I am against the wholesale introduction of GM (Genetically Modified) crops.

I realize that under specific situations those crops create larger yields or are cheaper to weed or insecticide (as they are resistant to, say, Roundup ™). Here are some of the potential downsides of GM crops:

• Many are sterile. You have to buy new seeds every year.
• Monocultures (which they all are) have no genetic variability. If there is a drift, or gradient, of conditions across a field or across a country, small variations in natural plants allow some optimization for differing conditions (light, heat, water, soil quality, and so on). As climate change continues, monocultures will uniformly find themselves with yesterday’s optimization to today’s real world.
• Monocultures are frequently self-sterile. You cannot fertilize a Bosc pear with another Bosc pear, as both trees think it’s their own pollen. Flowering plants in general implement strategies for self-sterility as crosses are the secret to remixing genes and staying ahead of parasites. See W.D.Hamilton, The Narrow Roads of Gene Land, Volume II for details. Or later researchers.
• Gene flow from engineeered plants to nearby plants does happen. There was an experiment in Nature whereby they put genes into the chloroplasts of a plant, with promoters that work in the chloroplast and with ones that work in the nucleus. The point was, if the gene showed up in a chloroplast, it might (for example) fluoresce green, and if the nearby gene showed up in a cell nucleus, it might fluoresce yellow. The idea was to see if these genes, theoretically trapped in the chloroplast and thus not included in the pollen, could somehow get into nearby fields. They could. The frequency was low, but when you consider the enormous amount of pollen and nearby fields, obviously inserted genes are going to escape. That means our genetically engineered invulnerability to Roundup (TM) could spread to noxious weeds, despite GM companies telling us that it cannot.
• I distrust monopolies. Remember the Haitian pigs, which could forage for themselves and live off the land. We North Americans introduced our pigs, which cannot do these things, and in addition require antibiotics and food and water in abundance. The Haitians called them Princess Pigs. However, once the Haitian pigs were replaced, the need was to buy our, splendid, fatter, but more poorly adapted pigs. I fear that, once all wheat in an area (country, say) is from a GM seed that has to be made (and bought) every year, that the monopoly power of the GM seed maker will maximize profits. Really.