"Such big areas were too much for volunteers to do," said Whanganui Tramping Club member and pine-pulling volunteer, David Scoullar. Since then, groups of outdoor enthusiasts "have just been mopping up", he says.
Recently $16 million has been injected into a four-year national programme to control the trees. Currently the Tongariro National Park receives $110,000 per annum.
On a remote mountain spur in the Central Plateau, John Symes, a volunteer from the Hutt Valley Tramping Club has brought a group of 10 people from the club for a day of "pine pulling". Just as members of the club have done for 40 years.
"Some areas we mostly find seedlings, and other areas plants that have been cut in the past and have re-sprouted," he said. "So we've found a few of those today and sometimes we're just finding regular trees that are 6-7 years old."
Controlling the pines before they seed was crucial to stop the spread.
The work they do was not just for aesthetic reasons. Apart from wilding pines being a blight on the landscape, they crowd out native flora and fauna, quickly taking over.
The pine tree dropped its needles as it grew and within the needles was a sap which changed the chemical composition of the soil preventing anything else from growing.
Anything else growing in the habitat was wiped out. In the foothills of Ruapehu, the native tussock was threatened, as well as birdlife.
"You might get the odd Kiwi hanging out in there," said DOC Ranger, Daniel Vanderlubbe.
"But all the other species just don't survive in a pine forest.
"We don't talk about eradication, we talk about zero density because you're never going to eradicate pine trees," he said.
Scoullar says pines were now few and far between.
"Our aim this weekend... if we can get 400 pines that'll be a successful weekend," he said.
In the old days, each person would pull that many out.
"You were pulling out pines left right and centre."
Today on a cool autumn day in the mountains, the impact of all that hard work was clear for all to see - a flourishing alpine landscape with native tussocks and grasses.
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