Dave Hansford

The march of the pines

In our rush to plant more trees, are we creating an environmental nightmare?

Written by       Photographed by Dave Hansford

I. The Branch River, Marlborough

Simon Moar heels the helicopter against the sun to give me a better view of the foreign country below. This might be Oregon, the Canadian Rockies, or the Siberian taiga. Every ridge, every face, even the gravelly riverbed, is crowded with conifers from another hemisphere: Douglas fir, contorta pine, Scots pine. This is the Branch River valley in Marlborough, but it’s no longer Aotearoa.

This invasion is no accident—we did it to ourselves. Moar levels the LongRanger and shows me ground zero. I can make out below a neat, rectangular clearing in the forest where the government conducted one of its first trial plantings, in 1964, of Pinus contorta—20,000 seedlings. Later, the Forest Service flew aeroplanes across these faces, tipping sacks of seeds out the door—more than two tonnes of them, here and in the neighbouring Leatham River valley. You can still see striations of contorta across the headwalls where they
took root.

In the back seat, Ket Bradshaw looks out with feelings of regret. As a forester in the 1970s, she was responsible for plantings like this one. Now, as coordinator of the South Marlborough Landscape Restoration Trust, she’s dedicated to getting rid of the same trees. “I see it as a personal responsibility,” she says.

Young contorta pines invade native shrublands in the Waihopai catchment, Marlborough. Contorta produces cones by age ten, releasing seeds that float on the wind. Gales across exposed sites like this can carry seeds up to 40 kilometres.

This is probably the worst example in New Zealand of a blight called wilding conifers—exotic trees that won’t stay where they’re put. Moar swings the helicopter south, to where the Raglan Range breaks in a low pass, and I can see wildings below, swarming out of the Barber Stream, and up through Waihopai Saddle, headed for our most iconic high-country station: Molesworth.

This area is part of the public conservation estate—a sanctuary for native wildlife. South Marlborough is considered one of the country’s top five hotspots for endemic biodiversity—in particular, for subalpine plants found nowhere else on Earth. Neither are they found anywhere in the Branch, now.

[Chapter Break]

“I’d never thought of a tree as being bad—I always thought that any tree’s a good tree, no matter where it is,” says Rowan Sprague, who has a PhD in the ecology of invasive species.

So to drive around the Mackenzie Basin and see that sea of green, knowing that pretty much all those trees weren’t planted—you realise you’ve got a massive problem.”

Sprague, a genial Virginian who’s candid about the misperceptions she brought here, coordinates the New Zealand Wilding Conifer Group, which advises the government on its control efforts. In 2020, the government spent $40 million on killing trees at 43 South Island sites and 11 North Island ones, spanning some 800,000 hectares.

In 2011, a survey calculated that wildings had occupied five per cent of New Zealand, and each year were invading a further 90,000 hectares, equivalent to half of Molesworth Station. By 2016, escapees from exotic plantings had spread over 1.8 million hectares—more than all commercial forests combined. A 2018 study by Sapere Research found that doing nothing would see another 5.5 million hectares of New Zealand covered in wildings within 30 years. More than 500,000 hectares of that land is worth $739 million in “productive potential”.

“I don’t think people are aware just how much they change the landscape,” says Sian Reynolds, who’s managing a wilding eradication programme on Molesworth. “We’re at the point where we really have to take them seriously, because wildings could completely annihilate every landscape we’ve got. They grow in wetlands, they grow in river gravels, they grow on rocky bluffs—they can grow anywhere, and it’s frightening.”

There can be no half-measures, says Reynolds, because wildings don’t share. “It’ll end up being this monoculture of pines throughout the country.”

You could argue for wilding eradication on the grounds of their thirst alone. Studies show that a bad infestation of Pinus radiata wildings can deplete surface water by between 30 and 80 per cent a year. Giving up the fight against wildings would surrender water, says the Sapere report, worth nearly $3 billion in hydro and irrigation potential. The wilding infestations in the Branch and Leatham valleys alone suck up around a third of normal river flows before they can get to Marlborough’s grapes.

In the end, says Reynolds, it comes down to whether New Zealanders want to live in some bastardised boreal pine forest—a mash-up of Europe, Russia and North America—or a place that looks and feels like Aotearoa, surrounded by the things that make it, and us, so very different.

[Chapter Break]

What makes a tree benign in one country yet pernicious in another?

