COMMENT:

Kauri dieback is one of the biggest crises ever to face New Zealand's forests. It threatens not only individual kauri trees, but the entire ecosystem around them. If kauri disappear, so do all the other plants and animals that depend on them.

This disease also threatens something else many New Zealanders hold dear: the ability to go into forests, to hunt, to walk, to unwind, and to relax.

Should government agencies do more to manage this, or is this a natural phenomenon that we should just accept and do nothing? How did it get to the point that many scientists, as well as affected iwi, believe interim forest closure is the only viable option?

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Unfortunately, this is a disease we still know very little about. Phytophthora agathidicida, or "killer of kauri", wasn't even named until 2015. But we do know that it eventually kills all the trees it infects - whether they are tiny seedlings or the majestic rakau rangatira (chiefly trees) such as Tāne Mahuta.

Right now, we have little - if anything - available to stop kauri dieback. Researchers are working to develop new tools to control its spread, test potential cures, and find trees that are genetically resistant.

But research takes time and money. For example, on average it takes 11 years and $268 million to develop and launch a new agrichemical to protect a crop. Any success will still be too late for many infected trees, including many in the Waitākere and Waipoua forests.

But government agencies seem unmovable in their approach to managing what has become a cultural and ecological crisis. After nine years we are no closer to stopping kauri dieback. This is perhaps unsurprising, given how little has gone towards research (an estimated $865,000 a year since 2014).

Boardwalks, track upgrades, and designer wash stations may provide some protection. But the limited evidence available shows that the sanitiser used in the wash stations doesn't kill Phytophthora oospores, which are a key part in the spread of disease. Also, people don't stay on the tracks, spreading the disease when they venture off.

Hygiene measures will only be effective if we know where kauri dieback is and is not. But research on dieback in Australia shows it takes six to 18 months after a site is infected for symptoms to emerge. If we wait for the disease to show before closing a forest, it's already too late.

Until we sort out a system that works, closing forests is the only option.

Long before kauri dieback, our kauri forests were decimated to make room for farmland, and cut down for timber. The once-mighty forests are now isolated pockets, cut off by development and subject to frequent human and animal intrusions. These small remnants are even more precious, as they are all that remains of a once-abundant ecosystem.

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We need to close all kauri forests now and we need monitoring to determine where the disease is and isn't.

Until we know how to stop kauri dieback we need to do everything we can to stop people from spreading it. And that means keeping people out of the forests.

If we lose these trees, we lose an entire ecosystem. We lose part of our culture and a piece of history. Surely we can do better.

Dr Amanda Black is a Senior Lecturer at the Bio-Protection Research Centre, based at Lincoln University.
Dr Monica Gerth is a Senior Lecturer in the School of Biological Sciences at Victoria University of Wellington.