Wilding Conifers

Wilding conifers are an invasive pest tree which affects landscapes and pastoral productivity across New Zealand, including Otago.

Helicopter Spraying

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.

Wilding conifers can survive from coastal Otago to the inland high country, and their seeds are easily spread. The western, central, and northern areas of Otago 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. 

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.

If nothing is done in Otago to control this problem, the area infested in this region is likely to triple from 300,000 ha to 900,000ha over the next 20 years if current management approaches remain.If current management levels do not increase, the extent of wilding conifer-infested land nationally is expected to treble over the next 20 years, to 5.43m ha, 20% of New Zealand’s land area. This could result in economic losses of around $244 million per annum (Scion, March 2015).

Management and control 

Controlling the spread of wilding conifers is a complex issue - long-term control and management requires an ongoing programme, with varying levels of intervention required depending on the location and degree of infestation.

The nature and extent of wilding conifers varies across Otago and it is likely that varying control approaches may be required in different areas. Recognising that it is impossible to completely eradicate the existing dense wilding conifer seed sources, there are three management scenarios which could apply to these different areas.

1. Contain and eradicate

Maintaining current areas that are free of the pest, identifying existing dense conifer stands that are to be contained within defined areas, and eradicating all other wilding conifers.

2. Progressive containment

Keeping areas that don’t currently have wilding conifers free of the pest, identifying existing conifer stands that are to be contained within defined areas, and controlling and limiting the spread back to a containment line over time, rather than complete eradication.

3. Reduce the spread

Keeping areas that do not currently have wilding conifers free of the pest, and require land-boundary controls elsewhere to limit the further spread.

Wilding conifers can survive from coastal Otago to the inland high country, and their seeds are easily spread, as the map below indicates. (click on the map to enlarge)

Wilding Pine Conifers map

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.

Graph for estimated increase in wilding pine cover for next 20 years

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.

We 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-based 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.

 

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.

Hills behind Alexandra. Photo: Chris Pascoe

Hills behind Alexandra. Photo: Chris Pascoe

Upper Manuherikia with Hawkduns in background

Upper Manuherikia with Hawkduns in background

Hills southeast of Alexandra

Hills southeast of Alexandra

Kakanui Range

Kakanui Range

Spread adjacent to Naseby forest

Spread adjacent to Naseby forest

Volunteers get ready for a day of wilding control at Ben Lomond, Queenstown in 2011.  Photo: ODT

Volunteers get ready for a day of wilding control at Ben Lomond, Queenstown in 2011. Photo: ODT

Department of Conservation ranger Brenton Wilson watches as a helicopter sprays wilding conifers above Fernhill, Queenstown in January 2015.  Photo: ODT

Department of Conservation ranger Brenton Wilson watches as a helicopter sprays wilding conifers above Fernhill, Queenstown in January 2015. Photo: ODT

Marty Grounds of Groundspray Environmental Weed Control instructs participants on wilding pine control methods at a 2014 ORC field day near Naseby

Marty Grounds of Groundspray Environmental Weed Control instructs participants on wilding pine control methods at a 2014 ORC field day near Naseby

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