FAQs
Vegetation management is one component of the overall cycle of forest management. It refers to the tools and methods used by foresters to ensure that specific crop trees are given the best possible conditions to grow quickly and sustainably.
When natural or artificial methods are used to regenerate the forest, forest managers often take steps to ensure that regeneration favors desired species – because not all regenerating trees or tree species grow well on a given site – and that the individual desirable trees (crop trees of the final stand) have access to sufficient sunlight, soil moisture, nutrients, and space. Activities performed to guide species composition and reduce competition are generally referred to as silvicultural care or vegetation management treatments; these activities include measures such as thinning (to reduce the density of final stand) and weeding (to reduce or eliminate plants growing where they are not desired). Regardless of the measure, the goal is to increase the resources available to support the growth of the final stand, thereby increasing the likelihood of survival and growth of the final stand, in the same way that weed control results in a more productive garden at home. Good vegetation management ensures that regeneration objectives are met in a timely manner and that forest survival and growth are adequate to maintain wood supply (Wagner et al. 2001).
For additional information, please see FAQ How long does glyphosate remain in the soil, water, plants and sediments after treatment? (Environment and Wildlife)
Herbicides, such as glyphosate, play an important role in maintaining a viable wood supply for economic purposes and also contribute to an appropriate balance of conifer, deciduous, and mixed stands across the forest landscape.
Herbicides are typically used in Canadian forest vegetation management only where conifer crops (e.g., spruce and pine species) are to be regenerated and grown for products such as lumber, paper and wildlife habitat. Following harvest, numerous pioneer plant species (e.g., Canada blue-joint grass, raspberry, trembling aspen) that are well-adapted to invading disturbed sites and open growing conditions, easily outcompete young conifer seedlings for nutrients, light, water and growing space (Wagner et al. 2001, Balandier et al. 2006). Reducing competition from adjacent plants is essential for crop-tree survival and growth, much the way that weeding ensures success in the home garden. Of course, in contrast to the home garden, the scale at which forestry operations occur makes hand-weeding highly impractical. Herbicides allow effective, highly selective competition reduction in conifer crop production, at minimum cost (McDonald and Fiddler 1993, Wagner et al. 2006, Newton 2006, Dampier et al. 2006, Homagain et al. 2011). The use of herbicides in Canadian forest vegetation management is also heavily regulated and controlled in an effort to ensure environmental and human safety
For additional information, please see FAQ Who decides whether a product is safe or not? How do they know?. (Health)
There are five herbicide active ingredients registered for use in Canadian forestry: Glyphosate, Triclopyr, Hexazinone, 2,4-D, and Simazine. In Canadian forestry, glyphosate-based herbicides have been used on over 96% of the forest area treated in the past decade.
There are five herbicide active ingredients registered for use in Canadian forestry (glyphosate, triclopyr, hexazinone, 2,4-D and simazine). In Canadian forestry, glyphosate-based herbicides account for more than 96% of the forest area treated with herbicides in the past decade. Uses of other herbicides, particularly in recent years, are sufficiently minor that they do not warrant further discussion here (statistics on pesticide use in Canadian forestry are freely available through the National Forestry Database Program website, http://nfdp.ccfm.org/). Since the patent has expired on glyphosate, several manufacturers now produce various end-use formulations of this compound, sold in the forestry market under trade names such as VisionMax, Forza, Vantage and Weed-Master (Mihilovich et al. 2004). While all of these formulated products contain glyphosate as the active ingredient and a surfactant to enhance uptake across plant leaf cuticles, the actual chemical constitution of each formulation may vary (i.e., one formulated glyphosate product does not necessarily equal another).
There are three key reasons that glyphosate-based herbicides are so dominant in Canadian and international forestry and agriculture: a) its excellent record of efficacy and reliability in controlling most competitive species including those that resprout through rhizomes, roots or basal buds; b) its favourable environmental behaviour profile (e.g., non-persistent in soils, vegetation and water, does not accumulate in animals, has very low potential to leach into ground water) (How long does glyphosate remain in the soil, water, plants and sediments after treatment?); and c) its low innate toxicity to humans and wildlife. In forestry applications, glyphosate does not easily kill conifers, particularly after they have had a chance to fully develop a waxy cuticle on their needles (usually near the end of August). This cuticular wax is sufficiently thick to protect the needles from disease, dehydration and the effects of glyphosate at doses that would otherwise be sufficient to injure the tree. Thus, glyphosate-based herbicides are particularly effective at controlling competition from undesired broadleaf vegetation that is immediately adjacent to young conifers.
Glyphosate-based products similar to those used in Canadian forestry are registered and used in more than 160 countries and play critical roles in the production of more than 100 terrestrial food crops, including wheat, corn and soybeans. While agricultural applications of glyphosate-based herbicides account for the majority of glyphosate use (75% by volume), these same herbicides are also important for vegetation control in residential home and garden (15%), industrial site management and rights of way (6%) and, of course, forestry (4%) applications (Michael Cunningham, Engage Agro, personal communication).
For additional information, please see FAQ How long does glyphosate remain in the soil, water, plants and sediments after treatment? (Environment and Wildlife)
For additional information, please see FAQ What are environmental and health regulators saying about IARC’s glyphosate classification? (Health)
Forest managers routinely design harvest and site preparation activities to minimize regrowth of undesirable vegetation, and rely on tools such as manual cutting, large nursery stock, and prescribed fire to maintain conifer growth, abundance, and dominance on areas where they choose not to use herbicides.
There are several cultural methods that forest managers routinely use to combat the competitive effects of non-crop vegetation in a pre-emptive fashion. For example, on sites capable of producing quality, high valued hardwoods, conifer regeneration (and the use of herbicides) is often avoided completely. Where conifer production is desired, stands can be harvested at times of the year, in a manner and with equipment designed to minimize the resprouting of non-crop vegetation (Myketa et al. 1998, Wagner and Columbo 2001). Site preparation timing, methods and equipment may similarly be tailored to specific site conditions for minimizing non-crop regrowth potential. Healthy, high quality conifer seedlings, with genetic selection for rapid growth are often planted to maximize their competitive advantage. On some sites, vegetation management methods are modified to promote the development of mixed stands of conifer and hardwoods (Pitt et al. 2004a, Pitt et al. 2004b, Pitt et al. 2010). Manual methods of weed control (e.g., cutting with brush saws; Bell et al. 1997, Bell et al. 1999, Pitt and Bell 2004, Pitt and Bell 2005, Greifenhagen et al. 2005) are used where the use of herbicides is constrained, particularly to provide an extra measure of safety for humans or the environment, such as near human habitation or in riparian zones. Fire, one of nature’s key weed control measures, may be used as a tool for vegetation control in site preparation, under some very specific conditions.
Not necessarily. There are risks associated with every forest activity or operation. Mechanical cutting exposes workers to known carcinogens through exhaust fumes; heavy equipment results in significant carbon emission and soil compaction. Eliminating risk entirely in forestry or any other industry is impossible, therefore we must understand and manage risk.
It is important to note that all vegetation management options carry some inherent degree of risk either to environmental or human health. The actual risks for non-herbicide options are certainly less well-studied and defined than those associated with herbicide use, a fact which is not necessarily a good thing. Risks of potentially deleterious effects of alternatives are technique specific. For example, mechanical site preparation with large machinery carries risks associated with harm to wildlife, soil compaction, increased erosion and excessive burning of fossil fuels (Newton 2006). Manual clearing with brush saws involves unequivocal risk to workers associated with repetitive direct exposure to proven carcinogens such as benzene in exhaust fumes, as well as demonstrable risks for stress- and strain-type injuries (Dubeau et al. 2003). Prescribed fire also carries risks associated with the safety of workers and the possibility that the fire will escape.
With herbicide use, risks may be associated with the potential for direct or indirect effects on wildlife species or to humans that may be inadvertently exposed to herbicide residues. However, such risks are significantly mitigated by the extensive scientific research that is invoked to enhance our understanding and define biological effects thresholds, resulting in the operational restrictions and practices that are put into place to reduce the probability that actual exposures will exceed such thresholds (e.g., buffer zones, signage, use of minimum effective rates, advanced application technologies to optimize targeting and reduce off-target drift potential) (Best Practices).
There are important differences between scientifically quantifiable risk or probability of occurrence, and the willingness of an individual or particular segment of society to tolerate those risks and probabilities. Risk tolerance varies dramatically from one segment of society to another and often directly reflects familiarity and knowledge (Wagner et al. 1998).
They are – most Forest managers use an integrated vegetation management approach that consists of a variety of pre-emptive techniques, in addition to direct tools such as herbicide treatments and manual cutting.
It is clear from the statistics, of the estimated 444,000 ha requiring tending each year in Canada, about 2/3 of these hectares are not treated using herbicides. In fact, all well-managed forests employ what is referred to as an Integrated Vegetation Management (IVM) Program that includes herbicides, as well as a number of other techniques that are available to forest managers to reduce the competitive effects of non-crop vegetation (Little et al. 2006). Under an IVM program, a forest manager will use the most appropriate combination of tools that safely maximize the potential for regeneration success on a site-specific basis.
Generally speaking, however, there are no alternatives which are as cost-effective, efficient, safe, or reliable as modern chemical herbicides in forest regeneration scenarios and so herbicides, glyphosate-based herbicides in particular, naturally play a dominant role in most IVM programs (McDonald et al. 1993, Newton 2006). Herbicides also offer the only effective means of reducing competition from broadleaf herbaceous plants, which have been shown in several studies to significantly reduce conifer growth and survival (Zutter and Miller 1998, Man et al. 2008, Pitt et al. 2009, Parker et al. 2009, Pitt et al. 2011). Glyphosate-based herbicides also tend to kill plant root systems, preventing the resprouting that often occurs following manual cutting (Bell et al. 1999). Still, through IVM, non-chemical techniques are in fact employed on a significant portion of the forest land base.
In the early- to mid-1990’s significant research was done across the country to explore and test a wide range of vegetation management alternatives. While this work has led to a better understanding of how to improve tools and techniques—such as manual cutting, alternatives such as grazing animals, fungi, and mulches were found to be both more costly and ineffective in forest management.
To date, several million dollars have been spent in Canada and elsewhere to investigate the role that tools such as grazing animals, fungi and mulches might play in Integrated Vegetation Management programs. The Vegetation Management Alternatives Program established by the Ontario Ministry of Natural Resources in the early 1990s is an excellent example of these efforts. Conclusions from this research indicate that the high cost, increased variability in success, and relatively low efficacy of these approaches make them impractical for all but very small-scale applications (Wagner et al. 2001). For example, a national effort was undertaken to develop and register the indigenous (native) fungus Chondrostereum purpureum as a microbial biocontrol agent for forest vegetation management (Thompson et al. 1992, Pitt et al. 1999, Harper et al. 1999). Results from these trials showed it to be effective in controlling re-sprouting of some woody competitive species. Two derivative commercial products were ultimately registered for use. However, use of these products has been minimal in operational forest practice for several reasons including: 1) a total lack of efficacy on herbaceous competitor species; 2) ineffectiveness on some particular woody species; and 3) the need for manual or mechanical cutting immediately prior to application of the fungus, which increases overall operational costs. Other alternative approaches, such as the use of mulch mats have also generally proven to be both ineffective and far too costly (Thomas et al. 2001, Harper et al. 2005) for widespread use in operational forestry.
What type of research has been conducted on the use of herbicides in the forest and who has done it?
Extensive research has been conducted by academics, industry, and government researchers on all aspects of herbicide use in our forests. To be considered safe for use, this research is reviewed regularly by Health Canada’s Pest Management Regulatory Agency (PMRA), under the authority of the Pest Control Products Act.
Pesticides, including herbicides, must be thoroughly tested to ensure that they perform according to label instructions and are safe to humans and the environment when used as directed. This testing may be performed by a variety of agencies and must have sufficient scientific rigor to satisfy Health Canada’s Pest Management Regulatory Agency (PMRA). To prevent data manipulation, the Organization of Economic Cooperation and Development (OECD) has developed an internationally accepted set of Test Guidelines and Principles of Good Laboratory Practices (GLP) to promote the quality and validity of test data. GLP covers the organizational process and conditions under which non-clinical studies are planned, performed, monitored, recorded and reported. Independent trail audits can be conducted under the GLP guidelines at any time to verify integrity of data used in the registration process.
Under the authority of the Pest Control Products Act, Health Canada only registers those compounds that promote sustainable pest management and satisfy stringent, science-based evaluations indicating that they pose minimal risk to human health and the environment. All registered pesticides undergo a scheduled re-evaluation every 15 years to ensure that the data supporting their continued use meets current scientific standards. The PMRA carefully reviews all data (including raw data) and may also compare its conclusions with regulatory counterparts in other countries such as the U.S. and members of the European Union to ensure consistency.
Canada has one of the most stringent pesticide regulatory and registration systems in the world.
In April 2015, the PMRA released their latest review of glyphosate and declared that the weight of evidence indicates that glyphosate does not present unacceptable risk to human health. The full PMRA glyphosate review can be found here or please visit here for a summary version of the full PMRA review.
