It is often claimed that the use of genetically engineered plants has so far proven that the technology is safe. This is, however, not true. Many of the risks have not been examined in detail. And even if not all concerns have manifested, there are enough examples of what has gone wrong and been overlooked for a long time.
One of these examples has had considerable consequences for the environment and agriculture: genetically modified glyphosate-resistant plants have been grown commercially for over 20 years, and are the most frequently used genetically engineered seeds worldwide. A gene for the formation of an additional enzyme was inserted into the genomes of these plants. This gene also occurs naturally in plants but is not sufficient in its natural form to protect them against the herbicide. Additionally, most of the genetically engineered plants grown in Argentina, Brazil and the USA (soybeans, maize, cotton, sugar beet and rapeseed) have been modified in their genetic makeup to contain certain other variants of these EPSPS enzymes (5-enolpyruvylshikimate-3-phosphate (EPSP) synthase).
According to research results published in 2018 by Chinese scientists who investigated a type of thale cress often used as a model plant, the additional enzymes formed in the plants not only make the plants resistant to glyphosate, they also affect plantmetabolism which controls growth and fertility. This can lead to the plant offspring forming more seeds and being more resistant to environmental stress. As a possible cause of the observed effects, the researchers cite interactions with the natural plant hormone auxin. This herbal hormone regulates growth, fertility and adaptation to environmental stress.
This finding overturns previous assumptions of risk assessment in regard to possible uncontrolled spread: if the genetically engineered plants cross with natural populations, the offspring have a clear survival advantage and can spread much faster than previously thought. The new studies show that this environmental risk depends on the additionally inserted gene itself (and the additionally formed enzyme) – and not, as previously assumed, solely on the use of glyphosate. Stress conditions such as heat and drought can further intensify the effect.
Evidence of an unexpectedly high spread potential of these transgenic plants had already been shown in previous studies. Nevertheless, the European Food Safety Authority EFSA and the biotech industry have always claimed that the additional EPSPS enzyme would not offer a survival benefit for the plants if they were not additionally treated with glyphosate. However, the new research from China shows that the genes which are additionally incorporated into the plants can increase the risk of their spreading in the environment, even if no glyphosate is used. As a result, genetically engineered plants could become invasive and displace natural species in the long-term.
There are other aspects that are important for agriculture. Some types of weeds adapt successfully to the use of glyphosate: they can increase the activity of the gene segments concerned and, in turn, in a quasi natural way, increase the effect of their EPSPS enzymes. The weed offspring are then also protected against the use of the herbicide. The new research results suggest that these weeds can also achieve higher biological fitness. The large-scale cultivation of genetically engineered plants can therefore result in more and more weeds being created through these adaptation mechanisms. In countries where the glyphosate-resistant genetically engineered plants are grown, herbicide-resistant weeds are actually spreading much faster than was originally expected.
This example shows: If genetically engineered organisms are released, damage to the environment can remain undetected for a long time. The current risk assessment is not sufficient to ensure the safety of the plants.