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.