Forest fires are a great example of a naturally occurring disturbance that assists in the forest renewal process. The practice of clear-cutting mimics the overall effects of disturbances, such as forest fires. This type of manual disturbance helps to keep our forests healthy and productive for years to come.
In agriculture, the objective of vegetation management is to ensure that the plants have little or no competition during the entire growth cycle. In forestry, the objective is to temporarily suppress competition so that the planted trees can become well-established and can grow to their maximum potential. Once a tree plantation is established and growing, incoming vegetation returns to the site and is not as much of a concern.
This difference in vegetation management objectives in forestry and agriculture shows why forestry treats planted trees with herbicides only once or twice during a rotation, while agriculture treats crops regularly. Planted trees represent considerable investments, which must be protected through effective vegetation management. Herbicide treatments are currently the least costly and most effective tool for vegetation management and are the preferred method for tending most planted stands.
Across Canada, approximately 45% of all harvested areas are left to regenerate naturally, without using herbicides. Many of these sites are intended to grow hardwood species (e.g., aspen, birch, maple), which readily regenerate by natural means. However, most conifer species, require very specific conditions to regenerate naturally. To maintain a healthy and productive forest, it is usually necessary to assist conifer establishment and growth through direct seeding, planting, herbicide treatments, and continued tending.
Good forest management strives to maintain a mosaic of different stand types (hardwood, conifer and mixed), in different age classes, emulating as closely as possible the expected natural spatial distribution of these features on the landscape. In Canada, just under half of the area harvested each year is left to regenerate naturally. The expectation is that hardwoods and mixed woods occupy these sites with little or no tending. Hardwood species, particularly in the boreal forest, regenerate from both coppice growth (root and stump suckering) and seed, allowing them to rapidly colonize disturbed areas on their own. Most conifer species, however, rely solely on seed for natural regeneration. Without rather exacting stand and soil conditions at time of harvest (e.g., those that often occur with natural fire events), conifer establishment can be difficult and variable without our help; through planting or direct seeding. An overreliance on natural regeneration, coupled with inadequate tending, can precipitate a substantive loss in the abundance and dominance of conifer on a landscape, resulting in both economic and ecological repercussions (Armson et al. 2001, Hearnden et al. 1992, OMNR 1986; 1988). The loss of pine and spruce dominated stands across the landscape continues to be recognized as a major challenge for the forest sector.
Without their use, it would be increasingly difficult to maintain the softwood forest needed to supply our mills and maintain broad landscape diversity of conifer, deciduous, and mixed wood forests. This affects the viability and the competitiveness of our forestry industry.
Because herbicides play a central role in IVM and ensuring the successful regeneration of conifers on previously conifer-dominated sites, if their use were to be curtailed or discontinued, the objectives of establishing conifers on many sites could simply not be met through affordable means and forest managers would have difficulty meeting sustainability targets and legal requirements. Ultimately, this would lead to increased deficits in the natural proportion of conifer-dominated stand types on the landscape; deficits which already exist in many areas across North America. A diminished conifer resource would have serious economic implications, through reduction of the sustainable wood supply, as well as ecological implications through loss of habitat.
For example, a detailed audit recently conducted on regeneration sites in Nova Scotia, where a decision was made not to use herbicides, provides good evidence of the probable outcomes. In this case, results showed that 87% of conifer plantations failed, with an additional 10% not meeting free-to-grow standards 6 to 8 years post-harvest (Nicholson 2007). Similar outcomes have been observed in research trials conducted in other forest ecosystems (Biring et al. 2003, Dampier et al. 2006). A 2001 decision to discontinue herbicide use on Crown lands in Quebec has resulted in plantation establishment and tending costs frequently exceeding $5,000/ha (Labbé et al. 2014), owing to the production and planting of large stock and the need for as many as 3 manual brush saw release treatments. The ultimate success of many of these plantations is currently unknown and statistics on the impacts of the herbicide restriction on conifer wood supply are not available in Quebec. Recently, the province’s Chief Forester identified appropriate monitoring of planted areas as a critical need (Bureau du forestier en chef, 2015).
Planting conifers can cost a landowner in excess of $1,000 per ha, when mechanical site preparation, seedling production, and planting costs are considered. To protect this investment, the landowner may spend approximately $200/ha for a single aerial glyphosate application, or between $1,000 and $4,000/ha for one or more manual brush saw treatments. Given the lessons learned in jurisdictions that have curtailed herbicide use, it can be very difficult to justify the higher tending costs, particularly if success is variable and uncertain. Recent wood-supply forecasts conducted by New Brunswick Department of Natural Resources and Energy Development staff suggest that if conifer planting were to be discontinued as result of a decision to not use herbicides, long-term total wood supply (20+ years hence) would drop by close to 20% (softwood 23% and hardwood 5%), resulting in the loss of as many as 730 direct jobs. If budgets were constrained to prevent the brush-sawing necessary to thin and tend natural regeneration, the total future available harvest could fall by nearly 60% (softwood 66% and hardwood 33%), with as many as 2400 direct jobs lost. An important aspect to emphasize is that the impact of such decisions may not be clearly evident until many years after they are made.
Health Canada has the legal authority to review, register, and regulate pesticide products in Canada. Every pesticide is assessed for potential risks to human health and the environment against a series of internationally recognized scientific studies.
The Pest Management Regulatory Agency (PMRA), a branch of Health Canada, is Canada’s federal pesticide regulator with legal authority to review, register and regulate pesticide products (PMRA, 2015) before the pesticide product is registered- that under typical conditions of use, the proposed product will not cause adverse health effects in humans or the environment. This precautionary approach of demonstrating the safety of the proposed pesticide product before being allowed for use in Canada supports the PMRA’s mandate that only those products, which satisfy the PMRA’s threshold of “reasonable certainty of no harm”, are registered for use in Canada. In addition, provincial and municipal regulations may impose further restrictions on how and where a pesticide product may be applied within their jurisdiction.
In April 2015, the PMRA released their latest review of glyphosate and declared that the weight of evidence indicates that glyphosate does not present unacceptable risk to human health.
Many organizations including Canada’s Pest Management Regulatory Agency (PMRA), the United States EPA, and the European Food Safety Authority have concluded that glyphosate does not pose a cancer risk when used according to regulations and label directions.
International reaction by the world’s leading health regulatory authorities to the March 15, 2015 IARC (International Agency for Research on Cancer) classification of glyphosate has been swift and consistent. On March 23, 2015, the German Federal Institute for Risk Assessment (BfR), which carried out the health risk assessment of glyphosate on behalf of the European Community, concluded that the human health risk assessment has assessed glyphosate as non-carcinogenic (BfR, 2015). The BfR noted that based on its evaluation of over 30 epidemiological studies, it came to the overall assessment that there is no validated or significant relationship between exposure to glyphosate and an in-creased risk of non-Hodgkin lymphoma or other types of cancer. On April 11, 2015, the US EPA declared (US EPA, 2015) that in 1991 it concluded that glyphosate should be classified as a Group E (evidence of non-carcinogenicity for humans) based on a lack of convincing carcinogenicity evidence and considering the US EPA criteria for classifying a carcinogen. The US EPA also noted that its assessment in 2014 included review of over 55 epidemiological studies conducted on the possible cancer and non-cancer effects of glyphosate. The US EPA concluded that the totality of this body of research does not provide evidence to show that glyphosate causes cancer, and it does not warrant any change in EPA’s classification of non – cancer for glyphosate. On April 13, 2015, the PMRA declared (PMRA, 2015) that in consideration of the strength and limitations of the large body of information on glyphosate, which included multiple short and long term (lifetime) animal toxicity studies, numerous in vivo and in vitro genotoxicity assays, as well as the large body of epidemiological information, the overall weight of evidence indicates that glyphosate is unlikely to pose a human cancer risk. The PMRA concluded that an evaluation of available scientific information found that products containing glyphosate do not present unacceptable risks to human health or the environment when used according to the proposed label directions. It should also be noted that the US EPA had previously affirmed its position on the non-carcinogenicity of glyphosate in 1993 US EPA, 1993) and then again in 2013 (US EPA, 2013); as did the WHO (2004) Joint meeting on Pesticide Residues 2004.
Recent developments
On May 16, 2016, a special meeting of the joint Food and Agriculture Organization and World Health Organization of the United Nations was held to re-evaluate glyphosate and other compounds in light of new studies that had become available since their last full assessment. The meeting concluded that glyphosate is unlikely to pose a carcinogenic or genotoxic risk to humans from exposure through the diet.
The safety of glyphosate has also been confirmed by New Brunswick's Acting Chief Medical Officer of Health, Nova Scotia's Chief Public Health Officer and the Chief Science Officer of the Public Health Agency of Ontario.
The distinction between hazard and risk is important in understanding the difference between what appears to be contradictory conclusions from IARC and the WHO. IARC considers the potential for a substance to cause harm under some circumstances, while regulatory agencies such as the PMRA, US EPA and the European Food Safety Authority, consider the likelihood (risk) of observing negative effects under realistic exposure levels. Regulatory agencies around the world, including PMRA, the United States Environmental Protection Agency (USEPA), the World Health Organization (WHO), and the European Food Safety Authority (EFSA) have, for many years, consistently concluded that registered uses of glyphosate in accordance with label directions do not pose a cancer risk, or any other risk, to human health.
In April 2015, the PMRA released their latest review of glyphosate and declared that the weight of evidence indicates that glyphosate does not present unacceptable risk to human health. The full PMRA glyphosate review can be found here or please visit here for a summary version of the full PMRA review.
The IARC is the specialized cancer agency of the World Health Organization. Glyphosate was evaluated by IARC in March 2015 and labelled as a “2a - probable human carcinogen”. The IARC study looked at the overall hazard posed by glyphosate, concluding that glyphosate is, under some circumstances, capable of causing cancer. This hazard assessment carried out by IARC did not consider how the chemical is used in real life, unlike the risk assessment conducted by regulatory agencies such as the Pest Management Regulatory Agency (PMRA), the U.S. EPA and the European Food Safety Authority which consider both the hazard as well as the risk to humans under actual and typical conditions of use.
The International Agency for Research on Cancer (IARC) is the specialized cancer agency of the World Health Organization (WHO). The objective of the IARC is to promote international collaboration in cancer research. The Agency is inter-disciplinary, bringing together skills in various disciplines, including epidemiology, laboratory sciences and biostatistics to identify the causes of cancer so that preventive measures may be adopted, and the burden of cancer may be reduced. A key component of IARC is the monograph program, which identifies environmental factors that can increase the risk of human cancer. These include individual chemicals, mixtures of several chemicals (e.g., tobacco smoke), occupational exposures, physical agents, biological agents, and lifestyle factors. National health agencies in countries all over the world then use this information as scientific support for their actions to prevent exposure to potential cancer-causing agents, known as carcinogens. IARC noted that glyphosate currently has the highest global production volume of all herbicides, potentially creating the opportunity for human exposure. Responding to advice from its international Advisory Group, glyphosate was evaluated at IARC’s monograph meeting in March 2015 (Lancet, 2015). On the basis of its evaluation of scientific evidence from studies in humans and in laboratory animals, IARC concluded that glyphosate should be classified as a “2a- probable human carcinogen”. It is important to be aware that IARC assessments are hazard based, meaning that the IARC evaluation considers whether a substance is capable of causing cancer, without necessarily considering if, under actual conditions of use, the substance will pose a real cancer risk. This contrasts sharply with risk-based assessments carried out by regulatory agencies around the world, including the PMRA, US EPA and the European Food Safety Authority, which carefully consider the uses of a substance and potential for human exposure in determining if the typical use of a substance poses an increased cancer risk. In Canada, only those pesticide products, which present “reasonable certainty of no harm”, are registered by the PMRA. The PMRA has determined that the use of glyphosate in Canada meets its standard of “reasonable certainty of no harm”.
Recent developments
On May 16, 2016, a special meeting of the joint Food and Agriculture Organization and World Health Organization of the United Nations was held to re-evaluate glyphosate and other compounds in light of new studies that had become available since their last full assessment. The meeting concluded that glyphosate is unlikely to pose a carcinogenic or genotoxic risk to humans from exposure through the diet.
The distinction between hazard and risk is important in understanding the difference between what appears to be contradictory conclusions from IARC and the WHO. IARC considers the potential for a substance to cause harm under some circumstances, while regulatory agencies such as the PMRA, US EPA and the European Food Safety Authority, consider the likelihood (risk) of observing negative effects under realistic exposure levels. Regulatory agencies around the world, including PMRA, the United States Environmental Protection Agency (USEPA), the World Health Organization (WHO), and the European Food Safety Authority (EFSA) have, for many years, consistently concluded that registered uses of glyphosate in accordance with label directions do not pose a cancer risk, or any other risk, to human health.
In April 2015, the PMRA released their latest review of glyphosate and declared that the weight of evidence indicates that glyphosate does not present unacceptable risk to human health. The full PMRA glyphosate review can be found here or please visit here for a summary version of the full PMRA review.
