Science in Society Archive

Study Based on Farmers’ Experience Exposes Risks of GM Crops

The first study of its kind in North America, possibly in the world, shows how the risks of GM technology outweigh the benefits especially in the longer term. Dr. Mae-Wan Ho

Canada, along with the United States and Argentina were the first countries in the world to commercialise GM crops. But more than a decade later, risk assessment for GM crops is still ignoring farmers’ knowledge and their years of experience in growing GM crops.

Ian Mauro and Stéphane McLachlan at the University of Manitoba, Winnepeg, in Canada, have now completed a study of farmers from Manitoba and across Canada based on interviews (n=15) and survey by mail (n=370) conducted between 2002 and 2003. It is especially useful in identifying the actual risks and benefits for farmers who are not yet committed to growing GM crops.  

“We’re very pleased with this study.” Mauro says. “Using quantitative and qualitative methods, we’ve documented the benefits and risks associated herbicide-tolerant (HT) canola. We found that farmers have been primarily placed at risk due to the proliferation of HT volunteers. Smaller farms and those with a longer history of GM canola use were at highest risk.”

Canadian farmers rapidly adopted HT canola following its commercial release in 1995. Three varieties of HT canola have been introduced: Roundup Ready (RR), Liberty Link (LL) and Clearfield (CF), tolerant to the herbicide glyphosate, glufosinate and imidazolinone respectively. RR and LL are genetically modified, whereas CF has been created by induced mutation. Currently, they represent 96 percent of the 5.25 million ha of canola grown in Canada: approximately 50 percent RR, 32 percent LL and 14 percent CF. The great majority are grown in the western Canadian provinces of Manitoba, Saskatchewan, and Alberta.

Thus, Canadian farmers have a great deal of experience in growing HT canola, and that’s what Mauro and McLachlan decided to focus on.

Comprehensive study on HT canola across Canada

The aims of their study were to:

· Evaluate risks of HT canola relative to other risks facing rural communities

· Characterize the benefits and risks associated with HT canola

· Identify the factors contributing to the risks and benefits associated with HT canola

· Explore the role that farmers’ knowledge plays in the risk analysis of HT crops and more generally agricultural technology.

Initial interviews were conducted in the Canadian Prairies Ecozone, which includes the provinces of Alberta, Saskatchewan and Manitoba, characterized by a continental climate having short warm summers and long cold winters, with an annual mean temperature range from 1.5 C to 3.5 C. The mean annual precipitation is 504.4 mm.

The mail survey of the study covered two ecoregions: Lake Manitobe Plain (LMP) and Aspen Parkland (AP), which dominate southern Manitoba. The average growing season for both ecoregions ranges from 173 to 187 days and the soils are predominantly ‘Black Chernozemic’ a black soil rich in organic matter. The LMP is generally recognized as having some of the most productive soils in Manitoba, especially suited to cereals, oilseeds and pulses. On average, canola is seeded on 1 million ha in the province.

The in-depth interviews with 15 farmers were conducted across western Canada between June and October 2002. The qualitative data collected during these interviews also helped in the development of a questionnaire and to ensure that its content and wording were appropriate. The 12-page questionnaire queried farmers on their experience and attitudes regarding HT canola. It assessed concerns regarding HT canola relative to other stresses that confront rural communities; the specific benefits and risks associated with the HT canola; and factors that contribute to risk perception among farmers, especially those that had experience in growing HT canola. The questionnaire used a 7-point rank order scale ranging from 1 for “strongly disagree”,  to 7 for “strongly agree”. Researchers associated with universities and industry as well as farmers reviewed the survey for comprehensiveness, technical accuracy and impartiality.

Within each of the two ecoregions, rural municipalities were equally divided into two classes of low or high abundance of volunteer canola, based on the 2001 Manitoba weed survey. The response rate was estimated to be 25 percent. The great majority (97 0ercent) were male, most (67 percent) were full-time farmers with an average of 28 years of farming experience. A large majority (85 percent) considered themselves knowledgeable about farming. The education background of 48 percent with postsecondary training was slightly higher than the Manitoba average (34 percent). The average farm size was 575 ha, again higher than the average Manitobe canola growers (409 ha). Minimum tillage was practiced by 51 percent of respondents, similar to the provincial average of 45.5 percent. The large majority (78 percent) grew HT canola, including RR (47 percent), LL (22 percent) CF (13 percent) and various combinations (15 percent), as reflected by the national data. For farmers growing HT canola, their attitude toward 10 benefits and 10 risk items were assessed.

Risk of HT compared to risk of other stresses for the rural community of farmers

Of the ten general risk items facing rural communities, input costs, cost of machinery and commodity prices top the list in that order, with high mean scores of 6.72, 6.67 and 6.60 respectively. Thus, farm economics were of paramount concern. This reflects the decline of net income of Canadian farmers over the last 20 years and farmers are now in the worst farm-income crisis in history. Environmental concerns that affected crop production, and hence income, were also ranked high; these included excessive moisture, drought, and natural disasters. HT crops ranked 9 out of the 10 general risks, but its score was still high at 5.08 (moderately risky). Its low ranking in comparison to other stresses explains why farmers took it up in the first place. These are farmers with big farms, averaging 575 ha, above the provincial, where ease of management is paramount, reducing input costs such as labour.

