likely every five years.
At 55% of the sites surveyed, kauri seedlings and saplings were present, even in areas where the pathogen was found.
“The hope is in future surveys, we will see these young trees survive and continue on their way to maturity,” Tolich said.
This series was produced with funding from Bruce Jesson Foundation.
