Killer Footprints of Kauri Dieback Disease

New Zealand Kauri trees are facing a catastrophic threat. The incurable kauri dieback disease has the potential to wipe out the entire kauri species within the next 30 years. With the deadly microbe spread via soil, people like us trampling dirt through the forest play a huge role. As a tramper, daywalker, or waterfall wanderer, you could be leaving killer footprints. However, there are many things you can do to help!

Not Just An Ordinary Tree: Why Kauri Matter

If you’ve ever seen one of these majestic, ancient giants reaching through the canopy, you’ll know that they are breathtaking. Towering above all else, kauri can grow 40-50m tall and live for over 2000 years. Found only in the north of New Zealand (primarily Northland, Auckland and Coromandel), kauri forests are truly unique.

In Māori culture and mythology, kauri are incredibly important. They are taonga (treasure), rangatira (chiefs) of the forest, and tupuna (ancestors). The famous kauri tree, Tane Mahuta, means “Lord of the Forest”. As the largest known living Kauri tree, it stands at over 50m tall, with an enormous 14m girth. If you are lucky enough to make it to Waipoua Forest to stand in front of this giant, you will experience the reverent atmosphere and solemn hush amongst the tourists created by this single tree.

Yet, it is the role of kauri behind the scenes that is perhaps the most incredible. They are the foundation of the forest and create a unique ecosystem of acidic leaf litter and special soil. This is key for the survival of the surrounding flora, with the canopy of Tane Mahuta alone boasting at least 100 plant species. However, this interdependence creates a domino effect. Fredrik Hjelm, a kauri management expert from The Living Tree Company, believes if kauri disappear, the whole forest will collapse too.

Tane Mahuta: Lord Of The Forest

Kauri Dieback Disease: A Mud Monster

Unfortunately, this domino-kauri situation is not a hypothetical. We’re at a tipping point right now, as the incurable kauri dieback disease continues to spread. To stop this, it’s important to understand what we are dealing with, so here’s a little background on this mud-dwelling monster.

Kauri dieback is a type of water mould known in Latin as Phytophthora agathidicida. This mould is not only closely related to another water mould with a taste for potatoes (causing the Irish Potato Famine), but the name literally means “plant-destroyer” or “kauri killer.” It’s deadly to all and kills all sizes and ages of trees without discrimination. Dieback first infects the roots where it kills the conductive tissues that transport water and nutrients. As it creeps further up the tree, the trunk bleeds out sap, a visible symptom of an invisible killer. Eventually, unable to draw food and water from the earth, the kauri starves to death. Left behind is a dead bare trunk, like an enormous piece of driftwood overlooking the forest.

The Waitakere Ranges are a particularly alarming example. Located less than an hour from Auckland, infection rates here have doubled within five years to almost 20%. Many more trees are likely infected but yet to show symptoms. The Waitakeres are the only monitored forest in the country, so the severity of the situation elsewhere is completely unknown.

To make matters worse, a similar water mould in Western Australia first targeted jarrah trees, before moving onto a range of other species like banksias and grass trees. There is evidence to suggest that kauri dieback could do the same and harm other species in kauri forests.

Dead kauri
Photo by Fredrik Hjelm | @thelivingtreecompany

Are You An Accomplice? How You Might Be Helping Dieback Spread

The thing is, kauri dieback disease does not act alone, this dirtbag is spread through soil. Humans like us, hiking mud through the forest and from forest to forest, are accelerating the rapid spread of dieback. In the Waitakere Ranges, 70% of infected trees are next to tracks.

To help reduce the spread, you should use the cleaning stations that are placed throughout many of the at-risk areas. The sterilising spray and scrubbing brushes at these stations should be used absolutely every time you pass a stop (even if you just used one 20 minutes ago) because containment of the disease is critical. This is the time to channel your inner Sheldon Cooper and let your OCD tendencies regin. It only takes a single pinhead of soil to take the fungus to its next kauri victim, so make sure you do a thorough job!

The Transformation: Oospores and Zoospores

To complicate matters, dieback comes in two forms: a zoospore and an oospore. The zoospore is the active killer. It can “swim” through the dirt to infect the roots of healthy kauri. Luckily, it can be killed by disinfectant. Meanwhile, its partner in crime, the inactive oospore, is a little more under the radar. An oospore can sit on your Dad’s old hiking boots in the garage for 10 years, dormant and waiting. Then, just like something out of a sci-fi horror movie, when it is taken back into the environment the oospore can transform into a killer zoospore ready to cause destruction. To make matters worse, an inactive oospore isn’t killed by a disinfectant spray. The only way to stop the spread of infection is to completely clean dirt off your boots. Every last speck.

Changes Afoot

By now it should be clear that the situation is extremely serious. So, in December 2017, fed up with a lack of action, the local Te Kawerau ā Maki iwi (Māori tribe) of the Waitakere region decided something needed to be done. They placed a rāhui over the region, which is a temporary, ritual closure of an area. Its purpose? To let the forest recuperate without the presence of humans. However, the rāhui was not supported by Auckland Council and was largely ignored by the public despite the warning signs.

With a change of heart, in February 2018, the Auckland Council opted to shut the majority of the Waitakeres, effective May 2018. Although this will have a big impact on everyone who enjoys this area, it is a major success for the kauri of the Waitakeres, so please respect the ban. It’s not heavy-handed bureaucracy, nor a challenge to sneak to Kitekite Falls. The ban is in place because without it, the future of kauri in the Waitakeres is almost set in stone.

The Redemption: What Can You Do To Stop Kauri Dieback Disease Spreading?

Even with closures in the Waitakere Ranges, many other kauri forests are at risk. So here are a few simple actions you can take to make a difference:

Stay out of the rāhui restricted and closed areas. Respect all the signage, and use the closures as an opportunity to explore somewhere new, away from kauri.

Clean your boots really well in the park. Follow the hygiene procedures at any park you visit, and at every single station you pass. Use the spray to kill the active zoospore, and clean every speck of mud off to stop the spread of the inactive oospore.

Clean everything at home as well. Once you get home, give everything a thorough clean (don’t forget about everything from mountain bike tyres to dog paws!) You don’t want to be the one responsible for introducing dieback into a new area.

Stay on the official tracks at all times. By venturing off-track, out into the wilderness you could easily be transporting dieback from infected tracks to new, unaffected areas.

Join the Kauri Rescue Project. If you want to do something above and beyond, get involved with the Kauri Rescue Project. It’s an awesome citizen science project which helps landowners with infected kauri trees to extend the life of their trees using phosphite injections.

At the centre of both the ecosystem and Māori culture, kauri matter. If things don’t change, this incredible species won’t be around for future generations. Don’t leave killer footprints; stay out of restricted areas, keep to the tracks, and clean your boots. When you’re out exploring, think about how you can stop the spread of dieback because your actions really will make a difference.

A massive thanks to Fredrik Hjelm who has dedicated immense efforts to protecting kauri, and who kindly offered his time to provide insight on kauri dieback for this article.