Something in Aotearoa is powering wildings to hyperabundance and, in some species, world-record growth rates.

“Mostly, they’re pines, and pines are pioneers all over the world,” says Thomas Paul, a forest ecologist at Scion Research in Rotorua. “They like open space, they like sunlight. They readily invade grasslands—they’re good at it. So the question then becomes, ‘Why are they doing that so well in New Zealand?’”

Well, for starters, the sunlight never stops here. Freed from dark boreal winters, wildings can photosynthesise all year round. They get plenty of rain, too, they don’t mind poor soils, and the wind carries pine seeds long distances. Here, pines are untroubled by most of the pests and diseases of their native lands. But most of all, by turning forest into farmland, tops into tussocks, we’ve given them practically unlimited habitat.

II. Birch Topping, Canterbury

It’s a dreary Queen’s Birthday Sunday in Hanmer Springs. A sou’wester has bunched the clag up against the Amuri Range, but holidaying families have turned out all the same for a ramble round the sculpture trail in Hanmer Forest.

This patch of forest is an arboretum, and everything is boreal, from the north. Here’s a common alder, and I learn from an interpretation panel that its timber is good for making clogs. That should come in handy. Next up is a Corsican pine—Pinus nigra—noted “for its tolerance of harsh and dry sites”. Dawdling on, I pass Norway spruce, Austrian pines, silver birch and European larches, leafless by now. And everywhere, Douglas fir. The forest floor bristles with saplings. It’s a sylvan showcase, a celebration of timber from the other side of the planet. Some of them have stood here since 1903, planted where once were wetlands, drained by prison labourers under a government policy to “use waste lands while improving the natural environment”. The government’s Forestry Branch (I like to think that’s a touch of Edwardian humour) saw that not so much as an indigenous twig remained. Exotic plantings eventually covered 3500 hectares of New Zealand. Then natural selection saw to it that they covered much, much more.

[Chapter Break]

With its back to the westering sun, Barcaldine farm lies maybe 15 kilometres southeast, as the seed blows, from Hanmer Forest. Hamish Roxburgh’s dad came here in 1945, to raise merinos. The first wildings had already taken root in the mānuka, and over the next few decades, he took to them with all he had—an axe. “I was eight years old,” remembers Roxburgh, of 1955. “My job was to look after the horses and boil the billy for lunch. It was three hours’ riding, and six hours of cutting. I remember my brothers got sunburned to hell.”

We climb into Roxburgh’s ancient Land Cruiser and set off across the home flats, crossing a brook shaded by kōwhai. The Land Cruiser scrabbles up the far bank and brings us face to face with Birch Topping, 1000 hectares of hill that Roxburgh bought from a neighbour in 2008. I can see Douglas fir, and a few yellowing larches. But for the large part, Birch Topping is overwhelmed by Corsican pines. All are descended from those stands back at Hanmer Forest. “That seed source’ll be there forever,” he offers bleakly.

He and his wife, Grace, paid $1.5 million for this swarm of trees. “We’ve still got the debt, and it produces nothing. But we had a wall of trees on our boundary. We wanted to try and contain them—try and protect Barcaldine. We knew that if we didn’t do something, we were going to lose it.”

The farm track turns us west, where it clings to a narrow bench carved from steep tussock gullies. Everywhere are the silver skeletons of Corsican pines. The Roxburghs own 2600 hectares, 1600 of which have been infested by wildings. “Eight hundred of those, we’ve probably saved, but the other 800 are still at risk,” Roxburgh says. “The job’s never done because the seeds just keep coming.” There’s only so much the farm can afford, he says: “When you’re talking large-scale wilding control, it’s telephone numbers—we’d be looking at three or four million, and this land is incapable of generating enough income for its own management.”

Over 30 years, Roxburgh reckons, they’ve probably spent $1.5 million fighting trees they didn’t plant. Silviculturally, these are Hanmer Forest’s pines. Legally, they’re the

About a third of wilding infestations have escaped from farm plantings. The remainder come from sources planted by past government entities. Which begs the question: should landowners be paying to fix a problem the government created?

III. Burnt Face, Canterbury

Somewhere up above me is Cora Lynn Station, along with the sun. According to the car, it’s -2°C here beside the Bealey Bridge, on the Waimakariri River flats. The hoar frost is halfway up the poplars, and this pea-souper of sullen morning cloud won’t let it melt. It won’t let the chopper fly either, so the ground crews have already bush-bashed their way up and onto Burnt Face pre-dawn, lugging loppers, saws, and packs full of fuel, chain oil and herbicide. Through the murk, I can make out ranks of Douglas fir. The rasp of chainsaws already floats down.