Risks versus benefits of HT canola

With regard to the benefits of HT canola, easier weed control, herbicide rotation and better weed control came top at scores of 5.47, 5.37 and 5.28 respectively. With regards to other purported benefits, 67 percent disagreed that HT crops were protecting “small farm heritage”, and 58 percent disagreed that HT crops were “the answer to feeding the world’s hungry”; while 39 percent rejected the notion that HT crops made “Canadian agriculture more competitive.”

Loss of markets, restriction of farmers’ rights in technology use contracts, and increased lawsuits were uppermost among the top risks at scores of 5.87, 5.56 and 5.36 respectively. One farmer interviewed said: “The loss of [European ] markets due to GMs had a huge financial impact. This was likely larger than cost of controlling volunteers or benefit of easy weed control.”

Operational risks also scored high at 5.08, 5,07, 5.02 and 4.97 for HT volunteers, gene spread, herbicide resistant weeds, and RR crops causing problems in zero-tillage systems. One farmer in Saskachewan indicated how he was sued over patented HT canola that contaminated his land, creating biological and legal risks that had implications for all farmers. He said: “What it means to farmers all around the world is the loss and right to use your own seed….My rights as a farmer have been taken away because now I can no longer grow canola under fear of a lawsuit.”

Farmers generally believed that it was not possible to control HT traits from spreading in the environment. Thus, most of respondents felt that “Terminator Technology” (75 percent), “segregation techniques “ (67 percent) and “good farming practices (51 percent) would not solve HT trait contamination problems.

Major risk variables of HT canola: volunteers, years of growing, and farm size

The respondents could be segregated into three groups, those for whom the benefits were higher than risks, those for whom risks and benefits were equal, and those for whom risks were higher than benefits. The simplest model that best fits the data identified three main factors affecting perception of risks versus benefits: farm size, years of using HT, and volunteers. The data suggests that farmers perceived greater risk if they have smaller farms.

Linking the demise of small family farms with HT technology, one farmer stated; “GM technology will most certainly hasten the demise of family farms if it is allowed to progress unchecked. When we started farming… seed could be saved from one year to year….now, each year, a tremendous monetary outlay for seed must be made in order to grow canola because of the new GMO systems….more and more family farms will disappear – simply because they are unable to shoulder these costs which will happen annually without relief.”

Those farmers growing HT canola for more than a year perceived higher risks. A number of interviewed farmers similarly expressed concern that these risks increased over time. Risks were also perceived to be greatest for those who had volunteer canola on their land. Indeed, many indicated having problems with HT volunteers.

“These volunteers are showing up in fields that have never been planted to these crops. Farmers that have never seeded genetically modified crops are finding volunteers on their farm and that the volunteer picture is much broader than we had expected to see.”

The three variables that contribute most to risk were in order of importance, HT volunteers, years of growing HT crops and farm size.  In total, 38 percent of HT farmers had experienced HT volunteer canola on their land. Of these 51 percent believed the source came from within their operations, 20 percent believed they came from outside, and 29 percent believed it came from both sources. Many respondents were concerned about the promiscuous and persistent nature of these volunteers, and that this would eventually compromise benefits currently associated with the technology.

“I had volunteer Roundup resistant canola in a sunflower field before I had ever used it, and, I could not remove it with Roundup [herbicide] or other means. We are finding resistant canola everywhere, even if it has never been seeded on that field. I like using Roundup as pre-emergent burn-off and it’s not working great anymore.”

Farmers who grew HT canola and had experienced HT volunteers believed that, on average, they were emerging in their field 2.5 years after planting these crops. Moreover HT volunteers were primarily Roundup Ready (72 percent) and emerged up to six years after have been planted. Multiple resistant volunteers were also prevalent (20 percent), followed by CF  (6 percent ) and LL (2 percent). Many methods have been used to control volunteers, including additional herbicides and tilling. Zero-till farmers actually reverted to tillage to control RR volunteers.

Monsanto is the only company that charges a $15/acre fee for HT canola. There is now a wider trend toward contract production that may increase seed costs and erode farmer rights to save, reuse and exchange seeds. Many of these contracts allow companies to investigate farmers, their land, and community for evidence of appropriation of proprietary seed technologies. This issue was addressed by the landmark Supreme Court of Canada decision, Monsanto v. Schmeiser, which essentially upheld industry’s intellectual property claims over GM seeds and plants, making farmers liable for patent infringement, despite the likelihood that the seed they plant may have contaminated by GM traits.

A large majority (76 percent) of respondents who used HT canola anticipated that HT volunteers would become “more of a problem in the future”, and 85 percent believed that industry had shifted the burden of responsibility for HT volunteers onto farmers. One respondent stated:

“Our biggest concern is Roundup Ready canola polluting our fields by being blown off neighbors fields and infesting our fields with voluntary plants. Is Monsanto going to compensate farmer in this situation?” 

The answer is yes. Schmeiser has just won an important victory over Monsanto in his lawsuit against the company for contaminating his land. In an out of court settlement, Monsanto has agreed to pay all the clean-up costs of HT canola with no gag-order. Schmeiser believes this precedent will ensure farmers are entitled to reimbursement when their field become contaminated [2]

Article first published 24/04/08


  1. Mauro IJ and McLachlan SM. Farmer knowledge and risk analysis: postrelease evalulation of herbicide-tolerant canola in Western Canada. Risk Analysis 2008, 28, DOI:10.1111/j.1539-6924.200801027.x
  2. Schmeiser pleased with victory over Monsanto, Monsanto vs Schmeiser,

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