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To ensure that a healthy, biodiverse forest grows back quickly after timber harvesting, Millar Western is required by law to begin forest renewal activities within two years. These activities include planting of conifer tree seedlings, natural regeneration of deciduous trees, and site preparation treatments to enhance new forest growth. Once planted, conifer seedlings in some areas must compete with fast-growing grasses, shrubs, and aspen trees for water, nutrients, and sunlight, making it difficult for the newly-planted seedlings to grow. In some instances, we use herbicides to temporarily reduce this competition.

Each year, only a very small proportion of the forest is treated with herbicide. Less than 1% of Alberta’s commercially allocated forests are harvested each year. Fewer than half of those harvested sites receive herbicide treatments, and those that do are typically treated only once. Where used, herbicides help conifer trees become successfully established and help restore harvested areas to their original biodiversity. Rather than eliminating the competition, we apply these herbicides in a manner that temporarily delays the growth of competing species, giving the conifer seedlings a head start.


Why are herbicides used in forestry?

In Alberta and across Canada, forest companies are required by law to regenerate harvested areas to pre-determined species compositions that maintain forest diversity across the landscape. In some areas, grasses, shrubs, and aspen trees, which thrive in the open spaces found after disturbances like wildfire and timber harvesting, can easily outcompete conifer seedlings in the first few years after planting. When planning for forest renewal, forest managers consider various tools and methods. A number of strategies may be employed to return harvested sites to their original biodiversity, and it’s only in some cases that herbicide applications will be used.

What kind of herbicide is used in Alberta’s forests?

Glyphosate is by far the most common type of herbicide used in forestry in Alberta. Millar Western chooses to use glyphosate because of its good environmental profile. Microbial organisms break the product down in soil, and it does not leach into groundwater nor does it move into surface water.

How does glyphosate work?

Glyphosate has been designed to target biological pathways that exist only in plants. Glyphosate inhibits a plant’s ability to make the amino acids necessary to grow.

Are the herbicides used in forest renewal dangerous to people and wildlife?

The herbicide most commonly used in forest operations, glyphosate, is a broad spectrum herbicide that targets grasses and broadleaf plants. When used according to the label, glyphosate poses no risk to human health or the environment. Herbicide applications are done by trained and licensed professionals, and care is taken to limit exposure to humans and wildlife. Each year, only a very small proportion of Alberta’s forests are treated with herbicide. Less than 1% of Alberta’s commercially allocated forests are harvested each year. Fewer than half of those harvested sites receive herbicide treatments, and those that do are typically treated only once. This occurs over a short period, usually in remote sites, away from human activity. Once applied, herbicides only remain in the environment briefly. Glyphosate does not bioaccumulate, meaning that it doesn’t build up in the tissues of organisms over time because it can be metabolized and excreted.

Are herbicides used in all regenerating forests?

No. Aspen stands do not require herbicides to help them regrow. In some areas, natural conditions are such that we can regrow conifer forests without the assistance of herbicides. 

Are there alternatives to herbicides?

Yes, other techniques, like mechanical site preparation, planting larger seedlings, and the removal of woody competition using brush saws, are used to reduce the need for herbicide applications. We must strike a careful balance; some alternative methods improve conditions for seedling germination but require additional roads to be built in the forest so that machinery can access the sites. These methods can leave a more substantial physical and carbon footprint than herbicide application, and the heavy machinery required can disturb soil health. With these considerations, sometimes we choose herbicides as a less disruptive option, or as a complement to other techniques.

How much herbicide is being used in the forest?

Herbicides are utilized by a variety of users. In Alberta, 96% of herbicides are used for agricultural purposes, 2% for domestic use, and 2% for commercial and industrial applications. Forestry falls into this last category, making up only a fraction of that 2%. Not all forest renewal sites require herbicides, and those that do typically receive only one application. Millar Western and other companies have significantly reduced our use of herbicide in recent years, as our understanding has grown of where applications are essential to meet reforestation needs, and where they are needed less.

How do herbicides affect the soil?

Most forestry herbicide applications in Alberta involve glyphosate. Studies have shown that glyphosate quickly breaks down and becomes inert, and does not remain in the soil for long periods. Long term studies show no change in soil quality and composition following glyphosate use.

What happens to glyphosate after it is applied?

In soils, water, and sediments, glyphosate does not persist, but is degraded by microbial organisms and broken down into to carbon dioxide and simple inorganic compounds.

How do herbicides affect wildlife?

Studies focused on the effects of herbicides on the environment and wildlife show that the herbicides used in Alberta’s forests don’t pose a risk to the environment or wildlife.

Do herbicides affect water quality?

Long term studies have not detected herbicides like glyphosate in groundwater. Glyphosate breaks down quickly on contact with microorganisms in soil, and it doesn’t leach into groundwater or transfer into surface water.

How are herbicides applied in forest operations?

We apply herbicides both through aerial spraying and by manual, on-the-ground application.

When are herbicides applied, and how often?

We apply herbicides between mid-August and mid-September each year. Trained technicians monitor weather conditions for humidity, wind, and temperature, and herbicides are applied when environmental conditions ensure that spray will not move outside of the approved treatment area. Most areas are only treated once.

How can the public stay informed about herbicide applications?

The Government of Alberta requires forest companies to inform the public about herbicide applications. Thirty days before applying herbicides, Millar Western issues public notices indicating where and when applications will occur, and providing an opportunity for the public to submit any concerns or comments. Following herbicide application, we post notices of which herbicide was applied and the date of application in areas that are accessible to the public.

Is glyphosate a carcinogen?

The International Agency for Research on Cancer (IARC), an arm of the World Health Organization, classified glyphosate as a probable carcinogen in 2015. Naturally, this finding causes many people concern. However, it is important to understand the distinction between a hazard classification and a health risk assessment. IARC has given glyphosate a hazard classification of “probable carcinogen” because, at very high exposures, it could have harmful effects. It is unrealistic for these doses to ever be encountered in real world situations.

Health Canada, along with most other regulatory agencies, has carried out rigorous evaluations of the data to determine the actual health risk of glyphosate, and has concluded that real world exposure levels are low enough that the risk is negligible. When used according to the label, glyphosate poses no risk to human health or the environment.

What steps are taken to mitigate risk when applying herbicides?

Who can I direct questions to?

Please direct any questions to:

Gareth Carey, Silviculture Supervisor at or 780-778-2221 ext. 2164, or;

Tim McCready, Forestry Superintendent at or 780-778-2221 ext. 2207.