Home Marquee Do We Need to Use Herbicides in Canada’s Boreal Forest?

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Although instances of their use have dropped significantly over the years, herbicides remain an important tool for regenerating harvested timberlands. Here’s why.

After the trees are harvested and an area is prepared for reforestation, the nutrient-rich soil and ample sunlight provide ideal conditions not only for timber regeneration, but for the growth of many other plant species. Herbicides help keep certain “pioneer” species like Canada blue-joint grass, raspberry, and trembling aspen from overtaking newly-planted tree seedlings like spruce and pine species.

Areas are typically only sprayed once, and most often that is during the first five years postharvest, either prior to or after planting seedlings.

Ensuring the health and safety of employees and neighbors is critical for Resolute and others conducting regeneration activities. Environmental considerations are also at the forefront of our approach to the sustainable and responsible management of the forests under our care. The spray program is one of the tools that we use to ensure the success of our regeneration initiatives and is conducted in compliance with government approved forest management plans. Spraying is only conducted where necessary, and only approved herbicides are applied by experienced and qualified experts.

Natural regeneration versus herbicide use

Since all of the areas that are harvested in Canada must be promptly regenerated, managing pioneer species is a recurring challenge. And there are different methods of dealing with it. Some of these spaces are naturally regenerated and some re-grow with the help of herbicides. In Ontario in 2013, for example, 46% of the harvested areas regenerated without the use of herbicides.

  1. If some areas regenerate without it, isn’t that proof it’s unnecessary?

The objective is to regenerate to a specific standard. Different areas see varying amounts of success depending on the method of control used. And many different methods have been tried, including laying down mulch mats, bringing in grazing livestock and even developing an indigenous fungus as a microbial biocontrol agent.[1]But the fact is, nothing is as effective as herbicides.

And if herbicides are not used, some areas see reduced crop growth and even outright crop failure. Just like a vegetable garden in your yard, if a competing species is left unchecked, it can overwhelm the seed crop. This happened in Nova Scotia forests where herbicide use was banned. A survey published in 2007 based on 101 plantations surveyed in the summer of 2005 found that most (87%) of their conifer plantations in the area failed outright and nearly all (97%) failed to meet the generally accepted regeneration standards 6-8 years after harvest.[2]

As a simplifying generalization, there are no alternatives that are as cost-effective, efficient or reliable as modern chemical herbicides in many forest regeneration scenarios. In fact, when the environmental impacts and risks of various site preparation techniques are weighed, herbicides can be far less dangerous than site preparation with large machinery, fires and manual brush clearing.

  1. Why must herbicides be applied aerially? Wouldn’t it be better to have crews apply it at ground level?

The areas scheduled for herbicide application average around 200 ha per day and are typically very remote. Aerial application of these products is not only economical, it is better than sending crews in, which can be disruptive to an area that is regenerating. As for accuracy, technologically advanced systems are used to minimize risks of drift outside of the target areas. And legislative requirements and guidance systems ensure that water-bodies next to aerially treated sites are protected by standing timber buffers.

In Ontario, Resolute only conducts aerial applications. We rely exclusively on helicopters, which increases the control over spray areas as compared to a fixed wing plane and provides precision when working with smaller areas.

  1. What is the most common herbicide used? What are its effects?

There are a few different types, but the most common active ingredient is glyphosate. Herbicides with glyphosate are some of the most thoroughly tested in the world. Their history of safe use is supported by one of the most extensive worldwide human health, crop residue and environmental databases ever compiled on a herbicide product.

Glyphosate is particularly effective at controlling competing vegetation in plantations of conifer trees, the dominant commercial tree species harvested throughout the boreal in Canada.

It also has a relatively favorable environmental behavior profile, which means that it doesn’t linger in soils, vegetation or water, it doesn’t accumulate in animals, and it has a very low potential to leach into ground water. It also has a relatively low innate toxicity to humans and wildlife.

  1. But is it really safe?

Based on the extensive body of scientific literature and studies, as well as information we have received from Health Canada, we believe that glyphosate-based herbicides are safe. They have an excellent fifty-plus year safety record, and their use has been approved by Health Canada.

In a recent re-evaluation of the use of glyphosate-based herbicides, Health Canada concluded that “products containing glyphosate do not present unacceptable risks to human health or the environment when used according to the proposed label directions.”

