Genetically modified crops
Genetically modified crops (GM crops) are plants used in agriculture, the DNA of which has been modified using genetic engineering methods. Plant genomes can be engineered by physical methods or by use of Agrobacterium for the delivery of sequences hosted in T-DNA binary vectors. In most cases, the aim is to introduce a new trait to the plant which does not occur naturally in the species. Examples in food crops include resistance to certain pests, diseases, environmental conditions, reduction of spoilage, resistance to chemical treatments (e.g. resistance to a herbicide), or improving the nutrient profile of the crop. Examples in non-food crops include production of pharmaceutical agents, biofuels, and other industrially useful goods, as well as for bioremediation.[1]
"GM Crops" redirects here. For the journal formerly printed under that name, see GM Crops & Food.
Farmers have widely adopted GM technology. Acreage increased from 1.7 million hectares in 1996 to 185.1 million hectares in 2016, some 12% of global cropland. As of 2016, major crop (soybean, maize, canola and cotton) traits consist of herbicide tolerance (95.9 million hectares) insect resistance (25.2 million hectares), or both (58.5 million hectares). In 2015, 53.6 million ha of Genetically modified maize were under cultivation (almost 1/3 of the maize crop). GM maize outperformed its predecessors: yield was 5.6 to 24.5% higher with less mycotoxins (−28.8%), fumonisin (−30.6%) and thricotecens (−36.5%). Non-target organisms were unaffected, except for lower populations some parasitoid wasps due to decreased populations of their pest host European corn borer; European corn borer is a target of Lepidoptera active Bt maize. Biogeochemical parameters such as lignin content did not vary, while biomass decomposition was higher.[2]
A 2014 meta-analysis concluded that GM technology adoption had reduced chemical pesticide use by 37%, increased crop yields by 22%, and increased farmer profits by 68%.[3] This reduction in pesticide use has been ecologically beneficial, but benefits may be reduced by overuse.[4] Yield gains and pesticide reductions are larger for insect-resistant crops than for herbicide-tolerant crops.[5] Yield and profit gains are higher in developing countries than in developed countries.[3] Pesticide poisonings were reduced by 2.4 to 9 million cases per year in India alone.[6] A 2011 review of the relationship between Bt cotton adoption and farmer suicides in India found that "Available data show no evidence of a 'resurgence' of farmer suicides" and that "Bt cotton technology has been very effective overall in India."[7] During the time period of Bt cotton introduction in India, farmer suicides instead declined by 25%.[6]
There is a scientific consensus[8][9][10][11] that currently available food derived from GM crops poses no greater risk to human health than conventional food,[12][13][14][15][16] but that each GM food needs to be tested on a case-by-case basis before introduction.[17][18][19] Nonetheless, members of the public are much less likely than scientists to perceive GM foods as safe.[20][21][22][23] The legal and regulatory status of GM foods varies by country, with some nations banning or restricting them, and others permitting them with widely differing degrees of regulation.[24][25][26][27]
Yield[edit]
In 2014, the largest review yet concluded that GM crops' effects on farming were positive. The meta-analysis considered all published English-language examinations of the agronomic and economic impacts between 1995 and March 2014 for three major GM crops: soybean, maize, and cotton. The study found that herbicide-tolerant crops have lower production costs, while for insect-resistant crops the reduced pesticide use was offset by higher seed prices, leaving overall production costs about the same.[3][105]
Yields increased 9% for herbicide tolerance and 25% for insect resistant varieties. Farmers who adopted GM crops made 69% higher profits than those who did not. The review found that GM crops help farmers in developing countries, increasing yields by 14 percentage points.[105]
The researchers considered some studies that were not peer-reviewed and a few that did not report sample sizes. They attempted to correct for publication bias, by considering sources beyond academic journals. The large data set allowed the study to control for potentially confounding variables such as fertilizer use. Separately, they concluded that the funding source did not influence study results.[105]
Under special conditions meant to reveal only genetic yield factors, many GM crops are known to actually have lower yields. This is variously due to one or both of: Yield drag, wherein the trait itself lowers yield, either by competing for synthesis feedstock or by being inserted slightly inaccurately, into the middle of a yield-relevant gene; and/or yield lag, wherein it takes some time to breed the newest yield genetics into the GM lines. This does not reflect realistic field conditions however, especially leaving out pest pressure which is often the point of the GM trait.[106] See for example Roundup Ready § Productivity claims.
Gene editing may also increase yields non-specific to the use of any biocides/pesticides. In March 2022, field test results showed CRISPR-based gene knockout of KRN2 in maize and OsKRN2 in rice increased grain yields by ~10% and ~8% without any detected negative effects.[107][108]