The fight against wildings to save the iconic high country landscape
Standing on the Braemar Road, looking south over the golden sweep of the Mackenzie Country, there is a hint of snow on the hills and clouds skud across the main divide. The tussocks stir in the early stages of a nor'wester. But it's not just the tussocks that stir. Studded across the landscape are christmas trees, green, tangled and ranging in size from spindly saplings to sturdy adolescents to full blown matriarchs.
Picturesque, but the problem with these conifers is their relentless march across the Canterbury high country, threatening productive land, water availability and biodiversity at an alarming rate. The "golden sweep" of tussock land threatens to become a dense carpet of green, rolled out, west to east, by the relentless prevailing nor'wester.
Department of Conservation (DOC) says 5 per cent more of the high country is being covered by wildings every year, and a fifth of the country could be taken over within the next 20 years. The pace is that dramatic.
Ministry for Primary Industries (MPI) programme manager for wilding conifer work Sherman Smith says wildings are "transformational" in their impact.
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"If the [Mackenzie] basin is taken over by wildings, that's 50 cumecs drained out of the Waitaki system, the biodiversity would suffer and there would be a lot of species that wouldn't survive," he says.
"Initially, it's scattered trees but they don't stay like that. In high-density areas - there is no grazing underneath them, they can't be walked through and this affects farming, recreation and impacts water yields."
The trees were originally planted for erosion control, research, shelter and landscaping, hydro lake stabilisation and production forests by both private occupiers and government, Christchurch forestry consultant Owen Springford says.
"In order to understand why pines have colonised the Canterbury high country, you have to understand their origin.
"They evolved to colonise the scraped-bare, nutrient poor ground left after the retreating North American glaciers following the last ice age. They love Canterbury's arid tussock land and it is no wonder they are threatening to smother it," he says.
Due to early neglect, the spread of wilding conifers has increased exponentially since about 1990. The areas of established thickly wooded wilding forest are still relatively small - a few hundred thousand hectares. But another 1.5 million hectares is now liberally sprinkled with seedlings and saplings.
"Historically there has been under-investment in wilding conifer control, a lack of understanding of the scale of the problem and the need for early intervention," says Smith.
However, there is some good news, he says.
A massive 137,000ha of the Godley area of the Mackenzie Basin has been cleared of wilding conifers as part of phase one of a $16m national wilding conifer control initiative.
The four-year programme looks to spend $4m a year on combating the wilding spread.
Along with the Godley area, there are five others being targeted in Canterbury; Craigieburn, Porters and Lewis in North Canterbury, Hakatere in Mid Canterbury and Four Peaks in South Canterbury.
"The wilding programme is a great example of a partnership between MPI and DOC that is working well," Smith says.
Forestry writer Jim Childerstone thinks these days there are three basic schools of thought on the wilding problem.
First, are the conservation purists wanting the eradication of all conifers and deciduous trees and the restoration of all indigenous vegetation costing vast amounts of public funding.
Second, are the practical conservationists who seek a balance of a sustainable resource with management systems to limit spread, particularly where native forest exists. A percentage of funding would be available on net returns from the wildings for this.
And third are the sceptics of the current policy, who see forest establishment as a means of carbon sequestration to mitigate climate control. Commissioner for the Environment Jan Wright advises the need for establishing at least one million hectares of new plantings as part of New Zealand's obligation to cut its carbon footprint.
Retired Scion researcher Nick Ledgard is a strong supporter of wilding control.
The threat from wildings has been around for a long time, he says, especially with species that have light, easily blown seeds. He says ideal conditions for seed dispersal include a big wind coupled with a wet growing season.
He says there is no doubt wilding spread needs to be curtailed. To take them out now as immature saplings is going to be a lot cheaper than waiting until they are a solid mass of mature trees.
New herbicides have come along which can either be sprayed by helicopter using booms and wands or dabbed on the base of the trees from the ground. This has completely changed the economics of control, says Ledgard.
"This will work particularly well, especially if we work from west to east with the prevailing wind, cleaning up areas that will never be invaded again because there will be no seed source."
Springford maintains there is income to be made in wildings by hill country farmers in excess of what they are earning. It could even beat most of the dairy farming, he claims.
"New Zealand needs about two million hectares of new forest to reach it's Paris 2010 commitments. Evidently, there are about 1.8 million hectares of degraded land, much of it DOC estate, that could be left to generate to forest."
"DOC has a current budget of about $259m a year. It could easily generate this amount again from wilding forest, bringing rapid reality to the objective of making NZ predator free."
Ledgard questions this view, saying," If the inevitable native regeneration is to happen all wilding forests need a native seed source nearby and at least 1000mm of rain annually to get through the wilding 'nurse' cover and support the native undergrowth. The majority of the eastern high country wilding areas do not have this."
Smith says there was a long piece of work setting the scene for the eradication programme.
"It started six years ago. Federated Farmers, the forestry industry, government and local government were all sitting around the table. At the time there was a lot of good work going on, but a lot of people were feeling the impact of wilding conifers and nobody really knew how we could get the system working for managing them.
"We dug to the bottom of the issue and got some clear direction that everyone could agree on. This laid the foundation for an approach to government which paved the way for a top budget announcement of $16m for phase one of the national control programme.
"We had to prioritise where to start and what were the highest priority areas. A lot of focus is on the early scattered stuff. As we move through the programme we will get into more of the dense entrenched stuff. "
If the plan is eradication rather than containment, Ledgard says a lot more money will be needed to eliminate every last tree. But the plan is to take out the priority spots and halt the spread in its tracks, which is great news from a conservation point of view.
"But the question on many people's mind as they see patches of sprayed hillside turning to grey is what is going to grow back in the conifers place. It's likely to be exotic weeds," Ledgard says.
"Gorse, broom and blackberry."
The ideal would be to have the areas that aren't farmland returned to native bush or tussock. The government response is that volunteers are likely to do the follow-up, which could include planting native seedlings.
However, Ledgard says it's not so simple. Dying wilding forest does make a perfect half shaded nursery for beech, but rabbits, possums and deer would munch away at the seedlings. The effort and cost look prohibitive without a proper replanting programme.
"It's obvious that the current mass helicopter spraying campaign is only step one. It has created a lot of dead and dying trees. The follow-up question is what can be done next with the land that makes both ecological and economic sense."
As he says, there are lots more exotic invaders lining up for their chance to claim spots on the landscape.
Smith says a lot of science has gone into determining which were the most spread-prone conifer species, what land was the most vulnerable, what community support was available, and " how much land do we protect for our investment."
"We are focusing first on areas where there is a lot of scattered wildings and preventing them from becoming the next Mid Dome, the next Molesworth. We want to get that early spread.
"We are working on a cost share basis. The new national funding is supported by contributing funding from land occupiers. The government, DOC, LINZ, defence and landowners like farmers and regional councils are putting in a substantial contribution as well," Smith said.
"There are 14 management units in the programme this year. The total area they cover is about two million hectares. Of that, we estimated that there are about one million hectares that are wilding-infected. Already we have killed 1.1 million hectares. This is tracking really well and we are expecting to have covered 1.2 million hectares by the end of the year. Not bad for a first step."