The Mid Dome project area surrounds the Cupola and Mid Dome ranges, encompassing an area of 68,602ha approximately mid-way between Invercargill and Queenstown.
The project area has extensive alpine tussock grassland interspersed with fellfields, pastoral farmland, and remnant beech forest. It is important for pastoral farming and also contains a range of ecological and scenic values.
The project area comprises a mix of land tenure:
|Land Tenure||Hectares||Proportion of Project Area|
|Public Conservation Land||10151||14.8%|
In 1947, the Mid Dome Soil Conservation Reserve was established on the western edge of the project area and planted with 250 hectares of Contorta pine (also known as Lodgepole pine or Pinus contorta). This was later supplemented by the planting of Dwarf mountain pine (Pinus mugo) with the aim of preventing soil erosion (Ledgard, 1999).
Both species can spread rapidly, with the open tussock grasslands to the east providing ample opportunity for their establishment. Concern about the spread of wilding pines from the Soil Conservation Reserve was expressed as early as the 1960s, and a number of initiatives to control their spread began at this time.
By 1999, Nick Ledgard estimated wilding pine spread from the Soil Conservation Reserve occurred throughout more than 13,000ha of the project area, with scattered outliers further east of the Mataura River (Ledgard, 1999).
The Mid Dome Wilding Trees Charitable Trust was established in 2007 and represents a collaborative approach to managing the wilding pine spread. The Trust is made up of local landowners and community members, as well as representatives from Ngai Tahu and central and local government agencies.
Mid Dome stands as a sentinel above the crossroads that mark halfway between Invercargill, Queenstown, and Fiordland National Park. In its shadow lie some of Southland and Otago’s most valuable and vulnerable high country tussock and pastoral grasslands.
Contorta pine was planted on Mid Dome between the 1950s and 1980s for erosion control. Strong prevailing nor’westerly winds make Mid Dome a perfect take-off point for the millions of seeds these wilding pines produce every year. Offspring from these very light, winged seeds have been found 40 kilometres downwind of Mid Dome and up to altitudes of 1400 metres. The shade beneath the canopy of dense wilding pines eliminate all other plants beneath them. The wilding pines at Mid Dome are stunted and have no commercial value as timber or firewood. They do not hold much more carbon than the snow tussocks and other vegetation they displace either.
These unplanned and unmanaged stands of wilding pines grow much faster than our native species. They threaten to totally change our southern landscapes forever. The future of native animals and plants living in these landscapes looks bleak. Productive farmland and recreational opportunities like mountain biking, horse riding, tramping, and four-wheel driving– would also disappear beneath an impenetrable monoculture of wilding pines.
The spread of wilding pines at Mid Dome and other areas throughout New Zealand threatens productive farmland, native landscapes and ecosystems, tourism opportunities, and our national economy.
The wildings can quickly grow and change ecosystems where there is no native forest, such as tussock grasslands. Once established, they outcompete other species. They form closed canopies which shade and acidify the soil, eliminating native plant and animal species. Wilding pines change the distinctive look and values of our New Zealand landscapes, such as iconic alpine tussock grasslands.
Wildings also reduce the flow of water and recharging of aquifers in water-sensitive catchments. Less flow means less water for irrigation, hydroelectric generation, or outdoor recreation use, and less water for those plants and animals that live in and around the rivers and streams.
The annual reduction in water yield ranges from 30 to 81 percent where pasture land has become covered in wilding pines.
The seeds from wilding pines can be blown many kilometres by wind, and they have spread into high country pasture and conservation land in the Mid Dome area.
Seedlings quickly infest an area and if they are not controlled, will grow into a dense impenetrable stand of wilding pines.
Land in the Mid Dome area is mainly used for low-intensity grazing or managed for conservation purposes. Native ecosystems need protection from being replaced by wilding pines. These ecosystems include tussock grasslands, subalpine shrublands, wetlands, and indigenous forests. Threatened and rare native plants and animals need to be protected by preserving their habitats from the threat of wilding pines invading these ecosystems.
If not eradicated, it is predicted that wilding pines in the Mid Dome area will totally overwhelm 61,000 ha of high country tussock and pastoral grassland in the short term, and infest a further 100,000 hectares by 2053.
If we lose this battle, the land will have no long-term ecological, economic, or recreational future.
One of our biggest challenges in the Mid Dome area is accessing the remote alpine areas where the wilding pines grow.
The wildings can quickly grow on farmland and significantly reduce the grazing available for stock if the seedlings aren’t managed through mob-stocking or other means.
Unlike commercial forests, where trees are thinned and there’s good road access, forests of wilding pines can be dense and impenetrable. Trees can also be different ages and shapes in a stand. All this makes removal difficult, with the costs of harvesting the trees being more than any return gained.
The costs of controlling wilding pines increase exponentially over time, and the chances of success drastically diminish each year. Wildings have the potential to be southern New Zealand’s most serious ecological disaster.
