For three decades, most Canadian farmers have been growing crops that are genetically modified to tolerate herbicides. And yet, the debate over these crops’ impact on the nation’s soil remains as unsettled as ever.
Supporters of genetically modified crops say they have improved soil conservation and farm profitability. Critics say they have had negative consequences for biodiversity and long-term soil health.
“For the most part, we do not understand that soil is alive, and we don’t treat it as if it was alive — we treat it like it was dirt,” said Jim Boak, a former Ontario dairy farmer who grew feed crops for his herd.
“It is a civilization.”
The debate comes as the federal government proposes major changes to pesticide laws, including reforms critics say could weaken environmental oversight.
Sources say the stakes are high — and not just for farmers. Soil health affects Canada’s long-term ability to produce food and ensure ecosystem stability.
“If all you had was one kind of person, your civilization wouldn’t flourish … the soil is the same,” said Boak, who is today a soil and crop management consultant with the University of Guelph and Ontario’s agriculture ministry.
“You have to have that diversity, and when you grow just corn and soybeans, corn and soybeans, you lose a lot of that soil life and soil resistance and nutrient regeneration.”
Weed control
Effective weed control is the single most important factor for farmers in producing crops, says Stuart Smyth, an agricultural biotechnology professor at the University of Saskatchewan.
Since the mid-20th century, farmers have used herbicides to control weeds, though their options were limited. Many chemicals that killed weeds could also harm crops.
Genetically modified crops changed that, allowing farmers to spray freely without risking their harvest.
By the late nineties, these crops were being widely used on Canadian farms. And herbicide use, measured by sales of key ingredients, has since risen by about 270 per cent.
Crop yield trends over the past three decades are more mixed. Statistics Canada data on major field crops show yields on some pulse and specialty crops, such as lentils and chickpeas, have generally increased since the 1990s. But yields vary significantly by crop and year.
What is clear is herbicide-tolerant crops have changed how farmers manage their soil.
“When GM crops were developed, farmers were able to get the effective weed control they wanted and no longer needed to till their soil,” said Smyth, referring to the practice of mechanically turning soil to control weeds.
Reduced tillage can reduce soil erosion and soil structure decline.
“Tillage is really something that does affect soil health, and so we are always trying to push [farmers to] try to minimize your tillage,” said Keri Dunfield, a soil microbiologist with Agriculture and Agri-Food Canada, a federal department.
Smyth says reduced tillage has been good for farm profitability and soil health.
“Given that Canadian farmers have been growing GM crops since 1997, this tells me that they are experiencing improved profitability and better soil health,” said Smyth, whose academic research is partially funded by industry partners, including the agricultural technology company Syngenta.
“If they weren’t receiving these benefits, they would not be using GM crops.”
Thomas Mueller, a professor of plant sciences at the University of Tennessee, agrees that genetically modified crops have boosted farm profitability. But he says they have come at a cost.
The use of herbicide-tolerant crops is closely tied to large-scale monoculture farming, where the same crop is planted year after year, Mueller says. Over time, this can reduce biodiversity and degrade soil health.
Like Mueller, Dunfield worries about the long-term impacts of monoculture on biodiversity.
“If you’re growing the same plant and using the same [herbicide] … you’re going to challenge the system eventually,” she said.
“You’re decreasing your biodiversity, and then that puts you at risk for different issues, like pathogens or … weeds.”
The ‘pesticide treadmill’
Others say the issue is not one crop or chemical, but the growing long-term reliance on agrichemical companies.
Lucy Sharratt, coordinator at the Canadian Biotechnology Action Network environmental coalition, says herbicide-tolerant crops create a dependency on specific chemical inputs — what she describes as a “pesticide treadmill.”
“Genetically engineered seeds are tied to specific herbicides,” she said, referring to patented seeds being paired with particular weed-killing chemicals.
“It’s not just an introduction of a new technology, it is an entrenchment of a system.”
Boak agrees. Farmers have become dependent on the agrichemical industry’s products, he says. Tillage, by contrast, does not lead to that dependence.