Over 800 studies have demonstrated that glyphosate does not cause cancer, birth defects, DNA damage, nervous system effects, immune system effects, endocrine disruption or reproductive problems. In addition, numerous field studies on this topic have been undertaken in Canadian forest ecosystems. What they found is perhaps best understood in terms of what glyphosate does NOT do:

  • It does NOT kill all other plants to create a single-species forest plantation.
  • It does NOT poison birds, fish, aquatic invertebrates, small mammals, large mammals or amphibians.
  • And it does NOT cause a reduction in soil microbial populations or significantly impair their function. [3] In fact, some studies even recommend the use of this treatment to create foraging conditions that support woodland caribou over moose.[4]

The International Agency for Research on Cancer (IARC) of the World Health Organization (WHO) rated glyphosate as “probably carcinogenic to humans,” the same category (2A) they use to classify sunshine, aloe vera, cell phones, coffee and being a barber.

Health Canada addressed this announcement in their re-evaluation decision published on April  13, 2015:

The WHO’s International Agency for Research on Cancer (IARC) recently assigned a hazard classification for glyphosate as “probably carcinogenic to humans”. It is important to note that a hazard classification is not a health risk assessment. The level of human exposure, which determines the actual risk, was not taken into account by WHO (IARC). Pesticides are registered for use in Canada only if the level of exposure to Canadians does not cause any harmful effects, including cancer.

  1. Can you eat blueberries that have been sprayed with glyphosate?

In the consultation documents from Health Canada, it was found that products containing glyphosate acid are unlikely to affect your health when used according to label directions and that dietary risks from food and water are not of concern.

The recommendation to avoid eating berries in posted areas after spraying with a glyphosate-based herbicide does not necessarily reflect a high level of risk, but rather is invoked as a simple extra precaution with no substantial down-side, according to Natural Resources Canada.[5] In following years, berries can be picked and eaten. Even without washing the fruit, the presence of the substance naturally diminishes at an exponential rate to approximately 50% of the initial value after 13 days and to 4% of the initial value after 61 days. [6] One study found that, a year after treatment with glyphosate, regrowth was normal and there was no effect on blueberry yield the season following treatment. [7], [8]

A recent survey of blueberry farmers in Maine showed that 76% of the growers surveyed use herbicides, such as glyphosate for weed management. In fact, a significant portion of growers who self-identified as “no-spray” or organic used the herbicides glyphosate and sethoxydim, (30% and 15%, respectively)[9] showing that some farmers may not consider herbicides as “pesticides,” as they are often less toxic to vertebrate wildlife and human beings than insecticides and fungicides.[10]

Resolute continues to monitor the research. We believe, however, that our use of herbicides as part of our sustainable forest management strategy is appropriate and evidence-based. It is also important to remember that Ontario’s forest management regimes and regulations are among the most stringent in the world and that Resolute supports and complies with them.

For more information:






[1] http://cfs.nrcan.gc.ca/pubwarehouse/pdfs/32344.pdf

[2] Nicholson, J. 2007. Survey of plantations established between 1998-2000 (6-8 years of age) on eastern Crown land without herbicides. Nova Scotia Department of Natural Resources, Forest Management Planning, Forest Research Report 83, 27 p. (http://novascotia.ca/natr/library/forestry/reports/REPORT83.PDF)

[3] Giesy, John P., Stuart Dobson, and Keith R. Solomon. “Ecotoxicological Risk Assessment for Roundup® Herbicide.” Reviews of Environmental Contamination and Toxicology (2000): 35-120.

[4] Mihajlovich, Milo, and Peter Blake. “An evaluation of the potential of glyphosate herbicide for woodland caribou habitat management.” Alces 40 (2004): 7-11.

[5] http://cfs.nrcan.gc.ca/pubwarehouse/pdfs/32344.pdf  Page 4

[6] Roy, D. N., et al. “Uptake and persistence of the herbicide glyphosate (Vision®) in fruit of wild blueberry and red raspberry.” Canadian Journal of Forest Research 19.7 (1989): 842-847.

[7] Hodges, Laurie; Talbert, Ronald E.; and Moore, J. N., “Effects of Glyphosate on Highbush Blueberry (Vaccinium corymbosum L.)” (1979). Agronomy & Horticulture — Faculty Publications. Paper 401. http://digitalcommons.unl.edu/agronomyfacpub/401

[8] Hanson, E. J. “Response of highbush blueberries to postemergent herbicides.” IX International Vaccinium Symposium 810. 2008.

[9] Farmer Survey: Rose, A., F.A. Drummond, D.E. Yarborough, and E. Asare. 2013. Maine wild blueberry growers: A 2010 economic and sociological analysis of a traditional Downeast crop in transition. Maine Agricultural & Forest Experiment Station Miscellaneous Report 445

[10] Herbicides are less toxic: D’Appollonio, J., D. Yarborough, and F. Drummond. 2010 Maine wild blueberry pesticides chart. University of Maine Cooperative Extension. http://www.extension.umaine. edu/blueberries/files/2010/06/2010PesticideChart3-2010forWeb.pdf

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