It’s mid-morning before helicopter pilot Luke Feast can see enough to fly. He hands me a hi-vis vest and helmet, and we take off to check on progress and look for more targets. In the jump seat is crewman Jack Murdoch, who compares the snowscape below against a map and GPS in his lap. As we crest a ridge, we startle a pair of red deer, and set them to stampede. In a roundabout way, they’re the reason Burnt Face—just like the Branch—ended up covered in wildings in the first place.

This hill is called Burnt Face because it used to be a beech forest before runholders put a match to it in the 1920s. Fifty years later, it was crumbling to a waste, so the Forest Service decided to try planting exotic conifers to stabilise the slipping land.

Back then, the service was part of a whole-of-government war on erosion. In those days, people saw scree slips and shingle fans as evidence of overbrowsing by deer. To hold the land, foresters recommended fast-growing, tenacious conifers from other

Dayna Reihana-Ruka drives a drill bit into a radiata pine at Rangi Point, near the Hokianga Heads. Next, she’ll squirt a herbicide mix into the hole. A tree this size will be dead inside eight months. As the climate warms, radiata is becoming a serious pest in the country’s sunnier regions—Nelson, Marlborough, and here, in Northland.

Nick Ledgard was one of them. He joined the service in the early 1970s. “I was in the revegetation section, looking at ways to get some cover back on these denuded slopes,” he says. “We tried over 300 different species—50 or 60 different natives, but also a whole lot of exotics—and the ones that did best on eroded, exposed sites like this, right up to the tree line, were the introduced conifers—particularly the pines. I could reel off six or eight that did particularly well.”

Perhaps the crowning tragedy is that the Forest Service was wrong. Deer weren’t to blame. Scree, we now understand, is naturally formed by the Pacific and Australian tectonic plates. New Zealand has a boisterous, tumbledown landscape thanks to continental collision. This infestation of wildings is the solution to a problem that didn’t exist.

Now, Ledgard is committed to getting rid of the trees he was responsible for planting. At Burnt Face, the Forest Service settled on Douglas fir and Corsican pine. “They were slow to get started, of course,” says Ledgard, “but once they were away…”

And away they are. High above Burnt Face, Steven Franklin is contemplating the latest of the many hundreds of Corsican pines he’s felled up here. Depending on the weed’s stature, he might pull it by hand, uproot it with a grubber, lop it, or cut through the trunk at ground level with a hand saw. But ones like this—department-store-Christmas-tree size, and taller—he has to fight his way in with a chainsaw, or, if there are rocks in the way, with a hatchet, lopping off the lower branches so he can get to the trunk. If the tree got nipped by hares as a seedling—a common occurrence—it might be a hydra: Franklin could have five or six separate boles to deal with. And it’s not over when the greenery’s on the ground: the moment he walks away, this thing will start growing again, so Franklin daubs the sappy stump with herbicide as a coup de grâce.

It’s difficult country, and demanding work that could easily turn dangerous if his mind should wander. Killing wildings, says his boss, Wayne Godfrey, hasn’t changed much in decades: “At the end of the day, we’re still cutting down trees with chainsaws.”

Godfrey Pest Management has a team of around 40 working on wildings—15 of them hired through COVID-19 relief programme Jobs for Nature. “There were a lot of people displaced from the tourism sector,” says Godfrey. “We were able to give them jobs, and some purpose in the meantime. That’s good for everybody.”

On this job, the crew’s staying at nearby Forest Lodge, high on the Cheeseman Skifield road. They come home to a cooked meal, says Godfrey, “then they’re in bed by 8.30. That’s because they’ll be driving out the gate at 4.30 the next morning.”

IV. Rangi Point, Northland

Entirely without warning, Pita Moana-Hati hurls down his tools with a shriek, then bounds breakneck through the cutty grass, flailing his arms.

“He really hates wasps,” says Dayna Reihana-Ruka.

These gorsey acres at Rangi Point, near the northern headland of Hokianga Harbour, must be his idea of hell, because late May or not, there are still droves of them—in the air, in the gorse, on the ground. But then, this is Te Tai Tokerau. If it can go feral, it will. Wilding control further north around Te Paki has been put on hold due to roaming packs of wild dogs. The most domesticated of trees can go rogue in the warm, wet north—even Pinus radiata. Here at Rangi Point, it’s rampant. As Reihana-Ruka works, I can barely make out the fuzzy line where legitimate production forest ends and illegitimate wildings begin their march over the dunes.

