loading . . . Unruly deer set up camp in NZ’s most precious places The Bioeconomy Science Institute is reporting wilding conifers growing more, larger, cones, which contain many more seeds than normal.
In addition to this, widespread plantings of the tough-as-old-boots Douglas fir, have now matured and are spreading at alarming rates.
In the fourth of Newsroom’s series on pest issues facing the southern region, we look at how wildings are swallowing up the high country faster than ever.
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Environment Southland’s general manager of integrated catchment management, Lucy Hicks, says Douglas fir is currently spreading across vast tracts of Southland, driven by an expanding network of seed sources: commercial forestry blocks, shelter belts and woodlots.
“Without decisive action now, Douglas fir could become one of Southland’s most significant ecological setbacks – a slow-moving, visible loss of the open landscapes, wetlands, and native ecosystems that define this region.”
Also spreading is the spectacularly vigorous Pinus contorta, although it’s now losing its claim to infamy as most hated of the 19 conifer species classified as wildings, as Douglas fir takes over.
Contorta’s adaptive trends were being seen at almost all sites studied across the North and South Island, according to Tom Carlin, Bioeconomy Science Institute invasion ecologist.
“In New Zealand some wilding conifers, such as contorta pine, are spreading much faster than in their native range and other countries they’ve been introduced to. We think adaptations since their arrival – producing more seeds per cone and more cones per tree – are increasing spread rates.”
He says research suggested a single contorta cone could, in some cases, hold up to 200 seeds. The norm is for cones to produce about 25 seeds per cone.
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From left: Dave Shaw from Oregon State University and Thomas Carlin from New Zealand’s Bioeconomy Science Institute view Pinus contorta in the Oregon badlands (part of its native range). The trees are estimated at approximately 80-100 years old. Right: In comparison, these Pinus contorta near Hanmer Springs are only 25 years old, showing the significantly faster growth rates in NZ compared to the native range.
The trees also appeared to be maturing faster although there was little data from the early days of their introduction, to compare to today’s wildings.
“Many conifers seem to be growing and maturing faster in New Zealand. Around Lake Pukaki [Mackenzie Basin], for example, contorta pine seems to cone early and frequently – potentially as early as three years old.”
Some of these trees may be a new contorta hybrid evolved here in New Zealand. This development is thought to be aiding more trees to produce some serotinous cones.
These remain closed and unlike other cones, don’t generously spew out their seed for the passing winds to scatter up to 30km away. The flip side, however, is their longevity – the ability to wait until a wildfire has occurred before opening. Years after an area is thought to be free of the giant weeds, seedlings reappear.
Contorta quickly produce a multitude of low-angled branches. Those tasked with manually felling them must first fight their way in with a chainsaw before getting to the trunks.
Carlin says the native ranges of many species are higher and colder than New Zealand, which seems to allow them to grow faster here. Being expert wind-spreaders, the frequent gales of the Southern Alps – ever increasing due to climate change – were broadcasting seeds far and wide.
All this and the trees’ ability to germinate and grow in little more than a slab of rock means invasions and re-invasions are quicker off the mark. Subsequently, native ecosystems and treasured landscapes are being erased ever faster.
Host environments are typical of those seen on New Zealand’s tourism promotional videos – snowy, tussock-covered mountains and rocky Central Otago crag-lands, often portrayed bathed in golden light.
The conifer’s success in swallowing up thousands of acres of this rugged terrain across the South Island fits with trends observed overseas.
Central Otago’s rugged landscape, revered for its beauty and golden light, is under threat from wilding pines. Photo: Central Otago Wilding Conifer Control Group
Plant invasions, a byproduct of globalisation, are increasing worldwide and mountainous environments are considered the most vulnerable, according to a research paper published in the Annual Review of Plant Biology in 2023.
“In the European Alps, non-native plants are spreading upwards approximately twice as fast as natives, with species in both categories spreading upwards faster than would correspond to the current velocity of climate change because the spread is accelerated by the proximity to roads and long-distance dispersal events.”
In Southland, new rules are needed urgently as well as coordinated funding and clear accountability for seed sources, says Environment Southland’s Lucy Hicks.
“Douglas fir seeds at around 10 years’ maturity, and after this our ability to control the spread rapidly diminishes. The species’ long commercial rotation, often extending to 50 years, means that unless urgent changes are made, Southland will face decades of uncontrolled seed spread from both historic and current plantings.
