GMO crops reduce greenhouse gas emissions, Canadian study finds

By Joseph Maina

November 22, 2021

As the world looks to reduce greenhouse gas emissions, a new study from Canada shows that genetically modified (GM) crops can help agriculture do its part.

The study suggests that herbicide-tolerant GM crops and glyphosate can increase soil carbon sequestration, thereby keeping carbon dioxide in the ground rather than releasing it into the atmosphere where it contributes to global warming.

During the recently convened COP26, governments recognized that soil and nutrient management practices and the optimal use of nutrients lie at the core of climate-resilient, sustainable food production systems and can contribute to global food security.

Using tillage as a form of weed control contributes to soil disturbances, with subsequent release of carbon to the atmosphere, notes the study, which was published in Sustainability, a peer-reviewed journal. Substituting tillage with weed-control measures that ensure minimal soil disturbance reduces the amount of carbon released and increases the sequestration of carbon through continuous crop production.

“Tillage releases carbon every time the soil is tilled, preventing the soil from being able to increase carbon sequestration,” Dr. Stuart Smyth, associate professor in the Department of Agricultural and Resource Economics at the University of Saskatchewan and one of the study authors, tells the Alliance for Science.

“The adoption of GM crops and the use of chemicals associated with these crops confirms that weed control is effective and tillage is no longer required,” he says. “Removing tillage [as a method] for weed control is the only way agriculture can increase carbon sequestration.”

Using a carbon accounting framework, the researchers were able to estimate carbon sequestration in the Canadian province of Saskatchewan over a period of 30 years. The authors also used data collected through an online survey of Saskatchewan crop farmers between November 2020 and April 2021. Survey participants responded to questions regarding their land management practices during two time periods, 1991–1994 and 2016–2019, to determine how their practices have changed over the past 25 years. The results quantify the transition from farmland being a net carbon emitter to being a net carbon sequesterer.

“This evidence confirms the correlation between genetically modified, herbicide-tolerant crops and glyphosate use is a driver of the increased soil carbon sequestration,” the authors note.

Based on the results, the researchers found that the adoption of GM crops and herbicide-tolerant (HT) varieties, which typically include the use of glyphosate, had facilitated substantial changes in land management practices by Saskatchewan crop farmers over the past 30 years. Further results indicated that farmers see these technologies as crucial to maintaining the sustainable practices they’ve adopted since 1995.

“The improved weed control contributed by these technologies provided farmers with an increased opportunity to reduce or eliminate tillage and summer fallow practices,” the paper notes. “Farmers indicate that without the availability of HT technology, hectares managed with summer fallow would increase from 1 percent to 23 percent, representing a decrease in annual sequestration from Saskatchewan soils of about 2.2 million Mg SOC.”

While many environmental organizations argue that regenerative and organic agriculture are the solutions for improved sustainability, they lack evidence to support these claims, Smyth says. Regenerative and organic practices ban synthetic chemicals and GM crops and therefore rely on tillage for weed control. Improved sustainability is not possible without innovative technologies like GM crops and synthetic chemicals, Smyth asserts.

“The evidence presented in our article illustrates the hypocrisy of environmental activists that call for improved agriculture sustainability yet call for bans on GM crops and the use of chemicals like glyphosate,” he notes.

Smyth urges government policy makers to ensure that agricultural policies are evidence-based, not based on environmental sentiments.

A prominent recent example is Mexico’s plan to phase out glyphosate use and ban GM corn cultivation and imports over the next three years — a decision deemed to have been motivated by ideology, rather than science.

The authors hold the view that any GM crops bans or legislation restricting glyphosate use are antithetical to the Canadian farm evidence and will not contribute to increasing agricultural sustainability.

“There is ample agricultural evidence from developing countries that inefficient weed control is the single biggest factor in limiting yield,” Smyth tells the Alliance. “Technologies that improve weed control are fundamental to improving yields, which contributes to improved sustainability and food security.”

Despite the significant contributions made by farmers adopting sustainable land management practices to support carbon sequestration, these contributions rarely make it to the high table of environmental or climate change mitigation policy discussions, the authors point out. Furthermore, the role of various technologies such as GM HT crops and glyphosate in these sustainable adoptions is often unrecognized.

As noted by the United Nations Food and Agriculture Organization, soil carbon sequestration has been shown to hold the largest sink potential in terrestrial ecosystems and agroecosystems.

Image: Alfalfa field in Saskatchewan, Canada. Photo: Shutterstock/Nalidsa