Crops genetically modified to poison pests can deliver significant environmental benefits, according to a study spanning two decades and 1.5 million square kilometres. The benefits extended to non-GM crops in neighbouring fields, researchers found…
Bt cotton is one type and now makes up 95% of China’s vast plantations. Since its introduction in 1997, pesticide use has halved and the study showed this led to a doubling of natural insect predators such as ladybirds, lacewings and spiders. These killed pests not targeted by the Bt cotton, in cotton fields, but also in conventional corn, soybean and peanut fields.
“Insecticide use usually kills the natural enemies of pests and weakens the biocontrol services that they provide,” said Professor Kongming Wu at the Chinese Academy of Agricultural Sciences in Beijing, who led the research team. “Transgenic crops reduce insecticide use and promote the population increase of natural enemies. Therefore, we think that this is a general principle.”
Professor Guy Poppy, an ecologist at the University of Southampton, said the scale of the work gave “robust” results that ended a long-running debate pitting plant scientists against ecologists. “The argument was that, with Bt crops needing no pesticide spraying, other pests would go crazy so you would subsequently have to spray lots more pesticide,” he said. But the study shows this did not happen for aphids, a major pest. “This is also the first time it has been shown comprehensively that the surrounding fields benefited from being next to GM crops…”
The new research, published in the journal Nature, monitored both insect pests and predators between 1990 and 2011, during which time Bt cotton swept aside traditional GM cotton. It examined 36 sites across six big cotton-growing provinces in northern China, where about 2.6m hectares of cotton and 33m hectares of other crops – notably maize, peanut and soybean – are grown each year, by more than 10 million small-scale farmers…
“As one of the measures for pest management, transgenic crops have a great advantage,” said Wu. He noted that predators usually disperse widely and can attack a range of pests: “Not only can they synchronously attack different insect pests in one field, but they can also colonise different habitats in different seasons.”
Of course, science won’t get in the way of those whose opposition to genetic modification is more religion than conclusion. The findings are a pleasant surprise. The sort of conclusion that often pops up from basic research when you’re spending your research time looking for what happens – and learning from the process – rather than trying to tailor results to serve a presupposition.
I don’t doubt that further research will produce positives and negatives. Agronomists will learn from both – and use the knowledge gained to guide future transformation of modern agriculture.