Using herbicides to control wildings
Article from the New Zealand Wilding Conifer Management Group
ADVOCATES FOR THE TONGARIRO RIVER INC
WILDING PINES PROJECT
A Department of Conservation – Advocates Partnership
Nga mihi manawhenua kaitiaki katoa
This Society – AFTR – envisions the Tongariro River corridor being returned as close as possible to its natural state so that the river valley’s landscape values and its biodiversity status are restored.
The project – dealing with a problem
One part of this vision is the control and removal of exotic pests such as wilding pines. These pines are a problem because they are aggressive colonisers in New Zealand growing conditions (unlike their more restrained growth in their native habitats of North America).
These pines are a nuisance especially in areas where native forest regrowth is being encouraged; here, alongside the Tongariro River. Pines are visually intrusive, an important factor where aesthetic landscape values are to be restored. The pest trees also overpower emerging native plants as they win the competition for forest space. For the fauna they offer none of the advantages of native trees, no berries nor nectar, which encourage bird and insect life. Further, pine needles inhibit regeneration of native forest floor flora.
Pines are a no-no in National Parks where pinus contorta is a strenuously attacked pest.
Nationwide there are many campaigns aimed at curtailing these pest trees. A simple Google search will show the vigour of the overall crusade as New Zealanders restore their respect for native flora; there are over 300 pages of websites. All Regional Councils are taking action against wilding pines as part of New Zealand’s Biodiversity Strategy. The Marlborough Sounds situation is an often quoted arm of this movement and nearer home, the Kinloch Community Association is dealing with these pines near there, and as one drives south from Taupo along State Highway 1 at Hatepe, there are many recently poisoned pine trees to be seen in the Hinemaiaia River Valley. Nearer home, the joint DoC – Tongariro Natural History Society project to restore the Motuoapa wetlands brought about the poisoning of pine trees, clearly visible from the highway.
The project to eliminate pines started several years ago, with poisoning in the Department of Conservation reserves on the left bank of the Tongariro River upstream of the Trout Centre and later, by the AFTR, on the right bank. The work, unfinished, has moved upstream to about 1 km above the Red Hut suspension bridge. The effect of the poisoning there is not subtle, there are many trees in the brown stage, in which the needles die and drop. Soon the skeletons will turn grey and later they will rot away.
Understandably, some people are upset by the effect of rust brown pine needles on large trees on the skyline. Of course, if the problem had been addressed say 20 years ago when the trees were much smaller the visual effects would have been much lower. And, conversely, if they were to be left any longer the ability to manage them would become far more difficult and perhaps cause the increasing persistence of a wilding pine forest. The Department of Conservation had no funding to do this work and it may have considered that there was little community interest anyway. Even now with some funding provided through grants made to the AFTR there is just enough to use this poisoning technique.
So at present there are many middle-sized wilding pines causing distress due to the continued presence of those poisoned trees. Can anything be done to improve the situation? The AFTR have explored several possible options.
Can the visual effect be dealt with quickly? Here are the facts
Poisoning and rotting down is the only cost-effective way of dealing with these trees. It would be prohibitively expensive to attempt to remove the trees at any stage in any other way.
Removing the skeletal trees, known as standing spars, by cutting them down is dangerous on two counts. First there is high risk to the safety of timber workers. Secondly un-rotted spars lying on the ground present heavy fuels which increase the risk of extreme fire damage should there be a bush fire. Further, the damage to any understorey of regenerating natives as whole spars crash down would be disastrous. So tree skeleton removal is not an option. The standing spars must be left to rot down.
How long might this take? Climate and weather will play a major role. From about five years the effects of rotting down should be noticeable.
This method is not only the most cost effective way of dealing with these pines, but it is also the most effective. The gradual shedding of needles as the trees die means that the light entering the forest floor gradually intensifies. This factor favours the natives; if the whole pest tree is suddenly removed the survival of young exotics would be favoured.
Already biodiversity gains have been detected. DoC Officers report that a stand of juvenile totara in the upper river has been given a better start and should grow to maturity now that the pines there have shed their needles, thus letting light in.
The AFTR appreciate the concern at the temporary harm done to the skyline landscape in parts of the river valley. But how else could this problem be addressed? The AFTR have taken the only course available.
Why are the Advocates involved?
The AFTR regard the river as a taonga of the highest rank in this district and the Society is committed to helping the river’s recovery and eventual restoration. This commitment takes in four practical steps at present; viz
– Protection of existing indigenous flora; mature and juvenile kahikatea of noble status on private land at Kowhai Flat have been listed in the Taupo District Council’s outstanding and notable trees registry. As such these specimens form a distinctive attraction to tourists.
– Planting further specimens of endemic species, especially kowhai, along the riverside walkway.
– Weeding amongst newly planted natives, involving AFTR members, residents and occasionally Corrections Department inmates.
– Eliminating wilding pines. This part of the restoration will achieve native plant germination and growth through better light conditions and through improved forest floor conditions etc as outlined above.
The AFTR has received funding from several sources. These include Trustpower awards, and grants from the Waikato Catchment Ecological Enhancement Trust, Pharazyn Trust and the Waikato Regional Council.
These bodies would not have committed their funds if they had not been sure of the quality of the applications mounted by the AFTR, the degree of accountability shown and the society’s growing track record of getting ecologically important things done.
The AFTR has received a number of awards for its ecological work. These include the TrustPower Community Award for the environment, and from the Tongariro Taupo Conservancy of the Department of Conservation an award which recognises the work done towards the conservation of the natural, historic and cultural resources of the Central North Island. There is a DoC – AFTR joint sign located on the riverbank showcasing the important work done by this community group in partnership with the Department of Conservation.
Further activity involving catchment management is in the pipeline.
The Society works within the guidelines of New Zealand’s Biodiversity Policy and it co-operates with the Department of Conservation in this task of controlling exotic pest species so that native flora and fauna may survive.
For more information about wilding pines enter these
or Google ‘wilding pines nz’
The AFTR website is www.tongariroriver.org.nz
The Origins of The Wilding Pines Project