Saturday, 13 January 2018

In Defence of Wilding Pines

Poisoned pines, from article here, similar to grove in news clip
The other day I caught a television news story about a house fire in Skipper’s Canyon in New Zealand. Part way into the news clip, they panned over the area around the house, and the journalist commented on how lucky they were the fire hadn’t spread to the dead pine trees.  Behind the house, a whole grove of dead pines—undoubtedly poisoned—looked, well, dead. “Those are not only seriously unsightly,” I thought to myself, “but also a huge fire risk. This is nuts!” (You can see the news clip in the video here; the trees and comment about them are at 58 seconds into the clip. 

New Zealand’s Department of Conservation (DOC) has been at war against “invasive” pine trees for some years now--see their website page on it here. In the category of “pine” trees—which they have defined as “weeds”--they include not only eight species of pine (lodgepole, mountain mugo pine, Corsican pine, maritime pine, Ponderosa pine, Scotch pine, bishop pine, and radiata pine) but also Douglas fir and European larch. Radiata pine and Douglas fir are also grown as commercial timber crops in New Zealand, which is fine, just so long as they stay in their neatly tended rows and don’t “jump the fence”.

Photo of wild pines by Neville Peat on DOC website page
Getting rid of invasive pines is challenging. Cutting and grubbing out “wilding” pines, or injecting poison into individual trunks requires intensive hands-on management, so increasingly vast tracts are simply aerial sprayed with herbicide, generally with a mix of glyphosate and metsulfuron. After the pines are killed, they are almost always left standing, in situ, grey skeletal hulks of no benefit to man nor beast and—to my mind at least—a huge eyesore and potential fire risk. It will be many years, maybe decades, before these dead trees eventually rot and fall. Ironically, the photo at the top of the DOC webpage on wilding conifers doesn’t show a hillside covered in dead trees, but one dotted with live ones.  I think it’s rather pretty.

Besides the aesthetic appeal of a green, living tree over a dead one, live trees provide shade and shelter and homes for birds and livestock and a variety of insects. They help stabilize the ground and prevent land slips (which is why many farm trees were planted in the first place). They offset global warming by absorbing CO2. When mature, in some areas they could be harvested for timber, firewood, or wood pump. 

NZ forest cover before man
One argument against these trees is simply that they are not native to New Zealand. Many of the areas they colonize, however, were forested before the first humans arrived here. Little attempt has been made, or is being made, to plant natives in these areas or to replace the unwanted pines with indigenous trees. I reckon the truth is, folks are so used to seeing bare hillsides of grass or tussock that the prospect of trees in historically grassed areas seems almost unnatural. It isn’t.

Another argument that DOC purports against wilding pines—and trees in general—is that trees reduce the amount of water in catchment areas because they pull it up from the ground and release it into the atmosphere—a big issue for farmers in dry areas. While trees do pull up water and release water vapour into the atmosphere, current scientific studies show that trees cool the air and create more rainfall—overall probably a win rather than a loss. Trees—not ocean evaporation--are responsible for an estimated 70% of earth’s atmospheric moisture.

A last argument that DOC uses on their webpage to support their campaign against wilding pines is that they “impact tourism”. I find it a stretch to imagine they think Asian tourists—who revere the pine as a symbol of peace, longevity, and virtue—want to come to New Zealand to see how we poison pines, or to see “wild” hillsides dotted with dead trees.

John McCrone wrote a good article last year titled SprayTactics: The $16m War on Wilding Coniferswhich also examines some of these issues, and more. It is worth reading.


  1. I enjoyed reading this. Not much i can add except i was chatting to a local framer about the South Island a week or two ago and a point he raised was the farmers down south have a problem withthe wilding pines . Many of the pines are here largely due to a desire to profit financially from growing them .But there is also profit to be had from eradicating them from pastural lands . Seems to me to be little to do with conservation values and more about ''our stuff''

  2. Hi Susan. Just a couple of points that you may have missed/misunderstood. While dead standing trees are not an ideal aesthetic, they are far better than the alternative. You may like the northern hemisphere look of exotic pines carpeting the landscape, but I would argue most NZer's and those visiting appreciate far more the vast landscapes of supalpine shrubs and grasses cut through with streams rather than conifer deserts. Most haven't traveled half way across the world to see a poorer version of what they left. Historically, as you state, they were forested up to 1,000 metres (mainly with beech), but exotic conifers will spread far higher than this. In so doing they will wipe out thousands of New Zealand endemic plants and animals, as well as invading existing native forest. You mentioned that the live conifers provide shelter for birds and insects, but if you spend anytime in the exotic conifer forests you'll quickly realise how depauperate these trees are for both native and exotic species. NZ's unique ecology has evolved to have a mix of native species, not a singular tree species. Exotic pines provide very little food source for most birds, and none for many of the specifically adapted nectar loving birds like tui. Their unchecked growth will smoother a range of different ecosystems which support a diverse range of birds, lizards, and insects. There are also extensive native fungal communities living under the ground that work in harmony with native species. Exotic conifers may look green, but they are in effect ecological deserts here. If you've visited any of the forests in North America, you don't just have Douglas fir living in isolation. You have a multitude of understory plants, insects, and mammals as part of the wider forest. We don't have those here, unless we plan on widescale importing of even more exotic species. You also mention C02 offsets, but there are suggestions that the native ecosystems they invade and destroy are better at carbon sequestration in addition to being much more resistant to climate change and factors like disease, not to mention our ever dwindling wetlands which clean and control water runoff. More research needs to be undertaken on native ecosystems in this area, as all the money has been poured into exotic forestry. You mention fire risk, while unavoidable with dead standing trees, doesn't also prevent wildfires in standing healthy forest. Just look at the wildfires that continually break out in the northwest of North America. You also talk about their uses for firewood, timber, and pulp. Trees for timber are only useful when properly managed and accessible. I wish you the best of luck trying to harvest trees in places that are barely accessible on foot, let alone viable for commercial harvest. There is potential for some of the trees to be harvested for pulp, but at a net profit loss plus the scarring of the landscape for access roads. Forestry is not a pleasing aesthetic to most. Where areas have been cleared of wildings or prevented their spread and stock have been removed, the native forests are starting to regenerate. If supported with extensive native plantings, NZ could once again have a healthy biodiversity with native forested hillslopes while maintaining the open mountain vistas. All these points above are supported by extensive research, both academic articles and on the ground. There are many reasons that wildings need to be eliminated, and we should not sacrifice much of NZ's unique nature because people see tree=always good. In many places, they are not.

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