She fights her way in to a big radiata with a pair of loppers, then draws a battery drill from a holster and drives a speedbit into the trunk, boring two holes to maybe 50 millimetres deep, angling the bit at 45º. Then, because this tree is out on its own, and carries more foliage, she bores an extra couple of holes.

In one smooth movement, she holsters the drill and draws a squeeze bottle filled with metsulfuron methyl. Each hole gets a squirt. Then she sprays a vivid pink cross on the trunk, facing uphill, so no-one has to bash all the way down here, just to find this one’s already been done. Following her around the wildings, I soon appreciate that the hardest part is getting from one to the other, pushing through head-high cutty grass and gorse. More than once, I stumble into a rabbit burrow. Then, of course, there are the wasps, but Reihana-Ruka’s done a lot of this, and she reckons Rangi Point is the easiest yet. Last year, she led an all-male crew at Kai Iwi lakes, and more recently tackled wildings at Riponui, northeast of Whangārei. That was the worst, she says: “It was steep. We had to hang off the trees just to drill them.”

Here, she leads a small team—mostly young women originally trained in propagating, planting and tending pines. Now, with funding from the National Wilding Conifer Control Programme, they’re re-skilling in killing. Jobs can be hard to come by in Northland, so work like this is welcome. “We live in the country. We’re not really into sitting inside on a computer.” She’s of Ngāpuhi and Tūhoe, and she doesn’t know her Northland side particularly well, “but we’ve got two on the team that whakapapa to this place.” And that adds a certain impetus to the work here.

Hokianga is where Kupe first made landfall, after guiding his double-hulled waka, Matawhaorua, across its notorious bar—“the canoe eater”, as Ngāpuhi call it. Even high atop these giant dunes, I can hear it roar. Far below is Nuia, one of two taniwha Kupe left to guard the harbour entrance when he returned to Hawaiiki. His descendant Nukutawhiti and his people founded what is believed to be one of the oldest Māori settlements in the land.

Steven Franklin fells a Corsican pine high on Burnt Face, in the Craigieburn Range. Ground control of wildings is risky, demanding work, but the government’s Jobs for Nature programme and $3 million of COVID-19 relief funding has seen former tourism and hospitality workers pulling on chaps and picking up chainsaws.

“Wilding pines are smothering urupā and wāhi tapu,” says Northland Regional Council biosecurity manager Don McKenzie. “I was in the Waitangi wetlands yesterday on a bike ride, and blow me down, there’s Pinus pinaster growing right next to the Treaty House.” Pinaster is native to the Mediterranean, so it loves Northland’s warm temperate airs. “And it can withstand the movement of dunes,” says McKenzie. “I’ve been amazed at how quickly it invaded the white sands of Kokota Spit—those beautiful landscapes of Pārengarenga Harbour.”

Te Tai Tokerau has a couple of the other usual suspects—Scots pine, black pine, contorta—but McKenzie’s mostly worried about “the new kid on the block”, Pinus radiata. He says there are hundreds of wilding sites in the region. “And the more we look, the more we find. We have 150 high-priority wetlands, and more than 400 dune lakes, which are very special to us. I’m not saying radiata’s in all of them, but it’s growing close to many, and they act as seed sources. It’s also marching into the gumlands.”

In 1978, a Northland resources survey noted big sweeps of marginal land producing a pittance, or simply growing gorse. The study declared that more than 334,000 hectares of the region could and should be put to other uses—notably timber production. The 1981 Forestry Development Conference set a planting target of 4800 hectares a year, so that by 2020, according to the Forest Owners Association, exotic forest covered almost 186,000 hectares of Northland—the third most expansive plantings in the country. The biggest proportion of it is harvestable right now, at between 21 and 25 years of age.

This means those trees have been producing viable seeds—tens of millions of them—for the past 11 years, at least. “I’m all for production forest in its place,” says McKenzie, “but it’s come at a big cost. A lot of people look at wilding pines and say, ‘Haven’t they always been there?’ But this has happened in their lifetime. It’s only been 50 years, and that’s a consequence of really poor management of production forestry.”