She says the most concerning infestations are in northern Southland and the Te Anau basin, where wildings are advancing across conservation land and high-country farms. Other incursions were appearing in Waikaia, the Catlins, Longwoods, Tauringatua, Bluff–Tiwai, and the Takitimu Mountains.
“The risk extends far beyond biodiversity loss. If left unchecked, Douglas fir will reduce Southland’s productive land base, increase fire risk, and threaten water quality and quantity and wetland systems.”
Tourism and the region’s identity is also suffering as open, iconic landscapes are being replaced by dark, dense forests.
The insidious creep of wilding pine invasion across a Central Otago landscape. Photo: Central Otago Wilding Conifer Control Group
“Ultimately, communities are left to bear the long-term costs of inaction, as currently the ‘polluter does not pay’,” Hicks says.
While the sale and planting of contorta was banned decades ago, planted Douglas fir is not classified as a pest under the Southland Regional Pest Management Plan.
This means Environment Southland, under its current form, has no authority to control seed sources and can only encourage landowners to remove the wildings that result.
Hicks says national funding for Southland is “fragmented and inadequate”.
“For the 2025-2026 financial year, an estimated $5–$6 million will be needed for Southland wilding control alone, with $3–$4 million required at Mid Dome to combat both the legacy contorta issue and the expanding Douglas fir invasion. The Mid Dome Wilding Tree Charitable Trust received only $1 million this year, just one fifth of what is required to stay ahead of spread.”
So-called good-neighbour provisions requiring landowners to control wildings within 200m of a neighbour’s treated boundary are ineffective in practice, she says.
When plantings occurred historically, knowledge about the species’ troublesome ability to spread was less widely understood. There are still warnings issued but they were not heeded, Central Otago Wilding Conifer Control Group operations manager Pete Oswald says.
Many of today’s problem areas across the entire South Island were retired from grazing for conservation purposes, most during a long tenure review period (officially 1998 to 2022). The subsequent planting of notoriously bad spreaders like contorta to contain erosion on the retired blocks has given today’s rural observers a new argument to chew over: which idea will eventually prove to be the worst environmental disaster – that or the introduction of rabbits.
Federated Farmers are today pushing for low-intensity summer grazing to again be permitted on selected blocks. The change is aimed at reducing accumulated rank grass, young pines and other weeds, while earning the Crown money to fund wilding control.
In Central Otago, Douglas fir from various sources is vigorously spreading into high country, including where native species are slowly regenerating, Oswald says.
A wilding pine growing from a crack in the rock beside the Otago Central Rail Trail near Alexandra. Photo: Jill Herron
“There’s pockets of kōwhai, there’s totara regenerating, dozens of native species where it looks from the road like only tussock. It’s just that there’s competition between weeds and natives. Without our help the weeds will win, pines will always win over the natives.”
He says if budgets are not increased to fight the pines now, it will reach a tipping point where the spread can’t be stopped.
“We’re not far off that. Then you’ve just got to watch it densify over the decades.”
The group is also looking for accountability from owners of seed source plantations but because the necessary rule changes will likely take too long, pursuing a legal nuisance case through the courts is currently the only option for affected landowners.
Douglas fir cannot be planted in the Queenstown-Lakes District but elsewhere it continues to be widely utilized commercially, selling at nurseries for around one dollar per seedling or $1000 per kg for seed. If not harvested, the trees can live for 500 years or more.
Ministry of Primary Industries data shows 8.2 million were planted in New Zealand between 2018 and 2023. In 2023 alone new plantings covered 1000ha with approximately 1000 Douglas Fir trees per hectare.
Pinus radiata is also a problem spreader although less prolific. It remains the dominant species for permanent(“carbon”) and production forestry in New Zealand. In stark contrast, at home in California, radiata are considered a rare or endangered species.
Oswald believes ongoing mass pine plantings will have wide-ranging future impacts.
“It feels like we’re fighting the same fight again but today with the Government’s Emissions Trading Scheme the financial incentive is so massive and it’s driving the planting of Douglas fir. It’s like we’re doing the erosion plantings all over again. Our kids are going to say, ‘What the hell were you thinking?’”
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