The Department of Conservation's classification of kauri as a threatened species is one more reminder that not nearly enough is being done to investigate and stop this disease called dieback. That very name says how little is known about it. The word describes what it does, not what it is.

Its biological name, Phytophthora agathidicida, is not much more help. Phyotophthora means "plant destroyer" and agathidicida means "kauri killer". Various types of Phyotophthora are common in the world but this one is a new type and we know almost nothing about it.

Biologists are reasonably certain it is transmitted by soil, not wind or birds, and a lot of soil adheres to human footwear. So walking tracks in infected areas around Auckland have been closed for the time being. But that cannot be the solution.

If closing the Waitakere walks proves to contain the spread of the disease it will be good news. But the question would arise, what then? Is bush-walking forever to be banned in the Waitakeres, the infected areas of the Coromandel or Waipoua Forest where the disease has also appeared?

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These magnificent trees are the crowning glory of our native forests. The ancient specimens in Waipoua have stood for hundreds of years, linking us to millions of years before human beings evolved on the planet, let alone migrated to this distant corner of the Pacific.

Kauri ruled the primeval forest when bird calls were the only sound to be heard and no mammals trod on the trees' shallow roots. But even if it was possible to lock people out of mainland forests indefinitely, it should not be contemplated.

People who love our native forests will respect the rahui so long as they know that scientific research is under way to provide the knowledge that could allow the disease to be managed if not eradicated. The Tree Council complaints are that too little is being done to discover what kills the microscopic organism that causes the deadly mould, where in the ground it is, where in the tree it takes hold and how it can be detected reliably and rapidly.

It is now 10 years since kauri dieback became apparent yet the council says we still do not even know where it came from or how long it has been in this country. It wants to see the Government put far more effort into a research programme overseen by the biological heritage unit in the Ministry of Business, Innovation and Employment. The council hopes DoC's classification of kauri as a threatened species will focus the Government's mind. This problem is more local, visible and urgent than some of those that attract the Green Party's energy.

Aerial surveys of the Waitakere Ranges have found he area of kauri dieback more than doubled in the five years to 2016. The Tree Council says dead trees are appearing in Waipoua Forest every month and Trounson Park has become "a kauri graveyard". At the this rate, it estimates, we could lose kauri within 30 years. That must not happen. We owe it to future generations to get to the root of this disease and stop it spreading.