Our mission and the job ahead
The Mid Dome Wilding Conifer Control Strategy provides a dual approach to removing the seed sources, by controlling the original plantings on the Mid Dome Soil Conservation Reserve (“the primary seed sources”) as well as adjacent areas of closed-canopy wilding pines (“the secondary seed sources”). There is also a containment approach of controlling scattered outliers of wildings in the east of the Mid Dome project area.
The programme has a goal to reduce Pinus contorta and Pinus mugo within the Mid Dome project area to such a level that by 2024 the ongoing maintenance needed to control any re-growth of wildings can be managed by the relevant landowner.
Despite the scale of the problem, wilding pines are relatively easy to control – their spread is often visible and predictable, and seeds rot quickly in the ground. Choosing the control technique best suited to an area depends on the density and spread of the infestation, its surrounding environment, and access to the area.
The only viable way to tackle the densest areas of wilding pines is by aerial spraying using herbicide, known as Aerial Foliar Spray Application.
Aerial Basal Bark Application is used for scattered wilding pines that cannot be safely or effectively controlled using ground control methods.
Ground control techniques including using chainsaws, scrub bars, herbicides or hand-pulling to remove the wildings and allow native plants to regenerate.
Each of these control techniques have been researched and refined during the development of methods to control wilding pines. These techniques capture the collective national knowledge of stakeholders and operators involved in wilding control nationally.
Aerial control techniques
Aerial Foliar Spray Application (AFSA)
AFSA involves using boom spraying of herbicide onto wilding pines using helicopters or fixed wing aircraft. This is a cost-effective way of treating large areas of closed canopy wilding pines where any potential damage to surrounding, woody vegetation is not a risk.
Aerial spot spraying of herbicide onto wilding pines is used where the canopy cover is less than 80% but the base of the trees does not allow the ABBA method to be used or if there is a potential to effect surrounding valued vegetation.
Aerial Basal Bark Application (ABBA)
ABBA uses an oil-based herbicide to chemically ring-bark wilding pines with trunk diameters of up to 20 cm. The effects of ABBA control can take a couple of years for the trees to die off completely.
The Nation programmes best practice guides for the above applications can be found here:
Ground control techniques
This involves drilling holes into the tree trunk, at regular spacing around the stem, and filling the holes with herbicide. It is useful for large trees as an alternative to felling them in difficult terrain where felling can be unsafe, or where cut down trees can reduce grazing or encourage the establishment of pests.
Hand-held tools/manual removal
Removing wilding pines by hand-pulling, using hand-saws or loppers, or by felling them with chainsaws. This is most effective in easily accessible areas, on seedlings and small trees.
Achievements to date
During the last five years, wilding pines have been controlled over 31,000 hectares in the Mid Dome project area. This has involved a combined approach of controlling the seed sources, and progressively containing the scattered outliers in the east of the project area.
This year’s goals
The aim for 2019/20 is to complete the initial control of the primary and secondary seed source areas. This will be a significant achievement for the Trust in terms of eliminating sources of wilding pine spread. Further work on controlling scattered outliers will also be completed to progressively contain both Contorta and Mountain pine in the project area.
You can access The Mid Dome Wilding Conifer Control Strategy 2014-24 here.
The following objectives have been set to achieve the Trusts’ goals of reducing the levels of Contorta and Mountain pine to a stage whereby landowners can manage any regeneration of wilding pines on their land;
- 1a. Successful (>85%) initial control of the Secondary Seed Source Area has been completed by 30 June 2020.
- 1b. Successful (>85%) initial control of the Primary Seed Source Area has been completed by 30 June 2022.
- 1c. An incidence of less than 5 coning P. contorta and P. mugo per hectare is progressively achieved in the Maintenance Control Area throughout the term of the Strategy.
- 2a. The Trust and landowner’s/land managers within the Project area are able to reach mutual agreement as to when the on-going control of P. contorta and P. mugo on each property is able to be handed back for self-management.
- 2b. The Self-Management Area encompasses the entire Project area by 2030.
- 2c. Following handover, landowner’s/land managers are able to sustain zero density of coning P. contorta and P. mugo on their properties.
- 3a. All conifer and tree weed plantings within and adjoining the Project area that pose a significant threat of wilding spread within the Project area have been identified by 30 June 2015.
- 3b. Voluntary agreement has been reached with the owners of all conifer and tree weed plantings that pose a significant threat of wilding spread on ways to eliminate or mitigate this risk by 30 June 2020.
- 3c. No new plantings of conifers or tree weed species that will pose a significant threat of wilding spread has occurred within and adjoining the Project area during the term of the Strategy, except where satisfactory mitigation measures have been instituted.
- 6. The Trust advocate for review of the National Environmental Standards for Plantation Forestry in order to have more ability to manage high-risk plantation forestry within and adjoining the Project area.