Wilding conifers could take over
Take the drive west of Christchurch to the Castle Hill Basin and just before the Craigieburn cutting you could be forgiven for thinking the apocalypse had struck.
Row upon row of tall, dying conifers reach skyward, their bleached spars ragged across the horizon. Some have begun to topple, leaning precariously against their neighbours. Others have already succumbed to their fate and lie prone across the mountainside. But this scene is not some aftermath of a disaster; it’s the product of the Government’s $16 million programme to rid the country of its No 1 one pest. Wilding conifers.
According to the Department of Conservation (DOC), 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 if drastic action is not taken. It’s that bad.
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.
Growing in the wrong place, wildings out-compete native plants and wildlife, reduce precious water resources, smother valuable grazing land and harbour pests. They also change the unique character of iconic natural landscapes such as our high country, says Wilding Conifer Programme manager Shermon Smith.
‘‘Wildings are transformational in their impact, and we are at a tipping point.
‘‘In preventing the spread of these trees, we must act now as delays will quickly put the costs beyond our reach.’’
But heartening news: Over the past three years the first phase of the Wilding Conifer Management Strategy 2015-2030 has eradicated over half a million hectares of wildings and searched the surrounding land for remote outliers.
‘‘The programme is making excellent progress,’’ Smith says. ‘‘The operations to date have exceeded phase one targets.
‘‘As of July 2018, just two years into the four-year programme for phase one, operations are already 85 per cent complete. Within the 1.5 million hectare area covered to date more than half a million hectares has been controlled. We have also searched over a million hectares for any remote outlier trees.’’
The Waimakariri Basin, of which the Craigieburn area is part of, is one of the success stories of the first phase, Smith says.
Despite a previous spend of $300,000 a year, the government and local groups struggled to contain wilding spread from old erosion control plantings from the 1950s to 1980s. The spread threatened productive farmland, and recreational areas and was a blot on the landscape.
About $2 million of wilding control programme funds allowed a concentrated effort to get on top of the problem and now farmers have regained use of their pastoral land and Arthurs Pass National Park and Korowai/ Torlesse Tussocklands have been protected from invasion.
Further south, a massive 137,000 hectares of the Godley area of the Mackenzie Basin has been cleared of wilding conifers.
‘‘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,’’ Smith says.
‘‘Initially, it’s scattered trees, but they don’t stay like that. In highdensity areas – there is no grazing underneath them, they can’t be walked through, and this affects farming, recreation and impacts water yields.’’
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 easily blown seeds.
He says there is no doubt wilding spread needs to be curtailed. To take them out now as young 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.