This would explain why crop circles always appear in grasses, and never in shrubs or trees. Humans can’t bend trees and shrubs, so they stick with easy-to-bend grasses. Extraterrestrials, however, would surely have no problems flattening a few conifers, or maybe even a district of skyscrapers.
I don’t buy the belief that crop circles are the work of extraterrestrials, and I can see no reasons as to why extraterrestrials would do such a thing. I think people who think extraterrestrials are creating crop circles need to be a little more discerning, and I think the people who create these circles need to reimburse the many farmers who have had their crops destroyed by their activities.