US farmers are having increasing trouble with weeds that are resistant to Roundup, the popular herbicide.
Roundup has become very popular chemical because it is safe to work with and breaks down quickly, which makes it less environmentally harmful than the alternatives. Thanks to the widespread use of Roundup, farmers have been able to drastically reduce the amount of plowing they do. Instead of plowing, they just spray Roundup on the field, wait a week, then use a seed planter that cuts little slits through the soil. This almost eliminates soil erosion. Because of resistant weeds, many farmers are now going back to regular plowing -- so, fewer toxic chemicals going into the nations rivers, but instead thousands of tons of soil. Everything's a trade-off.
But, you know, evolution is just a theory, so we should teach kids about the alternatives.