Regulations are in place to ensure that glyphosate does not come in direct contact with water. All streams have setback buffers and permits include weather restrictions on wind to reduce the risk of drift. In designated drinking watersheds there can be no glyphosate applied aerially less than 3.2km upstream from the point of intake. In some watersheds, drinking water is tested before and after application to make sure there has been no contamination and that regulations are being followed. At the application rates used in forestry, most of the glyphosate that is applied lands on the targeted vegetation. Any glyphosate that lands on soil will quickly bond to the soil and not leach from the site, so well water is not affected.
Federal and provincial pesticide use regulations specify how pesticide products are to be applied to minimize the likelihood of off-target drift and inadvertent exposure. Regulations may also impose pesticide free zones (PFZ) and buffer zones (BZ) to further reduce the likelihood of unintended off-target drift. To ensure that PFZs and BZs are observed, post application monitoring programs are carried out to assess the effectiveness of regulations. Thus, when pesticides are applied in accordance with labeled use restrictions, off-target drift is expected to be minimal, if at all, and not expected to pose a risk to human health or the environment (PMRA, 2015).
Health Canada has determined that there is no health concern associated with eating berries (e.g., blueberries, raspberries) sprayed during forestry applications. This applies to large quantities of berries eaten at one time, or smaller amounts over a longer period of time.
Pesticide regulations are always developed applying a precautionary principle; that is to say, the intent is always to minimize both direct and inadvertent human exposure, as much as possible, within the context of the intended use of the pesticide product. Glyphosate herbicide has many food uses for which acceptable Maximum Residue Limits (the amount of residue of a pesticide which may lawfully be present in or on a food crop) have been established.
The PMRA, like all major regulatory agencies all over the world, derive Reference Doses, which define levels of a pesticide residue to which an individual can be exposed over a single day (acute) or over a lifetime (chronic) with no significant adverse health effects. Generally, dietary exposure to glyphosate from food and water is acceptable if it is less than 100% of the acute reference dose or chronic reference dose (the Reference Dose is also commonly known as the Acceptable Daily Intake or ADI). The PMRA has estimated potential acute (short term) and chronic (long term or lifetime) dietary exposures to glyphosate from residues of glyphosate and relevant metabolites in both treated crops, and from drinking water. Exposure to different subpopulations, including children and women of reproductive age, were considered. The acute dietary exposure estimate (from both food and drinking water) at the 95th percentile represents 31% of the acute reference dose (ARfD) for females 13-49 years of age and ranges from 12% to 45% of the ARfD for all other population subgroups. The PMRA estimate indicates that the sum of exposure from dietary sources and from water represents only one eighth to one half of an exposure level not expected to be associated with adverse health effects. The PMRA also estimated that chronic dietary exposure for the general population represents 30% of the acceptable daily intake (ADI). Chronic exposure estimates for population subgroups range from 20% of the ADI (for adults aged 50 years or older) to 70% of the ADI (for children 1-2 years old). The PMRA concluded that acute and chronic dietary risks from exposure to glyphosate are not of concern (PMRA, 2015).
Glyphosate forestry products are also used in agricultural settings and it is therefore expected that the exposure to glyphosate from food products (i.e., fruits and vegetables from direct treatment with glyphosate) will cover potential exposure from inadvertent residues in berries following a forestry use. The potential inadvertent exposure from consumption of berries is therefore not of concern (PMRA, personal communication).
In April 2015, the PMRA released their latest review of glyphosate and declared that the weight of evidence indicates that glyphosate does not present unacceptable risk to human health.
Yes. Both lab and forest studies show that glyphosate does not accumulate in the tissue of animals living in treated areas. A moose study by Wolastoqey Nation in New Brunswick (WNNB) found glyphosate was not detected in tissue samples and showed that moose meat is not a source of glyphosate in the diet of humans.
Wolastoqey Nation in New Brunswick (WNNB) Moose and Traditional Food Quality Study
Based on laboratory studies, glyphosate does not bioaccumulate in tissues and is known to be rapidly excreted in the urine and feces of experimental animals even when exposed at very high experimental dose levels (Williams et al. 2000). Newton et al. (1984) reported that mammalian herbivores, carnivores and omnivores had visceral and body contents at or below observed levels in ground cover and litter and that residues were largely associated with the viscera (presumably largely in the digestive tract) and that other non-visceral body parts contained residues less than 0.5 ppm in all cases. Couture et al. (1995), summarizing results of studies conducted in Quebec, reported no detectable glyphosate residues in meat or liver of hares, moose or deer (1 sample only) collected in the hunting season (2 months after treatment), despite measurable residues in stomach contents, urine and feces of these animals. One of 19 kidney samples taken from hare contained a measurable level (0.208 ppm) of glyphosate.
Launtenschlager has reported results of a study, which investigated residues of glyphosate in moose meat from an area, which had been treated approximately two months before sampling. The authors reported that glyphosate residues were detected in only one sample out of 31 tested and that this single positive finding was likely the result of contamination.
Glyphosate forestry products are also used in agricultural settings, and it is therefore expected that the exposure to glyphosate from food products (i.e., fruits and vegetables from direct treatment with glyphosate) or animal commodities such as meat, milk and eggs (derived from livestock animals exposed to glyphosate -treated feed) will cover potential exposure from inadvertent residues in moose following a forestry use. The potential inadvertent exposure from consumption of moose meat is therefore not of concern.
In April 2015, the PMRA released their latest review of glyphosate and declared that the weight of evidence indicates that glyphosate does not present unacceptable risk to human health.
The Pest Management Regulatory Agency (PRMA) has conducted a thorough risk and hazard assessment for individuals who work handling glyphosate (mixers, loaders and applicators). It concluded that when handled correctly, according to all safety precautions, there is no concern for the health of these individuals. These studies also included individuals who work in the forest following application of glyphosate.
The PMRA has carried out a detailed hazard and risk assessment for those individuals who may be occupationally exposed during mixing, loading and application of glyphosate (PMRA, 2015). The PMRA has concluded that risks to glyphosate handlers are not of concern for all use scenarios. The PMRA has noted that based on their recent assessment of precautions and directions for use on the original product labels, risk estimates associated with mixing, loading and applying activities are not of concern. The PMRA also considered post-application occupational risks to workers who may be exposed when entering treated sites in agriculture. The PMRA concluded that based on their assessment of use patterns for agricultural scenarios, post-application risks to workers performing activities are not of concern. The PMRA may set re-entry intervals (REI) to protect workers who must re-enter treated areas. REIs are established to protect the most sensitive subset of the population who could be exposed when re-entering a treated area and are therefore precautionary in nature. The PMRA has proposed a REI of 12 hours for glyphosate in agricultural sites.
In April 2015, the PMRA released their latest review of glyphosate and declared that the weight of evidence indicates that glyphosate does not present unacceptable risk to human health.
Glyphosate formulations, which include both the active ingredient and other formulation ingredients such as surfactants and solvents, are assessed by the PMRA for their hazard and the risk they may potentially pose to human health under actual conditions of use. The Pest Management Regulatory Agency (PMRA) only approves those products, which do not pose an unreasonable risk of harm to human health or the environment.
Many pesticide formulations include various solvents and emulsifiers whose function it is to improve the performance of the active ingredient. In Canada, all components of the formulation, including the non-active ingredients such as the emulsifiers and solvents, are subject to health hazard and risk assessment and regulation by the PMRA. And the same PMRA safety threshold of “reasonable certainty of no harm” (PMRA, 2015.) The chemicals and solvents used in pesticide formulations are not unique to these products; in fact, they are found in a wide range of products formulated for personal care and household cleaning, where they serve a similar function.
In April 2015, the PMRA released their latest review of glyphosate and declared that the weight of evidence indicates that glyphosate does not present unacceptable risk to human health.
Some study reports have appeared in which the authors suggest that exposure to glyphosate may lead to an increased incidence of autism. These findings are based on “test tube” studies, making their relevance and ability to predict potential adverse health effects in humans, obscure. Moreover, these studies, as well as numerous others, which investigated various toxicological endpoints, were considered in the recent review of the safety of glyphosate by the EU and were not considered relevant to the assessment of the safety of glyphosate (BfR, 2015). It is also important to note that many authorities believe that the increased incidence of autism may be largely attributable to improved awareness and screening techniques.
Deer are well adapted to seek and feed on the most nutritious food sources possible. It isn’t that deer are trying to escape treated areas, they are simply finding the most nutritious and easily accessible foods available – the grasses, shrubs, trees, and other vegetation readily available in agricultural or suburban areas.
Deer have always sought the most nutritious foods available in their home ranges. When near humans they commonly feed in and around agricultural fields which have been enriched through fertilization, planting of nutrient rich species, and vegetation management (including plowing, disking, and herbicides). In suburban areas where deer are no longer hunted aggressively, their local populations have grown and they seek nutrient rich forage, like planted and fertilized vegetables, fruits, grass, shrubs, and trees found in yards. The foods being provided by homeowners in suburban areas, not the application of spray solutions containing glyphosate, are the primary reason deer have started using those areas extensively. It should be emphasized that artificially feeding any wildlife, including deer, is considered a very risky and inappropriate practice because animals may become dependent on that food source, drawn away from their natural habitat and less capable of foraging naturally.
In forestry scenarios, the risk to most aquatic organisms, including aquatic plants, is strongly mitigated by the use of protective buffer zones which are designed to minimize potential exposure levels. Risk analyses show that aquatic plants and algae are relatively more sensitive to glyphosate herbicides than aquatic animals. Among aquatic animals, fish and larval amphibians (tadpoles) are particularly sensitive to products containing POEA (a surfactant mixture used in some glyphosate-based herbicides). Amphibians associated with small, shallow wetlands within targeted spray site are considered to be at relatively great risk. However, several field studies examining the effects of glyphosate and POEA demonstrate no significant effects on amphibians under realistic exposure levels and environmental conditions.
Small, shallow wetlands which are not mapped or easily observed from the air present a special case of potentially higher risk, particularly to amphibians which frequent these habitats. Although laboratory studies clearly demonstrate that fish and amphibian larvae (i.e., tadpoles) are quite sensitive to formulated glyphosate products containing the POEA surfactant, several field studies show no significant effects under realistic exposure scenarios. Some species of algae and aquatic plants are also very sensitive to glyphosate-based herbicides. Field study results support the conclusions drawn by several independent reviews which suggest that the use of glyphosate-based herbicides in accordance with product labels and as typically used in Canadian forest vegetation management do not pose a significant risk to aquatic organisms. This is particularly true given the routine application of buffers specifically designed to protect sensitive aquatic systems.
An extensive number of studies have focused on the potential effects of glyphosate-based herbicides to aquatic organisms including zooplankton, fish and amphibians and these studies have been reviewed by several authors (Giesy et al 2000, Solomon and Thompson 2003, Durkin et al. 2003; Tatum 2004) all of whom conclude that he likelihood of direct acute toxic effects to aquatic organisms are unlikely. Fish and amphibian larvae (tadpoles) are known to be highly sensitive to glyphosate-based herbicide formulations, particularly those containing the polyethoxylated tallow amine (POEA) surfactant when exposed under laboratory conditions (e.g., Folmar et al. 1979; Wan et al. 1989; Howe et al. 2004; Edginton et al. 2004). As part of a watershed level investigation on the effects of a glyphosate-based herbicide applied to a western Canadian coastal forest system (Holtby and Bailey 1989), temporary stress effects and minor mortality (2.6%) were observed in caged coho salmon fingerlings held in an experimentally over-sprayed tributary and the mainstream below the sprayed area. However, no acute mortality, changes in over-winter mortality, growth rate or probability of using the tributary were observed for resident fingerlings. Similarly, several subsequent studies confirm the general sensitivity of amphibian larvae to these herbicide products when exposed under laboratory or mesocososm conditions (e.g. Chen et al. 2004; Relyea et al. 2005; Williams and Semlitsch 2009).In general, the lowest reported concentrations resulting in 50% or greater mortality in amphibian larvae after 96 hrs exposure under lab conditions approximates 0.8 mg a.e./L (Edginton et al. 2004; Relyea and Jones 2099), although Williams and Semlitsch have reported >80% mortality in 1 of 3 amphibian larval species following exposure to the Roundup WeatherMax formulation at an equivalent of 0.6 mg a.e./L. Coincidentally, the 0.8 mg a.e./L value is also considered to be threshold concentration below which all aquatic organisms would be protected irrespective of exposure period (CCME 2012). Given the demonstrated sensitivity of amphibian larvae and the potential for direct overspray or off-target drift inputs to small ephemeral wetlands under typical forest-use scenarios, raised legitimate questions with respect to potential risk to amphibians under typical forest-use scenarios (Thompson et al. 2004; Govindarajulu 2008). To address this issue directly an extensive hierarchical program of research was conducted including laboratory, in-situ mesocosm, whole wetland and operational monitoring. Based on operational monitoring studies of typical aerial spray programs in Ontario (Thompson et al. 2004), the maximum concentration expected in such wetlands would be less than 0.55 mg/L (ppm) 99 times out of 100 (i.e., below the threshold concentration for significant acute effects). No significant differences were observed in mortality of two different amphibian species that were variously exposed in buffered, adjacent and over sprayed wetlands. Several other field studies have confirmed no significant acute effects of formulated glyphosate herbicide products on larval amphibian survival, growth or development even at levels considered to represent a maximum worst case in small wetlands (Wojtaszek et al. 2004; Edge et al. 2014; Edge et al. 2012). Similarly, in situ enclosure studies conducted in naturalized wetlands showed no significant effects on juvenile frogs directly exposed to a formulated glyphosate-based herbicide even following direct exposure at the maximum permissible label rates (Edge et al. 2011; Edge et al. 2013). The differences between laboratory and field study results can be generally explained by sediment sorption and degradation process that are active in natural shallow wetland ecosystems and which limit exposure magnitude and duration to both glyphosate and the POEA surfactant (Wojtasek et al. 2004; Edge et al. 2012; Wang et al. 2005; Rodriguez Gil 2015 Personal communication) as compared to laboratory studies where these factor are either not included or minimized in standardized testing protocols. Overall, results of these field studies confirm that the use of glyphosate-based herbicides in accordance with product labels and as typically employed in Canadian forest vegetation management do not pose a significant risk to amphibians or other aquatic organisms.
