The environmental concerns of GM crops can be summed up quite generally in single statement. That being that the genetically modified crops will escape their designated areas and cause distributions in the local ecosystems. These disruptions could take many forms and I have tried to cover the main ones below.
By takeover I am referring to a scenario where the GM crop escapes its field and thrives so well in its surrounding environment that it out competes the local plants or causes harm to the animals living in the ecosystem thus completely altering its balance. However, this scenario is not really one we should worry about at all. In theory this is a scenario which shouldn’t just be restricted to GM crops. There is no reason why non-GM crops could also have this effect but we have been growing crops (both GM and non-GM) for many years now and we don’t see this occurring. This is because over thousands of years we have been selectively breeding our crops so that they resemble the plants we see today. These plants have been breed specifically for the traits which allow them to thrive in an agricultural environment. However, this ‘domestication’ of the crops has meant that they are no longer adapted to thrive naturally in the wild and thus if there ever was a case where the crops (GM or not) did escape the confines of its field then it would be so poorly adapted to its new environment that it would not survive long and definitely would not takeover the ecosystem.
Whilst a GM crop is not going to take over an ecosystem by itself there is still a possibility that the genes from a GM crop could be introduced to the surrounding ecosystem. However, once again this is a once again not an issue which is restricted just to GM crops. In fact it could be seen as potentially just as harmful if this occurs from non-GM crops as it would be for GM crops. This is because in the process of breeding crops to produce the species we know today, we have already naturally introduced some unusual genes into these species which have been placed into the middle of ecosystems without those genes.
The main question here is whether or not this is an issue we should be concerned about. This is quite a subjective question but I would generally favour an answer of no.This is because the whole concept of evolution through natural selection relies on the dispersion of new genes through species to produce better adapted varieties and stronger more diverse and resilient ecosystems. But this isn’t always the and thus it can sometimes be a concern. Surprisingly, this mainly occurs when a plant inherits a favourable gene from a foreign species. In this case the crop has given a species in the ecosystem a gene which makes it better suited to surviving in its environment. This may seem like a good thing, and it is for that particular species of plant. This species potentially could be so well suited now, that it is able to out compete the other species it used to survive naturally alongside thus causing their numbers to decrease. This would lead to an overall loss in biodiversity and thus result in a weaker ecosystem.
Once again though we need to look deeper to see how concerned we should be about this. As stated, this infiltration of foreign genes can happen from non-GM crops as well as just the GM varieties but from now on I am going to focus just on the case of GM crops. Please note though that the same comments still apply for non-GM crops.There are two main areas which I will explore in more detail regarding gene infiltration. Firstly, to judge if it is a concern or not we have to look closely at what we are worrying about. I.e what are the genes which could infiltrate the ecosystem and what effect would they have on the surrounding plants. Not all of the traits which are added to GM crops would have any impact at all if they infiltrated the surrounding ecosystem. Those such as herbicide resistance and added nutritional value would not have any impact. For example, herbicides are not used in the wild and thus any plant with herbicide resistance has no notable advantage over a plant from the same species without the resistance. On the other hand traits such as drought or disease resistance could potentially have a big impact in a wild ecosystem. If an ecosystem was hit by drought or disease then these plants would out compete those without the resistance and thus reduce the biodiversity in the environment. Therefore, it could be seen that some GM crops are more environmentally dangerous than others depending on what traits they have been engineered for.
The second area I wanted to explore is how the genes infiltrate the ecosystems. There are two ways in which this could happen which are called vertical and horizontal transfer. Vertical transfer is when the pollen from one plant comes into contact with another plant and thus through sexual reproduction the genes are transferred between plants. This process requires the two plants to be of the same species or at least very similar, and so is only really a risk when wild varieties of the GM crops are found in the ecosystem. The scenario can also occur where vertical transfer occurs between GM crops and non-GM crops of the same species. This could cause a whole host of new problems but I have explored these more in the political and economical post as they aren’t really environmental issues.
The other way in which genes can enter an ecosystem is through horizontal transfer. Horizontal transfer occurs when a gene is passed on between two plants through any other method other than sexual reproduction. This means the plants don’t necessarily have to be closely related and thus sounds like a much more threatening concept. However, the main methods which this can be achieved is through a virus or bacteria which incorporate the gene from the first plant before passing it on to other plants. The genes which we are engineering crops for provide no advantage to the survival of viruses and bacteria and thus the chances of gene infiltration through this method are very very low.
Harm to wildlife
The concerns for wildlife is very similar to the concerns about human health and GM crops. That is that the new GM varieties of the crops could be harmful to the wildlife in the local ecosystem, in particular insects who feed off the crops directly. Indeed there have been lab experiments suggesting that some GM crops such as Bt cotton (cotton with an added gene (Bt) which is harmful to pests but not other insects and higher order animals such as humans, thus giving the plants natural pest resistance) could be harmful to the beneficial insects but there have also been further experiments which have concluded that these effects would not be seen in actual field experiments.
In fact studies of fields with Bt cotton have been found to generally have a higher number of beneficial insects living in them than non-GM varieties. These studies have proved that the use of this pest resistant gene has been less harmful to the local wildlife than the alternative pesticides which would otherwise be used, however, there are other studies which show the opposite results and thus it is clear more research is needed before we can fully understand the complete impact of GM crops on local wildlife.
There is an additional risk to wildlife though which links to the above topic of gene infiltration above. That is if the pest resistant genes escaped into the ecosystem then they could start to harm more of the local wildlife as well as just the pests not wanted in the fields. With all of these risks there are measures in place to keep them minimal. For instance, organisations such as the RSPB are promoting the use of genes which repel pests rather than kill them which would reduce the number of animals unintentionally harmed.
- Genetically modified crops and agricultural development, Martin Qaim, 2016
- RSPB briefing, genetically modified crops and the environment, RSPB, 2013