It looks like a harmless Christmas tree but Pinus Contorta is wreaking havoc on the landscape in some parts of New Zealand.

Tragically, Contorta was originally planted in the central North Island for conservation, to help stabilise the alpine scree slopes, and for forestry.

Fifty years later it's an insidious wilding pine that is taking over the Central Plateau.

Craig Davey from Horizons Regional Council says that's because Contorta has the lightest seed of all our pinus species.

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"That light seed would blow upwards of 20km in a good wind, so a forest established some place, infected areas up to 20km away," he said.

Craig Davey from Horizons Regional Council. Photo / Georgie Ormond
Craig Davey from Horizons Regional Council. Photo / Georgie Ormond

For decades there has been an ongoing effort to keep these pine species from taking over the Central Plateau.

"Horizons has been one of the many organisations controlling Contorta particularly," he said. "But other wilding conifer species as well, at least since the eighties."

John Greenhead is a custodian of around 2500ha of land in the Central Plateau.

"We didn't cause the problem, but we're dealing with it the best way we can" he said.

John Greenhead is Custodian to 6,000 acres. Photo / Georgie Ormond
John Greenhead is Custodian to 6,000 acres. Photo / Georgie Ormond

He was so passionate about getting rid of wilding pines it affected his social life.

"I ran out of mates at one stage there because I used to give them a bottle of Vigilant and a handsaw."

Davey takes a broader approach, but with the same ultimate aim.

"Colonising is Contorta's game," he said. "It takes it from a rocky, tussocky, open environment into a forest that's impenetrable with up to 10,000 stems per hectare - huge numbers of trees, no birds, virtually no wildlife, and no native vegetation.

"A blanket of green like a marching army over a landscape."

Herbicide spray has been found to the best way to control the older pines.

"We're using the herbicide as opposed to cutting the trees down, if we can," said Davey.

"Because a cut tree, in its lying down state, holds the cones up off the ground so the seed remains viable for a lot longer and we end up with a problem that's almost as bad as having a coning tree".

Davey said many alternatives to spraying had been considered, including milling but the Contorta timber was only good for firewood.

"It can be used for pulp but where we find Contorta creating a problem, the extraction costs far outweigh the benefit you're going to get from it."

A unique environment at risk from fast growing wilding pines. Photo / Georgie Ormond
A unique environment at risk from fast growing wilding pines. Photo / Georgie Ormond

"At the moment we have a good handle on the projected future of Contorta, and it's not looking good for it because we've got investment from our ratepayers and government agencies.

"However, if we stop, if we don't deal to the source, we are either going to be doing it forever or we're going to start losing ground."

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