January 7 2019 by Jim Childerstone
Wilding Conifers – Complete elimination or control? As a semi-retired forester I have to disagree with the stance adopted by the national wilding conifer clearance groups. Millions of dollars are sought from various agencies, local authorities and Government to get rid of this pest plant. Wilding conifers have proven commercial value. I side with other foresters that advocate forestry management systems which could use these self-regenerating trees as a resource.
Many of these pest trees in our region can be harvested and sold, and the proceeds could be used to prevent outlier spread.
The prime invaders in the Wakatipu region are Douglas-fir, Lodgepole pine (Contorta), Corsican Pine (p Nigra), Scots (p Silvestris) and more recently, European Larch. Douglas-fir, known as NZ Oregon when sold as structural timber, currently earns between $130-$150 per tonne (at mill gate). Nearly 300 tonnes were sold this year from work done near the Skyline Gondola, but in the 1970s and early 80s, I milled hundreds of cubic meters on my portable mill across the district. In the past, Corsican Pine have been grown and harvested in Naseby Forest for building timber. Also, the Mackenzie Country has been a source of post timber cut from wilding Contorta. With the current building boom, there is demand for all species and grades of timber.
There are many commercial possibilities for by-products, too. Wood chips from these invasive species are a great source for biofuel and can be used as an alternative to fossil fuels. Local entrepreneurs have even processed branchwood from these trees for essential oils. Christchurch-based forestry scientist Owen Springford, revealed that if all wildings were registered in the Canterbury region, it would earn as much as $300,000 for the Department of Conservation to help control outlier spread.
Additionally, a 30-year research plan into afforestation of the South Island’s denuded high country in the 1950s showed that the most invasive of these species stemmed erosion and prevented land slips. It also improved soil quality which enabled the re-introduction of native plants in some areas. A 1911 photo of Queenstown shows a planted shelter belt above the township, introduced partly to prevent rock falls.
As for the indigenous versus exotic vegetation argument, I still question what constitutes an iconic landscape. For nearly 800 years, since human habitation, landscapes have been modified. Apart from areas in Westland and Fiordland, a few areas in the East and Central Otago, most vegetation is exotic. So are our commercial forests. The Douglas-fir being removed adjacent to the Skyline Gondola are about 80 years old, up to 70 meters in height with diameters of well over a meter – a fantastic resource with commercial viability. Go figure.
Forest Services. Author of THE WILDING CONIFER INVASION - Potential Resource or Pest Plant. (Lakes District Museum Arrowtown and Bounds Books Queenstown)