Genetic modification (GM) of crops refers to the insertion of a DNA sequence (transgene) into a plant’s genome to confer new characteristics such as pest resistance, longer shelf-life, and increased plant height.
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The DNA is inserted into plant cells that are then cultured and grown into plants. The inserted DNA becomes a permanent part of the plant’s genome and any seeds the plant produces will also contain the gene and possess the new characteristics.
According to a chapter recently published in the book Genetically Modified and Irradiated Food, the genetic modification of crops is perhaps the most well-investigated technology in agriculture.
A broad body of literature on the topic generally concludes that GM crops have no adverse impact on various farming, environmental and economic factors, yet concerns remain about the uptake of GM crop technology over conventional agriculture, particularly in Europe.
The impact of GM crops on agriculture has made great inroads into conventional agriculture in the sense of replacing the cultivation of non-GM varieties, in regions where field release and marketing of GM varieties have been generally permitted.”
Professor Alan Schulman from the Natural Resources Institute, Helsinki, Finland
Schulman says that to fully understand the effects that GM crops have on conventional agriculture, the economic impact of the long value chain from farmer to customer needs to be considered, as does the impact on agricultural practices; on soil; on the genetic diversity of crops; on the biodiversity of non-crop plants; and on production, marketing and distribution.
In a comprehensive review of the literature covering these areas, Schulman presents evidence supporting the use of GM in agriculture, as well as factors that fuel resistance to using GM crops as an alternative to non-GM crop farming.
Economic impact on the value chain
The list of advantageous properties that GM crops possess, compared with non-GM varieties, includes pest resistance; antibiotic, herbicide and drought tolerance; increased crop yield and longer shelf life. The list is still growing, says Schulman, and the beneficial impact on the value chain is almost undoubtable since people in the crop farming business are keen to choose the highest-yielding varieties that will make them the most profit.
Schulman refers to a 2014 metanalysis of studies analyzing GM maize and cotton cultivation which revealed an almost 70% profit compared with non-GM varieties. He also refers to the development of GM papaya in Hawaii that was resistant to the ringspot virus.
This decreased the viral load in farming areas meaning papaya could be provided to locals. It also enabled farmers to grow non-GMA papaya (that was previously vulnerable to ringspot) for export to Japan, which refused to import GM varieties.
In a broader context, virus resistance has been one of the main factors driving the success of GM crops.
The effects compared with conventional agriculture
The use of GM crops has had various beneficial impacts, compared with conventional farming. The reduction in insecticide use due to GM varieties that produce Bacillus thuringiensis insecticidal proteins, for example, has been one major change.
Another example is efficient weed management as a result of GM crops that can tolerate the broad spectrum weed killer glyphosate. In developing countries, one beneficial outcome of the reduced insecticide use that has been overlooked says Schulman, is an improvement in farmers’ health as a result of decreased exposure to toxic pesticides.
The impact on genetic diversity of crops
Concerns are surrounding whether the genetic diversity of crops may be affected by GM varieties due to the impact of breeding approaches being focused on costly GM crops with a high yield and value.
In his summary of the research around this, Shulman concludes that GM crops themselves do not reduce the genetic diversity, as the transgenes used are only one of about 30,000 other genes in the plant influencing this diversity.
In a more general context, however, the question applies to conventional crops as well because factors influencing diversity include policies regarding seed distribution, culture-specific uses of crops and the economics surrounding breeding and seeding.
The effect on the biodiversity of non-crop plants
Since the introduction of GM crops, concerns have arisen about the effects on wild plants growing near GM cultivars, as a result of the transgenes potentially being introduced into the wild plant relatives of the GM crops.
However, the studies Schulman reviewed suggested a positive impact on diversity as a result of GM cultivation. For example, one study showed reduced pesticide use decreased the chemical pollution that poses a risk to non-target insects that pollinate plants in nearby areas.
The effect on production, marketing, and distribution of agricultural products
Anti-GM campaigns and some NGO organizations have generated a distrust of GM products among consumers that has meant the marketing of foods has been split into GM and non-GM categories, especially in Europe.
This has presented significant challenges to farmers and triggered bans of GM products in much of the EU. Fears about GM products have also led to calls for labeling in the US and the first mandatory law became operative in Vermont in 2014.
One study Schulman referred to said models designed to assess the effect of labeling have suggested that producers of non-GM foods benefit more when labeling is mandatory rather than voluntary in settings where non-GM is viewed as beneficial and particularly when GM labeling is perceived as a warning.
Schulman concludes that since GM crops were introduced 30 years ago, more than 90% of farmers have opted for GM in countries where they can. The reason, says Schulman, is that GM varieties allow farmers to increase food production whilst reducing input and labor “primarily by controlling pests and weeds better than conventional varieties and approaches, thereby increasing farmers’ income.”
He also concludes that the widespread use of GM crops has also had various positive effects on the environment.
Referring to the large body of literature reporting on the use of GM in agriculture, Schulman says it “generally concludes that GM crops have had little or no negative impact on the environment and that any adverse effects have been smaller and fewer than those of conventional varieties.”
What is genetic modification (GM) of crops and how is it done? The Royal Society 2016. Available at: https://royalsociety.org/topics-policy/projects/gm-plants/what-is-gm-and-how-is-it-done/
Schulman A. Chapter 8 - The impact of GM crops on agriculture. Genetically Modified and Irradiated Food. Controversial Issues: Facts Versus Perceptions 2020: p195-213 https://doi.org/10.1016/B978-0-12-817240-7.00012-7