The high-yields and pest resistance of genetically-modified crops could be a crucial agricultural buffer against climate change. But at the same time, GM crops could be driving deforestation, biodiversity loss, and human health impacts.
These are the takeaways of a new Science study that delves into the potential environmental impacts of GM crops: it reviewed dozens of papers to reveal a nuanced picture of GM farming that highlights some of the surprising trade-offs of its agricultural prowess.
Most existing research focuses on two GM traits, the only ones that have been bred into plants and farmed on a commercial scale. The first is a trait isolated from a bacterium which makes the plant resistant to certain insect ‘pests’. The second trait gives plants herbicide resistance, so that chemicals that kill weeds can be applied to farmland without also harming the crop. These traits have been engineered into staple crops including maize, canola, cotton, and soybeans.
When the researchers delved into the body of literature, it revealed an interesting push and pull between the benefits and impacts of GM crops. For example, studies have shown that GM crops containing the insect-resistant trait required significantly less insecticide to manage agricultural pests. The spread of GM cotton in India has reduced millions of insecticide poisoning incidents due to reduced spraying on smallholder farms, the researchers say.
But other studies reveal that over time, insects also develop resistance, themselves, to the GM crops, which can actually trigger more pesticide application to fields in the long run. In other words, insect-resistant crops may not be as neat a solution as they first appear.
Studies on herbicide-tolerant crops revealed an even more mixed bag. On the one hand, it appears that herbicide resistant crops may encourage reduced tillage, because farmers can rely on chemical suppressants for weed control, instead of yanking them out of the ground. One study showed that herbicide-resistant soybeans increased conservation tillage and no-till practices by 10 and 20%, respectively.
On the other hand, concerning research indicates that herbicide-resistant crops may normalize the application of harsher chemicals to the land. Papers have documented a substantial increase in a powerful herbicide called glyphosate in places where glyphosate-resistant GM crops are grown, as farmers begin to substitute this chemical for the less intensive herbicides they used before.
Research has also identified significant herbicide drift into the surrounding environment, in places where farmers over-apply glyphosate to the land, knowing it will rid their farms of weeds without damaging their GM crops. Ironically, the drifting herbicide can also trigger wider farmer adoption of GM crops on surrounding lands, effectively so that their crops can tolerate the chemicals that arrive from surrounding fields.
A whole raft of papers have dug into the human health effects of spreading chemical use, finding that in different countries, widespread GM adoption and increased glyphosate use correlated with elevated childhood cancer rates, increased infant mortality, and preterm birth.
And then there’s the biodiversity impact. While some studies show that the higher yields of GM crops reduce pressure on wild lands, others show that economic factors may cause the opposite, if the increased profits motivate farmers to expand their production. One study in Brazil found that deforestation intensified in locations where there had been significant yield increases in GM crops. Drifting herbicide can also damage plants and animals, even at low concentrations, the researchers note.
In the study’s nuanced portrait of GM, it’s neither a silver bullet, nor a threat. No single effect can be viewed in isolation: each benefit comes with a potential risk. So what should we take from these discoveries?
First, the researchers emphasize that despite the dozens of papers, there are still huge knowledge gaps about GM’s environmental impact. If their review reveals anything, it’s that we need more information on these trade-offs, to quantify GM’s benefits.
And while the study sounds a note of caution about the dozens of traits now under development that haven’t yet reached the field, the spirit of innovation presents an opportunity, too, the authors write. “It is plausible that GM crops with other traits explicitly developed to reduce the environmental impacts of agriculture…would have unambiguous positive environmental consequences.”
Noack et. al. “Environmental impacts of genetically modified crops.” Science. 2024.
Image:©Anthropocene Magazine