The woody browse that deer like to eat is reduced on sites treated with herbicides, such as glyphosate. However, deer and moose are well adapted to locate and feed on the most nutritious food sources possible. A large-scale study is underway to better understand how deer are using our forests, how suitable our forests are to support deer in summer and winter months, and the effects of glyphosate on availability of food for deer.
Both deer and moose consume significant amounts of non-woody foods during the growing season, including foliage, shoots and twigs from deciduous trees and shrubs (e.g., maples, pin cherry, birch, dogwood). These food sources are commonly referred to as "woody browse." These same species are often the target of conifer release treatments and their biomass is commonly reduced 50-70% by successful conifer release treatments. However, herbaceous species contribute significantly to deer diets and are eaten by moose, and they commonly remain, or quickly “rebound,” in treated areas. Moose, which feed more on woody browse, do reduce their use of treated areas for five to seven years after treatment. However, that is only important in the short-term and then only if the landscape is dominated by young released stands. When the landscape is not dominated by young released stands these animals simply find and use better habitat found in other parts of their range.
Large mammals range over large areas of forested landscapes and hence potential effects must be considered in relation to the dynamic mosaic of forest conditions that exist on that landscape (Lautenschlager and Sullivan 2002). On an annual basis, based on a national average, less than 1/3 of clear-cut harvested areas are treated with glyphosate-based herbicides. There is no question that the abundance of deciduous woody browse species will be at least temporarily reduced on these treated areas. However, as many of these plant species regenerate from the soil seed bank, reduced browse effect, even on treated sites, will be transient as evidenced in the studies noted above. Moreover, copious amounts of browse material will typically occur on the 2/3rds of the forest cutover lands which are not treated with herbicide.
A specific area of concern is the potential for reduced winter browse availability for deer whose winter foraging range area may be limited by snow depth. The potential for such effects would depend on both the proportion of the foraging area around deer yards that is treated with glyphosate-based herbicides and the actual reduction in winter browse species typically used as winter forage by deer on those areas. Considering information from New Brunswick as an example, on the broader landscape, much of the clear-cut area (66% as a long-term average estimate on crown lands) is left to regenerate without the aide of glyphosate treatment. Assuming this is true on cut over sites close to deer wintering areas as well, suggests that 66% of the open areas in which deer might browse in winter would be unaffected by glyphosate-based herbicide treatment. Potential effects would also be further ameliorated given that:
- Deer habitat management in crown lands of New Brunswick is focused on identification of Deer Wintering Areas (DWAs) and maintenance of suitable winter habitat in these areas. This includes harvesting restrictions which are limited to single entry partial harvests. Under such harvest systems, herbicide treatments are not used and hence there can be no effect of herbicide treatments within the DWA per se.
- Under increasingly severe winter conditions and snow depths, deer tend to remain closer to mature conifer or conifer dominated mixed wood stands that intercept snowfall and thus facilitate localized movement (Morrison et al. 2003; Sabine et al 2001). While deer are known to browse on a wide variety of species in winter (Morrison et al. 2002) including in particular red and striped maple, under restricted movement scenarios cedar and balsam fir are important food sources (Morrison et al. 2002, Telfer 1972, Mautz et al. 1976, Gray and Servello 1995, Ditchkoff and Servello 1998) and neither of these species are influenced by glyphosate-based herbicide treatments (e.g., Gagne et al. 1999).
As noted by Morrison et al. (2002), by identifying browse species selected by deer and by understanding their associations with forest stand types, managers will be better able to meet the dual objectives of providing appropriate conifer dominated cover and an adequate supply of browse to support deer through winter. In this context, although it is quite unlikely that glyphosate-based herbicide use is a significant factor influencing deer winter browse availability, detailed geographic analysis of the proportion of deer foraging areas actually receiving glyphosate-based herbicide treatments would provide useful information furthering our understanding on this specific aspect. Broader assessment of deer population viability must consider a number of other potentially influencing factors such as natural predation (e.g., by coyotes, bears and wolves) facilitated predation through predator use of roads and trails, hunting pressure and poaching, disease and deleterious effects of artificial feeding.
Due to the chemical structure of glyphosate, the product binds quickly to soil particles and is very unlikely to leach into the soil and ground water.
Although glyphosate is quite water soluble, the molecule also carries both positive and negative charge that explain its strong binding affinity to soil organic matter and clay particles. As a result of its strong binding properties, it is considered to have very low potential to leach down through soils and into groundwater. Unlike agricultural scenarios, in forest vegetation management glyphosate-based herbicides are applied to sites with substantial competing vegetation cover and leaf litter on the forest floor. As such, much of the depositing spray cloud is intercepted by the target competing vegetation canopy or adsorbed to leaf litter, minimizing the amount of chemical that would actually reach the soil layer. Several studies in forest sites of Canada and the northern USA demonstrate that glyphosate and AMPA are strongly sorbed and typically retained within the upper 15 cm of soil and thus unlikely to move into surface or groundwater. In cases where there is sufficient rainfall residues bound to soil particles could be transferred to surface waters, although such residues are unlikely to be biologically available again owing to the strong binding affinity to organic matter and clay constituents.
In forest soils, glyphosate is rarely detected below the upper 15 cm level (Thompson et al 2000; Roy et al 1989; Feng et al. 1990; Legris et al. 1988; Newton et al. 1984; Newton et al. 1994), indicating that glyphosate is very unlikely to percolate down through forest soils and into groundwater. Given typical forest-use scenarios, the risk for groundwater contamination by glyphosate-based herbicides is substantially lower than that in agriculture, given the small percentage of the forest land base that is ever treated, that applications are typically made only once per site in 40–80-year period, that treatment sites are typically very remote from drinking water sources and that such source areas are protected by extensive buffers. However, even under agricultural scenarios where glyphosate-based herbicides are used extensively, typically only very low-levels of glyphosate are observed and even these occur very infrequently. Vereecken (2005) reported on several studies in European agriculture that also typically showed low level residues occurring infrequently in groundwater with no detections above drinking water standards in Denmark, the UK, the Netherlands or Norway. In another example, Battaglin et al. (2014) recently reported that of the total 1,171 groundwater samples analyzed from 807 different sites, glyphosate was detected in only 5.8% and AMPA in 14.3% of all groundwater samples. The maximum reported groundwater concentrations for the two compounds were 2.03 and 4.88 ppb respectively, far below the maximum acceptable concentration of 280 ppb established by Health Canada as protective of human health assuming a lifetime (70-year consumption) of 1.5 L of drinking water per day (Health Canada 2014). Similarly, a multiyear study of pesticide residues in 4 rivers in an agricultural region of southern Quebec showed the maximal concentrations of glyphosate ranging from 3.3 to 29.0 ppb (Giroux and Pelletier 2012). The latter value was considered to be the highest concentration of glyphosate observed in surface waters that might be considered as sources of drinking water (PMRA 2015) which concluded that dietary risk were not of concern either with respect to acute or chronic toxicity to humans generally or for subpopulations such as children and women of reproductive age.
In April 2015, the PMRA released their latest review of glyphosate and declared that the weight of evidence indicates that glyphosate does not present unacceptable risk to human health. The full PMRA glyphosate review can be found here or please visit here for a summary version of the full PMRA review.
Studies show when used according to product labels, herbicides, such as glyphosate, do not pose a significant toxicological risk to mammals or birds.
The application of glyphosate-based herbicides in forest vegetation management is not considered to pose a significant risk of direct toxicity to small mammals or birds. Indirect effects resulting from alteration of vegetative habitat or food availability do occur, however these are transient effects and depend on individual species preferences. In general terms, those species preferring more open habitats are temporarily favoured over those preferring brushy deciduous cover. Overall, studies indicate that richness and diversity of songbirds or small mammals resulting from glyphosate induced habitat alterations remain within the range of natural variations. It is important to note that only a small portion of the area harvested by clear cutting is treated in any year (national long-term average of 19%, based on the National Forestry Database) and that forest management plans are specifically designed to allow for a dynamic mosaic of stands across the landscape through time. Both of these factors mitigate the potential for widespread population level effects on these wildlife groups.
Numerous scientific and regulatory reviews have examined the potential direct effects of glyphosate on a wide variety of wildlife species including birds and small mammals Such reviews consistently conclude that the use of glyphosate products in accordance with product labels do not pose a significant risk of either direct acute or chronic toxicity to terrestrial wildlife species (PMRA 2015; USEPA 1993; Durkin 2003; Giesy et al. 2000; Tatum 2004; Couture et al. 1995; Thompson 2011). The detailed risk assessment conducted by Durkin 2003, calculated the risk to small mammals and birds based on the relationship between estimated exposure (e.g., via direct overspray or through consumption of contaminated vegetation, water, insects or fish) following application of glyphosate –based herbicides at a rate equivalent to 2.24 Kg a.e./ha, as compared to no observable effect levels in laboratory animals, considering both acute and chronic (longer term exposures). In summary the author stated that congruent with the USEPA 1993 assessment “none of the hazard quotients for acute or chronic scenarios reach a level of concern even at the upper ranges of exposure”.
While direct toxic effects on these wildlife groups are thus considered not to be of concern, potential indirect effects through habitat change must also be considered. There have been numerous studies examining this aspect and as noted by Guynn et al. 2004, wildlife response to herbicide-induced habitat alteration is highly variable ranging from studies that demonstrate no effect, short-term negative effects and for some species or communities positive effects. Species responses are reflective of their individual habitat preferences. In general terms, those species preferring more open habitats are temporarily favoured over those preferring brushy deciduous cover. A review by Sullivan and Sullivan (2003) involving 60 different published studies, noted that there were either no or very little significant reductions in richness and diversity of songbirds or small mammals resulting from glyphosate induced habitat alterations. Lautenschlager (1993), summarizing 14 studies conducted in northern conifer forests concluded that total songbird populations are seldom reduced during the growing season after treatment and also made the interesting observation that only studies that use kill or removal trapping show density reductions in small mammals. Gagne et al. (1999) reported no significant effects on species richness of small mammals following herbicide treatment in balsam fir forests of Quebec, but observed a reduction in red-backed vole abundance for two-years following a glyphosate-based herbicide treatment. The negative effect was associated with reduced cover and the authors concluded that in the short term, herbicide-treated plantations constitute poorer red-backed vole habitats than brush saw plantations, noting that this difference was likely due to the rapid recovery of vegetation by resprouting in the brush saw treatments and possibly also by residues of the cutting operation providing cover. Woodcock et al. (1997) assessed the effects on songbird densities as determined by territory mapping, mist netting, and banding and observed 20-38 species breeding within various treatment blocks. First year post-treatment assessments revealed that mean densities of the 11 most common species increased by 0.35/ha on the control plots. In contrast, densities on treated plots decreased by 1.1/ha (brush saw), 1.6/ha (Silvana Selective), 0.14/ha (Release) and 0.72/ha (Vision). A point of emphasis here is that essentially any effective vegetation management technique will alter available habitat to some degree. In at least this one study, songbird densities were relatively less impacted by herbicide treatments as compared to mechanical treatments. Response to habitat changes will vary with species, favouring certain species while resulting in out-migration of other species at least for some period of time depending upon their individual preferences and the temporal dynamics of the vegetation change post-treatment. An example of differential species response is provided by the study of MacKinnon and Freedman (1993) who also demonstrated that natural dynamic in avifaunal response to vegetation dynamics under natural successional pathways on forest clear-cuts.
In April 2015, the PMRA released their latest review of glyphosate and declared that the weight of evidence indicates that glyphosate does not present unacceptable risk to human health. The full PMRA glyphosate review can be found here or please visit here for a summary version of the full PMRA review.
Yes. Like treating weeds in your garden, the point of herbicide application is to reduce the population of competitive plant species in a woodlot. Herbicide treatment is one of many tools used by forest managers to promote the growth of softwood trees early in their development. However, plant communities rapidly regrow, providing softwoods with only a temporary head start. While a temporary impact on plant diversity will occur in planted stands, the use of herbicides, such as glyphosate, does not impact diversity at the forest landscape level. Only 1% of New Brunswick’s forests are harvested in any year. Only one third of the area harvested in any year is planted, resulting in 0.3% of the New Brunswick Forest being planted and treated with herbicide in any year.