“[W]eeds, insects and disease would never become resistant to [mechanical control with tillage],” he said. “[B]ut if you had no‑till then, you were entirely dependent on purchased inputs.”
Sharratt also points to consolidation in the seed and chemical industries. Four firms — Syngenta, Bayer, Corteva and BASF — now account for about 60 per cent of global seed and agrochemical sales.
Sharratt says this consolidation has resulted in a few powerful firms exerting undue influence over agricultural regulation.
“There’s a tremendous amount of money to be made from selling genetically engineered seeds and the associated technologies,” she said.
“The biotechnology industry has fought for and achieved a great deal of freedom from government regulation and oversight, and this increases the danger of genetically engineered seeds and foods, and it also increases the potential for public mistrust and conflict over these technologies.”
Canadian Affairs sought comment from the three dominant agri-chemical firms operating in Canada.
Syngenta referred inquiries to Stuart Smyth, while noting he is not authorized to speak on the company’s behalf. Bayer directed Canadian Affairs to its published materials. Corteva referred to CropLife International, a global trade association, whose spokesperson said herbicide-tolerant systems “have dramatically improved soil health and reduced greenhouse gas emissions.”
Health Canada said all pesticides undergo pre-market review for environmental risks, and that glyphosate, Canada’s most widely used herbicide, poses no “unacceptable risks” when used as directed.
Ottawa has recently proposed major reforms to the Pest Control Products Act that would expand the role of economic and food-security considerations in pesticide decisions and reduce some mandatory review requirements.
Critics say the changes could compromise environmental protection and public health.
“Under the proposed legislation, cabinet can overrule a minister who won’t approve a product because it carries unacceptable environmental risks, or who wants to outlaw a product already in use because its environmental risks are unacceptable,” Toronto Star columnist Althia Raj wrote in a recent column.
“It would make cabinet ministers more likely to be lobbied by industry, while shielding the health minister from lawsuits,” she added.
Soil science
Andrew Hammermeister, chair of plant, food and environmental sciences at Dalhousie University, says it is unhelpful to frame farming systems as inherently good or bad.
Instead, what matters is how different practices are combined over time — including tillage, genetically modified crops and organic systems, which do not use genetically modified inputs.
“While the benefits of organic farming systems on soil health are pretty well documented, it requires ‘systems thinking and management’ which includes a longer term view,” Hammermeister said.
Diversifying crop rotations and using organic inputs tends to support stronger soil function, he says. Organic inputs can include things like compost, manure, natural pest controls and cover crops — plants grown specifically to protect and improve soil rather than to be harvested.
“Overall, soils under good organic management practices are at least as healthy and often more healthy than those under non-organic systems.”
Dunfield, of Agriculture and Agri-Food Canada, says most farms are more likely to improve soil health by adjusting existing practices rather than overhauling their systems. That includes reducing unnecessary tillage, using cover crops and diversifying crop rotations.
She also says regulators need to improve how they monitor soil health over time.
“In Europe, they are monitoring soil biodiversity,” she said. “In Canada, it’s not there yet.”
The European Union is beginning to track soil life — including microbes and fungi — as an indicator of environmental health, similar to air or water quality monitoring.
Canada, she says, still relies largely on chemical-by-chemical risk assessments rather than long-term monitoring of soil ecosystems.
“There’s a lot of research going on in the area [of soil health and biodiversity] … but actually monitoring these things is not something that’s on the radar yet,” she said.
Boak, the soil and crop consultant, supports more targeted use of technology, including drones and spectral imaging to identify pest or disease hotspots so chemicals can be applied only where needed, rather than across entire fields.
He also argues that farming should be treated as a formally regulated profession, given its importance to food systems and land stewardship.
“One of the most important and most complex aspects of society is the ability to produce food … and there’s no licence required to do that,” he said. “Soil habitat management should be the number one qualification.”
“Soil life … is the very thing that creates the organic matter and the nutrition for plants,” he added.
“We are what we eat.”
