I am no alien enthusiast by any means, but one thing I can do is derive a reasonable conclusion based on the facts and evidence.
Fact: Many crop circls in the U.K. have been found to have been made by teams of hoaksters. This is still the case today.
Fact: Crop circles are a worldwide phenomena and have been for decades (centuries in certain places). The two brothers in England who made themselves famous in the 80's for revealing to a British magazine that they were responsible for England's crop circles said that they had derived the inspiration for the circles from a story out of Australia about a rash of circles there in the 70's. The Australian circles are still unexplained, as are a plethora of others in many nations around the world. (Hard to believe that people in starving Africa or the Orient will take the time out of their day to make crop circles when the news of crop circles in other locations has never reached them, thus giving them no place to derive their inspiration.
Fact: There have been crop circles pop up over night that are over 600,000 square feet in area, with hundreds of circles forming PERFECT geometrical formations.
Fact: A mathematician In New England derived the "5th theorem of Geometry" from a crop circle and actually published his findings in an academic journal.
Fact: Several reputable geologists, physicists and other types of scientists have studied these circles in depth and do not believe all of them are man made hoaxes.
Now, as for the last fact, let me post a link to a website that was published by a geophysicist from Michigan who has researched the circles for years. Not only does he find abnormal radiation readings around most circles, but he also finds that the crops continue growing but no longer can produce seeds in many cases. Also, many of the crops in the cirlce have expulsion cavaties created presumably from the extreme microwave radiation that was applied to the crops for a brief period of time. Click the link for a more in depth explanation of what this geophysicist feels is a purely natural phenomenon.
http://www.diagnosis2012.co.uk/blt1.htm
Regards