In answering this question, it is important to distinguish between diversity, richness and abundance of plants within a community. Species richness is simply the number of different species in a given community, whereas measures of diversity incorporate aspects of both richness and evenness (i.e., how equal the abundances of different species are). Glyphosate-based herbicides are most commonly applied to enhance conifer regeneration on recently harvested sites. Consistent with this objective, effective application of these products will temporarily reduce the abundance, cover and vigour of targeted competitive plant species (e.g., deciduous woody species, shrubs) such that growth of conifer seedlings is enhanced. Since glyphosate is strongly bound in soils, and not taken up appreciably by plants through roots, plant species that regenerate from seed will rapidly re-establish on treated sites. Manipulating the plant community dynamics to temporarily advantage conifers can be viewed as a means of shortening the early phase of a natural successional pathway and ensuring the replacement of conifer dominated stands on the landscape. Although abundance and vigour of targeted competitors is temporarily reduced, treatments with glyphosate-based herbicides typically do not result in significant reduction in richness of vascular plants on the site and do not generate plant monocultures.
As part of a broader review of glyphosate-based herbicide effects on plant and animal diversity, Sullivan and Sullivan (2003) reported that 10/12 studies showed that species richness and diversity of vascular plants was either unaffected or increased, particularly for herbaceous species, following glyphosate treatments. Of the two exceptional studies, Sullivan et al. (1988) observed a reduction in species richness of shrubs in the initial five years post-treatment and Santillo et al. (1989) observed lower species richness of shrubs and forbs in treated as compared to untreated sites. The silvicultural objective of herbicide treatments is to temporarily reduce competition from woody deciduous, shrub and other plants such that regeneration of desired crop tree species (typically conifers) is enhanced. In essence, the herbicide treatment provides conifers with a “jump-start” down the successional pathway toward a conifer dominated stand replacing that which was harvested. Largely because glyphosate is non-persistent and has no soil activity, the effect on the plant community is short-lived. Treatments with glyphosate-based herbicides are very effective at temporarily reducing the abundance and vigour of the targeted competing plant species (dominant woody deciduous, shrub and herbaceous species), but they do not generate single layer plant monocultures or reduce overall species richness (Freedman et al. 1994; Gagne et al. 1999; Bell and Newmaster 2002; Newmaster and Bell 2002). Results of the study by Bell and Newmaster (2002) may be considered typical in that they show herbicides had a relatively greater initial effect on plant community composition as compared to the two different mechanical vegetation control treatments, but that woody, herb, and grass layers showed substantial resilience to all treatments and recovered to pre-treatment levels within five years. Relatively greater effects were observed on ferns, mosses and lichens, but even these species groups recovered within the five-year time frame. (Newmaster and Bell 2002).
Laboratory and controlled field studies have found that when applied at the legal label rate, glyphosate has negligible effects on honeybees’ survival, honey production, brood survival, or development. Honey produced in hives from colonies that foraged on pollen from over sprayed fields does contain glyphosate, however the concentration is very low and unlikely to pose a risk to human health. Minimal or no effects are typically observed in studies on other “beneficial” insects or spiders.
Adequate laboratory data exist to demonstrate that glyphosate is essentially non-toxic to bees and other beneficial insects. Of the few higher tier studies examining potential effects of glyphosate-based herbicides on honeybees, one showed no significant effects on brood survival, development or mean pupal weight resulting from worst-case exposure scenarios, while two studies demonstrated deleterious effects on learning behaviour and carotenoid antioxidant levels in honeybees. In a study conducted under an agro-forestry scenario, glyphosate residues were observed in pollen and honey collected from hives placed at various distances from treated sites. Maximal levels occurred in pollen from a hive situated within the treated area. Toxicological risks associated with glyphosate in this study were reportedly negligible. Given that commercial apiaries or personal bee-keeping operations are quite unlikely to be located in operational forest environments, the potential effects of glyphosate-based herbicides in forestry on honeybees per se is generally not of concern. Of greater ecological interest is the potential effects of treatments on wild bees which might utilize disturbed forest cutover sites as foraging areas. Unfortunately, the differences in area treated, probability, frequency and magnitude of potential exposures as well as potential differences in foraging habits of wild bee species or other pollinators versus those of honeybees, severely limit the utility of agricultural scenarios in terms of estimating risks to these organisms. This is considered an area where further ecotoxicological research may be warranted, although it is likely that results would parallel those of several existing field studies which demonstrate that typically the only significant effect on other beneficial insects in forestry is temporary decline in abundance on treated sites related to changes in vegetative habitat.
Tier 1 laboratory toxicity testing demonstrates that glyphosate is not acutely toxic to bees and other beneficial insects (Giesy et al. 2000; Hassan et al. 1988; PMRA 2015). As cited by Durkin (2003) Palmer and co-workers have investigated the toxicity of glyphosate to bees (Palmer and Beavers 1997c; Palmer and Krueger, 2001a; Palmer and Krueger, 2001b). Based on these data, the U.S. EPA (1993) classified glyphosate as practically non-toxic to bees. Boily et al (2013) conducted studies on various pesticides, including glyphosate, on bees and found that chronic exposure to low-level glyphosate concentrations had no significant effect on bee mortality, weight or protein content, but did result in a significant depression in acetylcholine esterase activity. Ferguson (1988) showed that colonies supplied directly with sucrose solution containing 5% of a formulated glyphosate product had no effect on bee colonies. Burgett and Fisher (1990) conducted a field study in which Honeybee hives and the surrounding blooming vegetation were over sprayed with a formulated glyphosate product at 6.8 Kg a.e./ha and reported no acute or chronic effects for adult honeybees or for brood production. Laberge et al. (2007) reported on a field study conducted in an agro-forestry environment in which hives were placed within or at various distances from treated sites. Detectable residues of glyphosate were observed in approximately 50% of the pollen samples and 3 of 9 honey samples, with maximal residues of 8.2 mg/Kg in pollen sampled 3 days post-treatment from a hive situated directly within the treated area. Based on toxicological risk assessment, the authors concluded that risks associated with glyphosate were negligible. Similarly, Thompson et al. (2014) recently examined the effect of realistic worst-case exposure levels of glyphosate-based herbicide based on residues observed in pollen and nectar following applications at 2.88 Kg a.e./ha. In the exposure study, the maximum residues found in pollen taken from traps in an enclosed greenhouse where bees were allowed to forage on treated plants ranged from 87.2 to 629 mg a.e./Kg, were much higher than maximal residues found in nectar (2.78 -31.3 mg a.e./Kg) with both types of residues declining rapidly with time post-spray. Based on these data, the authors conducted a subsequent effects study in which colonies were exposed directly to three different levels of glyphosate in sucrose solution with the maximum test level being 301 mg a.e./L. The authors reported no significant effects on brood survival, development or mean pupal weight resulting from such exposures. Herbert et al. (2014) conducted studies at levels considered relevant to agricultural use scenarios and observed impaired learning and responsiveness to nectar as a reward, but no effect on foraging-related behavior. These workers postulated that trace glyphosate residues could be transferred to Honeybee broods with potential long-term consequences. Helmer et al. (2014) documented reduced carotenoid antioxidant levels in Honeybees exposed for 10 days to realistic levels glyphosate in sugar solution, but no effect on lipid peroxidation. Overall, results from a number of lab and simulated field studies generally suggest no significant risks of acute or chronic effects of glyphosate on adult Honeybees or brood production. The two studies conducted under agricultural scenarios which suggest potential effects on learning or antioxidant levels may be suggestive of aspects that should be included in potential future higher tier field studies examining glyphosate–based herbicide effects on wild bee species or other pollinators under typical forest use scenarios.
Preston and Trofymow (1989) examined potential effects on arthropod populations in a British Columbia red alder site and observed the only effect to be a temporary reduction in mites on one of the treatment sites at 20 days post-treatment, with no differences at 180 days. Whitehouse and Brown (1993) found no changes in the population of predatory insects following treatment of a clear-cut area in Maine at a rate of 1.7 Kg a.e./ha. Brust (1990) reported no significant acute or chronic effects on carabid beetle longevity or on their food consumption and showed no toxic or repellent effects in field studies. However, owing to changes in plant communities large carabids tended to leave glyphosate treated agricultural fields for a period of ~ 28 days. In contrast, Duchesne et al. (1999) reported no change in abundance and that species richness and diversity of carabids increased following glyphosate and other vegetation management treatments in a boreal mixed-wood ecosystem study. Haughton et al (2001) examined the effect of glyphosate on non-target spiders under both laboratory and field conditions and found no significant direct effects and only short-term indirect effects associated with vegetative habitat change. Young et al. (2001) also reported on potential toxic effects of glyphosate on spiders reporting no significant acute effects at exposure rates up to an equivalent of 2.16 Kg/ha, noting that results supported limited data suggesting general lack of effect on non-target arthropods. Santillo (1989) reported an 89% reduction in herbivorous insects captured on herbicide treated clear-cuts as compared to controls 1 year post treatment. Evidence of recovery (only 25% difference) was observed in year 3 for herbivorous insects, a 29% difference between treated and untreated sites through 3 years for invertebrates captured by pitfall traps, and no trend in predatory insect numbers. Gagne et al. (1999) observed reductions in arthropod numbers in sites where conifers were released via glyphosate herbicide treatment or via brush saw treatments, as well as in naturally regenerating boreal forest cutovers and attributed the observed differences to natural fluctuations. In this study, the relative abundance of foliar arthropods did not differ between treated and untreated sites two-years post-spray. Overall results suggest no or minimal direct effects on beneficial insects other than transient reductions in herbivorous species which occur in conjunction with changes in preferred habitat.
In April 2015, the PMRA released their latest review of glyphosate and declared that the weight of evidence indicates that glyphosate does not present unacceptable risk to human health. The full PMRA glyphosate review can be found here or please visit here for a summary version of the full PMRA review.
Several published scientific reviews and risk analyses conclude that the use of glyphosate-based herbicides poses a minimal risk to soil microorganisms, earthworms and invertebrates. Studies conducted in Canadian forests also show limited or no effect on soil organisms when tests use realistic exposure and environmental conditions.
Under typical use of glyphosate-based herbicides in forest vegetation management, soil organisms would have minimal exposure to glyphosate or its residues simply because most of the spray cloud is intercepted by the targeted competing vegetation. The majority of studies conducted with realistic exposure levels and environmental conditions demonstrate no significant impacts on soil microorganisms or their ecological functions such as nitrogen transformations. Similarly, field studies pertinent to use in Canadian forest ecosystems typically show no significant effects of glyphosate-based herbicides on soil micro-organisms or macro-organisms such as earthworms, ground beetles or snails and slugs.
In summarizing 15 different studies pertaining to potential effects of glyphosate-based herbicides on terrestrial invertebrates Sullivan and Sullivan 2003 noted that responses are variable and principally the result of changes in vegetation structure. Ratcliff et al. (2006) examined the effects of a glyphosate-based herbicide formulation applied at the recommended field rate to clay loam and sandy loam forest soils. The authors reported no major changes in microbial community structure assessed by several different methods. Treatment at much higher (100 x) rates simulating a spill of undiluted material resulted in a short-term stimulation of bacteria and minimal change to the fungal community. Preston and Trofymow (1989) reported no significant effects of glyphosate on either soil fauna or microflora populations, or several parameters of nitrogen transformations mediated by soil microbes in lab and field studies in British Columbia. Fletcher and Freedman (1986) conducted laboratory studies with two leaf litter and one forest floor substrate and found that the threshold for glyphosate effects on litter decomposition was more than 50 times higher than residue concentrations that occur in the field after silvicultural herbicide treatments. Duchesne et al. (1999) reported that total catch of carabid beetles in pitfall traps was not affected herbicide treatments including glyphosate (Vision) one year post treatment and that carabid species richness and diversity were slightly higher or equivalent to that observed in untreated controls or sites receiving mechanical vegetation control treatments. As part of this broader study, Houston et al. (1998) noted that conifer release treatments with the glyphosate-based herbicide Vision had no significant effect on basal respiration, microbial biomass carbon, metabolic quotients or nitrogen in either organic or mineral soils. They found that fungal species richness and community structure of check (77 species) and Vision treated plots (81 species) were similar. However, only 40 fungal species common to both Vision and check plots, and that forest harvesting increased fungal community richness and diversity in both near-surface organic and deeper mineral soils. Hawkins et al. (1997) examined effects on terrestrial gastropods in this study and reported that during the first growing season after release, neither surface-active densities nor species richness of gastropods were affected by the alternative vegetation management techniques tested, which included aerial application of a glyphosate-based herbicide. In follow-up studies, Prezio et al. (1999) noted that densities of surface-active gastropods were 50-60% lower in all sites receiving vegetation management treatments including herbicide, brush saw and mechanical clearing as compared to untreated controls 2 and 3 years post treatment, with some trends toward recovery apparent in year 3. Effects were attributed to decreased litter deposition and altered near ground microclimate on treated sites.
