Photo by Brand X Pictures / Getty Images.
Genetically engineered crops such as corn, cotton, and potatoes carry a bacterial gene from Bacillus thuringiensis (Bt) that produces a toxin lethal to insect larvae. Other varieties are engineered to resist specific herbicides. While these advances promise to support a growing global population, they also raise significant concerns for biodiversity.
Herbicides are toxic to many species. When applied across vast agricultural landscapes, they leach into surrounding ecosystems. The widespread adoption of herbicide‑resistant crops is believed to increase overall herbicide use, amplifying the influx of harmful chemicals into natural habitats. These chemicals can eradicate native plants that provide food for wildlife, directly poison amphibians, and ultimately reduce biodiversity.
When genes from genetically modified (GM) crops enter the environment, they can disrupt natural plant communities, threaten biodiversity, and contaminate human food supplies. In September 2000, an unapproved Bt corn variety—StarLink—was detected in taco shells in the United States. Over the following months, StarLink appeared in various yellow‑corn products, some abroad. Initial investigations suggested growers had either not received clear instructions or were told the variety would be approved before harvest. The exact entry points into the supply chain remain unknown, yet the incident illustrates how GM genes can infiltrate food systems. A Cornell Cooperative Extension series reports that StarLink may have reached more than half of U.S. corn supplies.
Regions with high crop diversity are particularly vulnerable to out‑crossing with local varieties. Mexico, home to over 100 unique corn types, prohibits GM corn, yet genes from GM varieties have been detected in Mexican corn. Research by plant geneticists at UC Riverside shows that gene flow from conventionally bred crops can increase weediness in wild relatives, with some GM crops becoming weeds. Transgenic sunflowers, for example, can produce 50 % more seed than conventional counterparts, raising concerns that GM plants may gradually displace valuable genetic diversity.
Bt toxins produced by GM crops pose a threat to biodiversity. The Sierra Club has described genetic engineering as environmentally dangerous. A Cornell University study demonstrates that Bt toxin kills larvae of beneficial non‑target species such as moths, butterflies, lacewings, and ladybugs. The toxin persists in Bt corn root systems and plant residues long after harvest, affecting millions of soil microorganisms that sustain fertility. When Bt toxin binds to soil particles, it can remain active for two to three months, negatively impacting aquatic and soil invertebrates and disrupting nutrient‑cycling processes in bacterial communities.
