Land Information New Zealand (Linz) started its control work at Lake Benmore in 2018, after it was identified that seeds from wilding conifers on the islands were invading vulnerable land downwind, biosecurity and biodiversity group manager Megan Reid said.
"In many parts of the islands the conifers have increased in size and density and there is now the risk they will fall into the lake and become a hazard to the nearby hydro dam," Ms Reid said.
The spread of invasive trees posed a threat to the ecological value of the area, she said.
"Wilding conifers take over natural environments, and on islands in Lake Benmore they are displacing Waitaki broom — a critically threatened native plant only found in South Canterbury."
The next stage of the operation would take one day and was expected to start later this week, depending on the weather.
It would include aerial spraying of Black Jacks, Turnagain and Whanau Islands, where tree cover was dense.
Ground control methods would be used in some places.
Linz had taken the community’s concerns about access to the islands into account, Ms Reid said.
"Targeted ground control will take place on Junction Island, allowing recreation to continue.
"Aerial spraying won’t take place on the island this year while we consider how best to approach control in future operations."
Signs would be put up at entry points to the lake to advise when work was being carried out.
The public should not enter an island when aerial or ground control work was being carried out, she said.
The work was being done in conjunction with the National Wilding Conifer Control Programme, which was also carrying out the work on the Benmore Peninsula.
Boffa Miskell was overseeing the operation, working closely with Meridian Energy, Environment Canterbury and neighbouring landowners.
"Over time, Linz will restore control areas with native plants, adding to the scenic and environmental value of the islands," Ms Reid said.
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Comments
I worked at both Benmore and Aviemore, and thought the pine trees were a great addition to the area, even planted one! So now they're all going to be rooted out as they could be a hazard to Benmore dam? Oh, come on!
Land Information New Zealand and its allies in government and media present us with one version of events based on a particular ideological viewpoint. Replacing a forest ecosystem with a selection of grasses and wiry shrubs isn't everyone's idea of improving scenic and environmental value. As a frequent visitor to area with an enthusiasm for art, horticulture and photography I can offer an alternative opinion: the forests of the Benmore region are/were a diverse mix of the world's most economically valuable and beautiful coniferous and deciduous trees that greatly added to the photographic and tourist appeal of the lake, provided a green oasis of shelter and shade together with vibrant autumn colour in an otherwise barren landscape and contributed far more to the much publicised need for atmospheric carbon capture than the native ecosystem. Limiting the spread of trees rather than exterminating established forest would have been an option for protecting both ecosystems and would have provided endless employment opportunities into the future.
Has the value of these so called wilding pines as a carbon sink been included in the evaluation of their future and if not why not?
It seems odd to me that the short sighted authorities are suggesting weed spraying as a control mechanism on what they claim are ecologically sensitive islands. Surely the unspecified weed killer, but likely to be a broad spectrum one, will kill all vegetation. That will also result in the elimination of any insects or reptiles that have survived there as well.
If the only native plant at risk is Waitaki Broom then why not make its seed commercially available to nurseries and the public. There are many NZ gardeners who would grow this plant.
Much more information is required on this decision and the control options that have been chosen. The question of what constitutes the best ecological answer needs to be taken from the exclusive purview of NZ native species zealots who have demonstrated their tendency to lose sight of the bigger picture.