I was assembling a new barbaque grill recently and I had to stop because I ran out of screws of one size. I had lost a few of them earlier in the process and there were no spares. Now I have to go to the hardware store to get more. 
    I think just about everyone can understand this problem, but they seem to have difficulty understanding essentially the same problem when it come to the world we live in. We think it is alright to loose a few “screws” because that won't make the world fall apart. We think we can exterminate a species of insects that is eating our crops, or an animal that is harming our farms, and there will be absolutely no consequences. That is simple not the case.
    Just take the simple example of spraying crops to kill harmful insects. The poisons work well, they not only kill the harmful insects, they also kill praying mantis, lady bugs and bees. They kill frogs and toads. Frogs, toads, praying mantis and lady bugs all help to control harmful insects by eating them. So do birds which are also killed in large numbers by insecticides. And bees are needed to pollinate the crops. Without the bees, many crops will fail. When the crops fail, prices go up on what supplies remain. The increased cost of those foods means people have less money to spend on other things, so sales of clothes, cars, movie tickets, etc. drop. So in this simple chain of events, spraying a pesticide can damage the economy of the nation.
     And this is just a very simplified example, the reality is much more complicated. Few, if any, of us really understand the complex interrelationships of all life on the planet so destroying some, supposedly to benefit ourselves, is foolish and, in the long run, has the opposite effect of what is desired.