Herbicide-tolerant canola lowers herbicide use, tillage
Graham Brookes and Peter Barfoot with PG Economics in Dorchester, U.K. estimate that genetic technology has reduced global pesticide use by 618.7 million kg, or 8.1 per cent, over the past 20 years. This drop is due to the change in herbicides typically used, going from a fairly broad range of mostly selective herbicides to one or two broad-spectrum herbicides.
They published these numbers in a report titled “Environmental impacts of genetically modified (GM) crop use 1996–2015: Impacts on pesticide use and carbon emissions,” in the journal GM Crops & Food in 2017.
The report includes specific reference to herbicide-tolerant (HT) canola in Canada: Use of HT canola in Canada from 1996-2015 resulted in a 21.1 million kg, or 20 per cent, reduction in active ingredient use “relative to the amount reasonably expected if this crop area had been planted to conventional canola.”
Brookes and Barfoot note the downsides to an over-reliance on single active ingredients in these systems, referencing an increase in tank mixing over the past decade. But the paper notes that herbicide use on conventional crops also went up, and that herbicides used in conventional systems also had resistance issues.
Brookes and Barfoot add that HT technology also reduced fuel use and tillage, resulting in a significant reduction in greenhouse gas emissions. Their numbers indicate that in 2015 alone, this was equivalent to removing 11.9 million cars from the roads. Reduced tillage also increases carbon sequestration in the soil and reduces soil erosion.
“It is widely accepted that increases in atmospheric levels of greenhouse gases such as carbon dioxide, methane and nitrous oxide are detrimental to the global environment,” they write. “Therefore, if the adoption of crop biotechnology contributes to a reduction in the level of greenhouse gas emissions from agriculture, this represents a positive development for the world.”
Table. GM HT canola: Summary of active ingredient usage
and associated EIQ changes 1996-2015.
| Country | Change in active ingredient use (million kg) | % change in amount of active ingredient used | % change in EIQ indicator |
|---|---|---|---|
| U.S. | -3.1 | -33.5 | -46.5 |
| Canada | -21.1 | -19.8 | -32.4 |
| Australia | -0.8 | -3.5 | -3.0 |
| Source: Brookes & Barfoot, “Environmental impacts of genetically modified (GM) crop use 1996–2015: Impacts on pesticide use and carbon emissions,” GM Crops & Food, 8:117–147, 2017 | |||
What is the Environmental Impact Quotient?
Brookes and Barfoot use a measurement called the Environmental Impact Quotient (EIQ). It goes beyond a comparison of the volume of active ingredient applied to draws on toxicity and environmental exposure data related to individual products. It also includes benefits from reduced tillage production systems, which are made easier with HT crops. These benefits included reduced fuel use, increased soil carbon and reduced erosion.
The kilogram-based drop in global pesticide use since the commercial launch of biotech HT traits, which was noted at the top of the article, also decreased the EIQ for herbicide and insecticide use on GM crops by 18.6 per cent.