A new US study suggests genetically modified (GM) crops do not pose a risk to human health and the environment, but that more research is urgently needed to test any future GM products to ensure they are safe.
The report also reveals there is no evidence GM crops are increasing yields in the US.
The report out yesterday (17 May) from the National Academies of the Sciences, Engineering and Medicine said 'evolved resistance' to current genetically engineered characteristics in crops is a major agricultural problem.
New plant varieties that have intended or unintended novel characteristics that may present potential hazards should undergo safety testing - regardless of whether they were developed using genetic engineering or conventional breeding techniques.
New “-omics” technologies, which dramatically increase the ability to detect even small changes in plant characteristics, will be critical to detecting unintended changes in new crop varieties.
Since the 1980s, biologists have used genetic engineering to produce particular characteristics in plants such as longer shelf life for fruit, higher vitamin content, and resistance to diseases.
However, the only genetically engineered characteristics that have been put into widespread commercial use are those that allow a crop to withstand the application of a herbicide or to be toxic to insect pests.
The fact that only two characteristics have been widely used is one of the reasons the committee avoided sweeping, generalized statements about the benefits and risks of GE crops.
Claims about the effects of existing GE crops often assume that those effects would apply to the genetic engineering process generally, but different characteristics are likely to have different effects.
A genetically engineered characteristic that alters the nutritional content of a crop, for example, is unlikely to have the same environmental or economic effects as a characteristic for herbicide resistance.
Effects on human health
The committee carefully searched all available research studies for persuasive evidence of adverse health effects directly attributable to consumption of foods derived from GE crops but found none.
Studies with animals and research on the chemical composition of GE foods currently on the market reveal no differences that would implicate a higher risk to human health and safety than from eating their non-GE counterparts.
Though long-term epidemiological studies have not directly addressed GE food consumption, available epidemiological data do not show associations between any disease or chronic conditions and the consumption of GE foods.
There is some evidence that GE insect-resistant crops have had benefits to human health by reducing insecticide poisonings.
In addition, several GE crops are in development that are designed to benefit human health, such as rice with increased beta-carotene content to help prevent blindness and death caused by vitamin A deficiencies in some developing nations.
Effects on the environment
The use of insect-resistant or herbicide-resistant crops did not reduce the overall diversity of plant and insect life on farms, and sometimes insect-resistant crops resulted in increased insect diversity, the report says.
While gene flow – the transfer of genes from a GE crop to a wild relative species – has occurred, no examples have demonstrated an adverse environmental effect from this transfer.
Overall, the committee found no conclusive evidence of cause-and-effect relationships between GE crops and environmental problems.
However, the complex nature of assessing long-term environmental changes often made it difficult to reach definitive conclusions.
Effects on agriculture
The available evidence indicates that GE soybean, cotton, and maize have generally had favourable economic outcomes for producers who have adopted these crops, but outcomes have varied depending on pest abundance, farming practices, and agricultural infrastructure.
Although GE crops have provided economic benefits to many small-scale farmers in the early years of adoption, enduring and widespread gains will depend on such farmers receiving institutional support, such as access to credit, affordable inputs such as fertilizer, extension services, and access to profitable local and global markets for the crops.
Evidence shows that in locations where insect-resistant crops were planted but resistance-management strategies were not followed, damaging levels of resistance evolved in some target insects.
If GE crops are to be used sustainably, regulations and incentives are needed so that more integrated and sustainable pest-management approaches become economically feasible.
The committee also found that in many locations some weeds had evolved resistance to glyphosate, the herbicide to which most GE crops were engineered to be resistant.
Resistance evolution in weeds could be delayed by the use of integrated weed-management approaches, says the report, which also recommends further research to determine better approaches for weed resistance management.
Insect-resistant GE crops have decreased crop loss due to plant pests. However, the committee examined data on overall rates of increase in yields of soybean, cotton, and maize in the U.S. for the decades preceding introduction of GE crops and after their introduction, and there was no evidence that GE crops had changed the rate of increase in yields.
It is feasible that emerging genetic-engineering technologies will speed the rate of increase in yield, but this is not certain, so the committee recommended funding of diverse approaches for increasing and stabilizing crop yield.
'Report shows GM technology is old and failing'
Emma Hockridge, head of policy for farming and land use at the Soil Association said: "This detailed report highlights that GM is an old and failing technology.
"Despite huge promises of all kinds of benefits, and many years of huge investment, the only genetically engineered characteristics that have been put into widespread use are those that allow a crop to withstand the application of a herbicide or be toxic to insect pests.
"The only commercial GM crops are still just maize, soybean and cotton.
"Golden rice is mentioned as an example of a potentially beneficial GM crop, yet despite 15 years of hype, golden rice is still no-where near ready and cheaper, more effective dietary interventions are already being deployed with success.
"The report highlights that there have been no long epidemiological studies which have directly addressed the human health impact of GM food consumption.
"The report strongly rebuts the argument that GM crops are needed to feed the world by concluding that there is no evidence that GM crops have changed the rate of increase in yields.
"The Soil Association agrees with the recommendation for pre-market human and environmental safety assessments for a wider range of breeding techniques."