Herbicide Spraying in Forest Management

The most controversial aspect of silvicultural practice (the practice of controlling the growth, composition/structure, as well as quality of forests to meet values and needs, specifically timber production) in Ontario’s Crown forest is the spraying of vast areas of land with the toxic herbicide glyphosate. What makes the controversy intense is that the foresters in charge feel that there is a deep need for this practice and from a certain perspective they are on solid scientific footing.

It must be explained that this spraying is largely a feature of lands that are managed to harvest what in lumber stores is as known as SPF dimensional lumber. Spraying is not extensively used in lumbering of red and white pine stands. Most of the SPF comes from boreal forest stands where the valuable trees are the coniferous species white spruce, black spruce, jack pine and balsam fir (hence, SPF). The hardwoods of the boreal, those being mainly white birch and two species of aspen are not commercially desirable (except for the limited demand for trembling aspen used for OSB).

These patches of boreal forest are managed using a modified clear cut technique which attempts to leave a terrain similar to that of the natural pattern left after boreal forest fires. It is recognized that these fire patches create an aspect on the land that the tree communities and wildlife respond to in restoring the natural systems of the boreal forest.

However, there is a major problem with this approach. There was no fire forming the patch and there is never a prescribed burn after the cut to remove the slash and scorch the surface. But there is always ample seed source for the aspen and birch seeds to blow in and aggressively establish a new forest. If left to nature the new forest that replaces the coniferous (or mixed) forest that was harvested will be a non-commercial stand of broad-leafed hardwoods. Young conifers even if they are manually planted in will be overshadowed and stunted in growth or completely shaded out. However, it is possible to ‘release’ the conifers if the broad-leaf completion is suppressed at a critical stage and the conifers can then secure a dominant place in the developing crown. Hence the foresters prescription of spraying to kill the broad-leafed vegetation despite its ecological and human health consequences.

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