Why are they a pest?
Wilding conifers can have significant impacts on native ecosystems, by shading out low-stature native plants. Where there is thick wilding conifer growth, this can lead to local extinction of native plant communities, the drying of wetlands and riparian areas, and resulting impacts on native fauna through the loss of habitat. Soil and soil fauna are also altered when wilding conifers replace native ecosystems.
Otago’s iconic landscape is vulnerable to the invasion of wilding conifers. If not controlled, they would significantly change the landscape and impact on our recreational, hydrological and conservation values. Particularly at risk is our high country and tussock grasslands. The growing problem has been recognised for some years and as a result, the Wakatipu Wilding Conifer Control Group and the Central Otago Wilding Control Group established themselves solely to fight wilding conifers.
It is estimated that wilding conifers are spreading at around 5% annually. Failure to control their spread at an early stage can quickly lead to increasing numbers of trees taking hold, and the costs of control escalating exponentially. This is the case in parts of Otago, where the cost of eradicating some areas of historically-planted conifers (known as legacy plantings) has now become prohibitive.
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The different types of wilding conifers
Wilding conifers are any introduced conifer tree, including (but not limited to) any of the species listed in Table 3, established by natural means. This doesn’t apply if to conifers within a forest plantation that don’t create any greater risk of wilding conifer spread to neighbouring or nearby land than the forest plantation that it is a part of.
For the purposes of this definition, a forest plantation is an area of 1ha or more of predominantly planted trees. This excludes planted conifers of less than 1ha, such as windbreaks and shelterbelts existing before March 2019.
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Table 3: Introduced conifer trees in our pest plan
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Common name
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Botanical name
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Bishops pine
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Pinus muricata
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Contorta (lodgepole) pine
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Pinus contorta
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Corsican pine
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Pinus nigra
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Douglas fir
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Pseudotsuga menziesii
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Larch
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Larix decidua
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Maritime pine
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Pinus pinaster
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Mountain pine and dwarf mountain pine
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Pinus mugo and P.uncinata
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Ponderosa pine
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Pinus ponderosa
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Radiata pine
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Pinus radiata
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Scots pine
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Pinus sylvestris
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Most wilding conifer species do not pose a significant threat to established native forests, however some species are adapting to new areas. Douglas fir in particular has a higher shade tolerance than other introduced conifer species and can consequently spread into shrublands, regenerating native forest and mature forest where there are canopy gaps and a relatively sparse understory.
Contorta (lodgepole) pine, Corsican pine, Scots pine, dwarf mountain pine, mountain pine and larch have very limited commercial value and are also highly invasive. This is why these are defined as pests in their own right as well as coming under the wilding conifer definition. This stops new plantings of these species and also ensures that where they are cleared using publicly funded control operations, stay clear.
Contorta in particular, is an unwanted organism, is the most invasive introduced conifer species and represents a significant proportion of all wilding conifers and original sources of wilding conifer spread.
For help identifying what kind of conifer you may have, see this Quick ID Guide.
What are the rules?
Over the life of the pest plan (10 years) the goal is to ensure that the spread of wilding conifers, contorta, Corsican, Scots, mountain and dwarf mountain pines and/or larch doesn’t cause unreasonable costs to the occupiers of neighbouring properties where control operations have taken place, or where the neighbouring occupier is undertaking active wilding conifer management.
Below are the rules for wilding confiers in our pest plan, these can be complex so if you want to someone in our biosecurity team about these rules call ORC on 0800 474 082 or email pests@orc.govt.nz.
Plan Rule 6.3.4.1 Within the Otago Region occupiers shall destroy all wilding conifers, contorta, Corsican, Scots, mountain and dwarf mountain pines and/or larch present on land that they occupy prior to cone bearing, if:
- The wilding conifers, contorta, Corsican, Scots, mountain and dwarf mountain pines, and/or larch are located within an area which has had control operations carried out to destroy wilding conifers since January 2016; and
- The control operations were publicly funded (either in full or in part).
Plan Rule 6.3.4.2 Within the Otago Region occupiers shall destroy all wilding conifers, contorta, Corsican, Scots, mountain and dwarf mountain pines and/or larch present on land they occupy within 200m of an adjoining property boundary prior to cone bearing, if:
- Wilding conifers, contorta, Corsican, Scots, mountain and dwarf mountain pines and/or larch have previously been destroyed through control operations on the adjoining property; and
- The control operations on the adjoining property were within 200m of the boundary and were undertaken since January 2016.
