New study: GMO crops reduce pesticide use, greenhouse gas emissions

By Joan Conrow

July 27, 2020

In the two decades since their adoption, genetically modified (GM) crops have achieved significant environmental benefits by reducing pesticide use and greenhouse gas emissions and increasing yields, a new study finds.

“GM crop technology continues to make an important contribution to reducing the environmental footprint of agriculture and securing global food supplies in a sustainable way,” says Graham Brookes, director of PG Economics and co-author of the paper published in the peer review journal GM Crops & Food. “It has also helped lift many small, resource-poor farmers and their families in developing countries out of poverty.”

Though anti-GMO groups frequently claim that GM crops are associated with higher pesticide use, the paper notes that the issue is more complicated and nuanced, varying by countries and crops.

Overall, however, farmers reduced pesticide spraying by 776 million kilograms, or 8.6 percent, between 1996-2018 by adopting GM crops with insect-resistant (IR) and herbicide-tolerant (HT) traits. This is equal to more than 1.6 times China’s total crop protection product use each year. As a result, farmers who grow GM crops have reduced the environmental impact associated with their crop protection practices by 19 percent, according to an indicator known as the Environmental Impact Quotient (EIQ).

GM crops also have brought about major reductions in tillage and fuel use, resulting in a decrease in greenhouse gas emissions equivalent in 2018 to removing 15.27 million cars from the roads, the paper finds.

“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,” the authors 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.”

GM crops also increased yields, which allows farmers to grow more food without using more land. Over the past 22 years, yields increased by an average of 16.5 percent for IR corn and 13.7 percent for IR cotton. Some 17 million farmers globally now grow GM crops. Crop biotechnology has been responsible for the additional global production of 278 million tonnes of soybeans, 498 million tonnes of corn, 32.6 million tonnes of cotton lint and 14 million tonnes of canola, the study finds.

If farmers had not had access to crop biotechnology in 2018, they would have needed to plant an additional 12.3 million hectares (ha) of soybeans, 8.1 million ha of corn, 3.1 million ha of cotton and 0.7 million ha of canola to maintain global production levels. This is equivalent to needing an additional 14 percent of the arable land in the United States, roughly 38 percent of the arable land in Brazil or 16 percent of the cropping area in China. 

“This seed technology has helped farmers be more efficient with their application of crop protection products, which not only reduces their environmental impact, but saves time and money,” the authors note. “The technology is also changing agriculture’s carbon footprint, helping farmers adopt more sustainable practices such as reduced tillage, which has decreased the burning of fossil fuels and allowed more carbon to be retained in the soil.”

Farmers have achieved significant environmental benefits over the past 22 years by adopting insect-resistant (IR) varieties of maize and cotton. This has resulted in a 112.4 million kg reduction in maize insecticide active ingredient use and a 331 million kg reduction in cotton insecticide active ingredient use.

Weed resistance to glyphosate, a commonly used herbicide, has been recorded in some areas where GM crops with the HT traits are widely grown, the paper notes. “This can be attributed to how glyphosate was originally used with GM HT crops, where because of its highly effective, broad-spectrum post-emergence activity, it was often used as the sole method of weed control,” the authors write. “This approach to weed control put tremendous selection pressure on weeds and as a result contributed to the evolution of weed populations dominated by resistant individuals.”

As a result, herbicide use with GM HT crops has increased in most regions and the EIQ indicator has deteriorated, compared to the early 2000s.

“This increase in herbicide use is often cited by GM technology opponents (eg, Benbrook) as an environmental failing of the technology,” the authors note. “However, what such authors fail to acknowledge is that the amount of herbicide used on conventional crops has also increased over the same time period and that compared to the conventional alternative, the environmental profile of GM HT crop use has continued to represent an improvement compared to the conventional alternative.”

In some countries, the paper reports, farmers have achieved aggregate reductions in both the volume of herbicides used (in terms of weight of active ingredient applied) and the associated field EIQ values, in comparison to conventional crops.

In other countries, though the average amount of herbicide active ingredient applied to GM HT crops is higher than conventional crops, the environmental profile of the GM crops is better, as measured by the EIQ indicator, due to the use of more environmentally benign herbicides.

Over the past 22 years, the use of HT crops resulted in lower herbicide use and improved environmental indicators for maize (corn), canola, sugar beets and cotton. Herbicide use in HT soybean production increased slightly, but the EIQ indicator improved by 12.9 percent due to the increased usage of more environmentally benign herbicides, the paper finds.