NRC: Focus on Northland's wilding pines

NRC biosecurity manager Don McKenzie about to pluck a wilding conifer just off the roadside on Whangārei's Mt Parihaka. NRC

The Northland Regional Council is keen to see a regional stakeholder group formed to examine wilding conifers and their impacts on the region's coastal margins, dune lakes and rare gumland ecosystems.

Such a group, it says, would be well placed, with assistance from Landcare Research, to fully assess the extent and impact wilding conifers are having on the North.

The council's biosecurity manager, Don McKenzie, said wilding conifers had long been an issue in Northland, many of them the descendants of escapees from commercial forestry plantations or shelter belt plantings decades ago, but the council was not looking to blame or penalise commercial foresters or other land owners.

"What we're saying is 'right tree, right place, right purpose'," he said.

The council had rules regarding control of wilding pines along property boundaries, but not wider controls for the trees, in its Northland Regional Pest and Marine Pathways Management Plan 2017-2027.

Wilding conifers could be any of several species, such as cedars, pines (including pinus radiata), firs, cypress, larches and spruces. While the impact of wilding conifers in the South Island was well known and understood, and had attracted significant control funding in recent years, the situation in Northland was less clear.

"We know from our staff's own observations in the field, and our examination of recent aerial imagery, that wilding pines are having an increasing, and unwanted, impact on our coastal margins, dune lakes and rare gumland ecosystems," Mr McKenzie said.

And the problem appeared to be worsening, trees slowly increasing their reach and scale, especially in places like the Ngunguru Sandspit and dune lakes in both the Far North and the Kaipara District, including the Kai Iwi Lakes system.

"Wilding conifers are an issue because not only do they colonise and change the existing environment, displacing native species, but they can adversely impact on water tables.

Roadside wilding conifers can also be problematic for power and other infrastructural companies, costing them significant sums to trim and remove to protect that infrastructure from potential tree-related damage," he said.

Northland's subtropical climate also appeared to be especially favourable to the conifers, which were typically unwanted commercially because their poor form and heavy branches produced low-grade logs with minimal value.

Mr McKenzie believed wilding conifers should carry the same pest status as other species like wild ginger, given their potential impacts.

On that basis, the NRC would convene a regional stakeholder group of key agencies and interests this month to examine the wider wilding conifer issue. It was hoping various parties including local and central government agencies, commercial foresters and iwi would attend.

While it was too early to say with any certainty how much (if any) central government funding could potentially be applied to the in Northland, he was hoping to see an investment of about $900,000 annually over the next decade or so.

"That level of funding would certainly allow us to make reasonable in-roads into addressing any local wilding conifer issues," he said, adding that an upcoming scientific paper examining New Zealand's wilding conifers could be of value to Northland in the future.