Now, taxpayers are footing the bill for the collateral damage: the government has funded 10 wilding control projects in the north to the tune of $1.5 million. “There are probably more than 80 [wilding infestations] on our register,” says McKenzie. “We’ve got probably about 10 years’ work ahead of us, and that’s just the projects that are front of mind. It really is the responsibility of forestry companies to play a much bigger part than they’re playing at the moment.”


In 2020, there were around 1.5 million hectares of planted radiata in the country—our most common plantation tree. The sheer weight of that presence means it’s the third most prevalent wilding, even though it’s not an especially aggressive invader.

In its native North America, it won’t open its cones for anything short of a wildfire—an adaptation called serotiny. Studies show the mercury has to nudge 45ºC before seeds fly, so the assumption has always been that in cool, temperate Aotearoa, those cones would stay firmly shut. So how has radiata become a major weed in Te Tai Tokerau? The Marlborough Sounds? Nelson-Tasman?

Those places all have something in common—a superabundance of sunshine. According to work by Sarah Wyse at Lincoln University, in hot weather, radiata cones exposed to the sun can bake to a higher temperature than the surrounding air—up to 15ºC more, which is enough to pull the tree’s serotiny trigger, even though it might only be a 27°C day. “It is likely that P. radiata naturalisation will become more prevalent in the future,” wrote Wyse in a 2019 paper, “as the frequency of summer days with temperatures >30°C is expected to increase due to climate change.”

A distant second among commercial plantings after radiata, at just 100,000 hectares, is Douglas fir. Its common name celebrates the Scotsman who first realised its extraordinary timber potential: David Douglas. As a botanist, Douglas would be chuffed with the eponymy, but likely irked by the “fir” moniker, because Pseudotsuga menziesii isn’t actually a fir. But in New Zealand, it’s most assuredly a weed.

Douglas fir is especially invasive because it can cope with shade, which makes it the bane of native forests and shrublands. Conservation managers spit its name, but builders love it. Douglas fir is superior to radiata in pretty much every respect: it’s way more resistant to shrinking, and it doesn’t bow, spring or twist. It’s also more water repellent. All of which sets up something of a botheration: even as demand drives the planting of more Douglas fir, you and I are forking out money to contain it. Last year, Southland District Council gave the go-ahead to Mataura Valley Station to plant 2300 hectares of trees, mostly Douglas fir.

The station lies barely 20 kilometres north of Mid Dome, scene of a catastrophic Pinus contorta infestation. Between the 1950s and 1980s, 250 hectares of contorta were planted; today, a community group is battling it over more than 25,000 hectares. Contorta is the country’s worst wilding, but Douglas fir comes a close second.

The Mid Dome Wilding Trees Charitable Trust has now spent 14 years and $10 million fighting wildings, and along with Federated Farmers and the Department of Conservation, it’s aghast that the council seems hellbent on repeating the mistakes of what is only recent history. Yet there was nothing in the council’s pest management plan to stop it.

Meanwhile, around a third of the government’s One Billion Trees fund has been earmarked for further exotic plantings, and as it stands, the main official handbrake on any of this is a Ministry for Primary Industries flowchart: the Wilding Tree Risk Calculator, which crunches six different values, such as “spread vigour” and “wind conditions”, to calculate a total score that may or may not trigger a resource consent application. (The new calculator, says Forest and Bird, has succeeded only in stripping councils of more effective controls they used to have under the Resource Management Act.)

“Because radiata and Douglas fir are still planted in forestry, I don’t know if we could ever be wilding free,” says Rowan Sprague, the government’s advisor on wildings. “But we can have proper regulations, so we don’t need this huge control programme forever.

Instead, we could have proper rules in place, and they could actually be enforced, so those responsible for these trees will be controlling them.”

As Minister for both Agriculture and Biosecurity, Damien O’Connor appreciates the contrarieties better than many. “There’s an enthusiasm to plant more trees to help our international obligations,” he says, “and the right tree in the right place has always been the driver, but we can’t always ensure that, because we’ve got private property rights.”

Tougher rules around containment, he says, “absolutely have to be put in there”. A review released in May 2021, says Sprague, “lays out some recommendations in the right direction, but so far there haven’t been any promises to act on them”.

In fact, there’s a way we could have carbon farming and quality construction timber without the corresponding invasion. But the government won’t allow it.