Busse (2001) reported that microbial respiration was unchanged at expected field concentrations and that long-term repeated application of glyphosate had minimal effect on seasonal microbial activity. A number of other studies also demonstrate that glyphosate herbicide treatments do not significantly reduce soil microbial populations or impair key microbial functions (e.g., Haney et al. 2000; Hart and Brookes 1996; Wardle and Parkinson 1990). Estok et al. (1989) examined the effects of glyphosate on ectomycorrhizal fungi and found 2 of 3 species showed significant growth reduction effects only at concentrations greater than 100 ppm, with the third having significant effects at 1 ppm. The authors noted that tests on fungi growing on agar medium predispose fungi to herbicide toxicity. Dalby et al. (1995) reported no effect of glyphosate on survival and condition of 4 species of earthworms exposed at “recommended” rates, although these rates were not specified. Similarly, Edwards and Bholen (1992) noted that glyphosate at exposures ranging from 1 to 100 ppm in soils had no toxic effects on earthworms. Risk assessments (PMRA 2015; Durkin 2003; Giesy et al. 2000) conclude that typical use patterns of glyphosate do not pose an acute or chronic risk to earthworms or other soil organisms.
In April 2015, the PMRA released their latest review of glyphosate and declared that the weight of evidence indicates that glyphosate does not present unacceptable risk to human health. The full PMRA glyphosate review can be found here or please visit here for a summary version of the full PMRA review.
Numerous independent scientific and regulatory reviews consistently conclude that glyphosate-based herbicides, when used in accordance with product labels, do not pose a significant risk of direct toxicity to wildlife, including moose, deer and small mammals. Therefore, direct toxicity is considered an exceedingly low risk. Indirect effects through reduction of deciduous woody brush species are known to at least temporarily limit the utilization of herbicide treated sites by moose. However, given that annually only 1/3rd of forest cutover areas are treated with glyphosate-based herbicides, small and large mammals will typically adapt to this temporary change on a small portion of the landscape by moving to, or feeding in, alternative areas including the 2/3rds of cutover areas annually that are regenerated without herbicide treatment.
Risk assessments and independent scientific reviews consistently conclude that the use of glyphosate-based herbicides in accordance with product labels do not pose a significant risk of direct toxicity to wildlife (PMRA 2015, Thompson 2011; Durkin 2003, Tatum et al. 2004, Guynn 2004, Sullivan and Sullivan 2003, Solomon & Thompson 2003, Giesy et al. 2000, Couture et al 1995). These strongly congruent conclusions are further supported by the fact that after more than 30 years of registered use in forest vegetation management, there has never been a scientifically documented case of direct mortality of moose, deer or other animals attributed to glyphosate-based herbicide exposure.
Indirect effects, through herbicide induced change to the plant community on treated sites do occur and have been scientifically studied and documented, including with respect to altered habitat utilization by moose. The most important change induced by glyphosate-based herbicide treatments is reduction in relative amounts of woody deciduous brush (e.g., maple, aspen, birch, pin cherry and alder species) that moose favour as browse. Reduced amounts of this food source will typically result in a transient pattern of lower moose abundance on treated sites. For the period in which their preferred woody browse material remains suppressed, typically for several years after treatment (Sullivan and Sullivan 2003; Lautenschlager et al. 1999; Raymond et al. 1996; Escholz et al. 1996), moose will tend lower use of these sites in favour of others that contain higher amounts of browse at their preferred browsing height. In that context, it should be recognized that only ~ 1/3rd of the forest area harvested in each year is treated with glyphosate-based herbicides, while the majority (2/3rds) is left to regenerate without chemical treatment. Most of these untreated cutover areas will contain copious amounts of woody browse material. Additionally, moose utilize a wide variety of plant foods for sustenance and particularly aquatic vegetation through much of the summer. Aquatic systems are not intentionally sprayed with glyphosate-based herbicides and larger permanent wetlands, ponds and lakes are protected by no spray-buffers, ensuring no significant changes to the aquatic plant food base that are utilized heavily by moose during summer. Finally, it should be noted that plant communities on recently harvested forest cutovers are highly dynamic, growing and changing rapidly through the first few years of successional development. Most animals which naturally use these early successional habitats are well adapted to plant community dynamics and to seeking out feeding sites that meet their nutritional requirements.
Glyphosate is considered non-persistent in plants, soils, water and sediments. This can be attributed largely to a number of microorganisms that break down glyphosate for food, removing it from the ecosystem. Studies show that it takes only a few days to a few weeks for 50% of the glyphosate to dissipate from various environmental compartments in a treatment site. In soils and sediments, low residue levels may be detected for up to a year following treatment; however, such residues are considered to be strongly bound, biologically unavailable and not of toxicological significance.
Glyphosate is highly susceptible to degradation by microbial organisms (bacteria and fungi) in soils, water and sediments and also readily dispersed by plants and thus considered to be non-persistent in the environment. The time for 50% dissipation (DT50) for glyphosate in forest plants, soils water and sediments ranges from a few days to a few weeks, depending largely upon environmental conditions which influence microbial activity. The major transformation product in soil, sediments and water is aminomethylphosphonic acid (AMPA) which typically shows a pattern of transient increase as it is formed through the glyphosate degradation process and then declines as the degradation product itself begins to degrade. This pattern typically results in AMPA residues persisting longer in soils and sediments than glyphosate itself.
In plants, glyphosate is taken up largely through the foliage and redistributed through the plant to roots and actively growing areas and metabolized within the plant with an approximate time to 50% dissipation of foliar residues ranging from approximately 2 days (Thompson et al. 1994) to 10-27 days (Newton et al. 1984; Feng and Thompson 1990). Legris and Couture 1990, documented glyphosate residues peaking in raspberry foliage at 3 weeks post-treatment and then declining rapidly (~ 90%) in the five-week period thereafter.
Glyphosate is readily metabolized by soil bacteria and many species of soil microorganisms can use glyphosate as sole carbon source (Durkin 2003). In soils, water and sediments, glyphosate is degraded primarily by microbial organisms to form the primary degradation product amino methyl phosphonic acid (AMPA) and subsequently to carbon dioxide and simple inorganic compounds, therefore it does not persist (Torstensson 1985). The time taken for glyphosate concentrations in forest litter or soils to decrease by 50% ranges from approximately 10 to 60 days depending upon environmental conditions (Thompson et al. 2000; Roy et al. 1989; Newton et al. 1994; Newton et al. 1984, Feng et al. 1990; Legris and Couture 1988). In general soils which are warm, moist and rich in organic matter show the most rapid degradation, largely because these conditions are conducive to higher microbial populations and activity. In a forestry study conducted in New Brunswick, Thompson et al. (2000) showed that glyphosate residues in both the forest floor and mineral soil layers dissipated rapidly with average half-lives < 12 days for three different glyphosate formulations tested. A recent study conducted in Alaska (Newton et al. 2008) demonstrated significant degradation of glyphosate soil residues even under extreme conditions of late summer/fall application and long subsequent periods of freezing conditions.
In aquatic systems, glyphosate is degraded by microorganisms and attenuated from the water column by sorption to bottom sediments and in moving waters by dilution. In standing water, the time required for 50% dissipation of glyphosate residues in water depends upon the environmental conditions including temperature, water depth, presence of macrophytes and water: sediment ratios and generally range from a few days to approximately 4 weeks. (Legris and Couture 1990; Couture et al. 1995; Goldsborough and Beck 1989; Goldsborough and Brown 1993; Wojtaszek et al. 2004; Newton et al. 1994; Edge et al. 2014). In moving water systems, glyphosate dissipates rapidly and typically reaches non-detectable levels within 1- 4 days (Feng et al. 1990; Newton et al. 1984; Newton et al. 1994). In both standing and running waters, bottom sediments tend to be a primary sink for glyphosate residues where they typically show a transient peak as residues partition or carried down into the sediments and then declining levels thereafter (Goldsborough and Brown 1993; Feng et al. 1990; Newton et al. 1984; Edge et al 2014), although sediment residues may be somewhat more persistent, they are also believed to be biologically unavailable due to strong binding in bottom sediments (Newton et al. 1994).
In a British Columbia forestry study, Feng and Thompson (1990) showed residues of the primary degradation product AMPA in leaf litter dissipate readily with time post-application and were at or below limits of detection within 29 days. In soils, AMPA concentrations showed a transient increase associated with initial degradation of glyphosate with generally declining levels thereafter reaching low levels equivalent to 6-27% of initial glyphosate residue concentrations by one-year post-treatment. Similarly, Roy et al. (1989) reported transient increases in AMPA in Ontario Forest soils, with low concentrations relative to glyphosate levels at any discrete sampling time and concentrations approximating 2% of initial glyphosate levels by one-year post-treatment.
Hundreds of scientific studies have been conducted on this topic and published as peer-reviewed journal papers. Collectively, they form a substantial knowledge base that lets scientists and regulatory bodies draw conclusions about the potential risks of glyphosate-based herbicides to forest ecosystems and associated wildlife.
The scientific information base pertinent to environmental fate and effects of glyphosate-based herbicides is extensive. Peer-reviewed journal papers on these aspects including both laboratory and field studies number into the thousands, with a few hundred of these documenting studies conducted in forest ecosystems across Canada or in the northern USA, which can be considered most directly pertinent. The scientific knowledge base on fate and effects of glyphosate-based herbicides is quite arguably greater than that for any other forest-use herbicide, or any other alternative vegetation management technique. The primary literature, published in peer-reviewed scientific journals, has been reviewed by scientific experts and regulatory authorities both in Canada and internationally. Scientific reviews and risk analyses consistently conclude that when used in the accordance with product labels and applicable regulations, glyphosate-based herbicides do not pose a significant risk of harm to the environment or to wildlife. Results of studies conducted specifically in forest ecosystems pertinent to use in Canadian forest vegetation management are consistent with and support those general conclusions.
Scientific studies pertinent to the fate and effects of glyphosate-based herbicides have been published in the peer-reviewed scientific literature. This knowledge base includes both laboratory and field studies, conducted on a wide variety of sub-topics, by a large number of academic, government and other scientists. Many environmental fate and ecotoxicology studies have been conducted in Canadian forest ecosystems including in the provinces of British Columbia, Alberta, Ontario, Quebec and New Brunswick. Much of the literature has been assessed in independent regulatory and scientific reviews and risk assessments (USDA-FS 1984; Grossbard 1985; Sullivan 1985; Lautenschlager and Sullivan 2002; USEPA 1993, Reynolds et al. 1993; WHO 1994; Williams et al. 2000; Giesy et al. 2000; Solomon and Thompson 2003; Durkin 2003; Tatum 2004; Sullivan and Sullivan 2003; Couture et al. 1995; Guynn et al. 2004; Thompson 2011, PMRA 2015). The general conclusion, drawn consistently from all of these reviews and risk assessments, is that when used in accordance with product labels and applicable regulations, glyphosate-based herbicides do not pose a significant risk of harm to the environment or to wildlife.
In April 2015, the PMRA released their latest review of glyphosate and declared that the weight of evidence indicates that glyphosate does not present unacceptable risk to human health. The full PMRA glyphosate review can be found here or please visit here for a summary version of the full PMRA review.
Several published scientific reviews and risk analyses conclude that the risk of direct toxic effects to terrestrial wildlife species including small mammals, large mammals and birds which may be exposed both directly and indirectly through consumption of contaminated food or water is minimal. This conclusion is supported more specifically by a simple worst-case example comparing the maximal residues observed in berries from treated forest sites and no-observable effect thresholds in experimental mammals.
As noted in the review by Durkin (2003), terrestrial animals might be exposed to herbicides via direct spray, the ingestion of contaminated food or water, grooming activities or via contact with contaminated vegetation. In the risk assessment conducted by the latter author, all of these potential exposures were considered and compared to levels having no observable effects in experimental animals. Given an application rate equivalent to 2.1 Kg a.e./ha, which closely approximates the average use rate of glyphosate-based herbicides in Canadian forestry, risk quotients calculated for small mammals, large mammals and birds were all below levels of concern (Durkin et al. 2003). Parallel risk quotient analysis conducted by Giesy et al. (2000) and by PMRA (2015) drew the same general conclusion. In such analyses, small mammals are often considered because there is direct relevance to toxicity studies which are often conducted on mice, rats and rabbits. For acute toxicity the no observable effect threshold for small mammals exposed to glyphosate is 175 mg/kg of body weight based on rabbits exposed for a period of 21 days. The threshold level in this case is considered appropriate for risk assessment in large mammals as well (Durkin 2003).
