Genetically modified crops are edible crops developed by modifying the genetic profile of existing crops to enhance certain traits like those that result in an increase in crop yields, provide the plants with an ability to resist attacks by pests, etc.
When genetically modified crops are planted in fields there can be a negative impact on the environment in many ways. For example it has been found that the use of genetically modified crops in Mexico has influenced the genes of several wild plants growing far away from the fields. The spread of genes from genetically modified plants to wild plants reduces the latter's inherent qualities to survive in the wild and this threatens the rich diversity of wild plants.
Another negative impact of genetically modified crops on the environment is that the their inherent qualities to resist pests can prove to be dangerous for other species that pose no threat to crops. A case illustrating this was the discovery that genetically modified corn could harm the monarch butterfly. After it was discovered that the monarch butterfly's larvae could be affected in the same way that other larvae that actually harm corn are, a detailed study was launched to investigate this further. It was finally discovered that one strain of the GM corn did have the potential to harm monarch butterflies. Fortunately, this particular strain had not been adopted on a large scale and was not used much. This gave the manufacturers time to withdraw the crop from the market and the butterfly was saved.