Messing with nature - you never can do just one thing

One of the most basic of ecological lessons, and a lesson most commonly ignored, is that you never can do just one thing.  Interactions among organisms and between organisms and their environment are complex and complicated, and when you willingly change one thing it can set off an entire chain or worse, an entire cascade of events.  Knock over one domino and it knocks down the next and so on, this is the simple case; what if when you knock over one domino, it knocks down three, and so on?  This lesson is at the absolute base of the problem of invasive species.  Here's an example.  Kudzu is a legume, a bean, and a vine.  It's a handsome enough plant under some circumstances and it was imported to North America as an ornamental species decades ago.  Because it can fix nitrogen like other legumes, kudzu will grow well on poor soil, so it was promoted across the south to help prevent soil erosion and help reclaim strip mine moonscapes.  But kudzu didn't stop there, and now the vine towers of kudzu are a familiar sight across the south as the vine clamors over trees, and fences, and barns, and anything else that isn't too fast moving.  The next event started in 2009 when a kudzu eating stink bug, also from Asia, was found in Georgia.  Somebody imported it because stink bugs just don't disperse that far on their own, and supposedly kudzu was its favorite food, but favorite doesn't mean only food.  What can possibly go wrong?  Well, what if this stink bug developed a taste for other legumes?  What if the legume was the soybean?  Somebody tries to be a do-gooder and import a bug that eats an invasive vine and the bug becomes a potential agricultural pest on a crop that is one of the USA's most important agricultural commodities.  See those dominos dropping?  Kudzu is also adapting to cooler climates and has been reported in Lincolnland as far north as Peoria, right in the middle of the maize and soybean desert.  And it appears this new invasive bug may be able to survive anywhere soybeans can grow.  So, there's the lesson.  Remember, you can't do just one thing.  Organisms just don't do what you expect them to do or want them to do, and you just start another cascade of unintended and unexpected events.  Let that be your lesson.