The level of residues observed in berries depends largely upon the rate of herbicide applied, the method of application (e.g., ground based versus aerial) and how long after treatment that samples are taken. Following ground- based applications at a rate of 1.5 Kg a.e./Ha Legris and Couture (1989) observed maximal residues in raspberries of 36.5 ppm at 7 days post-spray, declining to 0.139 ppm by 27 days post treatment. In blueberries, residues were initially 7.90 ppm 1 day post spray and dropped to 2.09 mg/g after 22 days. Similarly, Roy et al. (1989) reported maximal residues in raspberry and blueberry of 19.49 and 7.94 ppm respectively on the day glyphosate herbicide treatments were made with backpack sprayers at a rate of 2 kg a.e/ha, with slow decline of residue levels to values approximating 1.22 ppm by 33 days post-spray. Based on several worst-case assumptions, for example that wildlife consume only highly contaminated berries as a food source, that residue levels in the berries are constant for the entire time period which they might be available after the spray season, and that animals feed only in treated sites the toxicological risk from this source can be calculated. For example, using the maximal residue level observed in berries of 36.5 ppm (Legris and Couture 1989), food consumption rates per unit body weight for small mammals and large mammals of 15% (Durkin 2003) and 34% (Welch 1977) respectively, and a typical body mass of 0.02 Kg and 100 Kg for a typical rodent and bear, the calculated ingested dose rates would be 5.48 and 12.4 ppm body weight per day respectively, both values being far below the no observable toxic effects threshold of 175 mg/kg of body weight per day.
Regulatory bodies require buffer zones to be created around streams, lakes, rivers and ponds near aerial treatment sites. The use of buffers around such systems essentially negates the potential for direct overspray of these aquatic systems. Buffer zones, in combination with advanced aerial application technologies including GIS-based mapping, electronic guidance systems and low-drift nozzles also help to ensure the herbicide does not enter such bodies of water either by accidental overspray or via off-target drift.
Owing to the application of advanced aerial application techniques, including GIS-based mapping, electronic guidance systems on aircraft, low-drift nozzles and the requirement for buffers around aquatic systems, there is a very low probability of toxicologically significant concentrations of glyphosate occurring in lakes, streams, or ponds. Well-validated aerial dispersal models predict very low proportions (< 2 %) of the depositing beyond 25 m downwind of spray blocks under aerial application scenarios as typically employed in major use provinces of New Brunswick, Alberta and Ontario. Several operational or semi-operational monitoring studies provide confirmatory evidence that the probability of inputs to aquatic systems protected by buffer zones is very low, and that where measurable concentrations do occur they are well below levels known to have toxicological effects on aquatic organisms. Potential inputs into small ephemeral wetlands via direct overspray or off-target drift represent a special case of relatively higher risk to species such as amphibians that inhabit these type of aquatic systems where these may occur within or immediately adjacent to spray blocks.
Under operational scenarios in Canadian forestry, spray blocks and surrounding areas are mapped using detailed GIS-based techniques. Buffer zones designed to minimize any potential for direct input into water bodies such as streams, rivers, ponds and lakes are imposed as a protective measure. Advanced aerial application technologies including electronic guidance systems and low drift nozzles are employed and meteorological monitoring is undertaken to ensure that spray applications are made only to the target spray block and within established parameters of wind speed, temperature and humidity (Thompson et al. 2009; Thompson et al. 2012). In combination, all of these controls and mitigation measures reduce the potential for biologically significant inputs into aquatic systems. Based on validated modeling results, the amount of glyphosate depositing at distances of 25 to 65 m downwind of the spray block edge are estimated to be between 2% and 5.6% of the full application rate (Thompson et al. 2012 Payne 1993; Riley et al. 1991). Interception by vegetation within the buffer zone further reduces the potential for input. Field studies confirm both the low probability and magnitude of inputs into buffered systems under typical aerial spray operations (Thompson et al. 2004, Feng and Thompson 1990; Gluns et al. 1989; Adams et al. 2007). Similarly, Couture et al. (1995) summarizing multiple forestry studies conducted in the province of Quebec concluded that the 90th percentile of concentrations observed in water were <0.3% of the concentrations that cause high short-term mortality in aquatic organisms. Small, shallow, unmapped wetlands which may occur within spray blocks or immediately adjacent thereto are the aquatic systems most likely to receive direct chemical input via overspray or off-target drift.
The amount of area treated, frequency of applications and rate of product applied are some of the many factors that determine the exposure of plants and animals to glyphosate. Only plants and animals living directly in treatment sites, or that visit the sites within a few weeks of the treatment, are likely to be exposed to significant levels of glyphosate or surfactants in the formulated products.
Across Canada glyphosate-based herbicides are applied to approximately 150,000 ha annually, equivalent to approximately 1/3rd of the area harvested by clearcutting. The most common use scenario is for release of conifer seedlings from competing vegetation and involves aerial applications made to specifically targeted regeneration sites within a few years (1-4 years) post-harvest. Treated sites are distributed throughout the forest landscape and will typically receive a treatment, at a rate of ~ 2 kg acid equivalent (a.e.) per hectare, once or twice in a 40–80-year rotation cycle. Plants within the targeted competing vegetation canopy (deciduous brushy species or tall herbaceous species such as trembling aspen, raspberry or calamagrostis grass) are likely to intercept a relatively higher proportion of the spray than plants closer to ground level. Animals resident within the targeted spray blocks at the time of application (Aug-mid September) and which have limited forage range or mobility are likely to experience relatively higher exposures. Resident animals or those which visit the site shortly after treatment may also be exposed to residues via ingestion of contaminated foods or in the much shorter-term via desorption from treated surfaces. Since glyphosate is relatively non-persistent, such environmental exposures will be short in duration (a few days to a few weeks) and will involve concentrations that diminish rapidly through those time frames. In forest-use scenarios, major water bodies such as streams, rivers, ponds and lakes are usually protected by buffer zones, thus most aquatic organisms are unlikely to be exposed to toxicologically significant levels. Aquatic and terrestrial life-stages of amphibians which frequently are associated with small, shallow and commonly ephemeral wetlands, and which may occur within treated areas, represent a unique case of relatively higher potential for exposure
Recent risk analyses (PMRA 2015) conclude that typical uses of glyphosate-based herbicides, including forest use and even those involving multiple applications as typical of various agricultural crops, pose low risk to birds, mammals, soil organisms, fish and amphibians. In the more specific context of glyphosate-based herbicide use in forest management, where single exposures at lower rates approximating 2 kg a.e/ha are involved, Durkin (2003) concluded that none of the hazard quotients for acute or chronic scenarios reach a level of concern and that such analyses support the conclusions previously reached by the USEPA that potential effects on birds, mammals, fish and invertebrates are minimal.
In forest use scenarios, exposure of plants or animals is a function of the frequency, method and rate of application which control the initial levels in various environmental compartments and the probability of any particular organism actually being exposed. Persistence and fate of residues within the various compartments (e.g., soils, vegetation, water) determine the potential duration of exposure and whether such residues may be biologically available. Finally, the characteristic growth pattern of plants or natural behavior of animals including how it forages and interacts with its environment, may influence the potential route and degree of exposure. Given that glyphosate-based herbicides are typically applied only once within the first 1-4 years in a forest successional cycle that may vary from 40-80 years, the probability of exposure for most organisms is quite low. The potential for significant exposures are further restricted to only those plants or animals that occur or forage within these regenerating blocks at the time of application, or given known herbicide residue dissipation rates, within say 8 weeks post-treatment. In Canada, the area of forest land area treated with glyphosate-based herbicides is estimated to be approximately 150,000 ha annually or approximately 19% of the area that is clear-cut harvested, while the majority of the area is regenerated naturally or using non-chemical alternatives. This is a particularly important aspect as it governs the probability that wildlife will actually be directly exposed as well as the proportion of habitat that may be influenced by the herbicide treatment in the context of potential indirect effects. Glyphosate-based herbicides are typically applied by air at an average application rate of 1.9 kg a.e./ha (Thompson 2011). Much of the aerially applied spray is intercepted by the target woody/shrub layer, with proportionally lower amounts of chemical being vertically distributed to ground herbaceous vegetation and soil layers (Thompson et al. 1997). As such, plants that occur in the upper layers of the typically tiered plant community (e.g., alder, trembling aspen) and organisms that may be foraging in this layer (e.g., birds, moose) at the time of spray or shortly thereafter are likely to experience relatively higher exposures than those which are restricted to the ground layer (e.g., earthworms, small mammals). As no direct application to streams, rivers, ponds and lakes are permitted and given that these systems are protected by buffer zones, most aquatic organisms will not be directly exposed. As an exception, there is potential for direct exposure to aquatic organisms (e.g., amphibians) associated with small, shallow, typically ephemeral wetlands that may occur within or immediately adjacent to spray blocks but not mapped or visible from the air and thus not excluded from the over-sprayed area (Thompson et al. 2004). Several ecotoxicological field studies have now been conducted in Canada to explicitly address this issue with results indicating that risk to either aquatic larval or terrestrial adult amphibians are minimal.
In April 2015, the PMRA released their latest review of glyphosate and declared that the weight of evidence indicates that glyphosate does not present unacceptable risk to human health.
For more information on aquatic and terrestrial life stages of amphibians, see also Are glyphosate-based herbicides harmful to aquatic organisms? (Environment and Wildlife)
POEA is an acronym which stands for polyoxyethylene amine. This is a surfactant mixture that is included in some glyphosate-based herbicides to enhance uptake of the active ingredient (glyphosate) across the waxy layers and membranes of plants. It is well known from laboratory studies that POEA can cause toxic effects in sensitive aquatic organisms. Because of this known risk, more in-depth studies have specifically examined the toxicity of formulated products which may contain POEA or other types of surfactants. These studies show that when used under typical conditions for forest management in Canada, these products pose a minimal risk to aquatic organisms, largely because surfactants such as POEA rapidly absorbs to sediments and quickly degrades therein.
Glyphosate is a highly water-soluble compound that does not cross waxy surfaces or biological membranes well. In order for the active compound to be taken up effectively by plants, surfactants are typically added to the formulation to facilitate the transfer across those barriers. POEA is a mixture of several compounds rendered from animal fat that have soap-like properties and are very effective in the facilitated transfer of glyphosate into plants. Unfortunately, surfactants such as POEA, also affect membranes in animals resulting in relatively greater toxicity of end-use products to organisms such as fish and amphibians that have exposed membranes or permeable skin. This fact has been recognized for many years and is one example of why higher tier pesticide ecotoxicology studies are conducted on end-use products rather than glyphosate alone. Using this approach ensures that the toxicity of the formulated product, inclusive of potential effects of the surfactant, are captured in the evaluation. Similarly, regulatory agencies specifically incorporate fate and effects of POEA and end-use products containing these surfactants in their risk analyses (e.g., PMRA 2015). This Canadian regulatory agency noted that all glyphosate-based herbicide products currently registered in Canada contain less than 20% POEA by weight and when used in accordance with their product labels, do not pose an unacceptable risk to wildlife including sensitive aquatic organisms. The relative sensitivity of aquatic plants, fish and amphibians to products containing POEA surfactants is the fundamental reason why intentional direct application of such products to water bodies is prohibited and why ponds, streams and lakes receive additional protection through the requirement for no-spray buffers as stated on glyphosate product labels.
PMRA (2015) notes that in general glyphosate formulations that contain POEA are more toxic to freshwater organisms than formulations that do not but do not pose an unacceptable risk to the environment when used as directed on the label. Multiple laboratory studies, extending at least as far back as 1979 (Folmar et al. 1979) have documented the fact that POEA is largely responsible for acute toxicity in fish and amphibians exposed to glyphosate-based herbicide formulations containing this surfactant (e.g., Folmar et al. 1979; Wan et al. 1989; Howe et al. 2004; Edginton et al. 2004; Moore et al. 2011). However, the degree of toxicity observed in laboratory studies is typically much greater than that observed in field studies. The general lack of effect observed in field studies is largely attributable to reduced exposure which results from the rapid dissipation of both glyphosate and POEA from the water column via both microbial degradation and strong sorption to sediments (Legris and Couture 1990; Couture et al. 1995; Goldsborough and Beck 1989; Goldsborough and Brown 1993; Wojtaszek et al. 2004; Newton et al. 1994; Edge et al. 2014; Wang et al. 2005; Rodriguez 2015). Results from the latter two studies indicate that aquatic organisms are unlikely to be exposed to POEA in aqueous phase for a period of more than a few hours and that sediments are a primary sink for POEA. In sediments POEA concentrations decline through time following a biphasic process which is initially fast but slower over the second phase, presumably due to limited bioavailability for microbial degradation.
In April 2015, the PMRA released their latest review of glyphosate and declared that the weight of evidence indicates that glyphosate does not present unacceptable risk to human health.
Glyphosate-based herbicides are absorbed by the leaves of plants. Once there, the chemical prevents the production of a plant-specific enzyme necessary for survival. This enzyme is only found in plants, which is why glyphosate has such low toxicity in animals and humans. Glyphosate is strongly bound by organic matter and clay in soils and thus glyphosate residues are very unlikely to be taken up by seeds, new germinants or into plant roots. This allows forest vegetative communities to redevelop quickly on sites following treatment
Glyphosate-based herbicides are nonselective, moving systemically throughout plants once they penetrate their leaf cuticles. However, since they are typically highly water soluble, they do not penetrate waxy cuticles well and require the use of a surfactant (a detergent) to enhance transfer across this protective barrier. Once inside the plant, glyphosate functions by inhibiting a very plant-specific enzyme necessary for synthesizing essential amino acids. This particular enzyme does not occur in animals and humans, thus glyphosate itself has very low acute and chronic toxicity levels in these organisms.
