Controlling Wilding Pines in Otago

New Zealand’s largest-ever private land protection agreement, the Mahu Whenua covenant, was finalised with the QEII National Trust in 2015. International music producer Robert ‘Mutt’ Lange of Soho Property Ltd has protected more than 53,000 hectares of continuous high country landscape between Lake Wanaka and Arrowtown, bordered by the Shotover River and the Cardrona Valley.

The total area of QEII covenants in New Zealand is 181,347 hectares.

Left uncontrolled, wilding pines are predicted to spread across 20 per cent of New Zealand within two decades costing the economy more than $1.2 billion. These unwanted trees are already growing on about 1.7 million hectares, almost 6% of New Zealand, and the area is increasing about 90,000 hectares per year.

The Ministry for Primary Industries released a National Wilding Conifer Management Strategy in late 2014 and there was widespread disappointment that no money was allocated to the problem in the 2015 Budget.

Trees including alder and sycamore, rowan and hawthorn (which are not conifers) are also aggressively spreading in natural areas, including established native forest.

Lange and ex-wife, Canadian singer Shania Twain, bought Motatapu and Mt Soho Stations in 2005, adding Glencoe Station in 2009 and Coronet Peak Station in 2011. All are Crown pastoral leases. The Coronet Peak purchase included an Overseas Investment Commission (OIA) requirement that Lange commit almost $1 million to wilding control. To date, $1,229,300 has been spent.

When these neighbouring Central Otago properties were purchased wilding Douglas fir, sycamore, lodgepole (contorta) pine and larch were spreading across the landscape, especially into areas protected for conservation.

Lange was determined to restore the country to a pristine condition so native fauna and flora could flourish. In 2015 he protected 51,300 hectares with a QEII National Trust conservation covenant and 4500ha was set aside for farming.

QEII Central Otago regional representative, Rob Wardle, said registering covenants against titles locked in conservation gains through any changes in ownership and management.

“A lot of the values protected in this covenant are quite severely threatened by wilding pines,” he says. “For all the effort and sexiness of restoration, there’s more bang for your buck in controlling trees in natural landscapes. If Soho had done nothing, many natural areas would be overwhelmed by exotic trees and the majority of the land area – now virtually free of trees – would be subject to much higher levels of invasion.

“Apart from biodiversity, wilding trees threaten Central Otago’s wide open landscapes and consume relics of a colourful gold-mining history.”

“At the moment if you flew over the place, looking very hard you’d see the occasional young tree. If the work hadn’t been done, the landscape would be dotted with them.”

Some of the most natural areas with the highest biodiversity were right behind Arrowtown, open to public access, Mr Wardle said. If nothing was done, areas of tussock land, native shrublands and mountain beech forest would be steadily degraded.

Russell Hamilton supervises management of the stations, farmed as Soho Properties Ltd, for both farming and conservation.

Clearing a mature block of wildings requires about a 20-year commitment, after initial spraying, Mr Hamilton said.

Working from the furthest extremities in, step one is taking out all seeding and juvenile trees. Five to six years later there’s a second sweep, by which time any new seedlings will be tall enough to see but not yet mature enough to cone. From then on, unless seed has come from an outside source, control work is mostly about destroying the odd tree that’s been missed.

“The second time you go back you take out an enormous amount of regrowth, the third time there are only remnants and by the fourth time you’ve virtually nailed it,” Mr Hamilton says.

Most work is done from the air with large blocks and mature trees boom-sprayed by helicopter. Single trees are treated with basal bark spray applied with a hand-held wand, again from a helicopter.

Seed in cones is viable for two to three years and require sunlight to germinate. For this reason, blocks of mature trees are left standing after spraying rather than clear-felled. Cut them down and a mass of seedlings come up underneath, explains Mr Hamilton.

Where wildings are reasonable sparse, ground crews of up to 10 contractors are moved about by helicopter, pulling or cutting trees and painting stumps of suckering species. They focus on trees which are scattered, hard to reach or along water-courses where spraying is not an option.

“Wilding species and type of country dictates the chemical and method we use,” says Mr Hamilton. “Sometimes ground-staff are the best way of cleaning out scattered immature trees, for example, with the helicopter crew doing the spotting.”

Areas on Coronet Peak are his biggest worry because of ongoing re-infestation from a Queenstown Lakes District and Central Otago District Council-owned Douglas fir plantation.

Less than 1km from this block, over a high ridge, was mixed beech forest.

The other challenge was larch and sycamore on Glencoe and Coronet Peak Stations behind Arrowtown, a colourful selling point for the town in autumn. OIA conditions for buying this property included agreement that residents’ community concerns must be addressed and these trees were much-loved.

“People often say, ‘I like the trees just as they are’. I answer, ‘that’s like saying you like being a little bit pregnant’.”

One costly and labour-intensive solution might be to slowly replant colourful but less invasive species such as oaks, claret ash and European beech, one spur at a time, Hamilton said. “But we won’t do anything without public support.”

Like most people who had lived in the area for much of their lives, the sudden spread of douglas fir over the last 20 years caught him by surprise and it had taken time to see the autumn beauty of larch and sycamore as deadly. “A lot of the control is not pretty but by killing mature wildings we’re protecting a vast area around it.”

Mr Hamilton has noticed that on farm country, grazing stock slow rather than control the wilding problem. Infestation became more rapid, once stock were removed.

Until now, Soho has organised and paid for most wilding control. However, as OIA conditions are satisfied Mr Hamilton’s anticipating future work should attract outside support on a par with similarly affected landowners.

Already, help has come from organisations including the Wakatipu Wilding Conifer Control Group, the Arrowtown Village Association and boy scouts. The QEII Trust arranged for Bachelor of Environmental Management students at Southland Institute of Technology to gain practical experience at Coronet Peak, lopping, chopping and spraying mostly larch and lodgepole pine.

Trampers on new public trails through Soho Properties are also enthusiastic about spotting and pulling out trees.

The Wakatipu Wilding Conifer Group supported Mr Lange’s application to the Overseas Investment Office to buy Coronet Peak due to his “impeccable record” of controlling wilding trees and goats to conserve native flora and fauna.

The group is spending $1.4 million on eradication of wilding trees in the Wakatipu Basin in 2015-16. Committee member, Grant McMaster said until recently, public awareness of wildings had been zero.

“We’ve had people writing to the paper saying what beautiful trees they are. But if you look at a photo of Queenstown in the 1930s or 40s, there’s not a tree around. I say, if people love New Zealand the way they’ve known it, there must be money directed to hitting wildings hard.”

The 85,000 hectares targeted by the group was aiming for containment of spread, not control, Mr McMaster said.