Plan Rule 6.3.4.3 (Note: This is designated a Good Neighbour Rule) Within the Otago Region occupiers shall destroy all wilding conifers, contorta, Corsican, Scots, mountain and dwarf mountain pines and/or larch present on land they occupy within 200m of an adjoining property boundary prior to cone bearing where:
- The adjoining land has previously been cleared through control operations since January 2016; and
- The occupier of that adjoining land is taking reasonable steps to manage wilding conifers, contorta, Corsican, Scots, mountain and dwarf mountain pines and/or larch on their land, within 200m of the boundary.
What if I use conifers for my shelter belt?
Contorta shelter belts and other conifer shelter belts are often used to provide shelter for stock. It can be difficult to successfully control or manage the spread of wilding conifers over the long-term if the existing planted seed sources are not removed or appropriately managed and contained. The pest plan does not require you to remove existing shelter belts and other existing planted conifers less than 1ha. However, ORC’s Biosecurity Strategy sets out transition arrangements for their long-term removal, starting with the removal of Contorta shelter belts.
What are we doing?
Otago Control Programme
Otago is divided into 17 management units for the purposes of controlling wilding conifers. Each management unit has a specific control plan with one or more project managers overseeing a contracting workforce for ground or aerial operations.
Programme funds are allocated to controlling wilding conifers in priority control areas, where scattered wildings are most prone to spreading and is aimed at supporting a wide range of stakeholder and community groups undertaking control work.
Operations aim to prevent the spread of these tree pests throughout Otago and to progressively remove them from much of the land already invaded. This involves controlling seedlings and outlying trees and working back to the original seed source. Types of control methods include manual control like hand-weeding and cutting with chainsaws to aerial herbicide application.
Through effective collaboration between central and local government, the Department of Conservation, Whakatipu Wilding Conifer Control Group, Central Otago Wilding Conifer Group and land occupiers, we are helping protect our region’s unique landscapes, primary industry, tourism and the economy from the impact of wilding conifers.
National Wilding Conifer Control Programme
In 2016 the National Wilding Conifer Control Programme was established to ensure a collaborative, coordinated and effective approach to national wilding management. The delivery of the programme is led by Biosecurity New Zealand in partnership with regional councils and unitary authorities who coordinate the activities regionally and support a wide range of stakeholder and community groups.
Find out more about the national programme here.
The graph below shows the estimated increase across Otago in hectares infested by wilding conifers over the next 20 years if the present management regime continues.
In 2015, a national wilding conifer management strategy was developed, promoting a co-ordinated and collaborative multi-agency approach to wilding conifer management by relevant agencies. Several groups are already actively engaged in the control of wilding conifers across Otago.
ORC administer central government funding for the control of wilding conifers in Otago. We also collect a regional rate to support community groups undertaking control work.
The Queenstown community-run Wakatipu Wilding Control Trust has produced a wilding conifer control strategy. This trust, and the Central Otago Wilding Conifer Control Group, which has developed its own strategy, have put thousands of volunteer hours into containing, controlling and eradicating wilding conifers.
What can you do?
Wilding conifers are a major problem in Otago, but we’re making progress. The more people that help, the quicker we can get the problem under control. If you're a landowner or landholder and want to find out more about control work in your area or funding opportunities to help with your wilding conifer problem, please get in touch with our Biosecurity Team by emailing pests@orc.govt.nz or calling 0800 474 082. For more information relating to wilding conifer control in Otago, problem species and control tips and techniques, see the following websites:
Which parts of Otago are most infested with wilding conifers?
The western, central and northern areas of the region have various levels of wilding conifer invasion. Many affected areas contain scattered trees, but heavily infested areas exist in western inland locations that are lightly vegetated and lightly grazed. The infestation is somewhat less in the middle areas and increases slightly in the north-east.
Wilding conifers are a significant issue in the Queenstown Lakes district, where dense infestations are associated with historical plantings around settlements, eroding slopes and recreation areas, as well as commercial plantations and woodlots.
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