Glyphosate-based herbicides are also very strongly bound to organic matter and clay particles in soils. As such, they are deactivated by soils and have no ability to control plants that sprout from seeds in the soil seed bank or from the roots or rhizomes of untreated plants. This is advantageous from an environmental perspective because it assures that sites will develop diverse vegetative communities within a few years following treatment.
For additional information, please see FAQ How long does glyphosate remain in the soil, water, plants and sediments after treatment? (Environment and Wildlife)
For additional information, please see FAQ What are environmental and health regulators saying about IARC’s glyphosate classification? (Health)
Forestry professionals develop plans annually based on the needs of the forests being managed—how old they are and how much competing vegetation there is. The provincial department of environment reviews these plans and issues the permits when all conditions around the policy and regulations of herbicides, including glyphosate, are met. All residents within 500 meters of a treatment area must be notified prior to the application.
Yes. About 33% of Canada’s productive forest lands are certified under one or more systems including Sustainable Forest Initiative (SFI), Canadian Standards Association (CSA) and Forest Stewardship Council (FSC), all of which recognize the important role that herbicides play in an integrated vegetation management program.
There are several certification systems for forest management that are designed to ensure that the certified forests are managed sustainably, using accepted “best practices”. These include the Sustainable Forest Initiative (SFI), Canadian Standards Association (CSA) and Forest Stewardship Council (FSC). About one third of Canada’s working forests are certified under at least one of these systems. Certification is designed to ensure the effective and efficient regeneration of both conifer and hardwood species. All three systems recognize the legitimate use of herbicides, including glyphosate-based herbicides, within an integrated vegetation management program aimed at meeting regeneration and sustainability requirements. It is true that systems such as SFI and FSC seek to reduce over-reliance on herbicides and require forest managers to show evidence of seeking or using non-chemical alternatives as well as other approaches in an attempt to reduce herbicide use over the longer term.
During the past decade, an average of 116,000 ha of publicly owned lands were treated with glyphosate herbicides each year. However, amounts used vary from province to province, and year to year based on the size of the harvested/replanted area. Forest Managers make these decisions after considering each factor affecting the forest regeneration cycle.
In Canada, an average of 116,000 ha of publicly owned forest lands have been reported as treated with glyphosate-based herbicides annually during the past decade. Private land holdings are not included in this figure, suggesting that the total area treated may be closer to 150,000 ha per year. The typical use rate for glyphosate-based herbicides in conifer release programs is 1.9 kg of active ingredient/ha (Thompson et al. 2004).
Most areas that are planted to conifer trees, and many naturally regenerating areas targeted for conifer dominance will require some degree of tending to maintain conifer dominance and promote adequate growth. As such, as many as 444,000 ha require tending each growing season in Canada. Provinces such as Ontario and New Brunswick apply herbicides to about as much area as they plant, relying on alternative methods to tend additional area. In contrast, a provincial restriction on herbicide use in Crown forests was invoked in the province of Quebec in 2001 (Thiffault and Roy 2010), forcing virtually all tending there to be done without herbicides.
Herbicides, including glyphosate-based herbicides, are used in areas of the forest using specialized aircraft. This is done either before new seedlings are planted, or 2-5 years after new seedlings become established. Areas of the forest are only ever sprayed once or twice in a 40-80 year growing cycle.
Where conifer production is desired, herbicides, including glyphosate-based herbicides, are applied under two different strategies, either prior to planting (chemical site preparation) or after seedlings are established (tending or release). Owing to the efficiency, effectiveness and low-impact-nature of the technique, aerial application using either fixed-wing or rotary-wing aircraft, is the most common method of distributing herbicides to target sites, accounting for more than 88% of all forestry applications in Canada over the last decade. Applications via tractor-mounted sprayers and personnel-carried backpack-sprayers account for the remaining 12%. Typically, herbicides are applied within the first five years post-harvest, and any given site receives one or at most two treatments during the life of the stand, typically 40 to 80 years in Canada.
In New Brunswick, residents are given notice via newspaper ads two weeks prior to spraying. Informational websites, including GeoNB, also provide notice about spraying operations.
In New Brunswick areas scheduled for treatment are posted on a website prior to the commencement of the project (usually near the end of the first week of August). At least two weeks prior to program commencement advertisements are placed in newspapers throughout the Province. Included in the advertisements are directions to informational websites and a toll-free telephone numbers. If an individual has concerns about areas to be treated, they can use these resources to get more information including the possible timing of applications.
As a final step, as the time of treatment becomes imminent normal entry points to individual treatments areas are signed to make the public aware of operations.
Treatment sites are approved by the provincial department of environment. Advanced technology and techniques, including; GIS mapping, GPS guidance systems, and low-drift nozzles are used. Buffers are required and regulated when it comes to herbicide application, such as glyphosate, around water. Buffer zones around habitation are also required and access to treatment areas during application is restricted. Personnel supervising or applying pesticides are trained and licensed by the provincial government.
Like most products that we use in daily life, safety is derived from the product itself, as well as how we use it. The use of forest herbicides is no different.
While some 5 different herbicide active ingredients are available for use in NB, managers rely almost solely on glyphosate-based products. The world has been safely using glyphosate for more than 40 years in agriculture and 30 years in forestry. It is the most widely studied herbicide in the world, registered on more than 100 food crops. The knowledgeable people that we entrust with product regulation in Canada and around the world have deemed glyphosate to be safe for humans and the environment, and not pose a cancer risk, when used as directed. So, we can be reasonably sure that the product we use is safe.
Forest managers decide on the most appropriate vegetation management tool to use only after careful site-specific scrutiny of a number of factors that include 1) need, 2) the efficacy of available approaches, and 3) potential for unwanted consequences. No matter what vegetation management tool is chosen, measures are then taken to mitigate the latter. For example, if manual cutting is chosen, timing and weather conditions may be restricted to avoid potential for heat exhaustion and exhaust inhalation by workers. Likewise, if herbicide application is chosen, the means of application, rates, equipment and weather parameters, will be selected to confine the herbicide to the vegetation being targeted. In fact, the herbicide label is a legal document that specifies tolerances for these factors that must be adhered to by applicators. Provincial regulators may choose to restrict these tolerances even further. Today’s applicators are trained, licenced professionals, using application equipment that includes GPS guidance and tracking for maximum precision and accountability. All applications are delineated spatially, pre-approved, and include buffer zones designed to ensure that herbicide deposit does not occur where it is not intended (such as streams, sensitive non-target vegetation, etc.).
Extensive science has gone into the establishment of the tolerances used in today’s herbicide applications, allowing us to conduct applications with significant margins of safety for known sensitive organisms, mitigating the risk of unwanted consequences. So, we can be reasonably sure that how we use the product is safe.
Forest Managers use Geographic Information Systems technology to plan exactly where spraying will occur. These plans must be approved by all regulatory bodies before spraying commences. Pilots and Applicators then use GPS technology to ensure they accurately spray the correct area.
To ensure adjacent lands are not treated, both recognized technology and checks and balances in procedures are employed. Provincial Base maps created using GIS technology are used to create perimeters for the areas to be treated. Mandatory buffers for private land, watercourses, etc. are built into the perimeter files. The files are then transferred to regulatory authorities for review and are either approved or modified if concerns arise. Once finalized the files are loaded into the aircraft navigational systems (GPS) that are used to guide the pilot to the site.
As a further step and before commencing applications, the pilot must do a visual inspection of the area (against maps & aerial photos) to ensure there are no apparent discrepancies regarding the location of the area to be treated.
sIn addition to digital maps, pilots and applicators use GPS technology to ensure that they are spraying the areas approved by the regulatory bodies.
In order to ensure the right areas are treated, applicators employ satellite technology (GPS) to guide aircraft to the locations selected. They continue to use GPS throughout the application process, guiding them line-by-line (excluding any areas designated not to be treated). Normally areas receiving treatment (i.e., cutovers) are easily recognized from the air and pilots are equipped with a map and aerial photograph to do a location check before commencing.
Application aircraft are equipped with systems to record the aircraft track and each file is reviewed post flight including verification of aircraft location.
All jurisdictions in Canada specify the acceptable weather conditions in which aerial applications can be completed. Applicators are well trained to consider factors such as wind speed and direction, spray release height, temperature and humidity that can influence the potential for off-target drift. Modeling studies demonstrate that under common use scenarios drift is unlikely to exceed 2% of the application rate at distances greater than 25 m downwind.
Aerial distribution systems for herbicide applications are designed and calibrated to produce large droplets. Large droplets deposit either directly beneath or immediately adjacent to the aircraft path.
For example, Thompson et. al. (2012) used a modelling exercise to plot deposit from aircraft as commonly equipped for applications in three Provinces (Alberta, New Brunswick, and Ontario). The model predicted very minor fractional amounts of downwind deposit in all scenarios with deposit beyond 25m, never exceeding 2% of the application rate.
Applicators are trained to be constantly aware of environmental factors (wind, temperature, etc.) that influence drift and to observe label and regulatory requirements designed to minimize off-target drift.
The Pest Management Regulatory Agency (PMRA) is the branch of Health Canada responsible for regulating herbicide use. Each province also has an environmental agency that oversees the herbicide application process, ensuring all regulations are upheld.
The Pest Management Regulatory Agency (PMRA) which is part of Health Canada, is responsible for setting the laws and regulations around glyphosate use in Canada. The PMRA periodically reviews the available research on glyphosate use to ensure that the accepted level of exposure to Canadians does not cause any harmful effects. If new research indicates changes in product safety, PMRA revises label requirements as needed. PMRA has recently done a review on glyphosate (April 2015) and concluded that it is safe to use in forestry, agriculture, industrial and residential applications under the current regulations and policies.
For example, in New Brunswick and Nova Scotia, all herbicide contractors must apply with the appropriate Department of Environment for pesticide application permits. The Provincial Permits provide additional measures of safety above the label requirements. Requirements for individual applicator certification, buffer zones and public notification are examples of some additional measures that are addressed through conditions on the herbicide treatment Permits.
The NB Department of Environment and Local Government (NBDELG) and the NS Environment and Labour (NSEL) require mandatory reporting, and frequently inspects operations. They also follow up on any complaints or concerns related to herbicide operations.
In April 2015, the PMRA released their latest review of glyphosate and declared that the weight of evidence indicates that glyphosate does not present unacceptable risk to human health. The full PMRA glyphosate review can be found here or please visit here for a summary version of the full PMRA review.
Protective equipment is used as a precautionary measure to minimize exposure. Glyphosate-based herbicides have a very low innate toxicity to humans, limiting exposure still makes sense as an extra precautionary measure.
Individuals who mix, load or apply glyphosate products are those with the greatest potential exposure to glyphosate-based herbicides. As noted in other sections of this document, risk is a function of both the innate toxicity (hazard) of the herbicide and exposure. Although glyphosate-based herbicides have a very low innate toxicity to humans, limiting exposure still makes sense as an extra precautionary measure. When mixing or loading glyphosate products, closed systems are utilized to minimize such exposures and individuals involved in these operations are directed to wear appropriate personal protective equipment (PPE) through conditions of the label.
Individuals mixing, loading or applying glyphosate products must meet the National and Provincial Standards for Pesticide Education, Training and Certification.
The Certificate is proof that the individual has received the necessary education and training to carry out glyphosate-based product applications in a safe and responsible manner. There are certification training programs for all types of pesticide applicators including professionals in lawn care, forestry, structural pest control and agricultural uses.
A direct comparison of the cost to protect a plantation using either herbicide or manual weeding depends on many factors, such as site, competing species, timing or quality of work. Based on a typical scenario, the average cost of vegetation management (herbicide and plantation cleaning) is approximately $400 per hectare. Using manual weeding alone, the average cost would be $1,500 per hectare. Manual treatments are also less effective in removing the competing vegetation and require follow-up treatments as this vegetation quickly returns the following year, increasing the cost further.
Typically, the landowner pays for any forest management activities on their land, including vegetation management. At the moment, this means that the New Brunswick Department of Natural Resources and Energy Development pays for herbicide treatments on N.B. Crown Land. In general, contractors are used to carry out this work.
All provinces support the Health Canada assessment that the herbicide glyphosate is safe. Quebec has decided to limit the use of herbicides, such as glyphosate, on Crown Land, while Nova Scotia has decided to stop provincial funding for herbicide treatments. Neither province has banned the use of glyphosate on private land, agricultural land, or in the industrial sector.
Many provinces continue to support the expert scientific assessment of Health Canada in registering products in Canada. When Health Canada registers a product for use in Canada, it is considered to be safe for use with no significant impact to human health or the environment when used according to label directions.
Some Provinces have unilaterally made decisions to limit herbicide on publicly owned property in the forestry sector. Provinces such as Quebec have limited its use on Crown Land while the Nova Scotia Government has chosen to stop funding herbicide treatments but not limit its use. These jurisdictions still permit glyphosate use on private land, all agriculture areas and industrial sectors.