A professor at the University of Northern British Columbia has been tapped to study the ecological impacts of glyphosate-based pesticides on forests.

Glyphosate pesticides are routinely used by logging companies across Canada to kill off leafy deciduous plants that compete with more lucrative spruce and fir, but their ecological and health impacts on woodlands and people who hunt and harvest wild foods are little understood and overlooked by federal regulators.

Canada's regulatory regime deems the pesticides safe, but its assessment does not account for the potential chronic impact of low-level exposure and does not examine forests. Researchers have found low-level exposure to glyphosate can impact the health of animals’ gut microbiomes, potentially causing health issues. The chemical is also considered potentially cancer-causing by the International Agency for Research on Cancer.

Because the federal government does not track where, when and how pesticides are used, it is impossible to know exactly how much glyphosate is sprayed on Canadian forests each year. However, researchers estimate tens of thousands of hectares are sprayed each year, except in Quebec where the practice was banned in 2001.

"Maybe it was a low-risk herbicide when it was used at smaller scales," said study leader Lisa Wood, who is working on the project with the Swan River First Nation in Alberta and trappers associations in B.C. and Alberta. "But because of the extent of the use, we start to think about how the previous research applies in these extensive-use cases — are there aggregate effects?"

Wood's previous research found glyphosate can linger for months in living plants after they are exposed. One of the other researchers on the project has previously found that even low levels of glyphosate can change what bacteria live in mammals' gut microbiomes.

A shift from Canada's existing regulatory approach for assessing the safety of glyphosate-based herbicides is needed, said Laura Bowman, a lawyer with Ecojustice who specializes in pesticides.

Canada's Pest Management Regulatory Agency (PMRA) does not review the ecosystem-wide impacts of any pesticide, including glyphosate, she said. Instead, the agency picks a group of "representative species" and conducts lab tests to determine how much glyphosate they can handle in one big shot before suffering health impacts. Those tests do not assess animals found in forests specifically, she said.

In a statement, the PMRA said that it "considers ecosystem-wide effects of all pesticides" and that "as a result of this rigorous scientific evaluation, certain products containing glyphosate require mitigation measures," pointing to a September document outlining their approach. Moreoever, it said "the organisms considered in the PMRA’s environmental assessments are representative of the broader Canadian environment, including forest ecosystems" and that it "continues to track emerging scientific literature, including studies on the effects of glyphosate on various types of microbiomes."

A professor at the University of Northern British Columbia has been tapped to study the ecological impacts of glyphosate-based pesticides on forests.

In contrast, Wood's research will evaluate the long-term consequences of glyphosate exposure on animal and forest ecosystem health. She emphasized the study is not looking at whether glyphosate is directly toxic to animals. It is designed to assess whether it is moving from plants into animals and impacting their long-term health. If it is, that could help push governments to change their current approach to using glyphosate on forests, she said.

Ecojustice is currently suing the government to force it to assess how glyphosate impacts forest ecosystems. Canada's pesticide laws require the PMRA to consider a pesticide's ecological impact when deciding if it should be approved for use or not, but has never completed these assessments for forests, Bowman said.

Beyond potentially causing ecological harm, the government's regulatory oversight also threatens to expose people who rely on forests for food and medicine to unknown levels of pesticide, she said.

"Are there residues of glyphosate in blueberries harvested by Indigenous Peoples, for example? Or does it make its way into moose meat?" she said. "These questions are being asked, and I don't think that the PMRA really has an answer because that's not part of their required testing."

That question haunts members of the Swan River First Nation in northern Alberta. Many rely on the plants and animals in their traditional territories for food and medicine, said Todd Bailey, the nation's director of forestry consultation.

"People have stopped going to areas they once frequented for years or generations if they know they've been logged and that (logging companies) spray glyphosate," he said. "They're not seeing the plants as abundant on the land, or they're completely absent, and there's anecdotal evidence the plants aren't the same in medicinal value."

The Alberta government and logging companies operating in the region have done little to alleviate concerns, he said. Loggers have rebuffed the nation's request to stop spraying some parts of its traditional territory, instead asking it to outline specific cutblocks or "a few hectares" to avoid. Provincial officials have also been unhelpful, he said.

The nation is partnering with Wood on the study to try to better understand glyphosate's impact on their territories and, hopefully, pressure governments to change their policies on the pesticide's use in forests.

Still, the impacts run beyond limiting people's access to traditional foods and medicines. Many people in the nation see glyphosate use as "poisoning" traditional territories they have a responsibility to steward. But faced with a resistant logging industry and a pro-industry provincial government, people "feel like they have not been able to uphold their responsibilities to the Creator as stewards of the land," Bailey said.

"The land is being poisoned and there's not much they've been able to do about it, so they feel this sense of grief," he said. "There is a great sense of grief in [sprayed] areas that they won't go."

Updates and corrections

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March 5, 2024, 10:30 am

Update: This story was updated to include comment from the federal Pest Management Regulatory Agency.

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Quite a bit of work on glyphosate fate in the environment has already been done:

Edge, Christopher B., William Haines, Matt Blaney, and Martin Noël. 2023 “Low Detection of Glyphosate in Rivers Following Application in Forestry.” Pest Management Science 79: 2951-2958. https://doi.org/10.1002/ps.7473.

Kepler, Ryan M., Dietrich J. Epp Schmidt, Stephanie A. Yarwood, Michel A. Cavigelli, Krishna N. Reddy, Stephen O. Duke, Carl A. Bradley, Martin M. Williams, Jeffrey S. Buyer, and Jude E. Maul. 2020. “Soil Microbial Communities in Diverse Agroecosystems Exposed to the Herbicide Glyphosate.” Applied and Environmental Microbiology 86 (5): 1744-19. https://doi.org/10.1128/AEM.01744-19.

Mamy, Laure, Benoît Gabrielle, and Enrique Barriuso. 2010. “Comparative Environmental Impacts of Glyphosate and Conventional Herbicides When Used with Glyphosate-Tolerant and Non-Tolerant Crops.” Environmental Pollution 158 (10): 3172–78. https://doi.org/10.1016/j.envpol.2010.06.036.

Schlatter, Daniel C., Chuntao Yin, Ian Burke, Scot Hulbert, and Timothy Paulitz. 2018. “Location, Root Proximity, and Glyphosate-Use History Modulate the Effects of Glyphosate on Fungal Community Networks of Wheat.” Microbial Ecology 76 (1): 240–57. https://doi.org/10.1007/s00248-017-1113-9.

Sullivan, T P, and D S Sullivan. 2003. “Vegetation Management and Ecosystem Disturbance: Impact of Glyphosate Herbicide on Plant and Animal Diversity in Terrestrial Systems.” Environmental Reviews 11 (1): 37–59. https://doi.org/10.1139/a03-005.

Always room for more work, of course, but the ecological work done so far suggests any impacts are small and transient. The other thing to note is that these types of studies require a team of researchers from a wide range of domain expertise (microbial DNA extraction and analysis, plant community structure, soil microbiology, etc). Has that been assembled? Not clear from the article.