The new genetic engineering techniques can also be used to alter natural populations. So-called 'gene drives' have been developed to change, decimate or even exterminate natural populations, e.g. pests. The essential feature of a gene drive is that it can bypass the rules of natural inheritance. Additionally inserted genes can spread faster in a population than would naturally be the case. CRISPR/Cas gene scissors are one of the main tools used for this purpose: the genetic material for the gene scissors is firmly anchored in the genome of the manipulated organism and is copied over and over again in the following generations. All offspring will carry the additional gene, whereas in natural conditions it would, on average, only be half the offspring in each generation.
The technology is meant for use on, e.g. fruit flies regarded as pests in agriculture, mosquitoes that can transmit diseases and rodent pests. It could also be used to combat invasive species or plants that are considered to be weeds. The problem: once released, it is hardly possible to stop the experiment. Even if damage to humans and the environment occurs, there would often be no effective method of removing the genetically engineered organisms from the environment. The long-term consequences cannot be reliably estimated. The technical characterisation of genetically engineered organisms, or even experiments in the laboratory, is insufficient to estimate all the relevant risks that may occur in future generations and in interaction with the environment. From the perspective of the precautionary principle, uncontrollable releases cannot therefore be approved.
This example shows that releases of genetically engineered organisms, whose spread cannot be controlled, must not be permitted.
There is no way to reliably estimate the long-term consequences of their release. If control fails, ecosystems can be seriously damaged and extinction of a species accelerated. The risk is also considerable for people if, for example, new diseases were to be transmitted.