The use of genetically modified crops in commercial agriculture has been in debate for many years now, and there exists a worry of how these crops may adversely affect humans, as well as other species. Carpenter (2011) reviews journal articles related to the effect of genetically modified crops on biodiversity, focusing the review on crop diversity, effect on non-target soil organisms, effect on target pests, changes in farming practices, weed diversity, use of pesticides and herbicides, and several other topics. The overall findings of Carpenter are that genetically modified crops have near negligible effects on non-targeted species, while being successful at reducing targeted species populations. There is also evidence that genetically modified crops are already aiding biodiversity by increasing farming yields, reducing the amount of land needed to convert from natural habitat to agricultural land. The increased yields, due to successful reduction of pests, has also resulted in more beneficial farming practices, including more conservative tillage practices and decreases in pesticide and herbicide use. The introduction of genetically modified crops has the potential to be extremely beneficial to both humans and our efforts in preserving biodiversity. –Mathew Harreld
Carpenter, J.E. 2011. Impacts of GM crops on biodiversity. Landes Bioscience 2:1, 1–17.
High crop yields are essential as the human population continues to grow. Genetically modified (GM) crops offer an opportunity to increase our crop yields, but what effect do genetically modified crops have on the surrounding environment? Carpenter reviewed research papers and review articles on the effect GM crops have on crop diversity, non-target soil organisms diversity, weed diversity, land use, target organisms, non-target above ground invertebrates, birds, tillage practices, and pesticide use. Using this framework Carpenter was able to outline the potential effect of introducing GM crops on biodiversity. From the beginning it is clear that the largest threat to biodiversity is the conversion of natural habitats into agricultural land. Reviewing the impact of GM crops will give us a better sense if the benefits of GM crops outweigh the costs.
The first issue at hand is changes in crop diversity. Over the history of commercial agriculture our crops have become less diverse as we seek to improve the economic efficiency of their production. This has the potential to put strain on our crops’ genetic resources, potentially lowering yield, pest resistance, and quality. The use of GM crops could be a source of re-diversifying our crop selection. The GM genetic strains might mix with wild strains, creating more diversity. It might also be the case that with GM crops lesser used, and previously less cost efficient crops, will be revitalized due to the development their GM varieties; sweet potato is one such example.
The quality of the soil is regulated not as much by what fertilizers we add, as by the organisms that live in it. Fungi and invertebrate species play key roles in sustaining arable soil, and therefore it is important to understand the effect GM crops might have on them. Carpenter used a review of 70 journal articles, which stated there was little to no impact on soil organisms due to the introduction of GM crops. There have been reports that GM crops adversely affect microbial communities, but most of the effect is thought to be due to differences in geography, temperature, plant variety, and soil type. Papers published after this review reached similar conclusions of little to no effect on soil organisms by GM crops. One of the few documented adverse effects was that long exposure to GM corn as the only food source, reduced the growth of snails. From these articles it is clear that GM crops have little impact on soil organisms, and what impact might exist might be due to regional abiotic differences.
The presence of weeds in farming communities has a large impact on local biodiversity. The more weeds present in an area the more herbicide needed, and more weeds will result in changes of tillage practices. In reviewing journal articles, Carpenter has found that the introduction of GM crops has resulted in declines of weed populations. In the U.S., a survey in six states found that farmers report a 36 to 70% decline in weed pressure. A study done in the U.K. found that introduction of GM sugar, beet, and oilseed rape resulted in declines of weeds and weed seed, but GM corn resulted in increased weed numbers. This resistance in corn fields is most likely due to the development of new strains of glyphosate resistant (GR) weeds, but however there are few reports of such weeds found globally.
As mentioned earlier, the most direct adverse effect on biodiversity is the conversion of natural land to agricultural land, so Carpenter’s results show GM crops are more productive and require less land. Carpeter shows that GM crops increase crop yields from 0 to 7% in developed countries and 16 to 30% in developing countries. Thus, GM crops have the potential to save biodiversity by allowing farmers to avoid converting natural lands.
Perhaps one of the more important direct aspects of use of GM crops is their effect on targeted pest species. Papers from around the globe unanimously show that GM crops decrease the levels of pest populations. Studies in China, California, Arizona, Mississippi, and Maryland all show declines in their respective pest populations over time. This has a very positive impact on other species biodiversity as the increase in pest control results in decreased use of pesticide.
The effect of GM crops on above ground invertebrates has been found to be negligible. Over 360 journal articles were reviewed that covered this topic, and they almost all support the use of GM crops when compared to their effects against non-target invertebrates. Papers that did find that beneficial species were declining due to the introduction of GM crops due to inadvertent poisoning through multitrophic exposure lose of prey, or reduction in prey quality, stated that these effects were nothing compared to the effect that physical agriculture practices had on these species.
The effect on birds was counter to theory; the decreased levels of invertebrates and weeds due to the introduction of GM crops was thought to decrease bird population levels, however crops of GM sugar beet and maize were found to have increased bird populations. This may be due, however, to local changes in bird populations outside of the introduction of GM crops.
Another very important change in agricultural practices due to the introduction of GM crops is the change in tillage practices. With the introduction of the stronger, more resistant GM crops farmers are adopting conservative tillage and no-tillage policies. Tillage disturbs the land, and hastens erosion, as well as releasing herbicides and pesticides beyond the farmland. Introduction of GM crops aid in reducing these adverse effects.
The introduction of GM crops, on a whole, seems to provide many more benefits than not. While there have been cases of GM crops hurting farming production, this has not been the case for most adopters. Carpenter concludes that the use of GM crops will greatly aid our fight to feed our growing population, while supporting our efforts to preserve local biodiversity. Many of the opined adverse effects of GM crops, if they exist, seem to be negligible. Thus, the future of GM crops is positive, especially as new technologies continue to be developed. The use of GM crops in commercial agriculture may go a long way to aiding efforts to preserve natural habitats.