V. Rotorua, Bay of Plenty

Te Whare Nui o Tuteata, Scion Research’s new centre, is a three-storey timber tiara of cross-laminated beams bolted together into diamond sections, or “diagrids” as Scion likes to call them. It’s a joyful outburst in Pinus radiata, and people are wandering in from the adjacent Redwoods Park just to admire it.

But to be escorted beyond, through a labyrinth of labs, is to be transported back to classic 1970s varnished-pine, wooden-windowed governmental austerity. Glenn Thorlby hands me a white lab coat and fends off a pair of double doors. Lining corridors off either side of the lab are ranks of shelves, all bearing glass jars. In each one are tiny conifer seedlings. The fluorescent lighting makes them seem impossibly viridescent; they almost glow a neon emerald. They are perfect little Douglas firs, and I feel an odd frisson, like a witness to something forbidden, because these seedlings are as close as we’re allowed to get to gene editing in Aotearoa.

If this experiment works, they’ll be sterile—or at least, lacklustre breeders—promising quality timber without the plague of trees. It will be another 12 years before they bear cones, telling Thorlby whether he’s succeeded, but New Zealand law won’t let them live that long. “It’s time New Zealand had an adult conversation about whether we want to use these technologies here,” he says.

Scion Research’s Cathie Reeves is finding ways to identify, and hopefully propagate, “shy-coners” among Douglas firs, one of the country’s most notorious weeds. Scion hopes to raise Douglas firs that are lacklustre breeders, allowing foresters to grow the valued timber trees without risk of them spreading.

Any genetically modified organism, or GMO, in New Zealand is bound by the Hazardous Substances and New Organisms Act, which was passed in 1996, before gene editing was even a thing. This means it’s incapable of navigating a crucial distinction that has arisen since. As far as the Act is concerned, there’s no difference between transgenesis, inserting genetic material from one species into another, and gene editing, which is confined to a species’ own genome. Both are forbidden.

This is despite glaring contradictions. Nurseries are free to hybridise one plant species with another by cross-pollination (ever tried a peacherine? a plumcot?) but they’re forbidden to do it using genetic modification. Dachshunds look nothing like wolves because people have for centuries been selectively crossing individuals of the same species to emphasise desired traits, while preventing unwanted ones. Do that in a kennel and it’s called selective breeding. Do it in a lab and it’s called gene editing.

Thorlby points out that biotech is far more precise and involves much less genetic alteration than crossing: “You’re able to change precisely that one thing you want.”

For years, scientists, including Sir Peter Gluckman, the first person appointed the Prime Minister’s Chief Science Advisor, and his successor, Dame Juliet Gerrard, have pleaded for a review.

“New Zealand’s regulation of GMOs and gene editing are probably amongst the most restrictive in the world,” says Thorlby, who points out that more than 20 years of breakneck genetic advances have passed since the law was introduced, “but we’re still adhering to what was thought to be the case back then.”

Meanwhile, the rest of the world has started plucking the ripe fruit of opportunity: “Australia recently ruled that it won’t be regulating gene editing as a GMO, much as South America has,” says Thorlby. “Japan recently decided that. The United States has decided that. Canada has decided that.”

Pinus contorta crowds a ridge high above the Branch River, in Marlborough. Contorta can produce seed at higher elevations than most other conifers—and any native tree species. These trees got a leg-up from the New Zealand Forest Service, which tipped sacks of contorta seed from aeroplanes across the Raglan Range in the 1960s.

In the meantime, it’s for Thorlby to solve the Douglas fir problem in what little space the law allows. Scion has a permit to conduct genetic trials on Douglas fir, but only indoors. Thorlby must wait until these seedlings bear cones to know if this experiment has worked, but these trees would be six metres high by then. “We can’t grow Douglas firs inside,” he says. “It’s just not practical.”

An outdoor permit would require Thorlby to destroy the trees before they reproduce, which leaves him pretty short of research options. For now, all he and colleague Cathie Reeves can do is hone their tissue-culture techniques and work on isolating the genes they think are responsible for reproduction. And they’ve cryopreserved some material from the gene-edited firs, just in case the law changes.

Instead, Thorlby’s working with Pinus radiata, as a kind of proxy Douglas fir, because it reproduces when it’s younger and smaller. “We’ve been attempting to edit the same genes as in Douglas fir, to give proof of concept.”

Of course, Scion is allowed to manipulate genes by crossing individual plants, although the tree’s leisurely lifecycle makes this a protracted quest: “Work with maize and you can get two or three generations a year. Cold-cross some Douglas fir and you might get three breeding populations over a scientist’s career.”

