A walk on the wilding side

By Alina Suchanski

Reading time: 11 minutes

Pine trees were introduced to New Zealand more than 160 years ago. They adapted very well to conditions in this country; too well, some might say. Wilding pines overwhelm our native landscapes, kill native plants and force out native animals. Alina Suchanski explains why, and visits one of the areas affected by their out-of-control spread.

Amongst Southland’s many mountains and hills, three landmarks stand high as if they were sisters looking over vast areas of farmland spread out like a tartan kilt.

Flanked by East Dome (1,349m) and West Dome (1,270m), the highest of the three, Mid Dome (1,478m), towers above SH6 halfway between Invercargill and Queenstown near the SH94 junction which winds its way west to Te Anau and Fiordland.

By Alina Suchanski

Reading time: 11 minutes

Pine trees were introduced to New Zealand more than 160 years ago. They adapted very well to conditions in this country; too well, some might say. Wilding pines overwhelm our native landscapes, kill native plants and force out native animals. Alina Suchanski explains why, and visits one of the areas affected by their out-of-control spread.

Amongst Southland’s many mountains and hills, three landmarks stand high as if they were sisters looking over vast areas of farmland spread out like a tartan kilt.

Flanked by East Dome (1,349m) and West Dome (1,270m), the highest of the three, Mid Dome (1,478m), towers above SH6 halfway between Invercargill and Queenstown near the SH94 junction which winds its way west to Te Anau and Fiordland.

On a crisp, early spring morning, members of the Fiordland Tramping and Outdoor Recreation Club met by a farm gate at the foot of Mid Dome. After a short chat with Blair the farmer, we set off with his permission across a green paddock to the start of a farm track zigzagging to the top of the mountain.

It was a steady climb through a low cloud shrouding the mountain’s midriff, offering glimpses of blue sky and promising stunning alpine vistas. Fresh snow rolled out its white carpet along our path. We walked up a slope where native tussocks competed for space with thousands of pine seedlings.

One of my companions, Richard Bowman, happened to be a trustee of the Mid Dome Wilding Trees Charitable Trust formed in 2006 by a group of locals, concerned about the spread of wilding pines. Walking with Richard, I soon learned that the main offender here was Pinus contorta, the most vigorously spreading conifer species in New Zealand that threatens landscape values, biodiversity, and farming productivity.

Pinus contorta is a native of North America, honoured as the provincial tree of Alberta, Canada. It was introduced to Mid Dome during the late 1960s, in an attempt to stabilise high country pasture erosion due to excessive burning, high stocking rates and impacts of rabbits.

The solution was effective, with the pines quickly taking hold of the western slopes of the mountain. However, 30 years later it was noted that the pines were spreading beyond control and efforts have been made since then to control them. Aerial spraying has been undertaken and has successfully reduced the pines covering the area, but left behind ugly skeletons of dead trees with new seedlings taking residence amongst them.

Aerial spraying in 1960s has successfully reduced the area of Mid Dome covered by the pines but left behind ugly skeletons of dead trees with new seedlings taking residence amongst them

After just over three hours, we reached the summit marked with a trig and several spiky cell phone and TV antennas. A rocky area on the top had sparkling snow drift clinging to the manmade structures softening all sharp edges. Steel-coloured clouds hung low, obscuring most views. It wasn’t until we were well on our way back that the sky cleared and the clouds lifted to reveal the panorama of farmland fringed with snow-capped mountains all around us. It also revealed the full extent of the pine infestation which spread east as far as the eye could see.

Pine trees have many uses. They are grown in New Zealand for timber, to stop erosion, as shelter for orchards and animals, and as ornamental plantings in parks and private gardens. Some of the pine species that have become common here are:

  • Monterey pine (Pinus radiata)
  • Lodgepole or contorta pine (Pinus contorta)
  • Dwarf mountain pine (Pinus mugo)
  • Corsican pine (Pinus nigra)
  • Maritime pine (Pinus pinaster)
  • Ponderosa pine (Pinus ponderosa)
  • Scots pine (Pinus sylvestris)
  • Bishop pine (Pinus muricata)

Any of these species can become a wilding conifer, or more commonly termed a ‘wilding pine’, when it spreads where it’s not wanted – to pastures, tussock land or national parks.