An interim option, says Reeves, could be to find the underperformers—called shy-coners—among the country’s seed orchards and make copies of them using conventional tissue-culture techniques. Reeves has crossed known shy-coners and taken embryos from the progeny. “The challenge is that offspring from two shy-coning lines may still not have the shy-coning combination of genes,” she says. Another problem is that trees can be shy-coners in an orchard but prolific breeders when they’re planted somewhere else.

Gene editing, with its laser-like precision, would eliminate all this uncertainty, cost and delay at a stroke, letting Thorlby get on with finding a solution to the Douglas fir problem. All he can hope for is that Aotearoa may yet have that adult conversation.

Damien O’Connor says “the door’s open to those discussions”, but he’s clear that the law’s unlikely to change until global public perception does.

“New Zealand has to sell things to survive. Ultimately, it’s consumer feedback that we have to be looking to, not the views of scientists and producers. And that feedback is that there’s a huge advantage for New Zealand in being non-GMO.”

And there’s the nub: O’Connor himself makes no distinction between transgenic and gene-edited organisms, because our markets don’t. “We live by the views, the values, and the buying decisions of international consumers. We’re not big enough to sell what we think is right, but they think is wrong.”

VI. Molesworth, Marlborough

It takes a while to get my eye in. I walk clean over the first few. Then, just like that, there it is: a tiny fleck of green in a dun waste of drought-brittle tussock—maybe three centimetres of carbon and cambium, xylem and phloem. This is Pinus sylvestris—Scots pine—and it’s a nightmare. It’s surprisingly hard to wrest from the thirsty earth. Already, there’s more of this infant tree below ground than above it. Left alone here, in the vast acreage of Molesworth Station, it would have thrived—better, in fact, than in its native Europe or Asia.

At this altitude, a Scots pine can start making cones when it’s 12 years old. A mature tree can produce 800 cones in a good season, and each cone can release 30 seeds, all designed to float on the wind. The runholders planted shelterbelts precisely where the wind blew hardest, so that wildings scattered eastwards in a plume down Travellers Valley, all the way to Isolated Saddle, 12 kilometres away near the Acheron River. Today, wildings afflict some 50,000 hectares of Molesworth. Scots pines now cover three times more acreage on this single farm than they do in all of their native Scotland.


[Chapter Break]

One contradiction of wilding control is that the worst infestations are the easiest to deal with. Here, Scots pines are so thick you’d be forgiven for thinking this is a plantation forest. But that means all pilot Luke Feast has to do is fit booms to his helicopter and fly transects back and forth, just as he would spray any other crop. It’s fast, and lethally efficient—here at the Maukuratawhai block, there are huge swathes of browning Scots pines, all treated in a matter of days.

At $1900 a hectare, it’s one reason Nelson-Marlborough will get more than $5 million of government funding this financial year, but Sian Reynolds says it ends up saving money. Ground control is cheaper, at $600 a hectare, but the cost soars when the crews have to start pulling seedlings by hand.

In between are those trees either too big or inaccessible for ground control, yet sufficiently sparse to rule out boom spraying. That’s the remit of ABBA—Aerial Basal Bark Application. It still involves a helicopter, but instead of using booms, a crew member doses one tree at a time with a spray wand. It’s fiddly, because the pilot must come at the tree from two sides, to make sure the target gets a good dousing. It relies entirely on the eyes of the pilot and crew to spot trees, some of which may only just be peeping above the tussock. “In this block, ABBA’s a seek-and-destroy tool,” says Reynolds. There are six wilding control areas here on Molesworth, she says, “and I’ve put each of them on a three-yearly ABBA rotation, to make sure we’re keeping on top of the coning trees.”

The holy grail of wilding control is to eliminate the human error, and a solution may be just around the corner.

[Chapter Break]

Remote sensing involves getting information about something on the earth’s surface without having to cover every square centimetre yourself. Usually, it’s done from the air, by satellites or aircraft carrying sensors that detect and record energy—such as the spectral silhouette of a wilding conifer, says Sherman Smith from the Ministry for Primary Industries, who leads the government’s national wilding control programme. “If we had something like LIDAR or multispectral imagery that could map an area and pinpoint trees, we could then send those waypoints to the helicopter guys and they could go straight to them, rather than spending their entire time searching for them.

“The key for us is being able to spot those small trees before they cone, which is often down to about a 30-centimetre crown diameter. The ultimate goal is being able to do it all by remote sensing—to identify where every tree is.”

John Rolleston is already working on it. His company, SPS Automation, has developed algorithms that can recognise different trees. A drone-mounted camera photographs a wilding, then sends the image to a processor which compares that image to a library of reference files in its database. If it checks out as a wilding, the drone knows exactly what to do about it.

Jack Murdoch takes aim at a Scots pine on Molesworth Station. This spray method comes into its own on scattered trees in country too steep or remote for ground control crews to reach, but it’s costly. Smart drones, which can identify and spray wildings autonomously, may solve that.

“Once we’ve got the system fully up and running,” says Rolleston, “you’ll have an operator driving a truck, which will have 10 spray drones on it. And they will then take off on predetermined routes. They’ll identify wilding conifers, measure them for height and volume, and spray exactly the right amount of chemical on them.”

“Different species,” says Brian Richardson from Scion Research, “have different responses to herbicide. As things stand, if there’s a mix of species, you’re just going to pick the one that’s hardest to kill and apply that maximum dose to everything. But if a computer can tell one pine from another, the drone knows to apply exactly the right amount of spray for the species in front of it.”

Drones, then, could bring both precision and optimisation to aerial spraying, even as they slash the costs of wilding control.

Which is a must, if we’re to have any chance of winning this, because wildings never sleep, and the costs of culling them just keep climbing. In 2016, the creation of the National Wilding Conifer Control Programme finally integrated efforts that had been piecemeal and hopelessly underfunded. That same year, the then-National Government allocated an extra $16 million over four years, tagged to critical infestations in danger of becoming lost causes, such as the Kaimanawa, the Remarkables, Craigieburn and here, the Molesworth. “We just caught them in the nick of time,” says Smith. “Any later and it would’ve been too late to stop these things.”

In 2020, the Labour Government announced a further $100 million over four years. “It’s by far the most money we’ve ever received for wilding control,” says Rowan Sprague. “It was amazing, but still it’s not enough. To remove all the wilding conifer invasions we know about would cost about $400 million.” Wilding control often means returning to a site every three years, perhaps as many as four times. “Then you might declare an area cleared. So this is a very long game, but we only receive funding in these short-term increments, and we’re at the mercy of the political will at the time. When that $100 million runs out in four years, we’re going to have a massive problem on our hands.” Sprague says there’s been good progress, but she knows the trees will soon be back, should that political will falter. “That makes future planning really difficult, because there’s no certainty of what we may or may not achieve. It also means the community groups don’t have any certainty, when they’ve already invested so much.”

Damien O’Connor says annual budgets are “one of the realities of political life, particularly in the COVID world”, so he’s not making any promises. But if he has his way, the war on wildings will continue. “We have to wind this back, because with every year that passes, the cost continues to escalate. We’ll have to justify the value of that position, and we should be able to do that, because it’s in everyone’s long-term interests.”

VII. Back where we started

It’s a shame that most people will never see the Branch valley, because there, writ large across every flat and face, is the alien future that Sian Reynolds forewarns us of if we let the wildings win—a land annexed, the very essence of Aotearoa erased, replaced by thickets from some other country.

As I watch the helicopter’s shadow chase across this perversity, it occurs to me that the story of wilding conifers is a veritable litany of perversities:

That, just over the next few hills, we are once again planting some of the very species that ruined this place, and that the same government paying a fortune to control them here is cheerleading their propagation.

That the legislation which guides that planting is almost laissez-faire compared to the iron-fisted rules that strangle the genetic research that might spare us all of this.

Some wilding stands have been recovered for timber, but the costs are mostly prohibitive. Because these infestations began long before 1989, they have no value under the Emissions Trading Scheme. A $100 million control programme has made good inroads, but relies critically on further funding if those gains are not to be lost in a matter of years.

That Glenn Thorlby’s genetic-engineering solution must stay in a freezer until a shopper in Frankfurt learns the difference between a transgenic and a gene-edited organism.

That community groups are running crowdfunding pages to help them mitigate the ecological fallout from multimillion-dollar forestry operations.

“You have to remember,” Nick Ledgard had told me back at Craigieburn, “it was all done in the absence of malice.”

That may be the case, but it was also done without wisdom—wisdom we must summon now. We must decide whether we really want to live in a foreign country.

More by

More by Dave Hansford