Pinus radiata, for example, mostly grown for timber, is a species of pine native to the Central Coast of California and Mexico (Guadalupe Island and Cedros Island). It is an evergreen conifer in the family Pinaceae. This tree, endemic to such a small area on this planet, is the most widely planted pine in the world, valued for rapid growth and desirable lumber and pulp qualities.

The first recorded planting of radiata pine in New Zealand was in 1859, at Mt Peel Station in South Canterbury. Today almost 90% of the country’s plantation forests are of this species. This includes the Kaingaroa Forest (on the central plateau of the North Island), which is one of the largest planted forests in the world. Mass plantings became common from 1900 in the Rotorua area where prison labour was used. Radiata pine is the most extensively used wood in New Zealand, however, in some areas it is considered an invasive species; a wilding conifer, where it has escaped from plantations.

Department of Conservation (DOC) calls pines “the country’s number one pest plant”. According to its website, wilding pines are more than weeds: they are an economic and environmental pest. Unlike the trees in commercial pine forests, wilding pines are self-seeded. Once they get established, they spread quickly, competing with native species.

Wilding conifers cover more than 1.8 million hectares of New Zealand. This includes some of our most iconic landscapes from Northland to Stuart Island. The most affected areas are Kai Iwi Lakes in Northland, Mt Tongariro, Coromandel Peninsula, Mackenzie Basin in South Canterbury, and Mid Dome in Southern Lakes District. Despite control efforts, wilding pines are spreading at an estimated rate of 5% a year.

“Without national intervention, wilding pines will spread to 7.5 million hectares of vulnerable land within 30 years. The cost of unchecked wilding pine spread would reach $4.6 billion over 50 years. We would lose biodiversity, including many of New Zealand’s most sensitive landscapes and water catchments,” (Department of Conservation, 2021).

Wilding conifers grow wild, often in inaccessible places. Without the care and maintenance afforded to plantation forests, they lack uniformity, are often malformed and have large branches, rendering their timber worthless or the extraction costs outweighing any timber value.

When conifer cones mature on the tree, they open to release masses of wind-blown seeds. These seeds travel kilometres downwind and need no special conditions to take root and grow.

The impact of wilding conifers is manyfold. They:

  • contribute to the reduction of plants and animals endemic to New Zealand
  • significantly reduce available grazing land
  • create a fire risk as they can grow in dense and impenetrable areas with limited road access
  • limit recreation and tourism related activities
  • can cause acidification of soils which leads to the depletion of some minerals such as calcium
  • use a lot of water, which affects other plants and streams in the catchment
  • release large volumes of water vapour to the atmosphere through their leaves
  • provide habitat for exotic pest plants, animals, and diseases.

In October 2020, a major pine forest fire destroyed 20 homes in the tiny Lake Ohau settlement in Mackenzie Basin, known to be infested with wilding pines. This was a poignant reminder of the importance of keeping these pest trees under control.

In recent years, the New Zealand government has become aware of the wilding conifers problem and in 2016 established the National Wilding Conifer Control Programme which aims to contain or eradicate all wilding pine infestations by 2030. Led by Biosecurity New Zealand, the programme is a collaboration between central and local government, landowners, farmers, forestry owners, iwi, researchers, and community trusts.

In 2020, as part of the Covid-19 recovery package, the government announced a $1.2 billion programme that manages funding across multiple government agencies to benefit the environment, people and the regions. The programme, called Jobs for Nature, aims to redeploy those who lost their jobs due to Covid-19 into work that will help New Zealand achieve its ambitious goal of becoming predator-free by 2050 (Jobs for Nature, 2021).

At the time of writing this article, 230 Jobs for Nature projects worth $773 million have been approved. Some of the projects in Northland, East Coast, Hawke’s Bay, and Canterbury are tackling the wilding pines. Similar projects exist in Waikato, Bay of Plenty, and Central North Island, with more being scouted in Marlborough, Otago, and Canterbury.

Whether they are pulled out, grubbed, cut down or sprayed with herbicide, wilding pines are a tough opponent. After decades of ignoring and denying the problem, the New Zealand government has finally acknowledged wilding pines as an ecological disaster. With government backing we can start to win some battles, and maybe even win the war against this national pest.

 

 

Sources: 1. DOC press release, Offices of the Minister for Biosecurity and the Minister of Conservation 2. Wilding conifers 3. Controlling Wilding Pines – Questions and Answers, Wilding Pines NZ 4. Wilding Pines, NZ Geographic 5. Jobs for Nature, environment.govt.nz

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